Stress-induced senescence is a global agro-economic problem. Cytokinins are considered to be key plant anti-senescence hormones, but despite this practical function their use in agriculture is limited because cytokinins also inhibit root growth and development. We explored new cytokinin analogs by synthesizing a series of 1,2,3-thiadiazol-5-yl urea derivatives. The most potent compound, 1-(2-methoxy-ethyl)-3-1,2,3-thiadiazol-5-yl urea (ASES - Anti-Senescence Substance), strongly inhibited dark-induced senescence in leaves of wheat (Triticum aestivum L.) and Arabidopsis thaliana. The inhibitory effect of ASES on wheat leaf senescence was, to the best of our knowledge, the strongest of any known natural or synthetic compound. In vivo, ASES also improved the salt tolerance of young wheat plants. Interestingly, ASES did not affect root development of wheat and Arabidopsis, and molecular and classical cytokinin bioassays demonstrated that ASES exhibits very low cytokinin activity. A proteomic analysis of the ASES-treated leaves further revealed that the senescence-induced degradation of photosystem II had been very effectively blocked. Taken together, our results including data from cytokinin content analysis demonstrate that ASES delays leaf senescence by mechanism(s) different from those of cytokinins and, more effectively. No such substance has yet been described in the literature, which makes ASES an interesting tool for research of photosynthesis regulation. Its simple synthesis and high efficiency predetermine ASES to become also a potent plant stress protectant in biotechnology and agricultural industries.

Department of Chemical Biology and Genetics Centre of the Region Haná for Biotechnological and Agricultural Research Palacký University Olomouc Czechia

Faculty of Science University of South Bohemia České Budějovice Czechia

Laboratory of Growth Regulators Centre of the Region Haná for Biotechnological and Agricultural Research Institute of Experimental Botany AS CR and Palacký University Olomouc Czechia

Laboratory of Photosynthesis Centre Algatech Institute of Microbiology Třeboň Czechia

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Abeles F. B., Dunn L. J., Morgens P., Callahan A., Dinterman R. E., Schmidt J. (1988). Induction of 33-kD and 60-kD peroxidases during ethylene-induced senescence of cucumber cotyledons. Plant Physiol. 87, 609–615. 10.1104/pp.87.3.609 PubMed DOI PMC

Allu A. D., Soja A. M., Wu A., Szymanski J., Balazadeh S. (2014). Salt stress and senescence: identification of cross-talk regulatory components. J. Exp. Bot. 65, 3993–4008. 10.1093/jxb/eru173 PubMed DOI PMC

Apel K., Hirt H. (2004). Reactive oxygen species: metabolism, oxidative stress, and signal transduction. Annu. Rev. Plant Biol. 55, 373–399. 10.1146/annurev.arplant.55.031903.141701 PubMed DOI

Balibrea Lara M. E., Gonzalez Garcia M. C., Fatima T., Ehness R., Lee T. K., Proels R., et al. . (2004). Extracellular invertase is an essential component of cytokinin-mediated delay of senescence. Plant Cell 16, 1276–1287. 10.1105/tpc.018929 PubMed DOI PMC

Bamberger E., Mayer A. (1960). Effect of kinetin on formation of red pigment in seedlings of Amaranthus retroflexus. Science 131, 1094–1095. 10.1126/science.131.3407.1094 PubMed DOI

Becker W., Apel K. (1993). Differences in gene expression between natural and artificially induced leaf senescence. Plant 189, 74–79. 10.1007/BF00201346 PubMed DOI

Bharti N., Pandey S. S., Barnawal D., Patel V. K., Kalra A. (2016). Plant growth promoting rhizobacteria Dietzia natronolimnaea modulates the expression of stress responsive genes providing protection of wheat from salinity stress. Sci. Rep. 6:34768. 10.1038/srep34768 PubMed DOI PMC

