共查询到20条相似文献,搜索用时 31 毫秒
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Kiba T Yamada H Sato S Kato T Tabata S Yamashino T Mizuno T 《Plant & cell physiology》2003,44(8):868-874
The Arabidopsis thaliana AHK4 histidine kinase (also known as CRE1 or WOL) acts as a cytokinin signal transducer, presumably, in concert with downstream components, such as histidine-containing phosphotransfer factors (AHPs) and response regulators (ARRs), through the histidine-to-aspartate (His-->Asp) phosphorelay. Among 10 members of the type-A ARR family, the cytokinin-induced expression of ARR15 in roots is selectively impaired in the cre1-1 mutant, which carries a mutation in the AHK4 gene, suggesting a link between this type-A response regulator and the AHK4-mediated cytokinin signal transduction in roots. To address this issue further, we characterized a T-DNA insertion mutant of ARR15, and also constructed transgenic lines (referred to as ARR15-ox) that overexpress the ARR15 gene in a manner independent of cytokinin. While the T-DNA insertion mutant (arr15-1) showed no apparent phenotype, the cytokinin-independent overexpression of ARR15 in ARR15-ox plants resulted in a reduced sensitivity toward exogenously applied cytokinin, not only in elongation of roots in plants, but also in green callus formation (or shoot formation) in explants. Cytokinin-induced expressions of certain type-A ARRs were also down-regulated in ARR15-ox plants. These results support the view that ARR15 acts as a repressor that mediates a negative feedback loop in the cytokinin and AHK4-mediated His-->Asp phosphorelay. 相似文献
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Jakub Horák Christopher Grefen Kenneth W Berendzen Achim Hahn York-Dieter Stierhof Bettina Stadelhofer Mark Stahl Csaba Koncz Klaus Harter 《BMC plant biology》2008,8(1):77
Background
The Arabidopsis response regulator 22 (ARR22) is one of two members of a recently defined novel group of two-component system (TCS) elements. TCSs are stimulus perception and response modules of prokaryotic origin, which signal by a His-to-Asp phosphorelay mechanism. In plants, TCS regulators are involved in hormone response pathways, such as those for cytokinin and ethylene. While the functions of the other TCS elements in Arabidopsis, such as histidine kinases (AHKs), histidine-containing phosphotransfer proteins (AHPs) and A-type and B-type ARRs are becoming evident, the role of ARR22 is poorly understood. 相似文献7.
Cytokinins are plant hormones that regulate diverse aspects of plant growth and development. Arabidopsis cytokinin signal transduction utilizes a multi-step two-component signaling (TCS) system by histidyl–aspartidyl phosphorelays.
We here show that phosphorylation of ARR7, an A-type response regulator that acts as a negative regulator of cytokinin signaling,
is required for its function in plants. Phosphorylation of ARR7 is inhibited in vitro by mutation in a putative phospho-accepting
Asp residue into an Asn residue (ARR7D85N). While ectopic expression of ARR7 decreases root-growth inhibition, callus formation, and cytokinin-inducible gene expression, overexpression of ARR7
D85N
at the similar level does not generate these phenotypes. ARR7D85N is localized to the nucleus and the half-life of this mutant protein is similar to that of ARR7 in Arabidopsis mesophyll protoplasts. These results suggest that the phosphorylation of ARR7 is necessary for ARR7-mediated cytokinin response. 相似文献
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A Imamura N Hanaki A Nakamura T Suzuki M Taniguchi T Kiba C Ueguchi T Sugiyama T Mizuno 《Plant & cell physiology》1999,40(7):733-742
His-Asp phosphorelays are evolutionary-conserved powerful biological tactics for intracellular signal transduction. Such a phosphorelay is generally made up of "sensor histidine (His)-kinases", "response regulators", and "histidine-containing (HPt) phosphotransmitters". In the higher plant, Arabidopsis thaliana, results from recent intensive studies suggested that His-Asp phosphorelays may be widely used for propagating environmental stimuli, such as phytohormones (e.g., ethylene and cytokinin). In this study, we first inspected extensively the occurrence of Arabidopsis response regulators in order to compile and characterize them. The results showed that this higher plant has, at least, 14 members of the family of response regulators that can be classified into two distinct subtypes (type-A and type-B), as judged from their structural designs, biochemical properties, and expression profiles. Comparative studies were conducted for each representative (ARR3 and ARR4 for type-A, and ARR10 for type-B). It was suggested that expression of the type-A response regulator is cytokinin-inducible, while that of the type-B response regulator appears to be not. Results from yeast two-hybrid analyses suggested that the type-B response regulator may have an ability to stably interact with a set of HPt phosphotransmitters (AHPs). These and other results will be discussed with special reference to the His-Asp phosphorelay signaling network in Arabidopsis thaliana. 相似文献
