Cytokinins are plant hormones, derivatives of adenine with a side chain at the N6-position. They are involved in many physiological processes. While the metabolism of trans-zeatin and isopentenyladenine, which are considered to be highly active cytokinins, has been extensively studied, there are others with less obvious functions, such as cis-zeatin, dihydrozeatin, and aromatic cytokinins, which have been comparatively neglected. To help explain this duality, we present a novel hypothesis metaphorically comparing various cytokinin forms, enzymes of CK metabolism, and their signalling and transporter functions to the comics superheroes Hulk and Deadpool. Hulk is a powerful but short-lived creation, whilst Deadpool presents a more subtle and enduring force. With this dual framework in mind, this review compares different cytokinin metabolites, and their biosynthesis, translocation, and sensing to illustrate the different mechanisms behind the two CK strategies. This is put together and applied to a plant developmental scale and, beyond plants, to interactions with organisms of other kingdoms, to highlight where future study can benefit the understanding of plant fitness and productivity.

Biology Department Trent University Peterborough ON K9L 0G2 Canada

Laboratory of Hormonal Regulations in Plants Institute of Experimental Botany The Czech Academy of Sciences Rozvojová 263 CZ 16502 Prague 6 Czech Republic

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Miller C.O., Skoog F., Von Saltza M.H., Strong F.M. Kinetin, a Cell Division Factor from Deoxyribonucleic Acid. J. Am. Chem. Soc. 1955;77:1392. doi: 10.1021/ja01610a105. DOI

Shantz E.M., Steward F.C. The Identification of Compound A from Coconut Milk as 1,3-Diphenylurea. J. Am. Chem. Soc. 1955;77:6351–6353. doi: 10.1021/ja01628a079. DOI

Jacobs W.P. Plant Hormones. Cambridge University Press; Cambridge, UK: 1979.

Ge L., Yong J.W.H., Goh N.K., Chia L.S., Tan S.N., Ong E.S. Identification of Kinetin and Kinetin Riboside in Coconut (Cocos Nucifera L.) Water Using a Combined Approach of Liquid Chromatography-Tandem Mass Spectrometry, High Performance Liquid Chromatography and Capillary Electrophoresis. J. Chromatogr. B Analyt. Technol. Biomed. Life Sci. 2005;829:26–34. doi: 10.1016/j.jchromb.2005.09.026. PubMed DOI

Barciszewski J., Siboska G.E., Pedersen B.O., Clark B.F., Rattan S.I. Evidence for the Presence of Kinetin in DNA and Cell Extracts. FEBS Lett. 1996;393:197–200. doi: 10.1016/0014-5793(96)00884-8. PubMed DOI

Letham D.S. Zeatin, a Factor Inducing Cell Division Isolated from Zea Mays. Life Sci. 1963;2:569–573. doi: 10.1016/0024-3205(63)90108-5. PubMed DOI

Skoog F., Armstrong D.J. Cytokinins. Ann. Rev. Plant Physiol. 1970;21:359–384. doi: 10.1146/annurev.pp.21.060170.002043. DOI

Pongs O., Reinwald E. Function of Y in Codon-Anticodon Interaction of TRNAPhe. Biochem. Biophys. Res. Commun. 1973;50:357–363. doi: 10.1016/0006-291X(73)90848-6. PubMed DOI

Agris P.F., Vendeix F.A.P., Graham W.D. TRNA’s Wobble Decoding of the Genome: 40 Years of Modification. J. Mol. Biol. 2007;366:1–13. doi: 10.1016/j.jmb.2006.11.046. PubMed DOI

Persson B.C., Esberg B., Ólafsson Ó., Björk G.R. Synthesis and Function of Isopentenyl Adenosine Derivatives in TRNA. Biochimie. 1994;76:1152–1160. doi: 10.1016/0300-9084(94)90044-2. PubMed DOI

Schweizer U., Bohleber S., Fradejas-Villar N. The Modified Base Isopentenyladenosine and Its Derivatives in TRNA. RNA Biol. 2017;14:1197–1208. doi: 10.1080/15476286.2017.1294309. PubMed DOI PMC

Zürcher E., Müller B. Cytokinin Synthesis, Signaling, and Function—Advances and New Insights. Int. Rev. Cell Mol. Biol. 2016;324:1–38. doi: 10.1016/bs.ircmb.2016.01.001. PubMed DOI

Lomin S.N., Krivosheev D.M., Steklov M.Y., Arkhipov D.V., Osolodkin D.I., Schmülling T., Romanov G.A. Plant Membrane Assays with Cytokinin Receptors Underpin the Unique Role of Free Cytokinin Bases as Biologically Active Ligands. J. Exp. Bot. 2015;66:1851–1863. doi: 10.1093/jxb/eru522. PubMed DOI PMC

Daudu D., Allion E., Liesecke F., Papon N., Courdavault V., Dugé de Bernonville T., Mélin C., Oudin A., Clastre M., Lanoue A., et al. CHASE-Containing Histidine Kinase Receptors in Apple Tree: From a Common Receptor Structure to Divergent Cytokinin Binding Properties and Specific Functions. Front. Plant Sci. 2017;8:1614. doi: 10.3389/fpls.2017.01614. PubMed DOI PMC

Kamínek M., Březinov A., Gaudinová A., Motyka V., Vaňková R., Zažímalová E. Purine Cytokinins: A Proposal of Abbreviations. Plant Growth Regul. 2000;32:253–256. doi: 10.1023/A:1010743522048. DOI

Mik V., Szüčová L., Spíchal L., Plíhal O., Nisler J., Zahajská L., Doležal K., Strnad M. N9-Substituted N6-[(3-Methylbut-2-En-1-Yl)Amino]Purine Derivatives and Their Biological Activity in Selected Cytokinin Bioassays. Bioorg. Med. Chem. 2011;19:7244–7251. doi: 10.1016/j.bmc.2011.09.052. PubMed DOI

Pokorná E., Hluska T., Galuszka P., Hallmark H.T., Dobrev P.I., Záveská Drábková L., Filipi T., Holubová K., Plíhal O., Rashotte A.M., et al. Cytokinin N-Glucosides: Occurrence, Metabolism and Biological Activities in Plants. Biomolecules. 2021;11:24. doi: 10.3390/biom11010024. PubMed DOI PMC

Galuszka P., Popelková H., Werner T., Frébortová J., Pospíšilová H., Mik V., Köllmer I., Schmülling T., Frébort I. Biochemical Characterization of Cytokinin Oxidases/Dehydrogenases from Arabidopsis Thaliana Expressed in Nicotiana Tabacum L. J. Plant Growth Regul. 2007;26:255–267. doi: 10.1007/s00344-007-9008-5. DOI

Zalabák D., Galuszka P., Mrízová K., Podlešáková K., Gu R., Frébortová J. Biochemical Characterization of the Maize Cytokinin Dehydrogenase Family and Cytokinin Profiling in Developing Maize Plantlets in Relation to the Expression of Cytokinin Dehydrogenase Genes. Plant Physiol. Biochem. PPB Société Fr. Physiol. Végétale. 2014;74:283–293. doi: 10.1016/j.plaphy.2013.11.020. PubMed DOI

Pertry I., Václavíková K., Depuydt S., Galuszka P., Spíchal L., Temmerman W., Stes E., Schmülling T., Kakimoto T., Van Montagu M.C.E., et al. Identification of Rhodococcus Fascians Cytokinins and Their Modus Operandi to Reshape the Plant. Proc. Natl. Acad. Sci. USA. 2009;106:929–934. doi: 10.1073/pnas.0811683106. PubMed DOI PMC

Žižková E., Dobrev P.I., Muhovski Y., Hošek P., Hoyerová K., Haisel D., Procházková D., Lutts S., Motyka V., Hichri I. Tomato (Solanum Lycopersicum L.) SlIPT3 and SlIPT4 Isopentenyltransferases Mediate Salt Stress Response in Tomato. BMC Plant Biol. 2015;15:85. doi: 10.1186/s12870-015-0415-7. PubMed DOI PMC

Jaworek P., Kopečný D., Zalabák D., Šebela M., Kouřil Š., Hluska T., Končitíková R., Podlešáková K., Tarkowski P. Occurrence and Biosynthesis of Cytokinins in Poplar. Planta. 2019;250:229–244. doi: 10.1007/s00425-019-03152-z. PubMed DOI

Kasahara H., Takei K., Ueda N., Hishiyama S., Yamaya T., Kamiya Y., Yamaguchi S., Sakakibara H. Distinct Isoprenoid Origins of Cis- and Trans.-Zeatin Biosyntheses in Arabidopsis. J. Biol. Chem. 2004;279:14049–14054. doi: 10.1074/jbc.M314195200. PubMed DOI

Takei K., Ueda N., Aoki K., Kuromori T., Hirayama T., Shinozaki K., Yamaya T., Sakakibara H. AtIPT3 Is a Key Determinant of Nitrate-Dependent Cytokinin Biosynthesis in Arabidopsis. Plant Cell Physiol. 2004;45:1053–1062. doi: 10.1093/pcp/pch119. PubMed DOI

Kuroha T., Tokunaga H., Kojima M., Ueda N., Ishida T., Nagawa S., Fukuda H., Sugimoto K., Sakakibara H. Functional Analyses of LONELY GUY Cytokinin-Activating Enzymes Reveal the Importance of the Direct Activation Pathway in Arabidopsis. Plant Cell. 2009;21:3152–3169. doi: 10.1105/tpc.109.068676. PubMed DOI PMC

Cedzich A., Stransky H., Schulz B., Frommer W.B. Characterization of Cytokinin and Adenine Transport in Arabidopsis Cell Cultures. Plant. Physiol. 2008;148:1857–1867. doi: 10.1104/pp.108.128454. PubMed DOI PMC

Gajdošová S., Spíchal L., Kamínek M., Hoyerová K., Novák O., Dobrev P.I., Galuszka P., Klíma P., Gaudinová A., Žižková E., et al. Distribution, Biological Activities, Metabolism, and the Conceivable Function of Cis-Zeatin-Type Cytokinins in Plants. J. Exp. Bot. 2011;62:2827–2840. doi: 10.1093/jxb/erq457. PubMed DOI

Schäfer M., Brütting C., Meza-Canales I.D., Großkinsky D.K., Vaňková R., Baldwin I.T., Meldau S. The Role of Cis-Zeatin-Type Cytokinins in Plant Growth Regulation and Mediating Responses to Environmental Interactions. J. Exp. Bot. 2015;66:4873–4884. doi: 10.1093/jxb/erv214. PubMed DOI PMC

Hall R.H., Csonka L., David H., McLennan B. Cytokinins in the Soluble RNA of Plant Tissues. Science. 1967;156:69–71. doi: 10.1126/science.156.3771.69. PubMed DOI

Mok M.C., Mok D.W.S., Armstrong D.J. Differential Cytokinin Structure-Activity Relationships in Phaseolus. Plant Physiol. 1978;61:72–75. doi: 10.1104/pp.61.1.72. PubMed DOI PMC

Schmitz R.Y., Skoog F., Playtis A.J., Leonard N.J. Cytokinins: Synthesis and Biological Activity of Geometric and Position Isomers of Zeatin. Plant Physiol. 1972;50:702–705. doi: 10.1104/pp.50.6.702. PubMed DOI PMC

Vreman H.J., Schmitz R.Y., Skoog F., Playtis A.J., Frihart C.R., Leonard N.J. Synthesis of 2-Methylthio-Cis- and Trans.-Ribosylzeatin and Their Isolation from Pisum TRNA. Phytochemistry. 1974;13:31–37. doi: 10.1016/S0031-9422(00)91263-9. DOI

Mauk C.S., Langille A.R. Physiology of Tuberization in Solanum Tuberosum L.: Cis-Zeatin Riboside in the Potato Plant: Its Identification and Changes in Endogenous Levels as Influenced by Temperature and Photoperiod. Plant Physiol. 1978;62:438–442. doi: 10.1104/pp.62.3.438. PubMed DOI PMC

Suttle J.C., Banowetz G.M. Changes in Cis-Zeatin and Cis-Zeatin Riboside Levels and Biological Activity during Potato Tuber Dormancy. Physiol. Plant. 2000;109:68–74. doi: 10.1034/j.1399-3054.2000.100110.x. DOI

Lulai E.C., Suttle J.C., Olson L.L., Neubauer J.D., Campbell L.G., Campbell M.A. Wounding Induces Changes in Cytokinin and Auxin Content in Potato Tuber, but Does Not Induce Formation of Gibberellins. J. Plant Physiol. 2016;191:22–28. doi: 10.1016/j.jplph.2015.11.006. PubMed DOI

Kolachevskaya O.O., Sergeeva L.I., Floková K., Getman I.A., Lomin S.N., Alekseeva V.V., Rukavtsova E.B., Buryanov Y.I., Romanov G.A. Auxin Synthesis Gene Tms1 Driven by Tuber-Specific Promoter Alters Hormonal Status of Transgenic Potato Plants and Their Responses to Exogenous Phytohormones. Plant Cell Rep. 2017;36:419–435. doi: 10.1007/s00299-016-2091-y. PubMed DOI

