Cytokinin is a phytohormone involved in the regulation of diverse developmental and physiological processes in plants. Its potential in biotechnology and for development of higher-yield and more resilient plants has been recognized, yet the molecular mechanisms behind its action are far from understood. In this report, the roots of barley seedlings were explored as a new source to reveal as yet unknown cytokinin-responsive proteins for crop improvement. Here we found significant differences reproducibly observed for 178 proteins, for which some of the revealed cytokinin-responsive pathways were confirmed in metabolome analysis, including alterations phenylpropanoid pathway, amino acid biosynthesis and ROS metabolism. Bioinformatics analysis indicated a significant overlap between cytokinin response and response to abiotic stress. This was confirmed by comparing proteome and metabolome profiles in response to drought, salinity or a period of temperature stress. The results illustrate complex abiotic stress response in the early development of model crop plant and confirm an extensive crosstalk between plant hormone cytokinin and response to temperature stimuli, water availability or salinity stress.

• Klíčová slova
• Hordeum vulgare, ROS, abiotic stress, metabolome, phenylpropanoid biosynthesis, proteome, root, zeatin,
• Publikační typ
• časopisecké články MeSH

Cytokinin is an indispensable phytohormone responsible for physiological processes ranging from root development to leaf senescence. The term "cytokinin" refers to several dozen adenine-derived compounds occurring naturally in plants. Cytokinins (CKs) can be divided into various classes and forms; base forms are generally considered to be active while highly abundant cytokinin-N-glucosides (CKNGs), composed of a CK base irreversibly conjugated to a glucose molecule, are considered inactive. However, results from early CK studies suggest CKNGs do not always lack activity despite the perpetuation over several decades in the literature that they are inactive. Here we show that exogenous application of trans-Zeatin-N-glucosides (tZNGs, a specific class of CKNGs) to Arabidopsis results in CK response comparable to the application of an active CK base. These results are most apparent in senescence assays where both a CK base (tZ) and tZNGs (tZ7G, tZ9G) delay senescence in cotyledons. Further experiments involving root growth and shoot regeneration revealed tZNGs do not always have the same effects as tZ, and have largely distinct effects on the transcriptome and proteome. These data are in contrast to previous reports of CKNGs being inactive and raise questions about the function of these compounds as well as their mechanism of action.

• MeSH
• Arabidopsis růst a vývoj   metabolismus   MeSH
• cytokininy metabolismus   MeSH
• glukosidy metabolismus   MeSH
• kořeny rostlin růst a vývoj   metabolismus   MeSH
• regulátory růstu rostlin MeSH
• zeatin metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cytokininy MeSH
• glukosidy MeSH
• regulátory růstu rostlin MeSH
• zeatin MeSH

Hydrogen peroxide (H₂O₂) is steadily gaining more attention in the field of molecular biology research. It is a major REDOX (reduction⁻oxidation reaction) metabolite and at high concentrations induces oxidative damage to biomolecules, which can culminate in cell death. However, at concentrations in the low nanomolar range, H₂O₂ acts as a signalling molecule and in many aspects, resembles phytohormones. Though its signalling network in plants is much less well characterized than are those of its counterparts in yeast or mammals, accumulating evidence indicates that the role of H₂O₂-mediated signalling in plant cells is possibly even more indispensable. In this review, we summarize hydrogen peroxide metabolism in plants, the sources and sinks of this compound and its transport via peroxiporins. We outline H₂O₂ perception, its direct and indirect effects and known targets in the transcriptional machinery. We focus on the role of H₂O₂ in plant growth and development and discuss the crosstalk between it and phytohormones. In addition to a literature review, we performed a meta-analysis of available transcriptomics data which provided further evidence for crosstalk between H₂O₂ and light, nutrient signalling, temperature stress, drought stress and hormonal pathways.

