Influence of White Clover Mosaic Potexvirus Infection on the Endogenous Cytokinin Content of Bean

Clarke, Sean F.; McKenzie, Marian J.; Burritt, David J.; Guy, P. L.; Jameson, Paula E.

doi:10.1104/pp.120.2.547

Cited by 38 publications

(25 citation statements)

References 27 publications

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“…PVX caused lesions on infected tobacco leaves, but did not induce expression of the GUS reporter gene from cytokinin oxidase/dehydrogenase 2, 3 or 4 promoters, suggesting that cytokinin oxidase/ dehydrogenases may not be involved in the profound changes in cytokinin metabolism that occur during virus infection in plants (Whenham 1989;Dermastia et al 1995;Dermastia and Ravnikar 1996;Clarke et al 1999;Jameson and Clarke 2002).…”

Section: Discussionmentioning

confidence: 81%

Expression of three Arabidopsis cytokinin oxidase/dehydrogenase promoter::GUS chimeric constructs in tobacco: response to developmental and biotic factors

et al. 2005

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Expression patterns of three Arabidopsis thaliana cytokinin oxidase/dehydrogenase promoter::GUS reporter fusions were investigated in tobacco plants. While cytokinin oxidase/dehydrogenase promoter 2 showed no expression in tobacco, the cytokinin oxidase/dehydrogenase promoters 3 and 4 were active in various tissues throughout development of the tobacco. Recently, the 1452 bp promoter region of AtCKX3 was reported as almost inactive in Arabidopsis. In contrast, the 1627 bp DNA fragment preceding the AtCKX3 coding region drove expression of the reporter GUS gene in various tobacco tissues. The promoter was mainly expressed in tobacco leaves and roots during early stages of development but also later in young flower buds as well as in pollen grains. The construct was particularly active before (hypocotyl region) and during (vascular system) lateral root initiation, supporting the idea of an inhibitory role of active cytokinins in the process of root initiation. The cytokinin oxidase/dehydrogenase promoter 4::GUS fusion in tobacco was shown to share some common (but weaker) expression patterns with promoter 3, namely in the leaves and pollen, but also conferred specific expression in tobacco root cap cells and trichomes. In addition, the response of cytokinin oxidase/dehydrogenase promoter::GUS reporter fusions to infection with the leafy gall-forming bacteria Rhodococcus fascians was examined. While an avirulent strain of R. fascians did not induce expression of any of the cytokinin oxidase/dehydrogenase promoters, the cytokinin oxidase/dehydrogenase promoter 3::GUS fusion was specifically induced at the site of infection when plants were challenged with a virulent strain of R. fascians, providing a possible explanation for the lack of significantly elevated cytokinin concentrations in tissues infected with virulent strains of R. fascians.

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Section: Discussionmentioning

confidence: 81%

Expression of three Arabidopsis cytokinin oxidase/dehydrogenase promoter::GUS chimeric constructs in tobacco: response to developmental and biotic factors

et al. 2005

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“…A link between cytokinin and biotic stress has been suggested because altered cytokinin levels have been observed after pathogen infection (Clarke et al, 1999; Maksimov et al, 2002) and an altered susceptibility to pathogens due to an altered cytokinin status has been observed (Clarke et al, 1998; Pertry et al, 2009). Therefore, it was not surprising that several defense-related genes were found to be regulated by cytokinin in multiple transcriptomic studies, among them three dirigent-like proteins.…”

Section: Genome-wide Analysis Of the Cytokinin-regulated Transcriptomementioning

confidence: 99%

Gene Regulation by Cytokinin in Arabidopsis

Brenner¹,

Ramireddy²,

Heyl³

et al. 2012

Front. Plant Sci.

145

133

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The plant hormone cytokinin realizes at least part of its signaling output through the regulation of gene expression. A great part of the early transcriptional regulation is mediated by type-B response regulators, which are transcription factors of the MYB family. Other transcription factors, such as the cytokinin response factors of the AP2/ERF family, have also been shown to be involved in this process. Additional transcription factors mediate distinct parts of the cytokinin response through tissue- and cell-specific downstream transcriptional cascades. In Arabidopsis, only a single cytokinin response element, to which type-B response regulators bind, has been clearly proven so far, which has 5′-GAT(T/C)-3′ as a core sequence. This motif has served to construct a synthetic cytokinin-sensitive two-component system response element, which is useful for monitoring the cellular cytokinin status. Insight into the extent of transcriptional regulation has been gained by genome-wide gene expression analyses following cytokinin treatment and from plants having an altered cytokinin content or signaling. This review presents a meta analysis of such microarray data resulting in a core list of cytokinin response genes. Genes encoding type-A response regulators displayed the most stable response to cytokinin, but a number of cytokinin metabolism genes (CKX4, CKX5, CYP735A2, UGT76C2) also belong to them, indicating homeostatic mechanisms operating at the transcriptional level. The cytokinin core response genes are also the target of other hormones as well as biotic and abiotic stresses, documenting crosstalk of the cytokinin system with other hormonal and environmental signaling pathways. The multiple links of cytokinin to diverse functions, ranging from control of meristem activity, hormonal crosstalk, nutrient acquisition, and various stress responses, are also corroborated by a compilation of genes that have been repeatedly found by independent gene expression profiling studies. Such functions are, at least in part, supported by genetic studies.