Watanabe N., Yokota T., Takahashi N. Transfer RNA, a Possible Supplier of Free Cytokinins, Ribosyl-Cis-Zeatin and Ribosyl-2-Methylthiozeatin: Quantitative Comparison between Free and Transfer Cytokinins in Various Tissues of the Hop Plant. Plant Cell Physiol. 1982;23:479–488. doi: 10.1093/oxfordjournals.pcp.a076372. DOI

Kudo T., Makita N., Kojima M., Tokunaga H., Sakakibara H. Cytokinin Activity of Cis-Zeatin and Phenotypic Alterations Induced by Overexpression of Putative Cis-Zeatin-O-Glucosyltransferase in Rice. Plant Physiol. 2012;160:319–331. doi: 10.1104/pp.112.196733. PubMed DOI PMC

Takagi M., Yokota T., Murofushi N., Ota Y., Takahashi N. Fluctuation of Endogenous Cytokinin Contents in Rice during Its Life Cycle-Quantification of Cytokinins by Selected Ion Monitoring Using Deuterium-Labelled Internal Standards. Agric. Biol. Chem. 1985;49:3271–3277. doi: 10.1271/bbb1961.49.3271. DOI

Emery R.J.N., Ma Q., Atkins C.A. The Forms and Sources of Cytokinins in Developing White Lupine Seeds and Fruits. Plant Physiol. 2000;123:1593–1604. doi: 10.1104/pp.123.4.1593. PubMed DOI PMC

Emery R.J.N., Leport L., Barton J.E., Turner N.C., Atkins C.A. Cis-Isomers of Cytokinins Predominate in Chickpea Seeds throughout Their Development. Plant Physiol. 1998;117:1515–1523. doi: 10.1104/pp.117.4.1515. PubMed DOI PMC

Veach Y.K., Martin R.C., Mok D.W.S., Malbeck J., Vaňková R., Mok M.C. O-Glucosylation of Cis-Zeatin in Maize. Characterization of Genes, Enzymes, and Endogenous Cytokinins. Plant Physiol. 2003;131:1374–1380. doi: 10.1104/pp.017210. PubMed DOI PMC

Vyroubalová Š., Václavíková K., Turečková V., Novák O., Šmehilová M., Hluska T., Ohnoutková L., Frébort I., Galuszka P. Characterization of New Maize Genes Putatively Involved in Cytokinin Metabolism and Their Expression during Osmotic Stress in Relation to Cytokinin Levels. Plant Physiol. 2009;151:433–447. doi: 10.1104/pp.109.142489. PubMed DOI PMC

Stirk W.A., Gold J.D., Novák O., Strnad M., van Staden J. Changes in Endogenous Cytokinins During Germination and Seedling Establishment of Tagetes Minuta L. Plant Growth Regul. 2005;47:1–7. doi: 10.1007/s10725-005-1767-z. DOI

Stirk W.A., Novák O., Žižková E., Motyka V., Strnad M., van Staden J. Comparison of Endogenous Cytokinins and Cytokinin Oxidase/Dehydrogenase Activity in Germinating and Thermoinhibited Tagetes Minuta Achenes. J. Plant Physiol. 2012;169:696–703. doi: 10.1016/j.jplph.2012.01.013. PubMed DOI

Quesnelle P.E., Emery R.J.N. Cis-Cytokinins That Predominate in Pisum Sativum during Early Embryogenesis Will Accelerate Embryo Growth in Vitro. Can. J. Bot. 2007;85:91–103. doi: 10.1139/b06-149. DOI

Goggin D.E., Emery R.J.N., Powles S.B., Steadman K.J. Initial Characterisation of Low and High Seed Dormancy Populations of Lolium Rigidum Produced by Repeated Selection. J. Plant Physiol. 2010;167:1282–1288. doi: 10.1016/j.jplph.2010.04.004. PubMed DOI

Stirk W.A., Václavíková K., Novák O., Gajdošová S., Kotland O., Motyka V., Strnad M., van Staden J. Involvement of Cis-Zeatin, Dihydrozeatin, and Aromatic Cytokinins in Germination and Seedling Establishment of Maize, Oats, and Lucerne. J. Plant Growth Regul. 2012;31:392–405. doi: 10.1007/s00344-011-9249-1. DOI

Tarkowská D., Filek M., Biesaga-Kościelniak J., Marcińska I., Macháčková I., Krekule J., Strnad M. Cytokinins in Shoot Apices of Brassica Napus Plants during Vernalization. Plant Sci. 2012;187:105–112. doi: 10.1016/j.plantsci.2012.02.003. PubMed DOI

Vondráková Z., Dobrev P.I., Pesek B., Fischerová L., Vágner M., Motyka V. Profiles of Endogenous Phytohormones Over the Course of Norway Spruce Somatic Embryogenesis. Front. Plant Sci. 2018;9 doi: 10.3389/fpls.2018.01283. PubMed DOI PMC

Záveská Drábková L., Dobrev P.I., Motyka V. Phytohormone Profiling across the Bryophytes. PLoS ONE. 2015;10:e0125411. doi: 10.1371/journal.pone.0125411. PubMed DOI PMC

Žižková E., Kubeš M., Dobrev P.I., Přibyl P., Šimura J., Zahajská L., Záveská Drábková L., Novák O., Motyka V. Control of Cytokinin and Auxin Homeostasis in Cyanobacteria and Algae. Ann. Bot. 2017;119:151–166. doi: 10.1093/aob/mcw194. PubMed DOI PMC

Morrison E.N., Knowles S., Hayward A., Thorn R.G., Saville B.J., Emery R.J.N. Detection of Phytohormones in Temperate Forest Fungi Predicts Consistent Abscisic Acid Production and a Common Pathway for Cytokinin Biosynthesis. Mycologia. 2015;107:245–257. doi: 10.3852/14-157. PubMed DOI

Miyawaki K., Tarkowski P., Matsumoto-Kitano M., Kato T., Sato S., Tarkowska D., Tabata S., Sandberg G., Kakimoto T. Roles of Arabidopsis ATP/ADP Isopentenyltransferases and TRNA Isopentenyltransferases in Cytokinin Biosynthesis. Proc. Natl. Acad. Sci. USA. 2006;103:16598–16603. doi: 10.1073/pnas.0603522103. PubMed DOI PMC

Köllmer I., Novák O., Strnad M., Schmülling T., Werner T. Overexpression of the Cytosolic Cytokinin Oxidase/Dehydrogenase (CKX7) from Arabidopsis Causes Specific Changes in Root Growth and Xylem Differentiation. Plant J. Cell Mol. Biol. 2014;78:359–371. doi: 10.1111/tpj.12477. PubMed DOI

Werner T., Motyka V., Strnad M., Schmülling T. Regulation of Plant Growth by Cytokinin. Proc. Natl. Acad. Sci. USA. 2001;98:10487–10492. doi: 10.1073/pnas.171304098. PubMed DOI PMC

Martin R.C., Mok M.C., Habben J.E., Mok D.W.S. A Maize Cytokinin Gene Encoding an O-Glucosyltransferase Specific to Cis-Zeatin. Proc. Natl. Acad. Sci. USA. 2001;98:5922–5926. doi: 10.1073/pnas.101128798. PubMed DOI PMC

Spíchal L., Rakova N.Y., Riefler M., Mizuno T., Romanov G.A., Strnad M., Schmülling T. Two Cytokinin Receptors of Arabidopsis Thaliana, CRE1/AHK4 and AHK3, Differ in Their Ligand Specificity in a Bacterial Assay. Plant Cell Physiol. 2004;45:1299–1305. doi: 10.1093/pcp/pch132. PubMed DOI

Yonekura-Sakakibara K., Kojima M., Yamaya T., Sakakibara H. Molecular Characterization of Cytokinin-Responsive Histidine Kinases in Maize. Differential Ligand Preferences and Response to Cis-Zeatin. Plant Physiol. 2004;134:1654–1661. doi: 10.1104/pp.103.037176. PubMed DOI PMC

Park E.J., Kim T.-H. Fine-Tuning of Gene Expression by TRNA-Derived Fragments during Abiotic Stress Signal Transduction. Int. J. Mol. Sci. 2018;19:518. doi: 10.3390/ijms19020518. PubMed DOI PMC

Kamínek M. Letter: Evolution of TRNA and Origin of the Two Positional Isomers of Zeatin. J. Theor. Biol. 1974;48:489–492. doi: 10.1016/S0022-5193(74)80018-4. PubMed DOI

Kamínek M. Tracking the Story of Cytokinin Research. J. Plant Growth Regul. 2015;34:723–739. doi: 10.1007/s00344-015-9543-4. DOI

Podlešáková K., Fardoux J., Patrel D., Bonaldi K., Novák O., Strnad M., Giraud E., Spíchal L., Nouwen N. Rhizobial Synthesized Cytokinins Contribute to but Are Not Essential for the Symbiotic Interaction between Photosynthetic Bradyrhizobia and Aeschynomene Legumes. Mol. Plant Microbe Interact. MPMI. 2013;26:1232–1238. doi: 10.1094/MPMI-03-13-0076-R. PubMed DOI

Hinsch J., Galuszka P., Tudzynski P. Functional Characterization of the First Filamentous Fungal TRNA-Isopentenyltransferase and Its Role in the Virulence of Claviceps Purpurea. New Phytol. 2016;211:980–992. doi: 10.1111/nph.13960. PubMed DOI

Koshimizu K., Kusaki T., Mitsui T., Matsubara S. Isolation of a Cytokinin, (−)-Dihydrozeatin, from Immature Seeds of Lupinus Luteus. Tetrahedron Lett. 1967;8:1317–1320. doi: 10.1016/S0040-4039(00)90693-2. DOI

Koshimizu K., Matsubara S., Kusaki T., Mitsui T. Isolation of a New Cytokinin from Immature Yellow Lupin Seeds. Agric. Biol. Chem. 1967;31:795–801. doi: 10.1080/00021369.1967.10858881. DOI

Choi J., Lee J., Kim K., Cho M., Ryu H., An G., Hwang I. Functional Identification of OsHk6 as a Homotypic Cytokinin Receptor in Rice with Preferential Affinity for IP. Plant Cell Physiol. 2012;53:1334–1343. doi: 10.1093/pcp/pcs079. PubMed DOI

Kuderová A., Gallová L., Kuricová K., Nejedlá E., Čurdová A., Micenková L., Plíhal O., Šmajs D., Spíchal L., Hejátko J. Identification of AHK2- and AHK3-like Cytokinin Receptors in Brassica Napus Reveals Two Subfamilies of AHK2 Orthologues. J. Exp. Bot. 2015;66:339–353. doi: 10.1093/jxb/eru422. PubMed DOI

Lomin S.N., Yonekura-Sakakibara K., Romanov G.A., Sakakibara H. Ligand-Binding Properties and Subcellular Localization of Maize Cytokinin Receptors. J. Exp. Bot. 2011;62:5149–5159. doi: 10.1093/jxb/err220. PubMed DOI PMC

Romanov G.A., Lomin S.N., Schmülling T. Biochemical Characteristics and Ligand-Binding Properties of Arabidopsis Cytokinin Receptor AHK3 Compared to CRE1/AHK4 as Revealed by a Direct Binding Assay. J. Exp. Bot. 2006;57:4051–4058. doi: 10.1093/jxb/erl179. PubMed DOI

Gaudinová A., Dobrev P.I., Šolcová B., Novák O., Strnad M., Friedecký D., Motyka V. The Involvement of Cytokinin Oxidase/Dehydrogenase and Zeatin Reductase in Regulation of Cytokinin Levels in Pea (Pisum Sativum L.) Leaves. J. Plant Growth Regul. 2005;24:188–200. doi: 10.1007/s00344-005-0043-9. DOI

Martin R.C., Mok M.C., Shaw G., Mok D.W.S. An Enzyme Mediating the Conversion of Zeatin to Dihydrozeatin in Phaseolus Embryos. Plant Physiol. 1989;90:1630–1635. doi: 10.1104/pp.90.4.1630. PubMed DOI PMC

Sondheimer E., Tzou D.-S. The Metabolism of Hormones during Seed Germination and Dormancy II. The Metabolism of 8-14C-Zeatin in Bean Axes. Plant Physiol. 1971;47:516–520. doi: 10.1104/pp.47.4.516. PubMed DOI PMC

Singh S., Letham D.S., Jameson P.E., Zhang R., Parker C.W., Bandenoch-Jones J., Noodén L.D. Cytokinin Biochemistry in Relation to Leaf Senescence: IV. Cytokinin Metabolism in Soybean Explants. Plant Physiol. 1988;88:788–794. doi: 10.1104/pp.88.3.788. PubMed DOI PMC

Podlešáková K., Zalabák D., Čudejková M., Plíhal O., Szüčová L., Doležal K., Spíchal L., Strnad M., Galuszka P. Novel Cytokinin Derivatives Do Not Show Negative Effects on Root Growth and Proliferation in Submicromolar Range. PLoS ONE. 2012;7:e39293. doi: 10.1371/journal.pone.0039293. PubMed DOI PMC

