Common centaury (Centaurium eryhtraea Rafn) is a medicinal plant species with vigorous morphogenic potential in vitro. The process of spontaneous shoot regeneration in a solid root culture is characteristic for this plant species. In this context, the aim of this work was to investigate the dynamic changes of endogenous phytohormones and carbohydrates content in root explants at different time points (0, 2, 4, 7, 14, 21, 28, and 60 days) during spontaneous centaury morphogenesis in vitro. Detailed analysis of cytokinins (CKs) showed that trans-zeatin (tZ) was the major bioactive CK at all time points. The corresponding riboside, tZ9R, was also determined in the majority of the identified transport forms, at all time-points. Further analysis of endogenous auxin revealed a significant increase in endogenous indole-3-acetic acid (IAA) after 21 days, when a huge jump in the ratio of IAA/bioactive CKs was also observed. The maximum total soluble sugar content was measured after 14 days, while a significant decrease was determined after 21 days, when the first regenerated adventitious shoots appeared. This undoubtedly indicates an increased energy requirement prior to the actual regeneration of the shoots. The obtained results indicate that the period from day 14 to day 21 involves the most dramatic disturbances in endogenous bioactive CKs, IAA and carbohydrate balance, which are very important and valuable factors for the onset of shoot regeneration.

• Klíčová slova
• auxin, centaury, cytokinin, morphogenesis, phytohormone, soluble sugars,
• Publikační typ
• časopisecké články MeSH

The genomes of charophyte green algae, close relatives of land plants, typically do not show signs of developmental regulation by phytohormones. However, scattered reports of endogenous phytohormone production in these organisms exist. We performed a comprehensive analysis of multiple phytohormones in Viridiplantae, focusing mainly on charophytes. We show that auxin, salicylic acid, ethylene and tRNA-derived cytokinins including cis-zeatin are found ubiquitously in Viridiplantae. By contrast, land plants but not green algae contain the trans-zeatin type cytokinins as well as auxin and cytokinin conjugates. Charophytes occasionally produce jasmonates and abscisic acid, whereas the latter is detected consistently in land plants. Several phytohormones are excreted into the culture medium, including auxin by charophytes and cytokinins and salicylic acid by Viridiplantae in general. We note that the conservation of phytohormone biosynthesis and signaling pathways known from angiosperms does not match the capacity for phytohormone biosynthesis in Viridiplantae. Our phylogenetically guided analysis of established algal cultures provides an important insight into phytohormone biosynthesis and metabolism across Streptophyta.

• MeSH
• biologická evoluce MeSH
• Chlorophyta metabolismus   genetika   MeSH
• cyklopentany metabolismus   MeSH
• cytokininy * metabolismus   MeSH
• ethyleny metabolismus   MeSH
• fylogeneze * MeSH
• kyselina abscisová metabolismus   MeSH
• kyselina salicylová metabolismus   MeSH
• kyseliny indoloctové * metabolismus   MeSH
• oxylipiny metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin * metabolismus   MeSH
• signální transdukce MeSH
• Viridiplantae metabolismus   genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cyklopentany MeSH
• cytokininy * MeSH
• ethylene MeSH Prohlížeč
• ethyleny MeSH
• jasmonic acid MeSH Prohlížeč
• kyselina abscisová MeSH
• kyselina salicylová MeSH
• kyseliny indoloctové * MeSH
• oxylipiny MeSH
• regulátory růstu rostlin * MeSH

De novo shoot organogenesis (DNSO) is a procedure commonly used for the in vitro regeneration of shoots from a variety of plant tissues. Shoot regeneration occurs on nutrient media supplemented with the plant hormones cytokinin (CK) and auxin, which play essential roles in this process, and genes involved in their signaling cascades act as master regulators of the different phases of shoot regeneration. In the last 20 years, the genetic regulation of DNSO has been characterized in detail. However, as of today, the CK and auxin signaling events associated with shoot regeneration are often interpreted as a consequence of these hormones simply being present in the regeneration media, whereas the roles for their prior uptake and transport into the cultivated plant tissues are generally overlooked. Additionally, sucrose, commonly added to the regeneration media as a carbon source, plays a signaling role and has been recently shown to interact with CK and auxin and to affect the efficiency of shoot regeneration. In this review, we provide an integrative interpretation of the roles for CK and auxin in the process of DNSO, adding emphasis on their uptake from the regeneration media and their interaction with sucrose present in the media to their complex signaling outputs that mediate shoot regeneration.