Buchanan-Wollaston V., Page T., Harrison E., Breeze E., Lim P. O., Nam H. G., et al. . (2005). Comparative transcriptome analysis reveals significant differences in gene expression and signaling pathways between developmental and dark/starvation-induced senescence in Arabidopsis. Plant J. 42, 567–585. 10.1111/j.1365-313X.2005.02399.x PubMed DOI

Cheng D., Wu G., Zheng Y. (2015). Positive correlation between potassium uptake and salt tolerance in wheat. Photosynthetica 53, 447–454. 10.1007/s11099-015-0124-3 DOI

Colebrook E. H., Thomas S. G., Phillips A. L., Hedden P. (2014). The role of gibberellin signalling in plant responses to abiotic stress. J. Exp. Bot. 217, 67–75. 10.1242/jeb.089938 PubMed DOI

Cortleven A., Nitschke S., Klaumünzer M., AbdElgawad H., Asard H., Grimm B., et al. . (2014). A novel protective function for cytokinin in the light stress response is mediated by the ARABIDOPSIS HISTIDINE KINASE 2 and ARABIDOPSIS HISTIDINE KINASE 3 receptors. Plant Physiol. 164, 1470–1483. 10.1104/pp.113.224667 PubMed DOI PMC

D'Agostino I. B., Deruère J., Kieber J. J. (2000). Characterization of the response of the Arabidopsis response regulator gene family to cytokinin. Plant Physiol. 124, 1706–1717. 10.1104/pp.124.4.1706 PubMed DOI PMC

Dobáková M., Sobotka R., Tichý M., Komenda J. (2009). Psb28 protein is involved in the biogenesis of the photosystem II inner antenna CP47 (PsbB) in the cyanobacterium Synechocystis sp. PCC 6803. Plant Physiol. 149, 1076–1086. 10.1104/pp.108.130039 PubMed DOI PMC

Dobrev P. I., Kamínek M. (2002). Fast and efficient separation of cytokinins from auxin and abscisic acid and their purification using mixed-mode solid-phase extraction. J. Chromatogr. A 950, 21–29. 10.1016/S0021-9673(02)00024-9 PubMed DOI

Dolezal K., Popa I., Kryštof V., Spíchal L., Fojtíková M., Holub J., et al. . (2006). Preparation and biological activity of 6-benzylaminopurine derivatives in plants and human cancer cells. Bioorg. Med. Chem. 14, 875–884. 10.1016/j.bmc.2005.09.004 PubMed DOI

Ferrante A., Hunter D. A., Hackett P. W., Reid M. S. (2002). Thidiazuron - a potent inhibitor of leaf senescence in Alstroemeria. Postharvest Biol. Technol. 25, 333–338. 10.1016/S0925-5214(01)00195-8 DOI

Ferrante A., Tognoni F., Mensuali-Sodi A., Serra G. (2003). Treatment with Thidiazuron for preventing leaf yellowing in cut tulips and chrysanthemum. Acta Hortic. 624, 357–363. 10.17660/ActaHortic.2003.624.49 DOI

Fišerová H., Kula E., Klemš M., Reinöhl V. (2001). Phytohormones as indicators of the degree of damage in birch (Betula pendula). Biológia 56, 405–409.

Fletcher R. A., Arnold V. (1986). Stimulation of cytokinins and chlorophyll synthesis in cucumber cotyledons by triadimefon. Physiol. Plant 66, 197–201. 10.1111/j.1399-3054.1986.tb02408.x DOI

Fletcher R. A., Hofsta G. (1985). Triadimefon: a plant multi-protectant. Plant Cell Physiol. 26, 775–778. 10.1093/oxfordjournals.pcp.a076970 DOI

Fletcher R. A., Nath V. (1984). Triadimefon reduces transpiration and increases yield in water stressed plants. Physiol. Plant. 62, 422–426. 10.1111/j.1399-3054.1984.tb04596.x DOI

Fletcher R. A., Osborne D. J. (1965). Regulation of protein and nucleic acid synthesis by gibberellin during leaf senescence. Nature 207, 1176–1177. 10.1038/2071176a0 DOI