Arnau J.A., Tadeo F.R., Guerri J., Primo-Millo E. Cytokinins in Peach: Endogenous Levels during Early Fruit Development. Plant Physiol. Biochem. 1999;37:741–750. doi: 10.1016/S0981-9428(00)86687-5. DOI

Strnad M. The Aromatic Cytokinins. Physiol. Plant. 1997;101:674–688. doi: 10.1111/j.1399-3054.1997.tb01052.x. DOI

Tarkowská D., Dolezal K., Tarkowski P., Astot C., Holub J., Fuksová K., Schmülling T., Sandberg G., Strnad M. Identification of New Aromatic Cytokinins in Arabidopsis Thaliana and Populus x Canadensis Leaves by LC-(+)ESI-MS and Capillary Liquid Chromatography/Frit-Fast Atom Bombardment Mass Spectrometry. Physiol. Plant. 2003;117:579–590. doi: 10.1034/j.1399-3054.2003.00071.x. PubMed DOI

Miller C.O., Skoog F., Okumura F.S., Von Saltza M.H., Strong F.M. Structure and Synthesis of Kinetin. J. Am. Chem. Soc. 1955;77:2662–2663. doi: 10.1021/ja01614a108. DOI

Haidoune M., Mornet R., Laloue M. Synthesis of 6-(3-Methylpyrrol-1-Yl)-9-β-d-Ribofuranosyl Purine, a Novel Metabolite of Zeatin Riboside. Tetrahedron Lett. 1990;31:1419–1422. doi: 10.1016/S0040-4039(00)88821-8. DOI

Hluska T., Dobrev P.I., Tarkowská D., Frébortová J., Zalabák D., Kopečný D., Plíhal O., Kokáš F., Briozzo P., Zatloukal M., et al. Cytokinin Metabolism in Maize: Novel Evidence of Cytokinin Abundance, Interconversions and Formation of a New Trans.-Zeatin Metabolic Product with a Weak Anticytokinin Activity. Plant Sci. 2016;247:127–137. doi: 10.1016/j.plantsci.2016.03.014. PubMed DOI

Sørensen J.L., Benfield A.H., Wollenberg R.D., Westphal K., Wimmer R., Nielsen M.R., Nielsen K.F., Carere J., Covarelli L., Beccari G., et al. The Cereal Pathogen Fusarium Pseudograminearum Produces a New Class of Active Cytokinins during Infection. Mol. Plant Pathol. 2018;19:1140–1154. doi: 10.1111/mpp.12593. PubMed DOI PMC

Laloue M., Fox J.E. Cytokinin Oxidase from Wheat: Partial Purification and General Properties. Plant Physiol. 1989;90:899–906. doi: 10.1104/pp.90.3.899. PubMed DOI PMC

Mok M.C., Martin R.C., Dobrev P.I., Vanková R., Ho P.S., Yonekura-Sakakibara K., Sakakibara H., Mok D.W.S. Topolins and Hydroxylated Thidiazuron Derivatives Are Substrates of Cytokinin O-Glucosyltransferase with Position Specificity Related to Receptor Recognition. Plant Physiol. 2005;137:1057–1066. doi: 10.1104/pp.104.057174. PubMed DOI PMC

Yong J.W.H., Ge L., Ng Y.F., Tan S.N. The Chemical Composition and Biological Properties of Coconut (Cocos Nucifera L.) Water. Molecules. 2009;14:5144–5164. doi: 10.3390/molecules14125144. PubMed DOI PMC

Stirk W.A., Novák O., Václavíková K., Tarkowski P., Strnad M., van Staden J. Spatial and Temporal Changes in Endogenous Cytokinins in Developing Pea Roots. Planta. 2008;227:1279–1289. doi: 10.1007/s00425-008-0699-z. PubMed DOI

Doležal K., Åstot C., Hanuš J., Holub J., Peters W., Beck E., Strnad M., Sandberg G. Identification of Aromatic Cytokinins in Suspension Cultured Photoautotrophic Cells of Chenopodium Rubrum by Capillary Liquid Chromatography/Frit-Fast Atom Bombarded Mass Spectrometry. Plant Growth Regul. 2002;36:181–189. doi: 10.1023/A:1015027906046. DOI

Edlund E., Novák O., Karady M., Ljung K., Jansson S. Contrasting Patterns of Cytokinins between Years in Senescing Aspen Leaves. Plant Cell Environ. 2017;40:622–634. doi: 10.1111/pce.12899. PubMed DOI

Horgan R., Hewett E.W., Purse J.G., Wareing P.F. A New Cytokinin from Populus Robusta. Tetrahedron Lett. 1973;14:2827–2828. doi: 10.1016/S0040-4039(01)96062-9. DOI

Chaves das Neves H.J., Pais M.S.S. Identification of a Spathe Regreening Factor in Zantedeschia Aethiopica. Biochem. Biophys. Res. Commun. 1980;95:1387–1392. doi: 10.1016/S0006-291X(80)80051-9. PubMed DOI

Ge L., Yong J.W.H., Tan S.N., Yang X.H., Ong E.S. Analysis of Positional Isomers of Hydroxylated Aromatic Cytokinins by Micellar Electrokinetic Chromatography. Electrophoresis. 2005;26:1768–1777. doi: 10.1002/elps.200410234. PubMed DOI

De Meutter J., Tytgat T., Witters E., Gheysen G., Van Onckelen H., Gheysen G. Identification of Cytokinins Produced by the Plant Parasitic Nematodes Heterodera Schachtii and Meloidogyne Incognita. Mol. Plant Pathol. 2003;4:271–277. doi: 10.1046/j.1364-3703.2003.00176.x. PubMed DOI

Murfin K.E., Dillman A.R., Foster J.M., Bulgheresi S., Slatko B.E., Sternberg P.W., Goodrich-Blair H. Nematode-Bacterium Symbioses—Cooperation and Conflict Revealed in the “Omics” Age. Biol. Bull. 2012;223:85–102. doi: 10.1086/BBLv223n1p85. PubMed DOI PMC

Juříková S. Bachelor’s Thesis. Universita Palackého v Olomouci; Olomouc, Czech Republic: 2016. Cytokininy v Řasách.

Kieber J.J., Schaller G.E. Cytokinin Signaling in Plant Development. Dev. Camb. Engl. 2018;145 doi: 10.1242/dev.149344. PubMed DOI

Rohmer M. The Discovery of a Mevalonate-Independent Pathway for Isoprenoid Biosynthesis in Bacteria, Algae and Higher Plants. Nat. Prod. Rep. 1999;16:565–574. doi: 10.1039/a709175c. PubMed DOI

Kuzuyama T., Seto H. Diversity of the Biosynthesis of the Isoprene Units. Nat. Prod. Rep. 2003;20:171–183. doi: 10.1039/b109860h. PubMed DOI

Kamada-Nobusada T., Sakakibara H. Molecular Basis for Cytokinin Biosynthesis. Phytochemistry. 2009;70:444–449. doi: 10.1016/j.phytochem.2009.02.007. PubMed DOI

Laule O., Fürholz A., Chang H.-S., Zhu T., Wang X., Heifetz P.B., Gruissem W., Lange M. Crosstalk between Cytosolic and Plastidial Pathways of Isoprenoid Biosynthesis in Arabidopsis Thaliana. Proc. Natl. Acad. Sci. USA. 2003;100:6866–6871. doi: 10.1073/pnas.1031755100. PubMed DOI PMC

Sakakibara H., Kasahara H., Ueda N., Kojima M., Takei K., Hishiyama S., Asami T., Okada K., Kamiya Y., Yamaya T., et al. Agrobacterium Tumefaciens Increases Cytokinin Production in Plastids by Modifying the Biosynthetic Pathway in the Host Plant. Proc. Natl. Acad. Sci. USA. 2005;102:9972–9977. doi: 10.1073/pnas.0500793102. PubMed DOI PMC

Abe I., Tanaka H., Abe T., Noguchi H. Enzymatic Formation of Unnatural Cytokinin Analogs by Adenylate Isopentenyltransferase from Mulberry. Biochem. Biophys. Res. Commun. 2007;355:795–800. doi: 10.1016/j.bbrc.2007.02.032. PubMed DOI

Chu H.-M., Ko T.-P., Wang A.H.-J. Crystal Structure and Substrate Specificity of Plant Adenylate Isopentenyltransferase from Humulus Lupulus: Distinctive Binding Affinity for Purine and Pyrimidine Nucleotides. Nucleic Acids Res. 2010;38:1738–1748. doi: 10.1093/nar/gkp1093. PubMed DOI PMC

Chu H.-M., Chen F.-Y., Ko T.-P., Wang A.H.-J. Binding and Catalysis of Humulus Lupulus Adenylate Isopentenyltransferase for the Synthesis of Isopentenylated Diadenosine Polyphosphates. FEBS Lett. 2010;584:4083–4088. doi: 10.1016/j.febslet.2010.08.038. PubMed DOI

Skoog F., Hamzi H.Q., Szweykowska A.M., Leonard N.J., Carraway K.L., Fujii T., Helgeson J.P., Loeppky R.N. Cytokinins: Structure/Activity Relationships. Phytochemistry. 1967;6:1169–1192. doi: 10.1016/S0031-9422(00)86080-X. DOI

Miyawaki K., Matsumoto-Kitano M., Kakimoto T. Expression of Cytokinin Biosynthetic Isopentenyltransferase Genes in Arabidopsis: Tissue Specificity and Regulation by Auxin, Cytokinin, and Nitrate. Plant J. 2004;37:128–138. doi: 10.1046/j.1365-313X.2003.01945.x. PubMed DOI

Sakamoto T., Sakakibara H., Kojima M., Yamamoto Y., Nagasaki H., Inukai Y., Sato Y., Matsuoka M. Ectopic Expression of KNOTTED1-like Homeobox Protein Induces Expression of Cytokinin Biosynthesis Genes in Rice. Plant Physiol. 2006;142:54–62. doi: 10.1104/pp.106.085811. PubMed DOI PMC

Ye C., Wu S., Kong F., Zhou C., Yang Q., Sun Y., Wang B. Identification and Characterization of an Isopentenyltransferase (IPT) Gene in Soybean (Glycine Max L.) Plant Sci. 2006;170:542–550. doi: 10.1016/j.plantsci.2005.10.008. DOI

Liu Z., Lv Y., Zhang M., Liu Y., Kong L., Zou M., Lu G., Cao J., Yu X. Identification, Expression, and Comparative Genomic Analysis of the IPT and CKX Gene Families in Chinese Cabbage (Brassica Rapa ssp. Pekinensis) BMC Genom. 2013;14:594. doi: 10.1186/1471-2164-14-594. PubMed DOI PMC

Chen Y., Chen W., Li X., Jiang H., Wu P., Xia K., Yang Y., Wu G. Knockdown of LjIPT3 Influences Nodule Development in Lotus Japonicus. Plant Cell Physiol. 2014;55:183–193. doi: 10.1093/pcp/pct171. PubMed DOI

Song J., Jiang L., Jameson P.E. Expression Patterns of Brassica Napus Genes Implicate IPT, CKX, Sucrose Transporter, Cell Wall Invertase, and Amino Acid Permease Gene Family Members in Leaf, Flower, Silique, and Seed Development. J. Exp. Bot. 2015;66:5067–5082. doi: 10.1093/jxb/erv133. PubMed DOI PMC

Li M., Wei Q., Xiao Y., Peng F. The Effect of Auxin and Strigolactone on ATP/ADP Isopentenyltransferase Expression and the Regulation of Apical Dominance in Peach. Plant Cell Rep. 2018;37:1693–1705. doi: 10.1007/s00299-018-2343-0. PubMed DOI

Tanaka M., Takei K., Kojima M., Sakakibara H., Mori H. Auxin Controls Local Cytokinin Biosynthesis in the Nodal Stem in Apical Dominance. Plant J. Cell Mol. Biol. 2006;45:1028–1036. doi: 10.1111/j.1365-313X.2006.02656.x. PubMed DOI

Landrein B., Formosa-Jordan P., Malivert A., Schuster C., Melnyk C.W., Yang W., Turnbull C.G.N., Meyerowitz E.M., Locke J.C.W., Jönsson H. Nitrate Modulates Stem Cell Dynamics in Arabidopsis Shoot Meristems through Cytokinins. Proc. Natl. Acad. Sci. USA. 2018;115:1382–1387. doi: 10.1073/pnas.1718670115. PubMed DOI PMC

Wang J., Lu K., Nie H., Zeng Q., Wu B., Qian J., Fang Z. Rice Nitrate Transporter OsNPF7.2 Positively Regulates Tiller Number and Grain Yield. Rice. 2018;11:12. doi: 10.1186/s12284-018-0205-6. PubMed DOI PMC

Galichet A., Hoyerová K., Kamínek M., Gruissem W. Farnesylation Directs AtIPT3 Subcellular Localization and Modulates Cytokinin Biosynthesis in Arabidopsis. Plant Physiol. 2008;146:1155–1164. doi: 10.1104/pp.107.107425. PubMed DOI PMC