• Klíčová slova
• H2O2, growth and development, plant hormone, signalling, stress,
• MeSH
• biologický transport MeSH
• fyziologický stres MeSH
• peroxid vodíku metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin genetika   metabolismus   MeSH
• rostliny genetika   metabolismus   MeSH
• signální transdukce * MeSH
• transkriptom MeSH
• vývoj rostlin * MeSH
• Publikační typ
• časopisecké články MeSH
• metaanalýza MeSH
• přehledy MeSH
• Názvy látek
• peroxid vodíku MeSH
• regulátory růstu rostlin MeSH

Cytokinin is a multifaceted plant hormone that plays major roles not only in diverse plant growth and development processes, but also stress responses. We summarize knowledge of the roles of its metabolism, transport, and signalling in responses to changes in levels of both macronutrients (nitrogen, phosphorus, potassium, sulphur) and micronutrients (boron, iron, silicon, selenium). We comment on cytokinin's effects on plants' xenobiotic resistance, and its interactions with light, temperature, drought, and salinity signals. Further, we have compiled a list of abiotic stress-related genes and demonstrate that their expression patterns overlap with those of cytokinin metabolism and signalling genes.

• Klíčová slova
• abiotic stress, cytokinin, drought, nutrient, stress tolerance, temperature,
• MeSH
• aklimatizace MeSH
• cirkadiánní hodiny MeSH
• cytokininy metabolismus   MeSH
• fyziologický stres * MeSH
• fyziologie rostlin * MeSH
• období sucha MeSH
• regulace genové exprese u rostlin MeSH
• rostliny genetika   metabolismus   MeSH
• salinita MeSH
• signální transdukce * MeSH
• světlo MeSH
• teplota MeSH
• vývoj rostlin MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• cytokininy MeSH

Cytokinins (CKs) are phytohormones regulating plant growth and development as well as response to the environment. In order to evaluate their function in heat stress (HS) responses, the effect of CK elevation was determined during three types of HS - targeted to shoots, targeted to roots and applied to the whole plant. The early (30min) and longer term (3h) responses were followed at the hormonal, transcriptomic and proteomic levels in Arabidopsis transformants with dexamethasone-inducible expression of the CK biosynthetic gene isopentenyltransferase (ipt) and the corresponding wild-type (Col-0). Combination of hormonal and phenotypic analyses showed transient up-regulation of the CK/abscisic acid ratio, which controls stomatal aperture, to be more pronounced in the transformant. HS responses of the root proteome and Rubisco-immunodepleted leaf proteome were followed using 2-D gel electrophoresis and MALDI-TOF/TOF. More than 100 HS-responsive proteins were detected, most of them being modulated by CK increase. Proteome and transcriptome analyses demonstrated that CKs have longer term positive effects on the stress-related proteins and transcripts, as well as on the photosynthesis-related ones. Transient accumulation of CKs and stimulation of their signal transduction in tissue(s) not exposed to HS indicate that they are involved in plant stress responses.

• Klíčová slova
• Abscisic acid, Arabidopsis thaliana, cytokinin, heat stress, isopentenyltransferase, proteome.,
• MeSH
• alkyltransferasy a aryltransferasy fyziologie   MeSH
• Arabidopsis účinky léků   metabolismus   fyziologie   MeSH
• cytokininy fyziologie   MeSH
• dexamethason farmakologie   MeSH
• kořeny rostlin metabolismus   fyziologie   MeSH
• kyselina abscisová fyziologie   MeSH
• proteomika MeSH
• reakce na tepelný šok fyziologie   MeSH
• regulace genové exprese u rostlin fyziologie   MeSH
• regulátory růstu rostlin fyziologie   MeSH
• signální transdukce účinky léků   fyziologie   MeSH
• spektrometrie hmotnostní - ionizace laserem za účasti matrice MeSH
• stanovení celkové genové exprese MeSH
• výhonky rostlin metabolismus   fyziologie   MeSH
• vysoká teplota MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adenylate isopentenyltransferase MeSH Prohlížeč
• alkyltransferasy a aryltransferasy MeSH
• cytokininy MeSH
• dexamethason MeSH
• kyselina abscisová MeSH
• regulátory růstu rostlin MeSH