Frébort I., Šebela M., Galuszka P., Werner T., Schmülling T., Peč P. (2002). Cytokinin oxidase/cytokinin dehydrogenase assay: optimized procedures and applications. Anal. Biochem. 306, 1–7. 10.1006/abio.2002.5670 PubMed DOI

Frébortová J., Galuszka P., Werner T., Schmülling T., Frébort I. (2007). Functional expression and purification of cytokinin dehydrogenase from Arabidopsis thaliana (AtCKX2) in Saccharomyces cerevisiae. Biol. Plant. 51, 673–682. 10.1007/s10535-007-0141-6 DOI

Gajdošová S., Spíchal L., Kamínek M., Hoyerová K., Novák O., Dobrev P. I., et al. . (2011). Distribution, biological activities, metabolism, and the conceivable function of cis-zeatin-type cytokinins in plants. J. Exp. Bot. 62, 2827–2840. 10.1093/jxb/erq457 PubMed DOI

Galuszka P., Popelková H., Werner T., Frébortová J., Pospíšilová H., Mik V., et al. (2007). Biochemical characterization and histochemical localization of cytokinin oxidases/dehydrogenases from Arabidopsis thaliana expressed in Nicotiana tabaccum L. J. Plant Growth Regul. 26, 255–267. 10.1007/s00344-007-9008-5 DOI

Gan S. (2003). Mitotic and postmitotic senescence in plants. Sci. Aging Knowl. Environ. 2003:RE7. 10.1126/sageke.2003.38.re7 PubMed DOI

Gan S., Amasino R. M. (1995). Inhibition of leaf senescence by autoregulated production of cytokinin. Science 270, 1986–1988. 10.1126/science.270.5244.1986 PubMed DOI

Gan S., Amasino R. M. (1997). Making sense of senescence: molecular genetic regulation of leaf senescence. Plant Physiol. 113, 313–319. 10.1104/pp.113.2.313 PubMed DOI PMC

Gepstein S., Glick B. R. (2013). Strategies to ameliorate abiotic stress-induced plant senescence. Plant Mol. Biol. 82, 623–633. 10.1007/s11103-013-0038-z PubMed DOI

Ghorbani-Javid M., Sorooshzadeh A., Morad F., Modarres-Sanavy S. A. M., Allahdadi I. (2011). The role of phytohormones in alleviating salt stress in crop plants. Aust. J. Crop Sci. 5, 726–734.

Goldschmidt H., Bardach B. (1892). Zur kenntniss der diazoamidokörper. Chem. Ber. 25, 1347–1378. 10.1002/cber.189202501204 DOI

Greene T. W., Wuts P. G. M. (1991). Protective Groups in Organic Synthesis, 2nd Edn. New York, NY: John Wiley and Sons.

Grossmann K., Retzlaff G. (1997). Bioregulatory effects of the fungicidal strobilurin kresoxim-methyl in wheat (Triticum aestivum). Pestic. Sci. 50, 11–20. 10.1002/(SICI)1096-9063(199705)50:1<11::AID-PS556>3.0.CO;2-8 DOI

Guo Y., Gan S. S. (2012). Convergence and divergence in gene expression profiles induced by leaf senescence and 27 senescence-promoting hormonal, pathological and environmental stress treatments. Plant Cell Environ. 35, 644–655. 10.1111/j.1365-3040.2011.02442.x PubMed DOI

Hasanuzzaman M., Hossain M. A., Fujita M. (2011). Nitric oxide modulates antioxidant defense and the methylglyoxal detoxification system and reduces salinity-induced damage of wheat seedlings. Plant Biotechnol. Rep. 5, 353–365. 10.1007/s11816-011-0189-9 PubMed DOI

He Y., Tang W., Swain J. D., Green A. L., Jack T. P., Gan S. (2001). Networking senescence-regulating pathways by using Arabidopsis enhancer trap lines. Plant Physiol. 126, 707–716. 10.1104/pp.126.2.707 PubMed DOI PMC

