Molecular Characterization of Cytokinin-Responsive Histidine Kinases in Maize. Differential Ligand Preferences and Response to cis-Zeatin

Yonekura‐Sakakibara, Keiko; Kojima, Mikiko; Yamaya, Tomoyuki; Sakakibara, Hitoshi

doi:10.1104/pp.103.037176

Cited by 188 publications

(175 citation statements)

References 46 publications

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“…The Arabidopsis genome harbors 3 loci for the cytokinin receptors, CRE1/WOL, AHK2, and AHK3, all of which belong to the superfamily of 2-component regulators (12,24). The CRE cytokinin receptor gene family has been shown to be conserved between the non-woody plant species Arabidopsis, rice, and maize (25,26).…”

Section: The Cre Cytokinin Receptor Gene Family Is Conserved Betweenmentioning

confidence: 99%

Cytokinin signaling regulates cambial development in poplar

Nieminen

Immanen²,

Laxell³

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

256

208

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Although a substantial proportion of plant biomass originates from the activity of vascular cambium, the molecular basis of radial plant growth is still largely unknown. To address whether cytokinins are required for cambial activity, we studied cytokinin signaling across the cambial zones of 2 tree species, poplar (Populus trichocarpa) and birch (Betula pendula). We observed an expression peak for genes encoding cytokinin receptors in the dividing cambial cells. We reduced cytokinin levels endogenously by engineering transgenic poplar trees (P. tremula ؋ tremuloides) to express a cytokinin catabolic gene, Arabidopsis CYTOKININ OXI-DASE 2, under the promoter of a birch CYTOKININ RECEPTOR 1 gene. Transgenic trees showed reduced concentration of a biologically active cytokinin, correlating with impaired cytokinin responsiveness. In these trees, both apical and radial growth was compromised. However, radial growth was more affected, as illustrated by a thinner stem diameter than in WT at same height. To dissect radial from apical growth inhibition, we performed a reciprocal grafting experiment. WT scion outgrew the diameter of transgenic stock, implicating cytokinin activity as a direct determinant of radial growth. The reduced radial growth correlated with a reduced number of cambial cell layers. Moreover, expression of a cytokinin primary response gene was dramatically reduced in the thin-stemmed transgenic trees. Thus, a reduced level of cytokinin signaling is the primary basis for the impaired cambial growth observed. Together, our results show that cytokinins are major hormonal regulators required for cambial development.cambial activity ͉ cambium ͉ secondary development ͉ Populus ͉ CYTOKININ OXIDASE

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Section: The Cre Cytokinin Receptor Gene Family Is Conserved Betweenmentioning

confidence: 99%

Cytokinin signaling regulates cambial development in poplar

Nieminen

Immanen²,

Laxell³

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

256

208

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“…Quantitative Real-Time PCR RNA Extraction and cDNA synthesis were performed as described previously (Yonekura-Sakakibara et al, 2004). The developmental stage of each organ used for analysis was as described previously (YonekuraSakakibara et al, 2007).…”

Section: Evaluation Of T-dna Insertion Mutantsmentioning

confidence: 99%

Comprehensive Flavonol Profiling and Transcriptome Coexpression Analysis Leading to Decoding Gene–Metabolite Correlations inArabidopsis

et al. 2008

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To complete the metabolic map for an entire class of compounds, it is essential to identify gene-metabolite correlations of a metabolic pathway. We used liquid chromatography-mass spectrometry (LC-MS) to identify the flavonoids produced by Arabidopsis thaliana wild-type and flavonoid biosynthetic mutant lines. The structures of 15 newly identified and eight known flavonols were deduced by LC-MS profiling of these mutants. Candidate genes presumably involved in the flavonoid pathway were delimited by transcriptome coexpression network analysis using public databases, leading to the detailed analysis of two flavonoid pathway genes, UGT78D3 (At5g17030) and RHM1 (At1g78570). The levels of flavonol 3-Oarabinosides were reduced in ugt78d3 knockdown mutants, suggesting that UGT78D3 is a flavonol arabinosyltransferase. Recombinant UGT78D3 protein could convert quercetin to quercetin 3-O-arabinoside. The strict substrate specificity of UGT78D3 for flavonol aglycones and UDP-arabinose indicate that UGT78D3 is a flavonol arabinosyltransferase. A comparison of flavonol profile in RHM knockout mutants indicated that RHM1 plays a major role in supplying UDPrhamnose for flavonol modification. The rate of flavonol 3-O-glycosylation is more affected than those of 7-O-glycosylation by the supply of UDP-rhamnose. The precise identification of flavonoids in conjunction with transcriptomics thus led to the identification of a gene function and a more complete understanding of a plant metabolic network.