Cytokinins (CKs) regulate plant development and growth via a two-component signaling pathway. By forward genetic screening, we isolated an Arabidopsis mutant named grow fast on cytokinins 1 (gfc1), whose seedlings grew larger aerial parts on MS medium with CK. gfc1 is allelic to a previously reported cutin mutant defective in cuticular ridges (dcr). GFC1/DCR encodes a soluble BAHD acyltransferase (a name based on the first four enzymes characterized in this family: Benzylalcohol O-acetyltransferase, Anthocyanin O-hydroxycinnamoyltransferase, anthranilate N-hydroxycinnamoyl/benzoyltransferase and Deacetylvindoline 4-O-acetyltransferase) with diacylglycerol acyltransferase (DGAT) activity in vitro and is necessary for normal cuticle formation on epidermis in vivo. Here we show that gfc1 was a CK-insensitive mutant, as revealed by its low regeneration frequency in vitro and resistance to CK in adventitious root formation and dark-grown hypocotyl inhibition assays. In addition, gfc1 had de-etiolated phenotypes in darkness and was therefore defective in skotomorphogenesis. The background expression levels of most type-A Arabidopsis Response Regulator (ARR) genes were higher in the gfc1 mutant. The gfc1-associated phenotypes were also observed in the cutin-deficient glycerol-3-phosphate acyltransferase 4/8 (gpat4/8) double mutant [defective in glycerol-3-phosphate (G3P) acyltransferase enzymes GPAT4 and GPAT8, which redundantly catalyze the acylation of G3P by hydroxyl fatty acid (OH-FA)], but not in the cutin-deficient mutant cytochrome p450, family 86, subfamily A, polypeptide 2/aberrant induction of type three 1 (cyp86A2/att1), which affects the biosynthesis of some OH-FAs. Our results indicate that some acyltransferases associated with cutin formation are involved in CK responses and skotomorphogenesis in Arabidopsis.

• MeSH
• acyltransferasy genetika   metabolismus   MeSH
• Arabidopsis genetika   růst a vývoj   metabolismus   účinky záření   MeSH
• cytokininy metabolismus   farmakologie   MeSH
• fenotyp MeSH
• membránové lipidy biosyntéza   MeSH
• meristém účinky léků   genetika   růst a vývoj   účinky záření   MeSH
• morfogeneze * účinky léků   účinky záření   MeSH
• mutace MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• regulace genové exprese u rostlin účinky léků   účinky záření   MeSH
• semenáček účinky léků   genetika   růst a vývoj   účinky záření   MeSH
• tma MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• acyltransferasy MeSH
• cutin MeSH Prohlížeč
• cytokininy MeSH
• membránové lipidy MeSH
• proteiny huseníčku MeSH

Arabidopsis (Arabidopsis thaliana) leaf development relies on subsequent phases of cell proliferation and cell expansion. During the proliferation phase, chloroplasts need to divide extensively, and during the transition from cell proliferation to expansion, they differentiate into photosynthetically active chloroplasts, providing the plant with energy. The transcription factor GROWTH REGULATING FACTOR5 (GRF5) promotes the duration of the cell proliferation period during leaf development. Here, it is shown that GRF5 also stimulates chloroplast division, resulting in a higher chloroplast number per cell with a concomitant increase in chlorophyll levels in 35S:GRF5 leaves, which can sustain higher rates of photosynthesis. Moreover, 35S:GRF5 plants show delayed leaf senescence and are more tolerant for growth on nitrogen-depleted medium. Cytokinins also stimulate leaf growth in part by extending the cell proliferation phase, simultaneously delaying the onset of the cell expansion phase. In addition, cytokinins are known to be involved in chloroplast development, nitrogen signaling, and senescence. Evidence is provided that GRF5 and cytokinins synergistically enhance cell division and chlorophyll retention after dark-induced senescence, which suggests that they also cooperate to stimulate chloroplast division and nitrogen assimilation. Taken together with the increased leaf size, ectopic expression of GRF5 has great potential to improve plant productivity.

• MeSH
• Arabidopsis účinky léků   genetika   fyziologie   MeSH
• buněčné dělení účinky léků   MeSH
• chlorofyl metabolismus   MeSH
• chloroplasty účinky léků   metabolismus   ultrastruktura   MeSH
• cytokininy farmakologie   MeSH
• dusík nedostatek   MeSH
• fotosyntéza * účinky léků   MeSH
• geneticky modifikované rostliny MeSH
• listy rostlin účinky léků   růst a vývoj   fyziologie   ultrastruktura   MeSH
• proteiny 14-3-3 genetika   metabolismus   MeSH
• regulace genové exprese u rostlin účinky léků   MeSH
• rostlinné geny MeSH
• trans-aktivátory genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chlorofyl MeSH
• cytokininy MeSH
• dusík MeSH
• GRF5 protein, Arabidopsis MeSH Prohlížeč
• proteiny 14-3-3 MeSH
• trans-aktivátory MeSH