Hensel L. L., Grbić V., Baumgarten D. A., Bleecker A. B. (1993). Developmental and age-related processes that influence the longevity and senescence of photosynthetic tissues in Arabidopsis. Plant Cell 5, 553–564. 10.1105/tpc.5.5.553 PubMed DOI PMC

Holub J., Hanuš J., Hanke D. E., Strnad M. (1998). Biological activity of cytokinins derived from Ortho- and Meta-Hydroxybenzyladenine. Plant Growth Regul. 26, 109–115. 10.1023/A:1006192619432 DOI

Huang W., Chen Q., Zhu Y., Hu F., Zhang L., Ma Z., et al. . (2013). Arabidopsis thylakoid formation 1 is a critical regulator for dynamics of PSII–LHCII complexes in leaf senescence and excess light. Mol. Plant 6, 1673–1691. 10.1093/mp/sst069 PubMed DOI

Hukmani P., Tripathy B. C. (1994). Chlorophyll biosynthetic reactions during senescence of excised barley (Hordeum vulgare L. cv IB 65) leaves. Plant Physiol. 105, 1295–1300. 10.1104/pp.105.4.1295 PubMed DOI PMC

Ihara M., Taya Y., Nishimura S., Tanaka Y. (1984). Purification and some properties of delta 2-isopentenylpyrophosphate: 5'AMP delta 2-isopentenyltransferase from the cellular slime mold Dictyostelium discoideum. Arch. Biochem. Biophys. 230, 652–660. 10.1016/0003-9861(84)90446-6 PubMed DOI

Inada N., Sakai A., Kuroiwa H., Kuroiwa T. (1998). Three-dimensional analysis of the senescence program in rice (Oryza sativa L.) coleoptiles. Investigations of tissues and cells by fluorescence microscopy. Planta 205, 153–164. 10.1007/s004250050307 PubMed DOI

Jaleel C. A., Gopi R., Alagulakshmanan G. M., Panneerselvam R. (2006). Triadimefon induced changes in the antioxidant metabolism and ajmalicine production in Catharanthus roseus (L.). G. Plant Sci. 171, 271–276. 10.1016/j.plantsci.2006.03.018 DOI

Jan A. U., Hadi F., Midrarullah N. M. A., Rahman K. (2017). Potassium and zinc increase tolerance to salt stress in wheat (Triticum aestivum L.). Plant Physiol. Biochem. 116, 139–149. 10.1016/j.plaphy.2017.05.008 PubMed DOI

Jeon J., Kim N. Y., Kim S., Kang N. Y., Novák O., Ku S. J., et al. . (2010). A subset of cytokinin two-component signaling system plays a role in cold temperature stress response in Arabidopsis. J. Biol. Chem. 285, 23371–23386. 10.1074/jbc.M109.096644 PubMed DOI PMC

Jing H. C., Schippers J. H., Hille J., Dijkwel P. P. (2005). Ethylene-induced leaf senescence depends on age-related changes and OLD genes in Arabidopsis. J. Exp. Bot. 56, 2915–2923. 10.1093/jxb/eri287 PubMed DOI

Jing H. C., Sturre M. J., Hille J., Dijkwel P. P. (2002). Arabidopsis onset of leaf death mutants identify a regulatory pathway controlling leaf senescence. Plant J. 32, 51–63. 10.1046/j.1365-313X.2002.01400.x PubMed DOI

Jordi W., Schapendonk A., Davelaar E., Stoopen G. M., Pot C. S., De V., et al. (2000). Increased cytokinin levels in transgenic PSAG12-IPT tobacco plants have large direct and indirect effects on leaf senescence, photosynthesis and N partitioning. Plant Cell Environ. 23, 279–289. 10.1046/j.1365-3040.2000.00544.x DOI

Jordi W., Stoopen G. M., Kelepouris K., van der Krieken W. M. (1995). Gibberellin-induced delay of leaf senescence of Alstroemeria cut flowering stems is not caused by an increase in the endogenous cytokinin content. J. Plant Growth Regul. 14, 121–127. 10.1007/BF00210913 DOI