Miura G.A., Miller C.O. 6-(γ,γ-Dimethylallylamino)Purine As A Precursor of Zeatin. Plant Physiol. 1969;44:372–376. doi: 10.1104/pp.44.3.372. PubMed DOI PMC

Miura G.A., Hall R.H. Trans-Ribosylzeatin: Its Biosynthesis in Zea Mays Endosperm and the Mycorrhizal Fungus, Rhizopogon Roseolus. Plant Physiol. 1973;51:563–569. doi: 10.1104/pp.51.3.563. PubMed DOI PMC

Chen C.M., Leisner S.M. Modification of Cytokinins by Cauliflower Microsomal Enzymes. Plant Physiol. 1984;75:442–446. doi: 10.1104/pp.75.2.442. PubMed DOI PMC

Takei K., Yamaya T., Sakakibara H. Arabidopsis CYP735A1 and CYP735A2 Encode Cytokinin Hydroxylases That Catalyze the Biosynthesis of Trans.-Zeatin. J. Biol. Chem. 2004;279:41866–41872. doi: 10.1074/jbc.M406337200. PubMed DOI

Kiba T., Takei K., Kojima M., Sakakibara H. Side-Chain Modification of Cytokinins Controls Shoot Growth in Arabidopsis. Dev. Cell. 2013;27:452–461. doi: 10.1016/j.devcel.2013.10.004. PubMed DOI

Chang L., Ramireddy E., Schmülling T. Cytokinin as a Positional Cue Regulating Lateral Root Spacing in Arabidopsis. J. Exp. Bot. 2015;66:4759–4768. doi: 10.1093/jxb/erv252. PubMed DOI PMC

Persson B.C., Björk G.R. Isolation of the Gene (MiaE) Encoding the Hydroxylase Involved in the Synthesis of 2-Methylthio-Cis-Ribozeatin in TRNA of Salmonella Typhimurium and Characterization of Mutants. J. Bacteriol. 1993;175:7776–7785. doi: 10.1128/JB.175.24.7776-7785.1993. PubMed DOI PMC

Kaminska K.H., Baraniak U., Boniecki M., Nowaczyk K., Czerwoniec A., Bujnicki J.M. Structural Bioinformatics Analysis of Enzymes Involved in the Biosynthesis Pathway of the Hypermodified Nucleoside Ms2Io6A37 in TRNA. Proteins Struct. Funct. Bioinform. 2008;70:1–18. doi: 10.1002/prot.21640. PubMed DOI

Bassil N.V., Mok D.W.S., Mok M.C. Partial Purification of a Cis-Trans.-Isomerase of Zeatin from Immature Seed of Phaseolus Vulgaris L. Plant Physiol. 1993;102:867–872. doi: 10.1104/pp.102.3.867. PubMed DOI PMC

Sasaki E., Ogura T., Takei K., Kojima M., Kitahata N., Sakakibara H., Asami T., Shimada Y. Uniconazole, a Cytochrome P450 Inhibitor, Inhibits Trans.-Zeatin Biosynthesis in Arabidopsis. Phytochemistry. 2013;87:30–38. doi: 10.1016/j.phytochem.2012.11.023. PubMed DOI

Cai L., Zhang L., Fu Q., Xu Z.-F. Identification and Expression Analysis of Cytokinin Metabolic Genes IPTs, CYP735A and CKXs in the Biofuel Plant Jatropha Curcas. PeerJ. 2018;6:e4812. doi: 10.7717/peerj.4812. PubMed DOI PMC

Eisermann I., Motyka V., Kümmel S., Dobrev P.I., Hübner K., Deising H.B., Wirsel S.G.R. CgIPT1 Is Required for Synthesis of Cis-Zeatin Cytokinins and Contributes to Stress Tolerance and Virulence in Colletotrichum Graminicola. Fungal Genet. Biol. 2020;143:103436. doi: 10.1016/j.fgb.2020.103436. PubMed DOI

Hluska T., Šebela M., Lenobel R., Frébort I., Galuszka P. Purification of Maize Nucleotide Pyrophosphatase/Phosphodiesterase Casts Doubt on the Existence of Zeatin Cis–Trans. Isomerase in Plants. Front. Plant Sci. 2017;8 doi: 10.3389/fpls.2017.01473. PubMed DOI PMC

Kuroha T., Kato H., Asami T., Yoshida S., Kamada H., Satoh S. A Trans.-Zeatin Riboside in Root Xylem Sap Negatively Regulates Adventitious Root Formation on Cucumber Hypocotyls. J. Exp. Bot. 2002;53:2193–2200. doi: 10.1093/jxb/erf077. PubMed DOI

Nandi S.K., Palni L.M.S. Metabolism of Zeatin Riboside in a Hormone Autonomous Genetic Tumour Line of Tobacco. Plant Growth Regul. 1997;23:159–166. doi: 10.1023/A:1005985331661. DOI

Trdá L., Barešová M., Šašek V., Nováková M., Zahajská L., Dobrev P.I., Motyka V., Burketová L. Cytokinin Metabolism of Pathogenic Fungus Leptosphaeria Maculans Involves Isopentenyltransferase, Adenosine Kinase and Cytokinin Oxidase/Dehydrogenase. Front. Microbiol. 2017;8 doi: 10.3389/fmicb.2017.01374. PubMed DOI PMC

Šmehilová M., Galuszka P., Bilyeu K.D., Jaworek P., Kowalska M., Šebela M., Sedlárová M., English J.T., Frébort I. Subcellular Localization and Biochemical Comparison of Cytosolic and Secreted Cytokinin Dehydrogenase Enzymes from Maize. J. Exp. Bot. 2009;60:2701–2712. doi: 10.1093/jxb/erp126. PubMed DOI

Václavíková K., Hluska T., Floková K., Slováková K., Galuszka P., Tarkowski P. The Cytokinin Metabolism in Maize; Proceedings of the 3rd ACPD International Symposium; Prague, Czech Republic. 10–14 July 2009.

Hluska T. Bachelor’s Thesis. Palacký University; Olomouc, Czech Republic: 2010. On the Hunt for Zeatin Cis-Trans. Isomerase.

Chen C. Cytokinin Biosynthesis and Interconversion. Physiol. Plant. 1997;101:665–673. doi: 10.1111/j.1399-3054.1997.tb01051.x. DOI

Kurakawa T., Ueda N., Maekawa M., Kobayashi K., Kojima M., Nagato Y., Sakakibara H., Kyozuka J. Direct Control of Shoot Meristem Activity by a Cytokinin-Activating Enzyme. Nature. 2007;445:652–655. doi: 10.1038/nature05504. PubMed DOI

Hinsch J., Vrabka J., Oeser B., Novák O., Galuszka P., Tudzynski P. De Novo Biosynthesis of Cytokinins in the Biotrophic Fungus Claviceps Purpurea. Environ. Microbiol. 2015;17:2935–2951. doi: 10.1111/1462-2920.12838. PubMed DOI

Samanovic M.I., Tu S., Novák O., Iyer L.M., McAllister F.E., Aravind L., Gygi S.P., Hubbard S.R., Strnad M., Darwin K.H. Proteasomal Control of Cytokinin Synthesis Protects Mycobacterium Tuberculosis against Nitric Oxide. Mol. Cell. 2015;57:984–994. doi: 10.1016/j.molcel.2015.01.024. PubMed DOI PMC

Seo H., Kim S., Sagong H.-Y., Son H.F., Jin K.S., Kim I.-K., Kim K.-J. Structural Basis for Cytokinin Production by LOG from Corynebacterium Glutamicum. Sci. Rep. 2016;6:31390. doi: 10.1038/srep31390. PubMed DOI PMC

Seo H., Kim K.-J. Structural Basis for a Novel Type of Cytokinin-Activating Protein. Sci. Rep. 2017;7:45985. doi: 10.1038/srep45985. PubMed DOI PMC

Seo H., Kim K.-J. Structural Insight into Molecular Mechanism of Cytokinin Activating Protein from Pseudomonas Aeruginosa PAO1. Environ. Microbiol. 2018;20:3214–3223. doi: 10.1111/1462-2920.14287. PubMed DOI

Mayaka J.B., Huang Q., Xiao Y., Zhong Q., Ni J., Shen Y. The Lonely Guy (LOG) Homologue SiRe_0427 from the Thermophilic Archaeon Sulfolobus Islandicus REY15A Is a Phosphoribohydrolase Representing a Novel Group. Appl. Environ. Microbiol. 2019;85 doi: 10.1128/AEM.01739-19. PubMed DOI PMC

Nishii K., Wright F., Chen Y.-Y., Möller M. Tangled History of a Multigene Family: The Evolution of ISOPENTENYLTRANSFERASE Genes. PLoS ONE. 2018;13:e0201198. doi: 10.1371/journal.pone.0201198. PubMed DOI PMC

Burroughs A.M., Zhang D., Schäffer D.E., Iyer L.M., Aravind L. Comparative Genomic Analyses Reveal a Vast, Novel Network of Nucleotide-Centric Systems in Biological Conflicts, Immunity and Signaling. Nucleic Acids Res. 2015;43:10633–10654. doi: 10.1093/nar/gkv1267. PubMed DOI PMC

Tokunaga H., Kojima M., Kuroha T., Ishida T., Sugimoto K., Kiba T., Sakakibara H. Arabidopsis Lonely Guy (LOG) Multiple Mutants Reveal a Central Role of the LOG-Dependent Pathway in Cytokinin Activation. Plant J. 2012;69:355–365. doi: 10.1111/j.1365-313X.2011.04795.x. PubMed DOI

Creason A.L., Vandeputte O.M., Savory E.A., Davis E.W., Putnam M.L., Hu E., Swader-Hines D., Mol A., Baucher M., Prinsen E., et al. Analysis of Genome Sequences from Plant Pathogenic Rhodococcus Reveals Genetic Novelties in Virulence Loci. PLoS ONE. 2014;9:e101996. doi: 10.1371/journal.pone.0101996. PubMed DOI PMC

Niehaus E.-M., Münsterkötter M., Proctor R.H., Brown D.W., Sharon A., Idan Y., Oren-Young L., Sieber C.M., Novák O., Pěnčík A., et al. Comparative “Omics” of the Fusarium Fujikuroi Species Complex Highlights Differences in Genetic Potential and Metabolite Synthesis. Genome Biol. Evol. 2016;8:3574–3599. doi: 10.1093/gbe/evw259. PubMed DOI PMC

Hirose N., Takei K., Kuroha T., Kamada-Nobusada T., Hayashi H., Sakakibara H. Regulation of Cytokinin Biosynthesis, Compartmentalization and Translocation. J. Exp. Bot. 2008;59:75–83. doi: 10.1093/jxb/erm157. PubMed DOI

Osugi A., Kojima M., Takebayashi Y., Ueda N., Kiba T., Sakakibara H. Systemic Transport of Trans.-Zeatin and Its Precursor Have Differing Roles in Arabidopsis Shoots. Nat. Plants. 2017;3:17112. doi: 10.1038/nplants.2017.112. PubMed DOI

Kind S., Hinsch J., Vrabka J., Hradilová M., Majeská-Čudejková M., Tudzynski P., Galuszka P. Manipulation of Cytokinin Level in the Ergot Fungus Claviceps Purpurea Emphasizes Its Contribution to Virulence. Curr. Genet. 2018;64:1303–1319. doi: 10.1007/s00294-018-0847-3. PubMed DOI

Pertry I., Václavíková K., Gemrotová M., Spíchal L., Galuszka P., Depuydt S., Temmerman W., Stes E., De Keyser A., Riefler M., et al. Rhodococcus Fascians Impacts Plant Development through the Dynamic Fas-Mediated Production of a Cytokinin Mix. Mol. Plant Microbe Interact. 2010;23:1164–1174. doi: 10.1094/MPMI-23-9-1164. PubMed DOI

Schoor S., Farrow S., Blaschke H., Lee S., Perry G., von Schwartzenberg K., Emery N., Moffatt B. Adenosine Kinase Contributes to Cytokinin Interconversion in Arabidopsis. Plant Physiol. 2011;157:659–672. doi: 10.1104/pp.111.181560. PubMed DOI PMC

Zhang X., Chen Y., Lin X., Hong X., Zhu Y., Li W., He W., An F., Guo H. Adenine Phosphoribosyl Transferase 1 Is a Key Enzyme Catalyzing Cytokinin Conversion from Nucleobases to Nucleotides in Arabidopsis. Mol. Plant. 2013;6:1661–1672. doi: 10.1093/mp/sst071. PubMed DOI

Kwade Z., Swiatek A., Azmi A., Goossens A., Inzé D., Van Onckelen H., Roef L. Identification of Four Adenosine Kinase Isoforms in Tobacco By-2 Cells and Their Putative Role in the Cell Cycle-Regulated Cytokinin Metabolism. J. Biol. Chem. 2005;280:17512–17519. doi: 10.1074/jbc.M411428200. PubMed DOI