In plants, numerous developmental processes are controlled by cytokinin (CK) levels and their ratios to levels of other hormones. While molecular mechanisms underlying the regulatory roles of CKs have been intensely researched, proteomic and metabolomic responses to CK deficiency are unknown. Transgenic Arabidopsis seedlings carrying inducible barley cytokinin oxidase/dehydrogenase (CaMV35S>GR>HvCKX2) and agrobacterial isopentenyl transferase (CaMV35S>GR>ipt) constructs were profiled to elucidate proteome- and metabolome-wide responses to down- and up-regulation of CK levels, respectively. Proteome profiling identified >1100 proteins, 155 of which responded to HvCKX2 and/or ipt activation, mostly involved in growth, development, and/or hormone and light signalling. The metabolome profiling covered 79 metabolites, 33 of which responded to HvCKX2 and/or ipt activation, mostly amino acids, carbohydrates, and organic acids. Comparison of the data sets obtained from activated CaMV35S>GR>HvCKX2 and CaMV35S>GR>ipt plants revealed unexpectedly extensive overlaps. Integration of the proteomic and metabolomic data sets revealed: (i) novel components of molecular circuits involved in CK action (e.g. ribosomal proteins); (ii) previously unrecognized links to redox regulation and stress hormone signalling networks; and (iii) CK content markers. The striking overlaps in profiles observed in CK-deficient and CK-overproducing seedlings might explain surprising previously reported similarities between plants with down- and up-regulated CK levels.

• Klíčová slova
• Arabidopsis thaliana, cytokinin, cytokinin oxidase/dehydrogenase, isopentenyl transferase, metabolome, proteome.,
• MeSH
• alkyltransferasy a aryltransferasy metabolismus   MeSH
• Arabidopsis účinky léků   genetika   metabolismus   MeSH
• chromatografie kapalinová MeSH
• cytokininy farmakologie   MeSH
• dexamethason farmakologie   MeSH
• geneticky modifikované rostliny MeSH
• hmotnostní spektrometrie MeSH
• ječmen (rod) účinky léků   metabolismus   MeSH
• metabolom účinky léků   genetika   MeSH
• metabolomika MeSH
• proteiny huseníčku metabolismus   MeSH
• proteom metabolismus   MeSH
• proteomika MeSH
• regulace genové exprese u rostlin účinky léků   MeSH
• semenáček účinky léků   genetika   MeSH
• upregulace účinky léků   genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adenylate isopentenyltransferase MeSH Prohlížeč
• alkyltransferasy a aryltransferasy MeSH
• cytokininy MeSH
• dexamethason MeSH
• proteiny huseníčku MeSH
• proteom MeSH

BACKGROUND AND AIMS: Cytokinins are positive regulators of shoot development. However, it has previously been demonstrated that efficient activation of the cytokinin biosynthesis gene ipt can cause necrotic lesions and wilting in tobacco leaves. Some plant pathogens reportedly use their ability to produce cytokinins in disease development. In response to pathogen attacks, plants can trigger a hypersensitive response that rapidly kills cells near the infection site, depriving the pathogen of nutrients and preventing its spread. In this study, a diverse set of processes that link ipt activation to necrotic lesion formation were investigated in order to evaluate the potential of cytokinins as signals and/or mediators in plant defence against pathogens. METHODS: The binary pOp-ipt/LhGR system for dexamethasone-inducible ipt expression was used to increase endogenous cytokinin levels in transgenic tobacco. Changes in the levels of cytokinins and the stress hormones salicylic, jasmonic and abscisic acid following ipt activation were determined by ultra-performance liquid chromatography-electrospray tandem mass spectrometry (UPLC-MS/MS). Trends in hydrogen peroxide content and lipid peroxidation were monitored using the potassium iodide and malondialdehyde assays. The subcellular distribution of hydrogen peroxide was investigated using 3,3'-diaminobenzidine staining. The dynamics of transcripts related to photosynthesis and pathogen response were analysed by reverse transcription followed by quantitative PCR. The effects of cytokinins on photosynthesis were deciphered by analysing changes in chlorophyll fluorescence and leaf gas exchange. KEY RESULTS: Plants can produce sufficiently high levels of cytokinins to trigger fast cell death without any intervening chlorosis - a hallmark of the hypersensitive response. The results suggest that chloroplastic hydrogen peroxide orchestrates the molecular responses underpinning the hypersensitive-like response, including the inhibition of photosynthesis, elevated levels of stress hormones, oxidative membrane damage and stomatal closure. CONCLUSIONS: Necrotic lesion formation triggered by ipt activation closely resembles the hypersensitive response. Cytokinins may thus act as signals and/or mediators in plant defence against pathogen attack.