Kim H. J., Ryu H., Hong S. H., Woo H. R., Lim P. O., Lee I. C., et al. . (2006). Cytokinin-mediated control of leaf longevity by AHK3 through phosphorylation of ARR2 in Arabidopsis. Proc. Natl. Acad. Sci. U.S.A. 103, 814–819. 10.1073/pnas.0505150103 PubMed DOI PMC

Kim J., Woo H. R., Nam H. G. (2016). Toward systems understanding of leaf senescence: an integrated multi-omics perspective on leaf senescence research. Mol. Plant 9, 813–825. 10.1016/j.molp.2016.04.017 PubMed DOI

Kopecná J., Sobotka R., Komenda J. (2013). Inhibition of chlorophyll biosynthesis at the protochlorophyllide reduction step results in the parallel depletion of photosystem, I., and photosystem II in the cyanobacterium Synechocystis PCC 6803. Planta 237, 497–508. 10.1007/s00425-012-1761-4 PubMed DOI

Kopecný D., Briozzo P., Popelková H., Sebela M., Končitíková R., Spíchal L., et al. . (2010). Phenyl- and benzylurea cytokinins as competitive inhibitors of cytokinin oxidase/dehydrogenase: a structural study. Biochimie 92, 1052–1062. 10.1016/j.biochi.2010.05.006 PubMed DOI

Kováčik J., Tomko J., Bačkor M., Repčák M. (2006). Matricaria chamomilla is not a hyperaccumulator, but tolerant to cadmium stress. Plant Growth Regul. 50, 239–247. 10.1007/s10725-006-9141-3 DOI

Kumar S., Beena A. S., Awana M., Singh A. (2017). Physiological, biochemical, epigenetic and molecular analyzes of wheat (Triticum aestivum) genotypes with contrasting salt tolerance. Front. Plant Sci. 8:1151. 10.3389/fpls.2017.01151 PubMed DOI PMC

Kusnetsov V. V., Oelmüller R., Sarwat M., Porfirova S. A., Cherepneva G. N., Herrmann R. G., et al. (1994). Cytokinins, abscisic acid and light affect accumulation of chloroplast proteins in Lupinus luteus cotyledons, without notable effect on steady-state mRNA levels. Planta 194, 318–327. 10.1007/BF00197531 DOI

Lerbs S., Lerbs W., Klyachko N. L., Romanko E. G., Kulaeva O. N., Wollgiehn R., et al. . (1984). Gene expression in cytokinin- and light-mediated plastogenesis of Cucurbita cotyledons: ribulose-1,5-bisphosphate carboxylase/oxygenase. Planta 162, 289–298. 10.1007/BF00396739 PubMed DOI

Liebsch D., Keech O. (2016). Dark-induced leaf senescence: new insights into a complex light-dependent regulatory pathway. New Phytol. 212, 563–570. 10.1111/nph.14217 PubMed DOI

Lohman K. N., Gan S., John M. C., Amasino R. M. (1994). Molecular analysis of natural leaf senescence in Arabidopsis thaliana. Physiol. Plant. 92, 322–328. 10.1111/j.1399-3054.1994.tb05343.x DOI

Lomin S. N., Yonekura-Sakakibara K., Romanov G. A., Sakakibara H. (2011). Ligand-binding properties and subcellular localization of maize cytokinin receptors. J. Exp. Bot. 62, 5149–5159. 10.1093/jxb/err220 PubMed DOI PMC

Makino A., Osmond B. (1991). Effects of nitrogen nutrition on nitrogen partitioning between chloroplasts and mitochondria in pea and wheat. Plant Physiol. 96, 355–362. 10.1104/pp.96.2.355 PubMed DOI PMC

Matile P., Hörtensteiner S., Thomas H. (1999). Chlorophyll degradation. Annu. Rev. Plant Physiol. Plant Mol. Biol. 50, 67–95. 10.1146/annurev.arplant.50.1.67 PubMed DOI

Mok M. C. (1994). Cytokinins and plant development-an overview, in Cytokinins: Chemistry, Activity and Function, eds Mok D. W. S., Mok M. C. (Boca Raton, FL: CRC Press; ), 155–166.