Bromley J.R., Warnes B.J., Newell C.A., Thomson J.C.P., James C.M., Turnbull C.G.N., Hanke D.E. A Purine Nucleoside Phosphorylase in Solanum Tuberosum L. (Potato) with Specificity for Cytokinins Contributes to the Duration of Tuber Endodormancy. Biochem. J. 2014;458:225–237. doi: 10.1042/BJ20130792. PubMed DOI

Chen C., Kristopeit S.M. Metabolism of Cytokinin: Deribosylation of Cytokinin Ribonucleoside by Adenosine Nucleosidase from Wheat Germ Cells. Plant Physiol. 1981;68:1020–1023. doi: 10.1104/pp.68.5.1020. PubMed DOI PMC

Chen C., Kristopeit S.M. Metabolism of Cytokinin: Dephosphorylation of cytokinin ribonucleotide by 5’-nucleotidases from wheat germ cytosol. Plant Physiol. 1981;67:494–498. doi: 10.1104/pp.67.3.494. PubMed DOI PMC

Kakimoto T. Identification of Plant Cytokinin Biosynthetic Enzymes as Dimethylallyl Diphosphate: ATP/ADP Isopentenyltransferases. Plant Cell Physiol. 2001;42:677–685. doi: 10.1093/pcp/pce112. PubMed DOI

Sakano Y., Okada Y., Matsunaga A., Suwama T., Kaneko T., Ito K., Noguchi H., Abe I. Molecular Cloning, Expression, and Characterization of Adenylate Isopentenyltransferase from Hop (Humulus Lupulus L.) Phytochemistry. 2004;65:2439–2446. doi: 10.1016/j.phytochem.2004.08.006. PubMed DOI

Parker C.W., Letham D.S., Gollnow B.I., Summons R.E., Duke C.C., Macleod J.K. Regulators of Cell Division in Plant Tissues: XXV. Metabolism of Zeatin by Lupin Seedlings. Planta. 1978;142:239–251. doi: 10.1007/BF00385073. PubMed DOI

Palni L.M., Palmer M.V., Letham D.S. The Stability and Biological Activity of Cytokinin Metabolites in Soybean Callus Tissue. Planta. 1984;160:242–249. doi: 10.1007/BF00402861. PubMed DOI

Badenoch-Jones J., Rolfe B.G., Letham D.S. Phytohormones, Rhizobium Mutants, and Nodulation in Legumes V. Cytokinin Metabolism in Effective and Ineffective Pea Root Nodules. Plant Physiol. 1984;74:239–246. doi: 10.1104/pp.74.2.239. PubMed DOI PMC

Entsch B., Letham D.S., Parker C.W., Summons R.E., Gollnow B.I. Metabolites of Cytokinins. In: Skoog F., editor. Proceedings of the Plant Growth Substances 1979. Springer; Berlin/Heidelberg, Germany: 1980. pp. 109–118.

Letham D.S., Summons R.E., Parker C.W., MacLeod J.K. Regulators of Cell Division in Plant Tissues: XXVII. Identification of an Amino-Acid Conjugate of 6-Benzylaminopurine Formed in Phaseolus Vulgaris Seedlings. Planta. 1979;146:71–74. doi: 10.1007/BF00381257. PubMed DOI

Elliott D.C., Thompson M.J. The Identity of the Major Metabolite of Benzylaminopurine in Soybean Cultures, and the Inhibition of Its Formation by Aminophylline. Plant Sci. Lett. 1982;28:29–38. doi: 10.1016/S0304-4211(82)80005-9. DOI

Entsch B., Parker C.W., Letham D.S. An Enzyme from Lupin Seeds Forming Alanine Derivatives of Cytokinins. Phytochemistry. 1983;22:375–381. doi: 10.1016/0031-9422(83)83008-8. DOI

Nomura T., Tanaka Y., Abe H., Uchiyama M. Cytokinin Activity of Discadenine: A Spore Germination Inhibitor of Dictyostelium Discoideum. Phytochemistry. 1977;16:1819–1820. doi: 10.1016/0031-9422(71)85097-5. DOI

Mik V., Mičková Z., Doležal K., Frébort I., Pospíšil T. Activity of (+)-Discadenine as a Plant Cytokinin. J. Nat. Prod. 2017 doi: 10.1021/acs.jnatprod.6b01165. PubMed DOI

Aoki M.M., Kisiala A.B., Li S., Stock N.L., Brunetti C.R., Huber R.J., Emery R.J.N. Cytokinin Detection during the Dictyostelium Discoideum Life Cycle: Profiles Are Dynamic and Affect Cell Growth and Spore Germination. Biomolecules. 2019;9:702. doi: 10.3390/biom9110702. PubMed DOI PMC

Adl S.M., Simpson A.G.B., Lane C.E., Lukeš J., Bass D., Bowser S.S., Brown M.W., Burki F., Dunthorn M., Hampl V., et al. The Revised Classification of Eukaryotes. J. Eukaryot. Microbiol. 2012;59:429–514. doi: 10.1111/j.1550-7408.2012.00644.x. PubMed DOI PMC

Turner J.E., Mok D.W.S., Mok M.C., Shaw G. Isolation and Partial Purification of an Enzyme Catalyzing the Formation of O-Xylosylzeatin in Phaseolus Vulgaris Embryos. Proc. Natl. Acad. Sci. USA. 1987;84:3714–3717. doi: 10.1073/pnas.84.11.3714. PubMed DOI PMC

Taylor J.S., Koshioka M., Pharis R.P., Sweet G.B. Changes in Cytokinins and Gibberellin-Like Substances in Pinus Radiata Buds during Lateral Shoot Initiation and the Characterization of Ribosyl Zeatin and a Novel Ribosyl Zeatin Glycoside. Plant Physiol. 1984;74:626–631. doi: 10.1104/pp.74.3.626. PubMed DOI PMC

Zhang H., Horgan K.J., Stewart Reynolds P.H., Norris G.E., Jameson P.E. Novel Cytokinins: The Predominant Forms in Mature Buds of Pinus Radiata. Physiol. Plant. 2001;112:127–134. doi: 10.1034/j.1399-3054.2001.1120117.x. PubMed DOI

Kobayashi H., Morisaki N., Tago Y., Hashimoto Y., Iwasaki S., Kawachi E., Nagata R., Shudo K. Identification of a Major Cytokinin in Coconut Milk. Experientia. 1995;51:1081–1084. doi: 10.1007/BF01946921. PubMed DOI

Letham D.S., Zhang R. Cytokinin Translocation and Metabolism in Lupin Species II. New Nucleotide Metabolites of Cytokinins. Plant Sci. 1989;64:161–165. doi: 10.1016/0168-9452(89)90020-4. DOI

Brzobohatý B., Moore I., Kristoffersen P., Bako L., Campos N., Schell J., Palme K. Release of Active Cytokinin by a β-Glucosidase Localized to the Maize Root Meristem. Science. 1993;262:1051–1054. doi: 10.1126/science.8235622. PubMed DOI

Sakakibara H. Cytokinins: Activity, Biosynthesis, and Translocation. Ann. Rev. Plant. Biol. 2006;57:431–449. doi: 10.1146/annurev.arplant.57.032905.105231. PubMed DOI

Letham D.S., Palni L.M.S. The Biosynthesis and Metabolism of Cytokinins. Ann. Rev. Plant Physiol. 1983;34:163–197. doi: 10.1146/annurev.pp.34.060183.001115. DOI

Letham D.S., Palni L.M.S., Tao G.-Q., Gollnow B.I., Bates C.M. Regulators of Cell Division in Plant Tissues XXIX. The Activities of Cytokinin Glucosides and Alanine Conjugates in Cytokinin Bioassays. J. Plant Growth Regul. 1983;2:103–115. doi: 10.1007/BF02042238. DOI

Fusseder A., Ziegler P. Metabolism and Compartmentation of Dihydrozeatin Exogenously Supplied to Photoautotrophic Suspension Cultures of Chenopodium Rubrum. Planta. 1988;173:104–109. doi: 10.1007/BF00394494. PubMed DOI

Jiskrová E., Novák O., Pospíšilová H., Holubová K., Karády M., Galuszka P., Robert S., Frébort I. Extra- and Intracellular Distribution of Cytokinins in the Leaves of Monocots and Dicots. New Biotechnol. 2016;33:735–742. doi: 10.1016/j.nbt.2015.12.010. PubMed DOI

Benková E., Witters E., Van Dongen W., Kolář J., Motyka V., Brzobohatý B., Van Onckelen H.A., Macháčková I. Cytokinins in Tobacco and Wheat Chloroplasts. Occurrence and Changes Due to Light/Dark Treatment. Plant Physiol. 1999;121:245–252. doi: 10.1104/pp.121.1.245. PubMed DOI PMC

Polanská L., Vičánková A., Nováková M., Malbeck J., Dobrev P.I., Brzobohatý B., Vaňková R., Macháčková I. Altered Cytokinin Metabolism Affects Cytokinin, Auxin, and Abscisic Acid Contents in Leaves and Chloroplasts, and Chloroplast Ultrastructure in Transgenic Tobacco. J. Exp. Bot. 2007;58:637–649. doi: 10.1093/jxb/erl235. PubMed DOI

Kiran N.S., Benková E., Reková A., Dubová J., Malbeck J., Palme K., Brzobohatý B. Retargeting a Maize β-Glucosidase to the Vacuole—Evidence from Intact Plants That Zeatin-O-Glucoside Is Stored in the Vacuole. Phytochemistry. 2012;79:67–77. doi: 10.1016/j.phytochem.2012.03.012. PubMed DOI

Fox J.E., Cornette J., Deleuze G., Dyson W., Giersak C., Niu P., Zapata J., McChesney J. The Formation, Isolation, and Biological Activity of a Cytokinin 7-Glucoside. Plant Physiol. 1973;52:627–632. doi: 10.1104/pp.52.6.627. PubMed DOI PMC

Parker C.W., Letham D.S. Regulators of Cell Division in Plant Tissues. XVI Metabolism of Zeatin by Radish Cotyledons and Hypocotyls. Planta. 1973;114:199–218. doi: 10.1007/BF00389036. PubMed DOI

Hallmark H.T., Černý M., Brzobohatý B., Rashotte A.M. Trans-Zeatin-N-Glucosides Have Biological Activity in Arabidopsis Thaliana. PLoS ONE. 2020;15:e0232762. doi: 10.1371/journal.pone.0232762. PubMed DOI PMC

Werner T., Motyka V., Laucou V., Smets R., Onckelen H.V., Schmülling T. Cytokinin-Deficient Transgenic Arabidopsis Plants Show Multiple Developmental Alterations Indicating Opposite Functions of Cytokinins in the Regulation of Shoot and Root Meristem Activity. Plant Cell. 2003;15:2532–2550. doi: 10.1105/tpc.014928. PubMed DOI PMC

Pospíšilová H., Jiskrová E., Vojta P., Mrízová K., Kokáš F., Čudejková M.M., Bergougnoux V., Plíhal O., Klimešová J., Novák O., et al. Transgenic Barley Overexpressing a Cytokinin Dehydrogenase Gene Shows Greater Tolerance to Drought Stress. New Biotechnol. 2016;33:692–705. doi: 10.1016/j.nbt.2015.12.005. PubMed DOI

Lomin S.N., Myakushina Y.A., Kolachevskaya O.O., Getman I.A., Arkhipov D.V., Savelieva E.M., Osolodkin D.I., Romanov G.A. Cytokinin Perception in Potato: New Features of Canonical Players. J. Exp. Bot. 2018;69:3839–3853. doi: 10.1093/jxb/ery199. PubMed DOI PMC

Simerský R., Chamrád I., Kania J., Strnad M., Šebela M., Lenobel R. Chemical Proteomic Analysis of 6-Benzylaminopurine Molecular Partners in Wheat Grains. Plant Cell Rep. 2017;36:1561–1570. doi: 10.1007/s00299-017-2174-4. PubMed DOI

Bajguz A., Piotrowska A. Conjugates of Auxin and Cytokinin. Phytochemistry. 2009;70:957–969. doi: 10.1016/j.phytochem.2009.05.006. PubMed DOI

Gawer M., Laloue M., Terrine C., Guern J. Metabolism and Biological Significance of Benzyladenine-7-Glucoside. Plant Sci. Lett. 1977;8:267–274. doi: 10.1016/0304-4211(77)90192-4. DOI

Faiss M., Strnad M., Redig P., Doležal K., Hanuš J., Van Onckelen H.A., Schmülling T. Chemically Induced Expression of the RolC-Encoded β-Glucosidase in Transgenic Tobacco Plants and Analysis of Cytokinin Metabolism: RolC Does Not Hydrolyze Endogenous Cytokinin Glucosides in Planta. Plant J. 1996;10:33–46. doi: 10.1046/j.1365-313X.1996.10010033.x. DOI

Zhang R., Letham D.S. Cytokinin Biochemistry in Relation to Leaf Senescence. III. The Senescence-Retarding Activity and Metabolism of 9-Substituted 6-Benzylaminopurines in Soybean Leaves. J. Plant Growth Regul. 1989;8:181–197. doi: 10.1007/BF02308087. DOI

