Nejvíce citovaný článek - PubMed ID 24513716
Arabidopsis ABCG14 protein controls the acropetal translocation of root-synthesized cytokinins
Plasmodiophora brassicae, a soil-borne biotroph, establishes galls as strong physiological sinks on Brassicaceae plants including Brassica napus and Arabidopsis thaliana. We compare transcriptional profiles of phloem dissected from leaf petioles and hypocotyls of healthy and infected B. napus plants. Our results highlight how pathogenesis accompanies phloem-mediated defence responses whilst exerting a strong influence on carbon-nitrogen (C-N) economy. We observe transcriptional changes indicating decreased aliphatic glucosinolate biosynthesis, fluctuating jasmonic acid responses, altered amino acid (AA) and nitrate transport, carbohydrate metabolism and modified cytokinin responses. Changes observed in phloem-dissected from upper versus lower plant organs point to phloem as a conduit in mediating C-N repartitioning, nutrition-related signalling and cytokinin dynamics over long distances during clubroot disease. To assess changes in physiology, we measured AAs, sugars and cytokinins, in phloem exudates from B. napus plants. Despite the decrease in most AA and sucrose levels, isopentyl-type cytokinins increased within infected plants. Furthermore, we employed Arabidopsis for visualising promoter activities of B. napus AA and N transporter orthologues and tested the impact of disrupted cytokinin transport during P. brassicae-induced gall formation using Atabcg14 mutants. Our physiological and microscopy studies show that the host developmental reaction to P. brassicae relies on cytokinin and is accompanied by intense nitrogen and carbon repartitioning. Overall, our work highlights the systemic aspects of host responses that should be taken into account when studying clubroot disease.
- Klíčová slova
- Brassica napus, Plasmodiophora brassicae, clubroot, laser dissection transcriptomics, oilseed rape, phloem,
- MeSH
- aminokyseliny metabolismus MeSH
- Arabidopsis * genetika fyziologie MeSH
- Brassica napus * genetika metabolismus fyziologie parazitologie MeSH
- cyklopentany metabolismus MeSH
- cytokininy metabolismus MeSH
- dusík metabolismus MeSH
- floém * metabolismus genetika MeSH
- glukosinoláty metabolismus MeSH
- listy rostlin genetika metabolismus MeSH
- nemoci rostlin * parazitologie genetika MeSH
- oxylipiny metabolismus MeSH
- Plasmodiophorida * fyziologie MeSH
- regulace genové exprese u rostlin * MeSH
- transkriptom MeSH
- uhlík metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- aminokyseliny MeSH
- cyklopentany MeSH
- cytokininy MeSH
- dusík MeSH
- glukosinoláty MeSH
- jasmonic acid MeSH Prohlížeč
- oxylipiny MeSH
- uhlík MeSH
Even though Sugars Will Eventually be Exported Transporters (SWEETs) have been found in every sequenced plant genome, a comprehensive understanding of their functionality is lacking. In this study, we focused on the SWEET family of barley (Hordeum vulgare). A radiotracer assay revealed that expressing HvSWEET11b in African clawed frog (Xenopus laevis) oocytes facilitated the bidirectional transfer of not only just sucrose and glucose, but also cytokinin. Barley plants harboring a loss-of-function mutation of HvSWEET11b could not set viable grains, while the distribution of sucrose and cytokinin was altered in developing grains of plants in which the gene was knocked down. Sucrose allocation within transgenic grains was disrupted, which is consistent with the changes to the cytokinin gradient across grains, as visualized by magnetic resonance imaging and Fourier transform infrared spectroscopy microimaging. Decreasing HvSWEET11b expression in developing grains reduced overall grain size, sink strength, the number of endopolyploid endosperm cells, and the contents of starch and protein. The control exerted by HvSWEET11b over sugars and cytokinins likely predetermines their synergy, resulting in adjustments to the grain's biochemistry and transcriptome.
- MeSH
- cukry metabolismus MeSH
- cytokininy * metabolismus MeSH
- ječmen (rod) * genetika metabolismus MeSH
- rostlinné proteiny genetika metabolismus MeSH
- sacharosa metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- cukry MeSH
- cytokininy * MeSH
- rostlinné proteiny MeSH
- sacharosa MeSH
C-TERMINALLY ENCODED PEPTIDE (CEP) and cytokinin hormones act over short and long distances to control plant responses to environmental cues. CEP and cytokinin pathway mutants share phenotypes, however, it is not known if these pathways intersect. We show that CEP and cytokinin signalling converge on CEP DOWNSTREAM (CEPD) glutaredoxins to inhibit primary root growth. CEP inhibition of root growth was impaired in mutants defective in trans-zeatin (tZ)-type cytokinin biosynthesis, transport, perception, and output. Concordantly, mutants affected in CEP RECEPTOR 1 showed reduced root growth inhibition in response to tZ, and altered levels of tZ-type cytokinins. Grafting and organ-specific hormone treatments showed that tZ-mediated root growth inhibition involved CEPD activity in roots. By contrast, root growth inhibition by CEP depended on shoot CEPD function. The results demonstrate that CEP and cytokinin pathways intersect, and utilise signalling circuits in separate organs involving common glutaredoxin genes to coordinate root growth.