Mok M. C., Mok D. W. S., Amstrong D. J., Okamoto T. (1982). Cytokinin activity of N-phenyl-N-1,2,3-thidiazol-5-ylurea (thidiazuron). Phytochemistry 21, 1509–1511. 10.1016/S0031-9422(82)85007-3 DOI

Mutui T. M., Mibus H., Serek M. (2005). Effects of thidiazuron, ethylene, abscisic acid and dark storage on leaf yellowing and rooting of Pelargonium cutting. J. Hortic. Sci. Biotech. 80, 543–550. 10.1080/14620316.2005.11511975 DOI

Nishiyama R., Watanabe Y., Fujita Y., Le D. T., Kojima M., Werner T., et al. . (2011). Analysis of cytokinin mutants and regulation of cytokinin metabolic genes reveals important regulatory roles of cytokinins in drought, salt and abscisic acid responses, and abscisic acid biosynthesis. Plant Cell 23, 2169–2183. 10.1105/tpc.111.087395 PubMed DOI PMC

Nisler J., Kopečný D., Končitíková R., Zatloukal M., Bazgier V., Berka K., et al. . (2016). Novel thidiazuron-derived inhibitors of cytokinin oxidase/dehydrogenase. Plant Mol. Biol. 92, 235–248. 10.1007/s11103-016-0509-0 PubMed DOI

Nisler J., Zatloukal M., Popa I., DoleŽal K., Strnad M., Spíchal L. (2010). Cytokinin receptor antagonists derived from 6-benzylaminopurine. Phytochemistry 71, 823–830. 10.1016/j.phytochem.2010.01.018 PubMed DOI

Novák O., Hauserová E., Amakorová P., DoleŽal K., Strnad M. (2008). Cytokinin profiling in plant tissues using ultra-performance liquid chromatography–electrospray tandem mass spectrometry. Phytochemistry 69, 2214–2224. 10.1016/j.phytochem.2008.04.022 PubMed DOI

Oh S. A., Lee S. Y., Chung I. K., Lee C. H., Nam H. G. (1996). A senescence-associated gene of Arabidopsis thaliana is distinctively regulated during natural and artificially induced leaf senescence. Plant Mol. Biol. 30, 739–754. 10.1007/BF00019008 PubMed DOI

Pagliano C., Barera S., Chimirri F., Saracco G., Barber J. (2012). Comparison of the α and β isomeric forms of the detergent n-dodecyl-D-maltoside for solubilizing photosynthetic complexes from pea thylakoid membranes. Biochim. Biophys. Acta 1817, 1506–1515. 10.1016/j.bbabio.2011.11.001 PubMed DOI

Procházková D., Haisel D., Wilhelmová N. (2008). Antioxidant protection during ageing and senescence in chloroplasts of tobacco with modulated life span. Cell Biochem. Funct. 26, 582–590. 10.1002/cbf.1481 PubMed DOI

Quirino B. F., Noh Y.-S., Himelblau E., Amasino R. M. (2000). Molecular aspects of leaf senescence. Trends Plant Sci. 5, 278–282. 10.1016/S1360-1385(00)01655-1 PubMed DOI

Richmond A. E., Lang A. (1957). Effect of kinetin on protein content and survival of detached Xanthium leaves. Science 125, 650–651. 10.1126/science.125.3249.650-a PubMed DOI

Riefler M., Novák O., Strnad M., Schmülling T. (2006). Arabidopsis cytokinin receptor mutants reveal functions in shoot growth, leaf senescence, seed size, germination, root development, and cytokinin metabolism. Plant Cell 18, 40–54. 10.1105/tpc.105.037796 PubMed DOI PMC

