114(P-64) 植物ホルモン、オーキシンの信号伝達阻害剤yokonolidesの単離、構造決定および作用機序(ポスター発表の部)

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Auxin controls cell division, elongation and differentiation and, therefore through its action at the level of the cell, exerts profound effects on growth and development throughout the life of the plant. Yokonolides A (YkA) and B (YkB), spiroketal-macrolide, were isolated from Streptomyces diastatochromogenes B59 in a screen for inhibitors of β-glucoronidase expression under the control of an auxin-responsive promoter in Arabidopsis. YkB inhibit the expression of auxin-inducible genes as shown using native and synthetic auxin promoters as well as using expression profiling of 8300 Arabidopsis gene probes but does not affect expression of an abscisic acid- and a gibberellin A_3-inducible gene. The mechanism of action of YkB is to block AUX/IAA protein degradation; however, YkB is not a general proteasome inhibitor. YkB blocks auxin-dependent cell division and auxin-regulated epinastic growth mediated by auxin-binding protein 1. Gain of function mutants such as shy2-2, slr1, and axr2-1 encoding AUX/IAA transcriptional repressors and loss of function mutants encoding components of the ubiquitin-proteolytic pathway such as axr1-3 and tir1-1, which display increased AUX/IAAs protein stability, are less sensitive to YkB, although axr1 and tir1 mutants were sensitive to MG132, a general proteasome inhibitor, consistent with a site of action downstream of AXR1 and TIR. YkB-treated seedlings displayed similar phenotypes as dominant AUX/IAA mutants. Taken together, these results indicate that YkB acts to block AUX/IAA protein degradation upstream of AXR and TIR, links a shared element upstream of AUX/IAA protein stability to auxin-induced cell division/elongation and to auxin-binding protein 1, and provides a new tool to dissect auxin signal transduction.
天然有機化合物討論会の論文
2003-09-01

114(P-64) 植物ホルモン、オーキシンの信号伝達阻害剤yokonolidesの単離、構造決定および作用機序(ポスター発表の部)

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