Hošek P., Hoyerová K., Kiran N.S., Dobrev P.I., Zahajská L., Filepová R., Motyka V., Müller K., Kamínek M. Distinct Metabolism of N-Glucosides of Isopentenyladenine and Trans.-Zeatin Determines Cytokinin Metabolic Spectrum in Arabidopsis. New Phytol. 2020;225:2423–2438. doi: 10.1111/nph.16310. PubMed DOI

Entsch B., Parker C.W., Letham D.S., Summons R.E. Preparation and Characterization, Using High-Performance Liquid Chromatography, of an Enzyme Forming Glucosides of Cytokinins. Biochim. Biophys. Acta BBA Enzymol. 1979;570:124–139. doi: 10.1016/0005-2744(79)90207-9. PubMed DOI

Dixon S.C., Martin R.C., Mok M.C., Shaw G., Mok D.W.S. Zeatin Glycosylation Enzymes in Phaseolus Isolation of O-Glucosyltransferase from P. Lunatus and Comparison to O-Xylosyltransferase from P. Vulgaris. Plant Physiol. 1989;90:1316–1321. doi: 10.1104/pp.90.4.1316. PubMed DOI PMC

Martin R.C., Mok M.C., Mok D.W.S. A Gene Encoding the Cytokinin Enzyme Zeatin O-Xylosyltransferase of Phaseolus Vulgaris. Plant Physiol. 1999;120:553–558. doi: 10.1104/pp.120.2.553. PubMed DOI PMC

Martin R.C., Mok M.C., Mok D.W.S. Isolation of a Cytokinin Gene, ZOG1, Encoding Zeatin O-Glucosyltransferase from Phaseolus Lunatus. Proc. Natl. Acad. Sci. USA. 1999;96:284–289. doi: 10.1073/pnas.96.1.284. PubMed DOI PMC

Hou B.-K., Lim E.-K., Higgins G.S., Bowles D.J. N-Glucosylation of Cytokinins by Glycosyltransferases of Arabidopsis Thaliana. J. Biol. Chem. 2004;279:47822–47832. doi: 10.1074/jbc.M409569200. PubMed DOI

Gandia-Herrero F., Lorenz A., Larson T., Graham I.A., Bowles D.J., Rylott E.L., Bruce N.C. Detoxification of the Explosive 2,4,6-Trinitrotoluene in Arabidopsis: Discovery of Bifunctional O- and C-Glucosyltransferases. Plant J. 2008;56:963–974. doi: 10.1111/j.1365-313X.2008.03653.x. PubMed DOI

Poppenberger B., Fujioka S., Soeno K., George G.L., Vaistij F.E., Hiranuma S., Seto H., Takatsuto S., Adam G., Yoshida S., et al. The UGT73C5 of Arabidopsis Thaliana Glucosylates Brassinosteroids. Proc. Natl. Acad. Sci. USA. 2005;102:15253–15258. doi: 10.1073/pnas.0504279102. PubMed DOI PMC

Pineda Rodó A., Brugière N., Vaňková R., Malbeck J., Olson J.M., Haines S.C., Martin R.C., Habben J.E., Mok D.W.S., Mok M.C. Over-Expression of a Zeatin O-Glucosylation Gene in Maize Leads to Growth Retardation and Tasselseed Formation. J. Exp. Bot. 2008;59:2673–2686. doi: 10.1093/jxb/ern137. PubMed DOI PMC

Cucinotta M., Manrique S., Cuesta C., Benková E., Novák O., Colombo L. CUP-SHAPED COTYLEDON1 (CUC1) and CUC2 Regulate Cytokinin Homeostasis to Determine Ovule Number in Arabidopsis. J. Exp. Bot. 2018;69:5169–5176. doi: 10.1093/jxb/ery281. PubMed DOI PMC

Shang X.-L., Xie R.-R., Tian H., Wang Q.-L., Guo F.-Q. Putative Zeatin O-Glucosyltransferase OscZOG1 Regulates Root and Shoot Development and Formation of Agronomic Traits in Rice. J. Integr. Plant Biol. 2016;58:627–641. doi: 10.1111/jipb.12444. PubMed DOI

Gan S., Amasino R.M. Inhibition of Leaf Senescence by Autoregulated Production of Cytokinin. Science. 1995;270:1986–1988. doi: 10.1126/science.270.5244.1986. PubMed DOI

Frébort I., Kowalska M., Hluska T., Frébortová J., Galuszka P. Evolution of Cytokinin Biosynthesis and Degradation. J. Exp. Bot. 2011;62:2431–2452. doi: 10.1093/jxb/err004. PubMed DOI

Schmülling T., Werner T., Riefler M., Krupková E., Manns I.B. y Structure and Function of Cytokinin Oxidase/Dehydrogenase Genes of Maize, Rice, Arabidopsis and Other Species. J. Plant Res. 2003;116:241–252. doi: 10.1007/s10265-003-0096-4. PubMed DOI

Pačes V., Werstiuk E., Hall R.H. Conversion of N6-(Δ2-Isopentenyl)Adenosine to Adenosine by Enzyme Activity in Tobacco Tissue. Plant Physiol. 1971;48:775–778. doi: 10.1104/pp.48.6.775. PubMed DOI PMC

Houba-Hérin N., Pethe C., D’Alayer J., Laloue M. Cytokinin Oxidase from Zea Mays: Purification, CDNA Cloning and Expression in Moss Protoplasts. Plant J. 1999;17:615–626. doi: 10.1046/j.1365-313X.1999.00408.x. PubMed DOI

Morris R.O., Bilyeu K.D., Laskey J.G., Cheikh N.N. Isolation of a Gene Encoding a Glycosylated Cytokinin Oxidase from Maize. Biochem. Biophys. Res. Commun. 1999;255:328–333. doi: 10.1006/bbrc.1999.0199. PubMed DOI

Galuszka P., Frébort I., Šebela M., Sauer P., Jacobsen S., Peč P. Cytokinin Oxidase or Dehydrogenase? Mechanism of Cytokinin Degradation in Cereals. Eur. J. Biochem. 2001;268:450–461. doi: 10.1046/j.1432-1033.2001.01910.x. PubMed DOI

Frébortová J., Novák O., Frébort I., Jorda R. Degradation of Cytokinins by Maize Cytokinin Dehydrogenase Is Mediated by Free Radicals Generated by Enzymatic Oxidation of Natural Benzoxazinones. Plant J. 2010;61:467–481. doi: 10.1111/j.1365-313X.2009.04071.x. PubMed DOI

Niemann M.C.E., Weber H., Hluska T., Leonte G., Anderson S.M., Novák O., Senes A., Werner T. The Cytokinin Oxidase/Dehydrogenase CKX1 Is a Membrane-Bound Protein Requiring Homooligomerization in the Endoplasmic Reticulum for Its Cellular Activity. Plant Physiol. 2018;176:2024–2039. doi: 10.1104/pp.17.00925. PubMed DOI PMC

Frébortová J., Galuszka P., Werner T., Schmülling T., Frébort I. Functional Expression and Purification of Cytokinin Dehydrogenase from Arabidopsis Thaliana (AtCKX2) in Saccharomyces Cerevisiae. Biol. Plant. 2007;51:673–682. doi: 10.1007/s10535-007-0141-6. DOI

Frébortová J., Greplová M., Seidl M.F., Heyl A., Frébort I. Biochemical Characterization of Putative Adenylate Dimethylallyltransferase and Cytokinin Dehydrogenase from Nostoc sp. PCC 7120. PLoS ONE. 2015;10:e0138468. doi: 10.1371/journal.pone.0138468. PubMed DOI PMC

Kowalska M., Galuszka P., Frébortová J., Šebela M., Béres T., Hluska T., Šmehilová M., Bilyeu K.D., Frébort I. Vacuolar and Cytosolic Cytokinin Dehydrogenases of Arabidopsis Thaliana: Heterologous Expression, Purification and Properties. Phytochemistry. 2010;71:1970–1978. doi: 10.1016/j.phytochem.2010.08.013. PubMed DOI

Chatfield J.M., Armstrong D.J. Regulation of Cytokinin Oxidase Activity in Callus Tissues of Phaseolus Vulgaris L. Cv Great Northern. Plant Physiol. 1986;80:493–499. doi: 10.1104/pp.80.2.493. PubMed DOI PMC

Kamínek M., Armstrong D.J. Genotypic Variation in Cytokinin Oxidase from Phaseolus Callus Cultures. Plant Physiol. 1990;93:1530–1538. doi: 10.1104/pp.93.4.1530. PubMed DOI PMC

Brugière N., Jiao S., Hantke S., Zinselmeier C., Roessler J.A., Niu X., Jones R.J., Habben J.E. Cytokinin Oxidase Gene Expression in Maize Is Localized to the Vasculature, and Is Induced by Cytokinins, Abscisic Acid, and Abiotic Stress. Plant Physiol. 2003;132:1228–1240. doi: 10.1104/pp.102.017707. PubMed DOI PMC

Motyka V., Vaňková R., Čapková V., Petrášek J., Kamínek M., Schmülling T. Cytokinin-Induced Upregulation of Cytokinin Oxidase Activity in Tobacco Includes Changes in Enzyme Glycosylation and Secretion. Physiol. Plant. 2003;117:11–21. doi: 10.1034/j.1399-3054.2003.1170102.x. DOI

Tsai Y.-C., Weir N.R., Hill K., Zhang W., Kim H.J., Shiu S.-H., Schaller G.E., Kieber J.J. Characterization of Genes Involved in Cytokinin Signaling and Metabolism from Rice. Plant Physiol. 2012;158:1666–1684. doi: 10.1104/pp.111.192765. PubMed DOI PMC

Panda B.B., Sekhar S., Dash S.K., Behera L., Shaw B.P. Biochemical and Molecular Characterisation of Exogenous Cytokinin Application on Grain Filling in Rice. BMC Plant Biol. 2018;18:89. doi: 10.1186/s12870-018-1279-4. PubMed DOI PMC

Ashikari M., Sakakibara H., Lin S., Yamamoto T., Takashi T., Nishimura A., Angeles E.R., Qian Q., Kitano H., Matsuoka M. Cytokinin Oxidase Regulates Rice Grain Production. Science. 2005;309:741–745. doi: 10.1126/science.1113373. PubMed DOI

Bartrina I., Otto E., Strnad M., Werner T., Schmülling T. Cytokinin Regulates the Activity of Reproductive Meristems, Flower Organ Size, Ovule Formation, and Thus Seed Yield in Arabidopsis Thaliana. Plant Cell. 2011;23:69–80. doi: 10.1105/tpc.110.079079. PubMed DOI PMC

Zhang L., Zhao Y.-L., Gao L.-F., Zhao G.-Y., Zhou R.-H., Zhang B.-S., Jia J.-Z. TaCKX6-D1, the Ortholog of Rice OsCKX2, Is Associated with Grain Weight in Hexaploid Wheat. New Phytol. 2012;195:574–584. doi: 10.1111/j.1469-8137.2012.04194.x. PubMed DOI

Yeh S.-Y., Chen H.-W., Ng C.-Y., Lin C.-Y., Tseng T.-H., Li W.-H., Ku M.S.B. Down-Regulation of Cytokinin Oxidase 2 Expression Increases Tiller Number and Improves Rice Yield. Rice. 2015;8:36. doi: 10.1186/s12284-015-0070-5. PubMed DOI PMC

Li Y., Song G., Gao J., Zhang S., Zhang R., Li W., Chen M., Liu M., Xia X., Risacher T., et al. Enhancement of Grain Number per Spike by RNA Interference of Cytokinin Oxidase 2 Gene in Bread Wheat. Hereditas. 2018;155:33. doi: 10.1186/s41065-018-0071-7. PubMed DOI PMC

Zhang J., Liu W., Yang X., Gao A., Li X., Wu X., Li L. Isolation and Characterization of Two Putative Cytokinin Oxidase Genes Related to Grain Number per Spike Phenotype in Wheat. Mol. Biol. Rep. 2011;38:2337–2347. doi: 10.1007/s11033-010-0367-9. PubMed DOI

Mrízová K., Jiskrová E., Vyroubalová Š., Novák O., Ohnoutková L., Pospíšilová H., Frébort I., Harwood W.A., Galuszka P. Overexpression of Cytokinin Dehydrogenase Genes in Barley (Hordeum Vulgare Cv. Golden Promise) Fundamentally Affects Morphology and Fertility. PLoS ONE. 2013;8:e79029. doi: 10.1371/journal.pone.0079029. PubMed DOI PMC

Werner T., Nehnevajova E., Köllmer I., Novák O., Strnad M., Krämer U., Schmülling T. Root-Specific Reduction of Cytokinin Causes Enhanced Root Growth, Drought Tolerance, and Leaf Mineral Enrichment in Arabidopsis and Tobacco. Plant Cell. 2010;22:3905–3920. doi: 10.1105/tpc.109.072694. PubMed DOI PMC

Ramireddy E., Hosseini S.A., Eggert K., Gillandt S., Gnad H., von Wirén N., Schmülling T. Root Engineering in Barley: Increasing Cytokinin Degradation Produces a Larger Root System, Mineral Enrichment in the Shoot and Improved Drought Tolerance. Plant Physiol. 2018;177:1078–1095. doi: 10.1104/pp.18.00199. PubMed DOI PMC

