Multistep phosphorelay (MSP) signaling integrates hormonal and environmental signals to control both plant development and adaptive responses. Type-A RESPONSE REGULATOR (RRA) genes, the downstream members of the MSP cascade and cytokinin primary response genes, are thought to mediate primarily the negative feedback regulation of (cytokinin-induced) MSP signaling. However, transcriptional data also suggest the involvement of RRA genes in stress-related responses. By employing evolutionary conservation with the well-characterized Arabidopsis thaliana RRA genes, we identified five and 38 novel putative RRA genes in Brassica oleracea and Brassica napus, respectively. Our phylogenetic analysis suggests the existence of gene-specific selective pressure, maintaining the homologs of ARR3, ARR6, and ARR16 as singletons during the evolution of Brassicaceae. We categorized RRA genes based on the kinetics of their cytokinin-mediated up-regulation and observed both similarities and specificities in this type of response across Brassicaceae species. Using bioinformatic analysis and experimental data demonstrating the cytokinin and abiotic stress responsiveness of the A. thaliana-derived TCSv2 reporter, we unveil the mechanistic conservation of cytokinin- and stress-mediated up-regulation of RRA genes in B. rapa and B. napus. Notably, we identify partial cytokinin dependency of cold stress-induced RRA transcription, thus further demonstrating the role of cytokinin signaling in crop adaptive responses.

• Klíčová slova
• Arabidopsis thaliana, Brassica napus, Brassica oleracea, Brassica rapa, cytokinins, multistep phosphorelay, osmotic stress, salinity, two-component signaling, type-A response regulator,
• MeSH
• Arabidopsis genetika   fyziologie   metabolismus   MeSH
• Brassica napus genetika   fyziologie   metabolismus   MeSH
• Brassica * genetika   fyziologie   metabolismus   MeSH
• cytokininy * metabolismus   MeSH
• fylogeneze MeSH
• fyziologický stres * MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin metabolismus   MeSH
• rostlinné proteiny * genetika   metabolismus   MeSH
• signální transdukce MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• cytokininy * MeSH
• regulátory růstu rostlin MeSH
• rostlinné proteiny * MeSH

The vast majority of agricultural land undergoes abiotic stress that can significantly reduce agricultural yields. Understanding the mechanisms of plant defenses against stresses and putting this knowledge into practice is, therefore, an integral part of sustainable agriculture. In this review, we focus on current findings in plant resistance to four cardinal abiotic stressors-drought, heat, salinity, and low temperatures. Apart from the description of the newly discovered mechanisms of signaling and resistance to abiotic stress, this review also focuses on the importance of primary and secondary metabolites, including carbohydrates, amino acids, phenolics, and phytohormones. A meta-analysis of transcriptomic studies concerning the model plant Arabidopsis demonstrates the long-observed phenomenon that abiotic stressors induce different signals and effects at the level of gene expression, but genes whose regulation is similar under most stressors can still be traced. The analysis further reveals the transcriptional modulation of Golgi-targeted proteins in response to heat stress. Our analysis also highlights several genes that are similarly regulated under all stress conditions. These genes support the central role of phytohormones in the abiotic stress response, and the importance of some of these in plant resistance has not yet been studied. Finally, this review provides information about the response to abiotic stress in major European crop plants-wheat, sugar beet, maize, potatoes, barley, sunflowers, grapes, rapeseed, tomatoes, and apples.

• Klíčová slova
• abiotic stress, cold stress, crop, drought, heat stress, metabolites, phytohormones, salinity,
• MeSH
• Arabidopsis * genetika   MeSH
• fyziologický stres genetika   MeSH
• pěstování plodin MeSH
• reakce na tepelný šok genetika   MeSH
• regulátory růstu rostlin * MeSH
• rostliny MeSH
• Publikační typ
• časopisecké články MeSH
• metaanalýza MeSH
• přehledy MeSH
• Názvy látek
• regulátory růstu rostlin * MeSH

Deserts exert strong selection pressures on plants, but the underlying genomic drivers of ecological adaptation and subsequent speciation remain largely unknown. Here, we generated de novo genome assemblies and conducted population genomic analyses of the psammophytic genus Pugionium (Brassicaceae). Our results indicated that this bispecific genus had undergone an allopolyploid event, and the two parental genomes were derived from two ancestral lineages with different chromosome numbers and structures. The postpolyploid expansion of gene families related to abiotic stress responses and lignin biosynthesis facilitated environmental adaptations of the genus to desert habitats. Population genomic analyses of both species further revealed their recent divergence with continuous gene flow, and the most divergent regions were found to be centered on three highly structurally reshuffled chromosomes. Genes under selection in these regions, which were mainly located in one of the two subgenomes, contributed greatly to the interspecific divergence in microhabitat adaptation.