- MeSH
- Arabidopsis * metabolismus MeSH
- cytokininy * metabolismus MeSH
- glutaredoxiny genetika metabolismus MeSH
- kořeny rostlin metabolismus MeSH
- peptidy metabolismus MeSH
- regulace genové exprese u rostlin MeSH
- výhonky rostlin metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- cytokininy * MeSH
- glutaredoxiny MeSH
- peptidy MeSH
Cytokinin and auxin are plant hormones that coordinate many aspects of plant development. Their interactions in plant underground growth are well established, occurring at the levels of metabolism, signaling, and transport. Unlike many plant hormone classes, cytokinins are represented by more than one active molecule. Multiple mutant lines, blocking specific parts of cytokinin biosynthetic pathways, have enabled research in plants with deficiencies in specific cytokinin-types. While most of these mutants have confirmed the impeding effect of cytokinin on root growth, the ipt29 double mutant instead surprisingly exhibits reduced primary root length compared to the wild type. This mutant is impaired in cis-zeatin (cZ) production, a cytokinin-type that had been considered inactive in the past. Here we have further investigated the intriguing ipt29 root phenotype, opposite to known cytokinin functions, and the (bio)activity of cZ. Our data suggest that despite the ipt29 short-root phenotype, cZ application has a negative impact on primary root growth and can activate a cytokinin response in the stele. Grafting experiments revealed that the root phenotype of ipt29 depends mainly on local signaling which does not relate directly to cytokinin levels. Notably, ipt29 displayed increased auxin levels in the root tissue. Moreover, analyses of the differential contributions of ipt2 and ipt9 to the ipt29 short-root phenotype demonstrated that, despite its deficiency on cZ levels, ipt2 does not show any root phenotype or auxin homeostasis variation, while ipt9 mutants were indistinguishable from ipt29. We conclude that IPT9 functions may go beyond cZ biosynthesis, directly or indirectly, implicating effects on auxin homeostasis and therefore influencing plant growth.
- Klíčová slova
- auxin, cytokinin, metabolism, plant hormones, root growth,
- Publikační typ
- časopisecké články MeSH
Molecular responses of plants to natural phytotoxins comprise more general and compound-specific mechanisms. How phytotoxic chalcones and other flavonoids inhibit seedling growth was widely studied, but how they interfere with seed germination is largely unknown. The dihydrochalcone and putative allelochemical myrigalone A (MyA) inhibits seed germination and seedling growth. Transcriptome (RNAseq) and hormone analyses of Lepidium sativum seed responses to MyA were compared to other bioactive and inactive compounds. MyA treatment of imbibed seeds triggered the phased induction of a detoxification programme, altered gibberellin, cis-(+)-12-oxophytodienoic acid and jasmonate metabolism, and affected the expression of hormone transporter genes. The MyA-mediated inhibition involved interference with the antioxidant system, oxidative signalling, aquaporins and water uptake, but not uncoupling of oxidative phosphorylation or p-hydroxyphenylpyruvate dioxygenase expression/activity. MyA specifically affected the expression of auxin-related signalling genes, and various transporter genes, including for auxin transport (PIN7, ABCG37, ABCG4, WAT1). Responses to auxin-specific inhibitors further supported the conclusion that MyA interferes with auxin homeostasis during seed germination. Comparative analysis of MyA and other phytotoxins revealed differences in the specific regulatory mechanisms and auxin transporter genes targeted to interfere with auxin homestasis. We conclude that MyA exerts its phytotoxic activity by multiple auxin-dependent and independent molecular mechanisms.