Rivero L., Scholl R., Holomuzki N., Crist D., Grotewold E., Brkljacic J. (2014). Handling Arabidopsis plants: growth, preservation of seeds, transformation, and genetic crosses. Methods Mol. Biol. 1062, 3–25. 10.1007/978-1-62703-580-4_1 PubMed DOI

Rivero R. M., Kojima M., Gepstein A., Sakakibara H., Mittler R., Gepstein S., et al. . (2007). Delayed leaf senescence induces extreme drought tolerance in a flowering plant. Proc. Natl. Acad. Sci. U.S.A. 104, 19631–19636. 10.1073/pnas.0709453104 PubMed DOI PMC

Romanov G. A., Kieber J. J., Schmülling T. (2002). A rapid cytokinin response assay in Arabidopsis indicates a role for phospholipase D in cytokinin signalling. FEBS Lett. 515, 39–43. 10.1016/S0014-5793(02)02415-8 PubMed DOI

Sakuraba Y., Park S. Y., Kim Y. S., Wang S. H., Yoo S. C., Hörtensteiner S., et al. . (2014). Arabidopsis STAY-GREEN2 is a negative regulator of chlorophyll degradation during leaf senescence. Mol. Plant 7, 1288–1302. 10.1093/mp/ssu045 PubMed DOI

Sakuraba Y., Park S. Y., Paek N. C. (2015). The divergent roles of STAYGREEN (SGR) homologs in chlorophyll degradation. Mol. Cells 38, 390–395. 10.14348/molcells.2015.0039 PubMed DOI PMC

Smith P. K., Krohn R. I., Hermanson G. T., Mallia A. K., Garmer F. H., Provenzano M. D., et al. . (1985). Measurement of protein using bicinchoninic acid. Anal. Biochem. 150, 76–85. 10.1016/0003-2697(85)90442-7 PubMed DOI

Sobotka R. (2014). Making proteins green; biosynthesis of chlorophyll-binding proteins in cyanobacteria. Photosyn. Res. 119, 223–232. 10.1007/s11120-013-9797-2 PubMed DOI

Spíchal L., Rakova N. Y., Riefler M., Mizuno T., Romanov G. A., Strnad M., et al. . (2004). Two cytokinin receptors of Arabidopsis thaliana, CRE1/ AHK4 and AHK3, differ in their ligand specificity in a bacterial assay. Plant Cell Physiol. 45, 1299–1305. 10.1093/pcp/pch132 PubMed DOI

Suzuki T., Miwa K., Ishikawa K., Yamada H., Aiba H., Mizuno T. (2001). The Arabidopsis sensor His-kinase, AHK4, can respond to cytokinins. Plant Cell Physiol. 42, 107–113. 10.1093/pcp/pce037 PubMed DOI

Tarkowská D., DoleŽal K., Tarkowski P., Ästot C., Holub J., Fuksová K., et al. . (2003). Identification of new aromatic cytokinins in Arabidopsis thaliana and Populus canadensis leaves by LC-(+)ESI-MS and capillary liquid chromatography/frit-fast atom bombardment mass spectrometry. Physiol. Plant. 117, 579–590. 10.1034/j.1399-3054.2003.00071.x PubMed DOI

Thomas J. C., Katterman F. R. (1986). Cytokinin activity induced by thidiazuron. Plant Physiol. 81, 681–683. 10.1104/pp.81.2.681 PubMed DOI PMC

Tian F. X., Gong J. F., Wang G. P., Wang G. K., Fan Z. Y., Wang W. (2012). Improved drought resistance in a wheat stay-green mutant tasg1 under field conditions. Biol. Plant. 56, 509–515. 10.1007/s10535-012-0049-7 DOI

Tran L. S., Urao T., Qin F., Maruyama K., Kakimoto T., Shinozaki K., et al. . (2007). Functional analysis of AHK1/ATHK1 and cytokinin receptor histidine kinases in response to abscisic acid, drought, and salt stress in Arabidopsis. Proc. Natl. Acad. Sci. U.S.A. 104, 20623–20628. 10.1073/pnas.0706547105 PubMed DOI PMC