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“…However, the riboside trans-zeatin riboside (tZR) did compete with radiolabeled tZ for binding to E. coli cells expressing CRE1, albeit with less affinity than unlabeled tZ (12). In many plant species, tZ is more abundant and more active than cZ (16); however, in some species, cZ is an abundant and biologically active cytokinin (17,18).In Dictyostelium discoideum, Agrobacterium tumefaciens, and plant tissues transformed with A. tumefaciens, cytokinins are produced by isopentenylation of AMP. This reaction is catalyzed by adenylate isopentenyltransferases (AMP IPTs) (19)(20)(21)(22).…”

mentioning

confidence: 99%

Roles of Arabidopsis ATP/ADP isopentenyltransferases and tRNA isopentenyltransferases in cytokinin biosynthesis

Miyawaki

Tarkowski

Matsumoto-Kitano

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

509

536

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Cytokinins, which are central regulators of cell division and differentiation in plants, are adenine derivatives carrying an isopentenyl side chain that may be hydroxylated. Plants have two classes of isopentenyltransferases (IPTs) acting on the adenine moiety: ATP͞ ADP isopentenyltransferases (in Arabidopsis thaliana, AtIPT1, 3, 4 -8) and tRNA IPTs (in Arabidopsis, AtIPT2 and 9). ATP͞ADP IPTs are likely to be responsible for the bulk of cytokinin synthesis, whereas it is thought that cis-zeatin (cZ)-type cytokinins are produced possibly by degradation of cis-hydroxy isopentenyl tRNAs, which are formed by tRNA IPTs. However, these routes are largely hypothetical because of lack of in vivo evidence, because the critical experiment necessary to verify these routes, namely the production and analysis of mutants lacking AtIPTs, has not yet been described. We isolated null mutants for all members of the ATP͞ADP IPT and tRNA IPT gene families in Arabidopsis. Notably, our work demonstrates that the atipt1 3 5 7 quadruple mutant possesses severely decreased levels of isopentenyladenine and trans-zeatin (tZ), and their corresponding ribosides, ribotides, and glucosides, and is retarded in its growth. In contrast, these mutants possessed increased levels of cZ-type cytokinins. The atipt2 9 double mutant, on the other hand, lacked isopentenyl-and cishydroxy isopentenyl-tRNA, and cZ-type cytokinins. These results indicate that whereas ATP͞ADP IPTs are responsible for the bulk of isopentenyladenine-and tZ-type cytokinin synthesis, tRNA IPTs are required for cZ-type cytokinin production. This work clarifies the long-standing questions of the biosynthetic routes for isopentenyladenine-, tZ-, and cZ-type cytokinin production.S ince the discovery of cytokinins as inducers of plant cell division (1) and differentiation (2), they have been recognized as central regulators of plant development (3). Cytokinins also increase nutrient sink strength, delay senescence, stimulate outgrowth from lateral buds, and inhibit cell elongation (4). The important roles for cytokinins in cell division were verified by overexpression of genes for cytokinin-degrading enzymes (cytokinin oxidases, CKXs) (5-7) and by examination of single and higher-order cytokinin-receptor null mutants (8-10).Most naturally occurring cytokinins are N 6 -isopentenyladenine (iP) derivatives. iP carries an unmodified isopentenyl side chain, whereas trans-zeatin (tZ) and cis-zeatin (cZ) carry hydroxylated side chains. Cytokinins exist in free-base, riboside, and ribotide forms, with varying degrees of biological activity. Cytokinins also may be modified in several ways. For example, the N7 and N9 positions of the adenine moiety of cytokinins may be glucosylated to form N-glucosides. Alternatively, the hydroxyl group of tZ and cZ may be glucosylated or xylosylated to form zeatin-O-glucosides or zeatin-O-xylosides. N-and O-glycosides are biologically inactive (3).Experimental evidence demonstrates that free-base cytokinins are biologically active. For example, iP (11) and t...

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Molecular Characterization of Cytokinin-Responsive Histidine Kinases in Maize. Differential Ligand Preferences and Response to cis-Zeatin

Cited by 188 publications

References 46 publications

Cytokinin signaling regulates cambial development in poplar

Cytokinin signaling regulates cambial development in poplar

Comprehensive Flavonol Profiling and Transcriptome Coexpression Analysis Leading to Decoding Gene–Metabolite Correlations inArabidopsis

Roles of Arabidopsis ATP/ADP isopentenyltransferases and tRNA isopentenyltransferases in cytokinin biosynthesis

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