Gao S., Fang J., Xu F., Wang W., Sun X., Chu J., Cai B., Feng Y., Chu C. CYTOKININ OXIDASE/DEHYDROGENASE4 Integrates Cytokinin and Auxin Signaling to Control Rice Crown Root Formation. Plant Physiol. 2014;165:1035–1046. doi: 10.1104/pp.114.238584. PubMed DOI PMC

Li W., Zhai L., Strauss S.H., Yer H., Merewitz E., Chen J., Wang X., Zhuang W., Fang C., Chen Y., et al. Transgenic Reduction of Cytokinin Levels in Roots Inhibits Root-Sprouting in Populus. Plant Physiol. 2019;180:1788–1792. doi: 10.1104/pp.19.00217. PubMed DOI PMC

Gao S., Xiao Y., Xu F., Gao X., Cao S., Zhang F., Wang G., Sanders D., Chu C. Cytokinin-Dependent Regulatory Module Underlies the Maintenance of Zinc Nutrition in Rice. New Phytol. 2019;224:202–215. doi: 10.1111/nph.15962. PubMed DOI

Vercruyssen L., Gonzalez N., Werner T., Schmülling T., Inzé D. Combining Enhanced Root and Shoot Growth Reveals Cross Talk between Pathways That Control Plant Organ Size in Arabidopsis. Plant Physiol. 2011;155:1339–1352. doi: 10.1104/pp.110.167049. PubMed DOI PMC

Chen L., Zhao J., Song J., Jameson P.E. Cytokinin Dehydrogenase: A Genetic Target for Yield Improvement in Wheat. Plant Biotechnol. J. 2020;18:614–630. doi: 10.1111/pbi.13305. PubMed DOI PMC

Heyl A., Brault M., Frugier F., Kuderová A., Lindner A.-C., Motyka V., Rashotte A.M., von Schwartzenberg K., Vaňková R., Schaller G.E. Nomenclature for Members of the Two-Component Signaling Pathway of Plants. Plant Physiol. 2013;161:1063–1065. doi: 10.1104/pp.112.213207. PubMed DOI PMC

Keshishian E.A., Rashotte A.M. Plant Cytokinin Signalling. Essays Biochem. 2015;58:13–27. doi: 10.1042/bse0580013. PubMed DOI

Hothorn M., Dabi T., Chory J. Structural Basis for Cytokinin Recognition by Arabidopsis Thaliana Histidine Kinase 4. Nat. Chem. Biol. 2011;7:766–768. doi: 10.1038/nchembio.667. PubMed DOI PMC

Steklov M.Y., Lomin S.N., Osolodkin D.I., Romanov G.A. Structural Basis for Cytokinin Receptor Signaling: An Evolutionary Approach. Plant Cell Rep. 2013;32:781–793. doi: 10.1007/s00299-013-1408-3. PubMed DOI

Upadhyay A.A., Fleetwood A.D., Adebali O., Finn R.D., Zhulin I.B. Cache Domains That Are Homologous to, but Different from PAS Domains Comprise the Largest Superfamily of Extracellular Sensors in Prokaryotes. PLoS Comput. Biol. 2016;12 doi: 10.1371/journal.pcbi.1004862. PubMed DOI PMC

Wang F.-F., Cheng S.-T., Wu Y., Ren B.-Z., Qian W. A Bacterial Receptor PcrK Senses the Plant Hormone Cytokinin to Promote Adaptation to Oxidative Stress. Cell Rep. 2017;21:2940–2951. doi: 10.1016/j.celrep.2017.11.017. PubMed DOI

Mähönen A.P., Higuchi M., Törmäkangas K., Miyawaki K., Pischke M.S., Sussman M.R., Helariutta Y., Kakimoto T. Cytokinins Regulate a Bidirectional Phosphorelay Network in Arabidopsis. Curr. Biol. CB. 2006;16:1116–1122. doi: 10.1016/j.cub.2006.04.030. PubMed DOI

Caesar K., Thamm A.M.K., Witthöft J., Elgass K., Huppenberger P., Grefen C., Horak J., Harter K. Evidence for the Localization of the Arabidopsis Cytokinin Receptors AHK3 and AHK4 in the Endoplasmic Reticulum. J. Exp. Bot. 2011;62:5571–5580. doi: 10.1093/jxb/err238. PubMed DOI PMC

Wulfetange K., Lomin S.N., Romanov G.A., Stolz A., Heyl A., Schmülling T. The Cytokinin Receptors of Arabidopsis Are Located Mainly to the Endoplasmic Reticulum. Plant Physiol. 2011;156:1808–1818. doi: 10.1104/pp.111.180539. PubMed DOI PMC

Romanov G.A., Lomin S.N., Schmülling T. Cytokinin Signaling: From the ER or from the PM? That Is the Question! New Phytol. 2018 doi: 10.1111/nph.14991. PubMed DOI

Lomin S.N., Savelieva E.M., Arkhipov D.V., Romanov G.A. Evidences for Preferential Localization of Cytokinin Receptors of Potato in the Endoplasmic Reticulum. Biochem. Mosc. Suppl. Ser. Membr. Cell Biol. 2020;14:146–153. doi: 10.1134/S1990747820010079. DOI

Grignon C., Sentenac H. PH and Ionic Conditions in the Apoplast. Ann. Rev. Plant Physiol. Plant. Mol. Biol. 1991;42:103–128. doi: 10.1146/annurev.pp.42.060191.000535. DOI

Geilfus C.-M. The PH of the Apoplast: Dynamic Factor with Functional Impact under Stress. Mol. Plant. 2017;10:1371–1386. doi: 10.1016/j.molp.2017.09.018. PubMed DOI

Jia W., Davies W.J. Modification of Leaf Apoplastic PH in Relation to Stomatal Sensitivity to Root-Sourced Abscisic Acid Signals. Plant Physiol. 2007;143:68–77. doi: 10.1104/pp.106.089110. PubMed DOI PMC

Antoniadi I., Novák O., Gelová Z., Johnson A., Plíhal O., Simerský R., Mik V., Vain T., Mateo-Bonmatí E., Karady M., et al. Cell-Surface Receptors Enable Perception of Extracellular Cytokinins. Nat. Commun. 2020;11:4284. doi: 10.1038/s41467-020-17700-9. PubMed DOI PMC

Jaworek P., Tarkowski P., Hluska T., Kouřil Š., Vrobel O., Nisler J., Kopečný D. Characterization of Five CHASE-Containing Histidine Kinase Receptors from Populus × Canadensis Cv. Robusta Sensing Isoprenoid and Aromatic Cytokinins. Planta. 2019;251:1. doi: 10.1007/s00425-019-03297-x. PubMed DOI

Zürcher E., Liu J., di Donato M., Geisler M., Müller B. Plant Development Regulated by Cytokinin Sinks. Science. 2016;353:1027–1030. doi: 10.1126/science.aaf7254. PubMed DOI

Zalabák D., Johnová P., Plíhal O., Šenková K., Šamajová O., Jiskrová E., Novák O., Jackson D., Mohanty A., Galuszka P. Maize Cytokinin Dehydrogenase Isozymes Are Localized Predominantly to the Vacuoles. Plant Physiol. Biochem. 2016;104:114–124. doi: 10.1016/j.plaphy.2016.03.013. PubMed DOI

Gelová Z., Ten Hoopen P., Novák O., Motyka V., Pernisová M., Dabravolski S., Didi V., Tillack I., Oklešťková J., Strnad M., et al. Antibody-Mediated Modulation of Cytokinins in Tobacco: Organ-Specific Changes in Cytokinin Homeostasis. J. Exp. Bot. 2018;69:441–454. doi: 10.1093/jxb/erx426. PubMed DOI

Kubiasová K., Montesinos J.C., Šamajová O., Nisler J., Mik V., Semerádová H., Plíhalová L., Novák O., Marhavý P., Cavallari N., et al. Cytokinin Fluoroprobe Reveals Multiple Sites of Cytokinin Perception at Plasma Membrane and Endoplasmic Reticulum. Nat. Commun. 2020;11:4285. doi: 10.1038/s41467-020-17949-0. PubMed DOI PMC

Marhavý P., Bielach A., Abas L., Abuzeineh A., Duclercq J., Tanaka H., Pařezová M., Petrášek J., Friml J., Kleine-Vehn J., et al. Cytokinin Modulates Endocytic Trafficking of PIN1 Auxin Efflux Carrier to Control Plant Organogenesis. Dev. Cell. 2011;21:796–804. doi: 10.1016/j.devcel.2011.08.014. PubMed DOI

Gupta R., Pizarro L., Leibman-Markus M., Marash I., Bar M. Cytokinin Response Induces Immunity and Fungal Pathogen Resistance, and Modulates Trafficking of the PRR LeEIX2 in Tomato. Mol. Plant Pathol. 2020 doi: 10.1111/mpp.12978. PubMed DOI PMC

Dortay H., Mehnert N., Bürkle L., Schmülling T., Heyl A. Analysis of Protein Interactions within the Cytokinin-Signaling Pathway of Arabidopsis Thaliana. FEBS J. 2006;273:4631–4644. doi: 10.1111/j.1742-4658.2006.05467.x. PubMed DOI

Lomin S.N., Myakushina Y.A., Arkhipov D.V., Leonova O.G., Popenko V.I., Schmülling T., Romanov G.A. Studies of Cytokinin Receptor-Phosphotransmitter Interaction Provide Evidences for the Initiation of Cytokinin Signalling in the Endoplasmic Reticulum. Funct. Plant. Biol. FPB. 2018;45:192–202. doi: 10.1071/FP16292. PubMed DOI

Kudla J., Bock R. Lighting the Way to Protein-Protein Interactions: Recommendations on Best Practices for Bimolecular Fluorescence Complementation Analyses. Plant Cell. 2016;28:1002–1008. doi: 10.1105/tpc.16.00043. PubMed DOI PMC

Capra E.J., Laub M.T. Evolution of Two-Component Signal Transduction Systems. Ann. Rev. Microbiol. 2012;66:325–347. doi: 10.1146/annurev-micro-092611-150039. PubMed DOI PMC

Samanovic M.I., Hsu H.-C., Jones M.B., Jones V., McNeil M.R., Becker S.H., Jordan A.T., Strnad M., Xu C., Jackson M., et al. Cytokinin Signaling in Mycobacterium Tuberculosis. mBio. 2018;9 doi: 10.1128/mBio.00989-18. PubMed DOI PMC

Hutchison C.E., Li J., Argueso C., Gonzalez M., Lee E., Lewis M.W., Maxwell B.B., Perdue T.D., Schaller G.E., Alonso J.M., et al. The Arabidopsis Histidine Phosphotransfer Proteins Are Redundant Positive Regulators of Cytokinin Signaling. Plant Cell. 2006;18:3073–3087. doi: 10.1105/tpc.106.045674. PubMed DOI PMC

Punwani J.A., Kieber J.J. Localization of the Arabidopsis Histidine Phosphotransfer Proteins Is Independent of Cytokinin. Plant Signal. Behav. 2010;5:896–898. doi: 10.4161/psb.5.7.12094. PubMed DOI PMC

Mähönen A.P., Bishopp A., Higuchi M., Nieminen K.M., Kinoshita K., Törmäkangas K., Ikeda Y., Oka A., Kakimoto T., Helariutta Y. Cytokinin Signaling and Its Inhibitor AHP6 Regulate Cell Fate during Vascular Development. Science. 2006;311:94–98. doi: 10.1126/science.1118875. PubMed DOI

Müller B. Generic Signal-Specific Responses: Cytokinin and Context-Dependent Cellular Responses. J. Exp. Bot. 2011;62:3273–3288. doi: 10.1093/jxb/erq420. PubMed DOI

Argyros R.D., Mathews D.E., Chiang Y.-H., Palmer C.M., Thibault D.M., Etheridge N., Argyros D.A., Mason M.G., Kieber J.J., Schaller G.E. Type B Response Regulators of Arabidopsis Play Key Roles in Cytokinin Signaling and Plant Development. Plant Cell. 2008;20:2102–2116. doi: 10.1105/tpc.108.059584. PubMed DOI PMC

Rashotte A.M., Carson S.D.B., To J.P.C., Kieber J.J. Expression Profiling of Cytokinin Action in Arabidopsis. Plant Physiol. 2003;132:1998–2011. doi: 10.1104/pp.103.021436. PubMed DOI PMC

Kiba T., Aoki K., Sakakibara H., Mizuno T. Arabidopsis Response Regulator, ARR22, Ectopic Expression of Which Results in Phenotypes Similar to the Wol Cytokinin-Receptor Mutant. Plant Cell Physiol. 2004;45:1063–1077. doi: 10.1093/pcp/pch128. PubMed DOI

Gattolin S., Alandete-Saez M., Elliott K., Gonzalez-Carranza Z., Naomab E., Powell C., Roberts J.A. Spatial and Temporal Expression of the Response Regulators ARR22 and ARR24 in Arabidopsis Thaliana. J. Exp. Bot. 2006;57:4225–4233. doi: 10.1093/jxb/erl205. PubMed DOI