Veach Y. K., Martin R. C., Mok D. W., Malbeck J., Vankova R., Mok M. C. (2003). O-glucosylation of cis-zeatin in maize. Characterization of genes, enzymes, and endogenous cytokinins. Plant Physiol. 131, 1374–1380. 10.1104/pp.017210 PubMed DOI PMC

Vogel J. P., Woeste K. E., Theologis A., Kieber J. J. (1998). Recessive and dominant mutations in the ethylene biosynthetic gene ACS5 of Arabidopsis confer cytokinin insensitivity and ethylene overproduction, respectively. Proc. Natl. Acad. Sci. U.S.A. 95, 4766–4771. 10.1073/pnas.95.8.4766 PubMed DOI PMC

Weaver L. M., Gan S., Quirino B., Amasino R. M. (1998). A comparison of the expression patterns of several senescence-associated genes in response to stress and hormone treatment. Plant Mol. Biol. 37, 455–469. 10.1023/A:1005934428906 PubMed DOI

Wei-yu H., Ya-lai W., Lin-jiang Y. (1990). The relationship between polyamines and senescence of detached wheat leaves. Acta Bot. Sin. 32, 125–132.

Werner T., Motyka V., Laucou V., Smets R., Onckelen H. V., Schmülling T. (2003). 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 15, 2532–2550. 10.1105/tpc.014928 PubMed DOI PMC

Wi S. J., Jang S. J., Park K. Y. (2010). Inhibition of biphasic ethylene production enhances tolerance to abiotic stress by reducing the accumulation of reactive oxygen species in Nicotiana tabacum. Mol. Cells 30, 37–49. 10.1007/s10059-010-0086-z PubMed DOI

Wittig I., Carrozzo R., Santorelli F. M., Schägger H. (2007). Functional assays in high-resolution clear native gels to quantify mitochondrial complexes in human biopsies and cell lines. Electrophoresis 28, 3811–3820. 10.1002/elps.200700367 PubMed DOI

Woeste K. E., Vogel J. P., Kieber J. J. (1999). Factors regulating ethylene biosynthesis in etiolated Arabidopsis thaliana seedlings. Physiol. Plant. 105, 478–484. 10.1034/j.1399-3054.1999.105312.x DOI

Wu Y. X., von T. A. (2002). Impact of fungicides on active oxygen species and antioxidant enzymes in spring barley (Hordeum vulgare L.) exposed to ozone. Environ. Pollut. 116, 37–47. 10.1016/S0269-7491(01)00174-9 PubMed DOI

Yamada H., Suzuki T., Terada K., Takei K., Ishikawa K., Miwa K., et al. . (2001). The Arabidopsis AHK4 histidine kinase is a cytokinin-binding receptor that transduces cytokinin signals across the membrane. Plant Cell Physiol. 42, 1017–1023. 10.1093/pcp/pce127 PubMed DOI

Yang W., Liu X.-D., Chi X.-J., Wu C.-A., Li Y.-Z., Song L.-L., et al. . (2011). Dwarf apple MbDREB1 enhances plant tolerance to low temperature, drought, and salt stress via both ABA-dependent and ABA-independent pathways. Planta 233, 219–229. 10.1007/s00425-010-1279-6 PubMed DOI

Yaronskaya E., Vershilovskaya I., Poers Y., Alawady A. E., Averina N., Grimm B. (2006). Cytokinin effects on tetrapyrrole biosynthesis and photosynthetic activity in barley seedlings. Planta 224, 700–709. 10.1007/s00425-006-0249-5 PubMed DOI

Yip W. K., Yang S. F. (1986). Effect of thidiazuron, a cytokinin-active urea derivative, in cytokinin-dependent ethylene production systems. Plant Physiol. 80, 515–519. PubMed PMC

Urea derivative MTU improves stress tolerance and yield in wheat by promoting cyclic electron flow around PSI

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