Yamagami Ayumi, Nakazawa Miki, Matsui Minami, Tujimoto Masafumi, Sakuta Masaaki, Asami Tadao, Nakano Takeshi
Plant Chemical Biology Research Unit, RIKEN Advanced Science Institute, Wako, Saitama, Japan.
Biosci Biotechnol Biochem. 2009 Feb;73(2):415-21. doi: 10.1271/bbb.80752. Epub 2009 Feb 7.
Steroid hormones are conserved between animals and plants as signaling molecules to control growth and development. Plant steroid hormones, brassinosteroids (BRs), appear to play an important role in plant cell elongation. BRs bind to leucine-rich repeat kinase BRASSINOSTEROID-INSENSITIVE 1 (BRI1) localized to the plasma membrane, activate transcription factors in collaboration with cytosolic kinases and phosphatases, and regulate BR-responsive gene expression, but the details regarding the BR signaling pathway from perception to nuclear events remain unknown. In this study we used chemical genetics to identify an evolutionarily conserved transmembrane protein, Brz-insensitive-long hypocotyls 4 (BIL4), and demonstrated its role as a critical component of plant cell elongation occurring upon BR signaling. A dominant mutation, bil4-1D, showed cell elongation in the presence of the BR-specific inhibitor Brz. Brz suppresses expression of the BIL4 gene in wild-type plants, and overexpression of BIL4 in bil4-1D suppresses the BR deficiency caused by Brz. Our results indicate that BIL4 mediates cell elongation on BR signaling.
类固醇激素作为控制生长和发育的信号分子在动物和植物之间是保守的。植物类固醇激素油菜素甾醇（BRs）似乎在植物细胞伸长中起重要作用。BRs与定位于质膜的富含亮氨酸重复序列的激酶油菜素甾醇不敏感1（BRI1）结合，与胞质激酶和磷酸酶协同激活转录因子，并调节BR响应基因的表达，但从感知到核事件的BR信号通路的细节仍然未知。在这项研究中，我们使用化学遗传学来鉴定一种进化上保守的跨膜蛋白，Brz不敏感长下胚轴4（BIL4），并证明了它作为BR信号传导时植物细胞伸长的关键组成部分的作用。一个显性突变体bil4-1D在BR特异性抑制剂Brz存在的情况下表现出细胞伸长。Brz抑制野生型植物中BIL4基因的表达，而在bil4-1D中过表达BIL4可抑制由Brz引起的BR缺乏。我们的结果表明，BIL4介导BR信号传导时的细胞伸长。