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Yan Li Jasmina Kurepa Jan Smalle 《The Plant journal : for cell and molecular biology》2013,74(1):13-24
The plant hormone cytokinin plays essential roles in many aspects of growth and development. The cytokinin signal is transmitted by a multi‐step phosphorelay to the members of two functionally antagonistic classes of Arabidopsis response regulators (ARRs): type B ARRs (response activators) and type A ARRs (negative‐feedback regulators). Previous studies have shown that mutations in AXR1, encoding a subunit of the E1 enzyme in the RUB (related to ubiquitin) modification pathway, lead to decreased cytokinin sensitivity. Here we show that the cytokinin resistance of axr1 seedlings is suppressed by loss of function of the type A ARR family member ARR5. Based on the established role of the RUB pathway in ubiquitin‐dependent proteolysis, these data suggest that AXR1 promotes the cytokinin response by facilitating type A ARR degradation. Indeed, both genetic (axr1 mutants) and chemical (MLN4924) suppression of RUB E1 increased ARR5 stability, suggesting that the ubiquitin ligase that promotes ARR5 proteolysis requires RUB modification for optimal activity. 相似文献
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《Bioscience, biotechnology, and biochemistry》2013,77(2):462-465
The evolutionarily-conserved histidine to aspartate (His-to-Asp) phosphorelay signal transduction is common in both prokaryotes and eukaryotes. Such a phosphorelay system is generally made up of ‘a histidine (His)-kinase’, ‘a histidine-containing phosphotransmitter (HPt)’, and ‘a phospho-accepting response regulator (RR)’. In general, an HPt factor acts as an intermediate in a given multistep His-to-Asp phosphorelay. In Arabidopsis thaliana, this model higher plant has five genes (named AHP1 to AHP5), each of which seems to encode an HPt factor. Recent studies suggested that the His-to-Asp phosphorelay involving the AHP factors is at least partly implicated in signal transduction in response to cytokinin (a plant hormone). Nevertheless, the properties of AHPs have not yet been fully clarified. Here we did comparative studies of all the AHP factors, in terms of (i) expression profiles in plants, (ii) intracellular localization, (iii) ability to acquire a phosphoryl group in vitro, and (iv) ability to interact with the downstream components, ARRs (Arabidopsis response regulators). The results of this study provided us with a comprehensive view at the molecular level for understanding the functions of the AHP phosphotransmitters in the His-to-Asp phosphorelay. 相似文献
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Arabidopsis cytokinin-resistant mutant, cnr1, displays altered auxin responses and sugar sensitivity
Based upon the phenotype of young, dark-grown seedlings, a cytokinin-resistant mutant, cnr1, has been isolated, which displays altered cytokinin- and auxin-induced responses. The mutant seedlings possess short hypocotyls and open apical hooks (in dark), and display agravitropism, hyponastic cotyledons, reduced shoot growth, compact rosettes and short roots with increased adventitious branching and reduced number of root hairs. A number of these features invariably depend upon auxin/cytokinin ratio but the cnr1 mutant retains normal sensitivity towards auxin as well as auxin polar transport inhibitor, TIBA, although upregulation of primary auxin-responsive Aux/IAA genes is reduced. The mutant shows resistance towards cytokinin in hypocotyl/root growth inhibition assays, displays reduced regeneration in tissue cultures (cytokinin response) and decreased sensitivity to cytokinin for anthocyanin accumulation. It is thus conceivable that due to reduced sensitivity to cytokinin, the cnr1 mutant also shows altered auxin response. Surprisingly, the mutant retains normal sensitivity to cytokinin for induction of primary response genes, the type-A Arabidopsis response regulators, although the basal level of their expression was considerably reduced as compared to the wild-type. The zeatin and zeatin riboside levels, as estimated by HPLC, and the cytokinin oxidase activity were comparable in the cnr1 mutant and the wild-type. The hypersensitivity to red light (in hypocotyl growth inhibition assay), partial photomorphogenesis in dark, and hypersensitivity to sugars, are some other features displayed by the cnr1 mutant. The lesion in the cnr1 mutant has been mapped to the top of chromosome 1 where no other previously known cytokinin-resistant mutant has been mapped, indicating that the cnr1 mutant defines a novel locus involved in hormone, light and sugar signalling. 相似文献
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Hana Pospíšilová Jaroslav Nisler Lukáš Spíchal Ivo Frébort 《Journal of Plant Growth Regulation》2009,28(4):321-330
Nebularine is known for its high cytotoxicity in animals, whereas in plants it was originally believed to be an anticytokinin.
