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论文题目:	A Small G Protein as a Novel Component of the Rice Brassinosteroid Signal Transduction
作者:	Zhang Ge, Song Xiaoguang, Guo Hongyan, Wu Yao, Chen Xiaoying, and Fang Rongxiang.
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刊物名称:	Mol Plant
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年份:	2016
影响因子:	6.885
论文下载:	下载地址
摘要:	Brassinosteroids (BRs) are a class of steroid hormones that are essential for plant growth and development. The BR signal transduction pathway in the dicot model plant Arabidopsis is well established, but the components connecting the BR signaling steps in rice have not been fully explored. For example, how the BR signaling is fine-tuned in rice, especially at the BR receptor level, is largely unknown. Here, we show that OsPRA2, a rice small G protein, plays a repressive role in the BR signaling pathway. Lamina inclination, coleoptile elongation, and root inhibition assays indicated that rice plants with suppressed expression of OsPRA2 were more sensitive to exogenously applied brassinolide than wild-type plants. Conversely, rice overexpressing OsPRA2 was less sensitive to exogenous brassinolide. Mechanistic study uncovered that OsPRA2 inhibited the dephosphorylation of, and thus inactivated the transcription factor BRASSINAZOLE-RESISTANT 1 (OsBZR1). More importantly, OsPRA2 was found to co-localize with and directly bind to rice BR receptor BRASSINOSTEROID-INSENSITIVE 1 (OsBRI1) on the plasma membrane. In vitro assays further indicated that OsPRA2 inhibit its autophosphorylation. This OsPRA2-OsBRI1 interaction led to the dissociation of OsBRI1 from its co-receptor OsBAK1, and abolished OsBRI1-mediated phosphorylation of OsBAK1. Together, these results revealed a possible working mechanism of OsPRA2 as a novel negative regulator on OsBRI1 and OsBZR1 in the BR signaling pathway in rice, and further extended the knowledge about the regulatory mechanism of rice BR signaling.