27 Aux/IAA リプレッサーとオーキシン初期応答遺伝子発現に対するオーキシンの信号伝達阻害剤 yokonolide B の作用

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Yokonolide B (YkB, also known as A82548A) is a spiroketal-macrolide isolated from Streptomyces diastatochromogenes B59 in a screen for inhibitors of GUS expression under the control of an auxin-inducible promoter in Arabidopsis. YkB inhibits 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 effect expression of an ABA- and a GA-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 the auxin-regulated epinastic growth mediated by auxin-binding protein 1 (ABP1). Arabidopsis seedlings treated with YkB displayed similar phenotypes to gain-of-function shy2-2,axr2-1 and axr1-12 mutants. Furthermore, iaa7/axr2-1 seedlings in which the steady state level of IAA7 is constitutively higher than in wild type is resistant to YkB. These results indicate that YkB acts on a key component in auxin signaling leading to gene regulation, links stability of the Aux/IAA proteins to auxin-induced cell division/elongation and to ABP1,and provides a new tool to dissect auxin signal transduction.
植物化学調節学会の論文
2002-10-31