In this study we show that in classical cytokinin bioassays, nebularine antagonized cytokinin function in senescence and callus
biotests but not in the Amaranthus bioassay. Nebularine reversed the inhibitory effect of cytokinin on lateral root formation in Arabidopsis seedlings, and when applied alone caused increased lateral root formation and shortening of the main root. Systematic spraying
of Arabidopsis plants with nebularine led to yellowing and formation of purple pigments, local drying, and withering, although younger plants
showed a greater resilience. Comparison of nebularine cytotoxicity in plant and animal cells showed that the growth of tobacco
BY-2 cells was inhibited with only about tenfold lower efficacy than mammalian cell lines. Most importantly, direct binding
assay with Arabidopsis cytokinin receptors AHK3 and CRE1/AHK4 showed that nebularine did not compete for binding with the natural cytokinin trans-zeatin. Although nebularine reduced cytokinin-induced expression of the cytokinin reporter ARR5:GUS in planta, the same effect was observed for DR5:GUS, an auxin reporter gene. Taken together, the results indicate that the mode of action of nebularine does not involve cytokinin
signaling and that the anticytokinin-like effect is rather a consequence of the inhibition of various processes as described
for animal systems. 相似文献
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John Vaughan-Hirsch Emily J. Tallerday Christian A. Burr Charlie Hodgens Samantha L. Boeshore Kevin Beaver Allison Melling Kartika Sari Ian D. Kerr Jan Šimura Karin Ljung Dawei Xu Wanqi Liang Rahul Bhosale G. Eric Schaller Anthony Bishopp Joseph J. Kieber 《The Plant journal : for cell and molecular biology》2021,106(1):159-173
The phytohormone cytokinin plays a significant role in nearly all aspects of plant growth and development. Cytokinin signaling has primarily been studied in the dicot model Arabidopsis, with relatively little work done in monocots, which include rice (Oryza sativa) and other cereals of agronomic importance. The cytokinin signaling pathway is a phosphorelay comprised of the histidine kinase receptors, the authentic histidine phosphotransfer proteins (AHPs) and type-B response regulators (RRs). Two negative regulators of cytokinin signaling have been identified: the type-A RRs, which are cytokinin primary response genes, and the pseudo histidine phosphotransfer proteins (PHPs), which lack the His residue required for phosphorelay. Here, we describe the role of the rice PHP genes. Phylogenic analysis indicates that the PHPs are generally first found in the genomes of gymnosperms and that they arose independently in monocots and dicots. Consistent with this, the three rice PHPs fail to complement an Arabidopsis php mutant (aphp1/ahp6). Disruption of the three rice PHPs results in a molecular phenotype consistent with these elements acting as negative regulators of cytokinin signaling, including the induction of a number of type-A RR and cytokinin oxidase genes. The triple php mutant affects multiple aspects of rice growth and development, including shoot morphology, panicle architecture, and seed fill. In contrast to Arabidopsis, disruption of the rice PHPs does not affect root vascular patterning, suggesting that while many aspects of key signaling networks are conserved between monocots and dicots, the roles of at least some cytokinin signaling elements are distinct. 相似文献
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N. V. Kudryakova V. V. Kusnetsov V. Y. Shtratnikova Olga N. Kulaeva 《Plant Growth Regulation》2008,56(1):21-30
ARR5-gene expression was studied in the course of natural leaf senescence and detached leaf senescence in the dark using Arabidopsis thaliana plants transformed with
the P
ARR5
-GUS gene construct. GUS-activity was measured as a marker of ARR5-gene expression. Chlorophyll and total protein amounts were also estimated to evaluate leaf senescence. Natural leaf senescence