- Klíčová slova
- ATP-binding cassette (ABC) transporter, PIN auxin efflux carrier, WRKY transcription factors, allelochemical and allelopathy, aquaporin-mediated water transport, auxin transport and homeostasis, cis-(+)-12-oxophytodienoic acid (OPDA) reductase, gibberellin metabolism, phytotoxin detoxification programme, seed germination,
- MeSH
- chalkonoidy MeSH
- homeostáza MeSH
- hormony metabolismus MeSH
- klíčení * genetika MeSH
- kyseliny indoloctové metabolismus MeSH
- Lepidium sativum * metabolismus MeSH
- regulace genové exprese u rostlin MeSH
- regulátory růstu rostlin metabolismus farmakologie MeSH
- semena rostlinná genetika MeSH
- semenáček metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- chalkonoidy MeSH
- hormony MeSH
- kyseliny indoloctové MeSH
- myrigalone A MeSH Prohlížeč
- 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
Growing evidence has highlighted the essential role of plant hormones, notably, cytokinins (CKs), in nitrogen-fixing symbiosis, both at early and late nodulation stages1,2. Despite numerous studies showing the central role of CK in nodulation, the importance of CK transport in the symbiosis is unknown. Here, we show the role of ABCG56, a full-size ATP-binding cassette (ABC) transporter in the early stages of the nodulation. MtABCG56 is expressed in roots and nodules and its messenger RNA levels increase upon treatment with symbiotic bacteria, isolated Nod factor and CKs, accumulating within the epidermis and root cortex. MtABCG56 exports bioactive CKs in an ATP-dependent manner over the plasma membrane and its disruption results in an impairment of nodulation. Our data indicate that ABCG-mediated cytokinin transport is important for proper establishment of N-fixing nodules.
- MeSH
- ABC transportér, podrodina G genetika metabolismus MeSH
- biologický transport MeSH
- cytokininy metabolismus MeSH
- fixace dusíku MeSH
- Medicago truncatula genetika mikrobiologie MeSH
- regulátory růstu rostlin metabolismus MeSH
- Rhizobium fyziologie MeSH
- rostlinné proteiny genetika metabolismus MeSH
- symbióza genetika MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- ABC transportér, podrodina G MeSH
- cytokininy MeSH
- regulátory růstu rostlin 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
Cytokinins are plant hormones, derivatives of adenine with a side chain at the N6-position. They are involved in many physiological processes. While the metabolism of trans-zeatin and isopentenyladenine, which are considered to be highly active cytokinins, has been extensively studied, there are others with less obvious functions, such as cis-zeatin, dihydrozeatin, and aromatic cytokinins, which have been comparatively neglected. To help explain this duality, we present a novel hypothesis metaphorically comparing various cytokinin forms, enzymes of CK metabolism, and their signalling and transporter functions to the comics superheroes Hulk and Deadpool. Hulk is a powerful but short-lived creation, whilst Deadpool presents a more subtle and enduring force. With this dual framework in mind, this review compares different cytokinin metabolites, and their biosynthesis, translocation, and sensing to illustrate the different mechanisms behind the two CK strategies. This is put together and applied to a plant developmental scale and, beyond plants, to interactions with organisms of other kingdoms, to highlight where future study can benefit the understanding of plant fitness and productivity.
- Klíčová slova
- Hulk/Deadpool, aromatic cytokinins, cis-zeatin, cytokinin biosynthesis, cytokinin oxidase/dehydrogenase, cytokinin signalling, cytokinin transport, cytokinins, isopentenyl transferase,
- MeSH
- Arabidopsis metabolismus MeSH
- biologické modely MeSH
- biologický transport MeSH
- biotest MeSH
- cytokininy metabolismus MeSH
- fyziologie rostlin * MeSH
- glykosylace MeSH
- hydrolýza MeSH
- kinetika MeSH
- kinetin metabolismus MeSH
- oxidoreduktasy metabolismus MeSH
- regulátory růstu rostlin metabolismus MeSH
- rostliny metabolismus MeSH
- signální transdukce * MeSH
- vazba proteinů MeSH
- zeatin analogy a deriváty MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
- Názvy látek
- cytokinin oxidase MeSH Prohlížeč
- cytokininy MeSH
- dihydrozeatin MeSH Prohlížeč
- kinetin MeSH
- oxidoreduktasy MeSH
- regulátory růstu rostlin MeSH
- zeatin MeSH
Cytokinin (CK) N-glucosides are the most abundant group of CK metabolites in many species; however, their physiological role in planta was for a long time perceived as irreversible storage CK forms only. Recently, a comprehensive screen showed that only vascular plants form CK N-glucosides in contrast to mosses, algae, and fungi. The formation of CK N-glucosides as biologically inactive CK conjugates thus represents an evolutionarily young mechanism for deactivation of CK bases. Even though CK N-glucosides are not biologically active themselves due to their inability to activate the CK perception system, new data on CK N-glucoside metabolism show that trans-zeatin (tZ) N7- and N9-glucosides are metabolized in vivo, efficiently releasing free CK bases that are most probably responsible for the biological activities observed in a number of bioassays. Moreover, CK N-glucosides' subcellular localization as well as their abundance in xylem both point to their possible plasma membrane transport and indicate a role also as CK transport forms. Identification of the enzyme(s) responsible for the hydrolysis of tZ N7- and N9-glucosides, as well as the discovery of putative CK N-glucoside plasma membrane transporter, would unveil important parts of the overall picture of CK metabolic interconversions and their physiological importance.