• Klíčová slova
• chromosomal structural variation, desert plants, microhabitat divergence, polyploidization,
• MeSH
• Brassicaceae klasifikace   genetika   fyziologie   MeSH
• ekosystém * MeSH
• fylogeneze MeSH
• fyziologická adaptace genetika   MeSH
• genom rostlinný * MeSH
• polyploidie MeSH
• vznik druhů (genetika) * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Plants growing in any particular geographical location are exposed to variable and diverse environmental conditions throughout their lifespan. The multifactorial environmental pressure resulted into evolution of plant adaptation and survival strategies requiring ability to integrate multiple signals that combine to yield specific responses. These adaptive responses enable plants to maintain their growth and development while acquiring tolerance to a variety of environmental conditions. An essential signaling cascade that incorporates a wide range of exogenous as well as endogenous stimuli is multistep phosphorelay (MSP). MSP mediates the signaling of essential plant hormones that balance growth, development, and environmental adaptation. Nevertheless, the mechanisms by which specific signals are recognized by a commonly-occurring pathway are not yet clearly understood. Here we summarize our knowledge on the latest model of multistep phosphorelay signaling in plants and the molecular mechanisms underlying the integration of multiple inputs including both hormonal (cytokinins, ethylene and abscisic acid) and environmental (light and temperature) signals into a common pathway. We provide an overview of abiotic stress responses mediated via MSP signaling that are both hormone-dependent and independent. We highlight the mutual interactions of key players such as sensor kinases of various substrate specificities including their downstream targets. These constitute a tightly interconnected signaling network, enabling timely adaptation by the plant to an ever-changing environment. Finally, we propose possible future directions in stress-oriented research on MSP signaling and highlight its potential importance for targeted crop breeding.

• Klíčová slova
• Arabidopsis, abiotic stress, abscisic acid, cytokinin, ethylene, light signaling, multistep phosphorelay (MSP), temperature,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Five poplar CHASE-containing histidine kinase receptors bind cytokinins and display kinase activities. Both endogenous isoprenoid and aromatic cytokinins bind to the receptors in live cell assays. Cytokinins are phytohormones that play key roles in various developmental processes in plants. The poplar species Populus × canadensis, cv. Robusta, is the first organism found to contain aromatic cytokinins. Here, we report the functional characterization of five CHASE-containing histidine kinases from P. × canadensis: PcHK2, PcHK3a, PcHK3b, PcHK4a and PcHK4b. A qPCR analysis revealed high transcript levels of all PcHKs other than PcHK4b across multiple poplar organs. The ligand specificity was determined using a live cell Escherichia coli assay and we provide evidence based on UHPLC-MS/MS data that ribosides can be true ligands. PcHK2 exhibited higher sensitivity to iP-type cytokinins than the other receptors, while PcHK3a and PcHK3b bound these cytokinins much more weakly, because they possess two isoleucine residues that clash with the cytokinin base and destabilize its binding. All receptors display kinase activity but their activation ratios in the presence/absence of cytokinin differ significantly. PcHK4a displays over 400-fold higher kinase activity in the presence of cytokinin, suggesting involvement in strong responses to changes in cytokinin levels. trans-Zeatin was both the most abundant cytokinin in poplar and that with the highest variation in abundance, which is consistent with its strong binding to all five HKs and activation of cytokinin signaling via A-type response regulators. The aromatic cytokinins' biological significance remains unclear, their levels vary diurnally, seasonally, and annually. PcHK3 and PcHK4 display the strongest binding at pH 7.5 and 5.5, respectively, in line with their putative membrane localization in the endoplasmic reticulum and plasma membrane.

• Klíčová slova
• Aromatic cytokinin, Histidine kinase, Hormone, Isoprenoid cytokinin, Poplar, Topolin,
• MeSH
• cytokininy metabolismus   MeSH
• histidinkinasa metabolismus   MeSH
• Populus metabolismus   MeSH
• tandemová hmotnostní spektrometrie MeSH
• terpeny metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• cytokininy MeSH
• histidinkinasa MeSH
• terpeny MeSH

Cytokinins and ethylene control plant development via sensors from the histidine kinase (HK) family. However, downstream signaling pathways for the key phytohormones are distinct. Here we report that not only cytokinin but also ethylene is able to control root apical meristem (RAM) size through activation of the multistep phosphorelay (MSP) pathway. We found that both cytokinin and ethylene-dependent RAM shortening requires ethylene binding to ETR1 and the HK activity of ETR1. The receiver domain of ETR1 interacts with MSP signaling intermediates acting downstream of cytokinin receptors, further substantiating the role of ETR1 in MSP signaling. We revealed that both cytokinin and ethylene induce the MSP in similar and distinct cell types with ETR1-mediated ethylene signaling controlling MSP output specifically in the root transition zone. We identified members of the MSP pathway specific and common to both hormones and showed that ETR1-regulated ARR3 controls RAM size. ETR1-mediated MSP spatially differs from canonical CTR1/EIN2/EIN3 ethylene signaling and is independent of EIN2, indicating that both pathways can be spatially and functionally separated. Furthermore, we demonstrated that canonical ethylene signaling controls MSP responsiveness to cytokinin specifically in the root transition zone, presumably via regulation of ARR10, one of the positive regulators of MSP signaling in Arabidopsis.