was accompanied by the progressive decline in the GUS-activity in leaves of the 2nd and 3rd nodes studied, and this shift
of GUS-activity was more pronounced than the loss of chlorophyll content. The ability of the ARR5-gene promoter to respond to cytokinin was not eliminated during natural leaf senescence, as was demonstrated by a cytokinin-induced
increase in GUS activity in leaves after their detachment and incubation on benzyladenine
(BA, 5 × 10−6 M) in the dark. Leaf senescence in the dark was associated with the further decrease in the GUS-activity. The ARR5-gene promoter response
to cytokinin was enhanced with the increase of the age of plants, taken as a source of leaves for cytokinin treatments. Hence,
although the expression of the ARR5 gene reduces during natural and dark/detached leaf senescence, the ARR5-gene sensitivity to cytokinin was maintained in both cases and even increased with the leaf age. This data suggest that the
ARR5 gene, which belongs to the type-A negative regulators of plant response to cytokinin, could be a feedback regulator able
to prevent retardation by cytokinin of leaf senescence when it is important for plant life. Growth regulators either reduced
ARR5 gene response to cytokinin during senescence of mature detached leaves
in the dark (SA, meJA, ABA, SP) or increased it (IAA), thus modifying the resulting rate of its expression. 相似文献
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His-Asp phosphorelay signaling: a communication avenue between plants and their environment 总被引:5,自引:0,他引:5
His-Asp phosphorelay systems have been recently discovered in plants and have emerged as some of the most important signaling systems. The phosphorelay systems in plants include components with sensor (His-protein kinase) domains, His-containing phosphotransfer (HPt) domains, and receiver (response regulator) domains. Recent studies implicate phosphorelay systems in sensing and propagating signals from a wide variety of external and/or internal stimuli such as ethylene, cytokinin, and osmolarity. In maize and Arabidopsis, some response regulators are up-regulated by both cytokinins and nitrate. These findings imply that the His-Asp phosphorelay may operate in an inorganic nitrogen-signaling pathway mediated by cytokinin in plants. 相似文献
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The 26S proteasome is a 2-MDa complex with a central role in protein turn over. The 26S proteasome is comprised of one 20S core particle and two 19S regulatory particles (RPs). The RPN12a protein, a non-ATPase subunit of the 19S RP, was previously shown to be involved in cytokinin signaling in Arabidopsis. To further investigate cellular roles of RPN12a, RNAi transgenic plants of RPN12a were constructed. As expected, the 35S:RNAi-RPN12a plants showed cytokinin signaling defective phenotypes, including abnormal formation of leaves and inflorescences. Furthermore, RNAi knock-down transgenic plants exhibited additional unique phenotypes, including concave and heart-shape cotyledons, triple cotyledons, irregular and clustered guard cells, and defects in phyllotaxy, all of which are typical for defective cytokinin signaling. We next examined the mRNA level of cytokinin signaling components, including type-A ARRs, type-B ARRs, and CRFs. The expression of type-A ARRs, encoding negative regulators of cytokinin signaling, was markedly reduced in 35S:RNAi-RPN12a transgenic plants relative to that in wild type plants, while type-B ARRs and CRFs were unaffected. Our results also indicate that in vivo stability of the ARR5 protein, a negative regulator of cytokinin signaling, is mediated by the 26S proteasome complex. These results suggest that RPN12a participates in feedback inhibitory mechanism of cytokinin signaling through modulation of the abundance of ARR5 protein in Arabidopsis. 相似文献