• Klíčová slova
• DNSO, auxin, cytokinin, de novo shoot organogenesis, gene regulatory network, hormone uptake, shoot regeneration, sucrose, transport,
• MeSH
• cytokininy metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• organogeneze rostlin * MeSH
• regulátory růstu rostlin metabolismus   MeSH
• výhonky rostlin cytologie   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• cytokininy MeSH
• kyseliny indoloctové MeSH
• regulátory růstu rostlin MeSH

It has been known for quite some time that cytokinins, hormones typical of plants, are also produced and metabolized in bacteria. Most bacteria can only form the tRNA-bound cytokinins, but there are examples of plant-associated bacteria, both pathogenic and beneficial, that actively synthesize cytokinins to interact with their host. Similar to plants, bacteria produce diverse cytokinin metabolites, employing corresponding metabolic pathways. The identification of genes encoding the enzymes involved in cytokinin biosynthesis and metabolism facilitated their detailed characterization based on both classical enzyme assays and structural approaches. This review summarizes the present knowledge on key enzymes involved in cytokinin biosynthesis, modifications, and degradation in bacteria, and discusses their catalytic properties in relation to the presence of specific amino acid residues and protein structure.

• Klíčová slova
• CKX, LOG, cytochrome P450 monooxygenase, cytokinin, isopentenyl transferase, tRNA modification,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

In the complex process of homeostasis of phytohormones cytokinins (CKs), O-glucosylation catalyzed by specific O-glucosyltransferases represents one of important mechanisms of their reversible inactivation. The CK O-glucosyltransferases belong to a highly divergent and polyphyletic multigene superfamily of glycosyltransferases, of which subfamily 1 containing UDP-glycosyltransferases (UGTs) is the largest in the plant kingdom. It contains recently discovered O and P subfamilies present in higher plant species but not in Arabidopsis thaliana. The cis-zeatin O-glucosyltransferase (cisZOG) genes belong to the O subfamily encoding a stereo-specific O-glucosylation of cis-zeatin-type CKs. We studied different homologous genes, their domains and motifs, and performed a phylogenetic reconstruction to elucidate the plant evolution of the cisZOG gene. We found that the cisZOG homologs do not form a clear separate clade, indicating that diversification of the cisZOG gene took place after the diversification of the main angiosperm families, probably within genera or closely related groups. We confirmed that the gene(s) from group O is(are) not present in A. thaliana and is(are) also missing in the family Brassicaceae. However, cisZOG or its metabolites are found among Brassicaceae clade, indicating that remaining genes from other groups (UGT73-group D and UGT85-group G) are able, at least in part, to substitute the function of group O lost during evolution. This study is the first detailed evolutionary evaluation of relationships among different plant ZOGs within angiosperms.

• MeSH
• Brassicaceae genetika   MeSH
• cytokininy genetika   MeSH
• glukosyltransferasy genetika   MeSH
• Magnoliopsida * genetika   metabolismus   MeSH
• regulace genové exprese u rostlin * MeSH
• rostlinné proteiny genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cytokininy MeSH
• glukosyltransferasy MeSH
• rostlinné proteiny MeSH

Cytokinins are a class of phytohormones, signalling molecules specific to plants. They act as regulators of diverse physiological processes in complex signalling pathways. It is necessary for plants to continuously regulate cytokinin distribution among different organs, tissues, cells, and compartments. Such regulatory mechanisms include cytokinin biosynthesis, metabolic conversions and degradation, as well as cytokinin membrane transport. In our review, we aim to provide a thorough picture of the latter. We begin by summarizing cytokinin structures and physicochemical properties. Then, we revise the elementary thermodynamic and kinetic aspects of cytokinin membrane transport. Next, we review which membrane-bound carrier proteins and protein families recognize cytokinins as their substrates. Namely, we discuss the families of "equilibrative nucleoside transporters" and "purine permeases", which translocate diverse purine-related compounds, and proteins AtPUP14, AtABCG14, AtAZG1, and AtAZG2, which are specific to cytokinins. We also address long-distance cytokinin transport. Putting all these pieces together, we finally discuss cytokinin distribution as a net result of these processes, diverse in their physicochemical nature but acting together to promote plant fitness.

• Klíčová slova
• ABCG14, AZG1, AZG2, PUP14, cytokinin distribution, cytokinin hydrophobicity, cytokinin transport, membrane transport,
• MeSH
• Arabidopsis metabolismus   MeSH
• biologický transport MeSH
• buněčná membrána metabolismus   MeSH
• cytokininy metabolismus   MeSH
• homeostáza MeSH
• hydrofobní a hydrofilní interakce MeSH
• kinetika MeSH
• kořeny rostlin metabolismus   MeSH
• membránové transportní proteiny metabolismus   MeSH
• proteiny huseníčku genetika   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin metabolismus   MeSH
• signální transdukce fyziologie   MeSH
• termodynamika MeSH
• výhonky rostlin metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• cytokininy MeSH
• membránové transportní proteiny MeSH
• proteiny huseníčku MeSH
• regulátory růstu rostlin MeSH