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“…In addition, most plant tissues analyzed contain cytokinin storage and deactivated forms, O-and N-glucosides (Auer, 1997;Vanková, 1999). Glucosides may accumulate to even higher levels than the free bases and ribosides under normal circumstances (Takagi et al, 1989;Frank et al, 2000;Veach et al, 2003) as well as stress conditions (Clarke et al, 1999). In a survey of endogenous cytokinins, some plant families were found to accumulate preferentially O-glucosides, others N-glucosides, and again others relatively high levels of both (Vanková, 1999).…”

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confidence: 99%

Topolins and Hydroxylated Thidiazuron Derivatives Are Substrates of Cytokinin O-Glucosyltransferase with Position Specificity Related to Receptor Recognition

et al. 2005

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Glucosides of trans-zeatin occur widely in plant tissues, formed either by O-glucosylation of the hydroxylated side chain or N-glucosylation of the purine ring structure. O-Glucosylation is stereo-specific: the O-glucosyltransferase encoded by the Phaseolus lunatus ZOG1 gene has high affinity for trans-zeatin as the substrate, whereas the enzyme encoded by the maize (Zea mays) cisZOG1 gene prefers cis-zeatin. Here we show that hydroxylated derivatives of benzyladenine (topolins) are also substrates of ZOG1 and cisZOG1. The m-OH and o-OH derivatives are the preferred substrate of ZOG1 and cisZOG1, respectively. Among the hydroxylated derivatives of thidiazuron tested, the only enzyme/substrate combination resulting in conversion was cisZOG1/(o-OH) thidiazuron. The abilities of these cytokinins to serve as substrates to the glucosyltransferases were in a large part correlated with their biological activities in the P. lunatus callus bioassay, indicating that there may be similarities between cytokinin-binding sites on the enzymes and cytokinin receptors. Further support for this interpretation is provided by cytokinin recognition studies involving the Arabidopsis (Arabidopsis thaliana) CRE1/WOL/AHK4 and maize ZmHK1 receptors. The AHK4 receptor responded to trans-zeatin and m-topolin, while the ZmHK1 receptor responded also to cis-zeatin and o-topolin. Three-dimensional molecular models of the substrates were applied to explain the results.Cytokinins are a group of plant growth regulators with important functions at all phases of plant development, from seed germination to senescence. The natural cytokinins are adenine derivatives, of which trans-zeatin ( Fig. 1) is considered central due to its general occurrence and high activity in bioassays (Skoog and Armstrong, 1970). Also, cis-zeatin ( Fig. 1) and its derivatives have been found in many plant species (discussed in Mok and Mok, 2001), often at relatively high levels; however, cis-zeatin has much lower cytokinin activity than trans-zeatin (Schmitz et al., 1972). Dihydrozeatin, the saturated counterpart of zeatin, also occurs in plant tissues, has high cytokinin activity in bioassays, and is more stable than trans-zeatin due to its resistance to cytokinin oxidases/dehydrogenases (Skoog and Armstrong, 1970;Armstrong, 1994).Although the isoprenoid cytokinins are the major components of endogenous cytokinins, aromatic cytokinins have been known to occur since their isolation from poplar (Horgan et al., 1973). Benzyladenine (BAP; Fig. 1) and its derivatives have now been identified in a number of plant species as minor components of the total cytokinins (Strnad, 1997; Sáenz et al., 2003). The hydroxylated derivatives of BAP were named topolins (Strnad, 1997). Of the topolins, only the meta form exhibits high cytokinin activity (Strnad, 1997;Holub et al., 1998).Many cytokinin derivatives occur in plant tissues (for review, see Auer, 1997). The free bases may represent only a small portion of the total cytokinins, while the corresponding ribosides and especially nucle...

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Influence of White Clover Mosaic Potexvirus Infection on the Endogenous Cytokinin Content of Bean

Cited by 38 publications

References 27 publications

Expression of three Arabidopsis cytokinin oxidase/dehydrogenase promoter::GUS chimeric constructs in tobacco: response to developmental and biotic factors

Expression of three Arabidopsis cytokinin oxidase/dehydrogenase promoter::GUS chimeric constructs in tobacco: response to developmental and biotic factors

Gene Regulation by Cytokinin in Arabidopsis

Topolins and Hydroxylated Thidiazuron Derivatives Are Substrates of Cytokinin O-Glucosyltransferase with Position Specificity Related to Receptor Recognition

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