• Klíčová slova
• crosstalk, cytokinin, ethylene, root development, signaling,
• MeSH
• Arabidopsis cytologie   účinky léků   růst a vývoj   metabolismus   MeSH
• cytokininy metabolismus   farmakologie   MeSH
• ethyleny metabolismus   farmakologie   MeSH
• fosforylace účinky léků   MeSH
• kořeny rostlin účinky léků   růst a vývoj   MeSH
• proteiny huseníčku metabolismus   MeSH
• receptory buněčného povrchu metabolismus   MeSH
• signální transdukce účinky léků   MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• cytokininy MeSH
• ethylene MeSH Prohlížeč
• ethyleny MeSH
• ETR1 protein, Arabidopsis MeSH Prohlížeč
• proteiny huseníčku MeSH
• receptory buněčného povrchu MeSH

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.

• Klíčová slova
• ASES, cytokinin, photosystem II, senescence, stress, thidiazuron, wheat,
• Publikační typ
• časopisecké články 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

Plant growth and development are critically influenced by unpredictable abiotic factors. To survive fluctuating changes in their environments, plants have had to develop robust adaptive mechanisms. The dynamic and complementary actions of the auxin and cytokinin pathways regulate a plethora of developmental processes, and their ability to crosstalk makes them ideal candidates for mediating stress-adaptation responses. Other crucial signaling molecules responsible for the tremendous plasticity observed in plant morphology and in response to abiotic stress are reactive oxygen species (ROS). Proper temporal and spatial distribution of ROS and hormone gradients is crucial for plant survival in response to unfavorable environments. In this regard, the convergence of ROS with phytohormone pathways acts as an integrator of external and developmental signals into systemic responses organized to adapt plants to their environments. Auxin and cytokinin signaling pathways have been studied extensively. Nevertheless, we do not yet understand the impact on plant stress tolerance of the sophisticated crosstalk between the two hormones. Here, we review current knowledge on the function of auxin and cytokinin in redirecting growth induced by abiotic stress in order to deduce their potential points of crosstalk.

• Klíčová slova
• ROS, abiotic stress, adaptation, auxin, crosstalk, cytokinin, growth,
• MeSH
• biologický transport MeSH
• cytokininy metabolismus   MeSH
• fyziologická adaptace MeSH
• fyziologický stres * MeSH
• fyziologie rostlin * MeSH
• genové regulační sítě MeSH
• kyseliny indoloctové metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin metabolismus   MeSH
• rostliny genetika   metabolismus   MeSH
• signální transdukce MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• cytokininy MeSH
• kyseliny indoloctové MeSH
• regulátory růstu rostlin MeSH

The phytohormone cytokinin is a regulator of numerous processes in plants. In Arabidopsis (Arabidopsis thaliana), the cytokinin signal is perceived by three membrane-located receptors named ARABIDOPSIS HISTIDINE KINASE2 (AHK2), AHK3, and AHK4/CRE1. How the signal is transmitted across the membrane is an entirely unknown process. The three receptors have been shown to operate mostly in a redundant fashion, and very few specific roles have been attributed to single receptors. Using a forward genetic approach, we isolated constitutively active gain-of-function variants of the AHK2 and AHK3 genes, named repressor of cytokinin deficiency2 (rock2) and rock3, respectively. It is hypothesized that the structural changes caused by these mutations in the sensory and adjacent transmembrane domains emulate the structural changes caused by cytokinin binding, resulting in domain motion propagating the signal across the membrane. Detailed analysis of lines carrying rock2 and rock3 alleles revealed how plants respond to locally enhanced cytokinin signaling. Early flowering time, a prolonged reproductive growth phase, and, thereby, increased seed yield suggest that cytokinin regulates various aspects of reproductive growth. In particular, it counteracts the global proliferative arrest, a correlative inhibition of maternal growth by seeds, an as yet unknown activity of the hormone.

• MeSH
• Arabidopsis anatomie a histologie   genetika   fyziologie   MeSH
• časové faktory MeSH
• cytokininy metabolismus   farmakologie   MeSH
• geneticky modifikované rostliny MeSH
• histidinkinasa genetika   MeSH
• květy genetika   fyziologie   ultrastruktura   MeSH
• meristém genetika   fyziologie   ultrastruktura   MeSH
• mikroskopie elektronová rastrovací MeSH
• mutace * MeSH
• polymerázová řetězová reakce s reverzní transkripcí MeSH
• proteiny huseníčku genetika   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin metabolismus   farmakologie   MeSH
• rozmnožování genetika   fyziologie   MeSH
• sekvence aminokyselin MeSH
• sekvenční homologie aminokyselin MeSH
• signální transdukce účinky léků   genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• AHK2 protein, Arabidopsis MeSH Prohlížeč
• AHK3 protein, Arabidopsis MeSH Prohlížeč
• cytokininy MeSH
• histidinkinasa MeSH
• proteiny huseníčku MeSH
• regulátory růstu rostlin MeSH