Two principal growth regulators, cytokinins and ethylene, are known to interact in the regulation of plant growth. However, information about the underlying molecular mechanism and positional specificity of cytokinin/ethylene crosstalk in the control of root growth is scarce. We have identified the spatial specificity of cytokinin-regulated root elongation and root apical meristem (RAM) size, both of which we demonstrate to be dependent on ethylene biosynthesis. Upregulation of the cytokinin biosynthetic gene ISOPENTENYLTRANSFERASE (IPT) in proximal and peripheral tissues leads to both root and RAM shortening. By contrast, IPT activation in distal and inner tissues reduces RAM size while leaving the root length comparable to that of mock-treated controls. We show that cytokinins regulate two steps specific to ethylene biosynthesis: production of the ethylene precursor 1-aminocyclopropane-1-carboxylate (ACC) by ACC SYNTHASEs (ACSs) and its conversion to ethylene by ACC OXIDASEs (ACOs). We describe cytokinin- and ethylene-specific regulation controlling the activity of ACSs and ACOs that are spatially discrete along both proximo/distal and radial root axes. Using direct ethylene measurements, we identify ACO2, ACO3, and ACO4 as being responsible for ethylene biosynthesis and ethylene-regulated root and RAM shortening in cytokinin-treated Arabidopsis. Direct interaction between ARABIDOPSIS RESPONSE REGULATOR 2 (ARR2), a member of the multistep phosphorelay cascade, and the C-terminal portion of ETHYLENE INSENSITIVE 2 (EIN2-C), a key regulator of canonical ethylene signaling, is involved in the cytokinin-induced, ethylene-mediated control of ACO4. We propose tight cooperation between cytokinin and ethylene signaling in the spatially specific regulation of ethylene biosynthesis as a key aspect of the hormonal control of root growth.

• Klíčová slova
• ACC OXIDASE, ACC SYNTHASE, Arabidopsis, cytokinin, ethylene, multistep phosphorelay,
• MeSH
• Arabidopsis * genetika   růst a vývoj   metabolismus   MeSH
• cytokininy * metabolismus   MeSH
• ethyleny * metabolismus   biosyntéza   MeSH
• kořeny rostlin * růst a vývoj   genetika   metabolismus   MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• cytokininy * MeSH
• ethylene MeSH Prohlížeč
• ethyleny * MeSH
• proteiny huseníčku MeSH

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

Plant hormones, pivotal regulators of plant growth, development, and response to environmental cues, have recently emerged as central modulators of epigenetic processes governing gene expression and phenotypic plasticity. This review addresses the complex interplay between plant hormones and epigenetic mechanisms, highlighting the diverse methodologies that have been harnessed to decipher these intricate relationships. We present a comprehensive overview to understand how phytohormones orchestrate epigenetic modifications, shaping plant adaptation and survival strategies. Conversely, we explore how epigenetic regulators ensure hormonal balance and regulate the signalling pathways of key plant hormones. Furthermore, our investigation includes a search for novel genes that are regulated by plant hormones under the control of epigenetic processes. Our review offers a contemporary overview of the epigenetic-plant hormone crosstalk, emphasizing its significance in plant growth, development, and potential agronomical applications.

• Klíčová slova
• Abscisic acid, auxin, cytokinins, epigenetics, ethylene, gibberellins, histone modifications,
• MeSH
• epigeneze genetická * MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin * metabolismus   MeSH
• rostliny genetika   metabolismus   MeSH
• vývoj rostlin genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• regulátory růstu rostlin * MeSH

The root is the below-ground organ of a plant, and it has evolved multiple signaling pathways that allow adaptation of architecture, growth rate, and direction to an ever-changing environment. Roots grow along the gravitropic vector towards beneficial areas in the soil to provide the plant with proper nutrients to ensure its survival and productivity. In addition, roots have developed escape mechanisms to avoid adverse environments, which include direct illumination. Standard laboratory growth conditions for basic research of plant development and stress adaptation include growing seedlings in Petri dishes on medium with roots exposed to light. Several studies have shown that direct illumination of roots alters their morphology, cellular and biochemical responses, which results in reduced nutrient uptake and adaptability upon additive stress stimuli. In this review, we summarize recent methods that allow the study of shaded roots under controlled laboratory conditions and discuss the observed changes in the results depending on the root illumination status.

• Klíčová slova
• D-rootsystem, abiotic stress, auxin, cytokinin, dark-grown roots, direct root illumination, flavonols, light escape mechanism, reactive oxygen species, root growth,
• MeSH
• fyziologická adaptace * MeSH
• kořeny rostlin metabolismus   účinky záření   MeSH
• regulace genové exprese u rostlin účinky záření   MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• rostliny metabolismus   účinky záření   MeSH
• semenáček metabolismus   účinky záření   MeSH
• světlo * MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• rostlinné proteiny MeSH