• Klíčová slova
• Cytokinin, Nicotiana tabacum, abscisic acid, hydrogen peroxide, hypersensitive response, jasmonic acid, lipid peroxidation, non-photochemical quenching, pathogenesis-related proteins, photosynthesis, salicylic acid, stomatal conductance,
• MeSH
• alkyltransferasy a aryltransferasy genetika   MeSH
• buněčná smrt MeSH
• chlorofyl metabolismus   MeSH
• chloroplasty genetika   metabolismus   MeSH
• cytokininy genetika   metabolismus   MeSH
• dexamethason farmakologie   MeSH
• fotosyntéza genetika   MeSH
• geneticky modifikované rostliny MeSH
• interakce hostitele a patogenu * MeSH
• listy rostlin cytologie   genetika   fyziologie   MeSH
• nekróza genetika   MeSH
• oxidační stres genetika   MeSH
• peroxid vodíku metabolismus   MeSH
• peroxidace lipidů MeSH
• průduchy rostlin fyziologie   MeSH
• regulace genové exprese u rostlin účinky léků   MeSH
• regulátory růstu rostlin genetika   metabolismus   MeSH
• tabák genetika   mikrobiologie   fyziologie   MeSH
• umlčování genů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adenylate isopentenyltransferase MeSH Prohlížeč
• alkyltransferasy a aryltransferasy MeSH
• chlorofyl MeSH
• cytokininy MeSH
• dexamethason MeSH
• peroxid vodíku MeSH
• regulátory růstu rostlin MeSH

Light is one of the most important factor influencing plant growth and development all through their life cycle. One of the well-known light-regulated processes is de-etiolation, i.e. the switch from skotomorphogenesis to photomorphogenesis. The hormones cytokinins (CKs) play an important role during the establishment of photomorphogenesis as exogenous CKs induced photomorphogenesis of dark-grown seedlings. Most of the studies are conducted on the plant model Arabidopsis, but no or few information are available for important crop species, such as tomato (Solanum lycopersicum L.). In our study, we analyzed for the first time the endogenous CKs content in tomato hypocotyls during skotomorphogenesis, photomorphogenesis and de-etiolation. For this purpose, two tomato genotypes were used: cv. Rutgers (wild-type; WT) and its corresponding mutant (7B-1) affected in its responses to blue light (BL). Using physiological and molecular approaches, we identified that the skotomorphogenesis is characterized by an endoreduplication-mediated cell expansion, which is inhibited upon BL exposure as seen by the accumulation of trancripts encoding CycD3, key regulators of the cell cycle. Our study showed for the first time that iP (isopentenyladenine) is the CK accumulated in the tomato hypocotyl upon BL exposure, suggesting its specific role in photomorphogenesis. This result was supported by physiological experiments and gene expression data. We propose a common model to explain the role and the relationship between CKs, namely iP, and endoreduplication during de-etiolation and photomorphogenesis.

• MeSH
• buněčný cyklus účinky léků   genetika   MeSH
• cyklin D3 genetika   metabolismus   MeSH
• cytokininy metabolismus   MeSH
• endoreduplikace fyziologie   účinky záření   MeSH
• fylogeneze MeSH
• hypokotyl fyziologie   účinky záření   MeSH
• isopentenyladenosin metabolismus   MeSH
• morfogeneze fyziologie   účinky záření   MeSH
• ploidie MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• semenáček fyziologie   účinky záření   MeSH
• Solanum lycopersicum fyziologie   účinky záření   MeSH
• světlo MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cyklin D3 MeSH
• cytokininy MeSH
• isopentenyladenosin MeSH
• N(6)-(delta(2)-isopentenyl)adenine MeSH Prohlížeč
• rostlinné proteiny MeSH