Rashotte A.M., Mason M.G., Hutchison C.E., Ferreira F.J., Schaller G.E., Kieber J.J. A Subset of Arabidopsis AP2 Transcription Factors Mediates Cytokinin Responses in Concert with a Two-Component Pathway. Proc. Natl. Acad. Sci. USA. 2006;103:11081–11085. doi: 10.1073/pnas.0602038103. PubMed DOI PMC

Rashotte A.M., Goertzen L.R. The CRF Domain Defines Cytokinin Response Factor Proteins in Plants. BMC Plant Biol. 2010;10:74. doi: 10.1186/1471-2229-10-74. PubMed DOI PMC

Cutcliffe J.W., Hellmann E., Heyl A., Rashotte A.M. CRFs Form Protein–Protein Interactions with Each Other and with Members of the Cytokinin Signalling Pathway in Arabidopsis via the CRF Domain. J. Exp. Bot. 2011;62:4995–5002. doi: 10.1093/jxb/err199. PubMed DOI PMC

Zwack P.J., Shi X., Robinson B.R., Gupta S., Compton M.A., Gerken D.M., Goertzen L.R., Rashotte A.M. Vascular Expression and C-Terminal Sequence Divergence of Cytokinin Response Factors in Flowering Plants. Plant Cell Physiol. 2012;53:1683–1695. doi: 10.1093/pcp/pcs110. PubMed DOI

Shi X., Gupta S., Rashotte A.M. Solanum Lycopersicum Cytokinin Response Factor (SlCRF) Genes: Characterization of CRF Domain-Containing ERF Genes in Tomato. J. Exp. Bot. 2012;63:973–982. doi: 10.1093/jxb/err325. PubMed DOI PMC

Zwack P.J., Robinson B.R., Risley M.G., Rashotte A.M. Cytokinin Response Factor 6 Negatively Regulates Leaf Senescence and Is Induced in Response to Cytokinin and Numerous Abiotic Stresses. Plant Cell Physiol. 2013;54:971–981. doi: 10.1093/pcp/pct049. PubMed DOI

Zwack P.J., De Clercq I., Howton T.C., Hallmark H.T., Hurny A., Keshishian E.A., Parish A.M., Benkova E., Mukhtar M.S., Van Breusegem F., et al. Cytokinin Response Factor 6 Represses Cytokinin-Associated Genes during Oxidative Stress. Plant Physiol. 2016;172:1249–1258. doi: 10.1104/pp.16.00415. PubMed DOI PMC

Zwack P.J., Compton M.A., Adams C.I., Rashotte A.M. Cytokinin Response Factor 4 (CRF4) Is Induced by Cold and Involved in Freezing Tolerance. Plant Cell Rep. 2016;35:573–584. doi: 10.1007/s00299-015-1904-8. PubMed DOI

Jeon J., Cho C., Lee M.R., Van Binh N., Kim J. CYTOKININ RESPONSE FACTOR2 (CRF2) and CRF3 Regulate Lateral Root Development in Response to Cold Stress in Arabidopsis. Plant Cell. 2016;28:1828–1843. doi: 10.1105/tpc.15.00909. PubMed DOI PMC

Qin L., Wang L., Guo Y., Li Y., Ümüt H., Wang Y. An ERF Transcription Factor from Tamarix Hispida, ThCRF1, Can Adjust Osmotic Potential and Reactive Oxygen Species Scavenging Capability to Improve Salt Tolerance. Plant Sci. Int. J. Exp. Plant. Biol. 2017;265:154–166. doi: 10.1016/j.plantsci.2017.10.006. PubMed DOI

Melton A.E., Zwack P.J., Rashotte A.M., Goertzen L.R. Identification and Functional Characterization of the Marshallia (Asteraceae) Clade III Cytokinin Response Factor (CRF) Plant Signal. Behav. 2019:1–6. doi: 10.1080/15592324.2019.1633886. PubMed DOI PMC

Chevalier F., Perazza D., Laporte F., Le Hénanff G., Hornitschek P., Bonneville J.-M., Herzog M., Vachon G. GeBP and GeBP-like Proteins Are Noncanonical Leucine-Zipper Transcription Factors That Regulate Cytokinin Response in Arabidopsis. Plant Physiol. 2008;146:1142–1154. doi: 10.1104/pp.107.110270. PubMed DOI PMC

Takei K., Sakakibara H., Taniguchi M., Sugiyama T. Nitrogen-Dependent Accumulation of Cytokinins in Root and the Translocation to Leaf: Implication of Cytokinin Species That Induces Gene Expression of Maize Response Regulator. Plant Cell Physiol. 2001;42:85–93. doi: 10.1093/pcp/pce009. PubMed DOI

Weiler E.W., Ziegler H. Determination of Phytohormones in Phloem Exudate from Tree Species by Radioimmunoassay. Planta. 1981;152:168–170. doi: 10.1007/BF00391189. PubMed DOI

Alvarez S., Marsh E.L., Schroeder S.G., Schachtman D.P. Metabolomic and Proteomic Changes in the Xylem Sap of Maize under Drought. Plant Cell Environ. 2008;31:325–340. doi: 10.1111/j.1365-3040.2007.01770.x. PubMed DOI

Field S.K., Smith J.P., Morrison E.N., Emery R.J.N., Holzapfel B.P. Soil Temperature Prior to Veraison Alters Grapevine Carbon Partitioning, Xylem Sap Hormones, and Fruit Set. Am. J. Enol. Vitic. 2019 doi: 10.5344/ajev.2019.19038. DOI

Foo E., Morris S.E., Parmenter K., Young N., Wang H., Jones A., Rameau C., Turnbull C.G.N., Beveridge C.A. Feedback Regulation of Xylem Cytokinin Content Is Conserved in Pea and Arabidopsis. Plant Physiol. 2007;143:1418–1428. doi: 10.1104/pp.106.093708. PubMed DOI PMC

Matsumoto-Kitano M., Kusumoto T., Tarkowski P., Kinoshita-Tsujimura K., Václavíková K., Miyawaki K., Kakimoto T. Cytokinins Are Central Regulators of Cambial Activity. Proc. Natl. Acad. Sci. USA. 2008;105:20027–20031. doi: 10.1073/pnas.0805619105. PubMed DOI PMC

Zhang R., Letham D.S., Willcocks D.A. Movement to Bark and Metabolism of Xylem Cytokinins in Stems of Lupinus Angustifolius. Phytochemistry. 2002;60:483–488. doi: 10.1016/S0031-9422(02)00085-7. PubMed DOI

Gillissen B., Bürkle L., André B., Kühn C., Rentsch D., Brandl B., Frommer W.B. A New Family of High-Affinity Transporters for Adenine, Cytosine, and Purine Derivatives in Arabidopsis. Plant Cell. 2000;12:291–300. doi: 10.1105/tpc.12.2.291. PubMed DOI PMC

Bürkle L., Cedzich A., Döpke C., Stransky H., Okumoto S., Gillissen B., Kühn C., Frommer W.B. Transport of Cytokinins Mediated by Purine Transporters of the PUP Family Expressed in Phloem, Hydathodes, and Pollen of Arabidopsis. Plant J. Cell Mol. Biol. 2003;34:13–26. doi: 10.1046/j.1365-313X.2003.01700.x. PubMed DOI

Xiao Y., Liu D., Zhang G., Gao S., Liu L., Xu F., Che R., Wang Y., Tong H., Chu C. Big Grain3, Encoding a Purine Permease, Regulates Grain Size via Modulating Cytokinin Transport in Rice. J. Integr. Plant Biol. 2019;61:581–597. doi: 10.1111/jipb.12727. PubMed DOI

Pastor-Anglada M., Pérez-Torras S. Who Is Who in Adenosine Transport. Front. Pharmacol. 2018;9:627. doi: 10.3389/fphar.2018.00627. PubMed DOI PMC

Hirose N., Makita N., Yamaya T., Sakakibara H. Functional Characterization and Expression Analysis of a Gene, OsENT2, Encoding an Equilibrative Nucleoside Transporter in Rice Suggest a Function in Cytokinin Transport. Plant Physiol. 2005;138:196–206. doi: 10.1104/pp.105.060137. PubMed DOI PMC

Sun J., Hirose N., Wang X., Wen P., Xue L., Sakakibara H., Zuo J. Arabidopsis SOI33/AtENT8 Gene Encodes a Putative Equilibrative Nucleoside Transporter That Is Involved in Cytokinin Transport In Planta. J. Integr. Plant Biol. 2005;47:588–603. doi: 10.1111/j.1744-7909.2005.00104.x. DOI

Wormit A., Traub M., Flörchinger M., Neuhaus H.E., Möhlmann T. Characterization of Three Novel Members of the Arabidopsis Thaliana Equilibrative Nucleoside Transporter (ENT) Family. Biochem. J. 2004;383:19–26. doi: 10.1042/BJ20040389. PubMed DOI PMC

Kudo T., Kiba T., Sakakibara H. Metabolism and Long-Distance Translocation of Cytokinins. J. Integr. Plant Biol. 2010;52:53–60. doi: 10.1111/j.1744-7909.2010.00898.x. PubMed DOI

Zhang K., Novák O., Wei Z., Gou M., Zhang X., Yu Y., Yang H., Cai Y., Strnad M., Liu C.-J. Arabidopsis ABCG14 Protein Controls the Acropetal Translocation of Root-Synthesized Cytokinins. Nat. Commun. 2014;5:3274. doi: 10.1038/ncomms4274. PubMed DOI

Ko D., Kang J., Kiba T., Park J., Kojima M., Do J., Kim K.Y., Kwon M., Endler A., Song W.-Y., et al. Arabidopsis ABCG14 Is Essential for the Root-to-Shoot Translocation of Cytokinin. Proc. Natl. Acad. Sci. USA. 2014;111:7150–7155. doi: 10.1073/pnas.1321519111. PubMed DOI PMC

Zhao J., Yu N., Ju M., Fan B., Zhang Y., Zhu E., Zhang M., Zhang K. ABC Transporter OsABCG18 Controls the Shootward Transport of Cytokinins and Grain Yield in Rice. J. Exp. Bot. 2019;70:6277–6291. doi: 10.1093/jxb/erz382. PubMed DOI PMC

Feng Y., Sun Q., Zhang G., Wu T., Zhang X., Xu X., Han Z., Wang Y. Genome-Wide Identification and Characterization of ABC Transporters in Nine Rosaceae Species Identifying MdABCG28 as a Possible Cytokinin Transporter Linked to Dwarfing. Int. J. Mol. Sci. 2019;20:5783. doi: 10.3390/ijms20225783. PubMed DOI PMC

Poitout A., Crabos A., Petřík I., Novák O., Krouk G., Lacombe B., Ruffel S. Responses to Systemic Nitrogen Signaling in Arabidopsis Roots Involve Trans-Zeatin in Shoots. Plant Cell. 2018;30:1243–1257. doi: 10.1105/tpc.18.00011. PubMed DOI PMC

Kim A., Chen J., Khare D., Jin J.-Y., Yamaoka Y., Maeshima M., Zhao Y., Martinoia E., Hwang J.-U., Lee Y. Non-Intrinsic ATP-Binding Cassette Proteins ABCI19, ABCI20 and ABCI21 Modulate Cytokinin Response at the Endoplasmic Reticulum in Arabidopsis Thaliana. Plant Cell Rep. 2020 doi: 10.1007/s00299-019-02503-0. PubMed DOI PMC

Laplaze L., Benková E., Casimiro I., Maes L., Vanneste S., Swarup R., Weijers D., Calvo V., Parizot B., Herrera-Rodriguez M.B., et al. Cytokinins Act Directly on Lateral Root Founder Cells to Inhibit Root Initiation. Plant Cell. 2007;19:3889–3900. doi: 10.1105/tpc.107.055863. PubMed DOI PMC

Tessi T.M., Brumm S., Winklbauer E., Schumacher B., Pettinari G., Lescano I., González C.A., Wanke D., Maurino V.G., Harter K., et al. Arabidopsis AZG2 Transports Cytokinins in Vivo and Regulates Lateral Root Emergence. New Phytol. 2020 doi: 10.1111/nph.16943. PubMed DOI

Tessi T.M., Shahriari M., Maurino V.G., Meissner E., Novák O., Pasternak T., Schumacher B.S., Flubacher N.S., Nautscher M., Williams A., et al. The Auxin Transporter PIN1 and the Cytokinin Transporter AZG1 Interact to Regulate the Root Stress Response. bioRxiv. 2020 doi: 10.1101/2020.10.22.350363. DOI

Mansfield T.A., Schultes N.P., Mourad G.S. AtAzg1 and AtAzg2 Comprise a Novel Family of Purine Transporters in Arabidopsis. FEBS Lett. 2009;583:481–486. doi: 10.1016/j.febslet.2008.12.048. PubMed DOI

Dynamic changes of endogenous phytohormones and carbohydrates during spontaneous morphogenesis of Centaurium erythraea Rafn

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