Nakamura Ayako, Nakajima Naoko, Goda Hideki, Shimada Yukihisa, Hayashi Ken-Ichiro, Nozaki Hiroshi, Asami Tadao, Yoshida Shigeo, Fujioka Shozo
RIKEN Plant Science Center, Tsurumi, Yokohama, Kanagawa 230-0045, Japan.
Plant J. 2006 Jan;45(2):193-205. doi: 10.1111/j.1365-313X.2005.02582.x.
We examined whether auxin/indole-3-acetic acid (Aux/IAA) proteins, which are key players in auxin-signal transduction, are involved in brassinosteroid (BR) responses. iaa7/axr2-1 and iaa17/axr3-3 mutants showed aberrant BR sensitivity and aberrant BR-induced gene expression in an organ-dependent manner. Two auxin inhibitors were tested in terms of BR responses. Yokonolide B inhibited BR responses, whereas p-chlorophenoxyisobutyric acid did not inhibit BR responses. DNA microarray analysis revealed that 108 genes were up-regulated, while only eight genes were down-regulated in iaa7. Among the genes that were up- or down-regulated in axr2, 22% were brassinolide-inducible genes, 20% were auxin-inducible genes, and the majority were sensitive neither to BR nor to auxin. An inhibitor of BR biosynthesis, brassinazole, inhibited auxin induction of the DR5-GUS gene, which consists of a synthetic auxin-response element, a minimum promoter, and a beta-glucuronidase. These results suggest that Aux/IAA proteins function in auxin- and BR-signaling pathways, and that IAA proteins function as the signaling components modulating BR sensitivity in a manner dependent on organ type.
我们研究了生长素信号转导的关键因子生长素/吲哚 - 3 - 乙酸（Aux/IAA）蛋白是否参与油菜素内酯（BR）响应。iaa7/axr2 - 1和iaa17/axr3 - 3突变体表现出异常的BR敏感性以及以器官依赖方式的异常BR诱导基因表达。测试了两种生长素抑制剂对BR响应的影响。洋橄榄内酯B抑制BR响应，而对氯苯氧异丁酸不抑制BR响应。DNA微阵列分析显示，在iaa7中108个基因上调，而只有8个基因下调。在axr2中上调或下调的基因中，22%是油菜素内酯诱导基因，20%是生长素诱导基因，大多数基因对BR和生长素均不敏感。BR生物合成抑制剂油菜素唑抑制了由合成生长素响应元件、最小启动子和β - 葡萄糖醛酸酶组成的DR5 - GUS基因的生长素诱导。这些结果表明，Aux/IAA蛋白在生长素和BR信号通路中发挥作用，并且IAA蛋白作为信号成分，以依赖器官类型的方式调节BR敏感性。
