Department of Agricultural Biotechnology, Seoul National University, Seoul 151-921, Korea.
Plant J. 2011 Mar;65(6):907-21. doi: 10.1111/j.1365-313X.2010.04477.x. Epub 2011 Feb 18.
Jasmonates play important roles in development, stress responses and defense in plants. Here, we report the results of a study using a functional genomics approach that identified a rice basic helix-loop-helix domain gene, OsbHLH148, that conferred drought tolerance as a component of the jasmonate signaling module in rice. OsbHLH148 transcript levels were rapidly increased by treatment with methyl jasmonate (MeJA) or abscisic acid, and abiotic stresses including dehydration, high salinity, low temperature and wounding. Transgenic over-expression of OsbHLH148 in rice confers plant tolerance to drought stress. Expression profiling followed by DNA microarray and RNA gel-blot analyses of transgenic versus wild-type rice identified genes that are up-regulated by OsbHLH148 over-expression. These include OsDREB and OsJAZ genes that are involved in stress responses and the jasmonate signaling pathway, respectively. OsJAZ1, a rice ZIM domain protein, interacted with OsbHLH148 in yeast two-hybrid and pull-down assays, but it interacted with the putative OsCOI1 only in the presence of coronatine. Furthermore, the OsJAZ1 protein was degraded by rice and Arabidopsis extracts in the presence of coronatine, and its degradation was inhibited by MG132, a 26S proteasome inhibitor, suggesting 26S proteasome-mediated degradation of OsJAZ1 via the SCF(OsCOI1) complex. The transcription level of OsJAZ1 increased upon exposure of rice to MeJA. These results show that OsJAZ1 could act as a transcriptional regulator of the OsbHLH148-related jasmonate signaling pathway leading to drought tolerance. Thus, our study suggests that OsbHLH148 acts on an initial response of jasmonate-regulated gene expression toward drought tolerance, constituting the OsbHLH148-OsJAZ-OsCOI1 signaling module in rice.
茉莉酸在植物的发育、应激反应和防御中起着重要作用。在这里，我们报告了一项使用功能基因组学方法的研究结果，该方法鉴定了一个水稻碱性螺旋-环-螺旋结构域基因 OsbHLH148，它作为茉莉酸信号模块的一个组成部分赋予水稻耐旱性。OsbHLH148 的转录本水平在茉莉酸甲酯（MeJA）或脱落酸处理后迅速增加，并且在非生物胁迫下包括脱水、高盐、低温和创伤。在水稻中过表达 OsbHLH148 赋予植物耐旱性。对转基因与野生型水稻的表达谱进行 DNA 微阵列和 RNA 凝胶印迹分析，鉴定出由 OsbHLH148 过表达上调的基因。这些基因包括 OsDREB 和 OsJAZ 基因，它们分别参与应激反应和茉莉酸信号通路。OsJAZ1，一种水稻 ZIM 结构域蛋白，在酵母双杂交和拉下测定中与 OsbHLH148 相互作用，但只有在存在冠菌素的情况下才与假定的 OsCOI1 相互作用。此外，在冠菌素存在的情况下，水稻和拟南芥提取物降解 OsJAZ1 蛋白，并且 26S 蛋白酶体抑制剂 MG132 抑制其降解，表明 OsJAZ1 通过 SCF(OsCOI1) 复合物进行 26S 蛋白酶体介导的降解。暴露于 MeJA 后，OsJAZ1 的转录水平增加。这些结果表明，OsJAZ1 可以作为 OsbHLH148 相关茉莉酸信号通路的转录调节剂，导致耐旱性。因此，我们的研究表明，OsbHLH148 作用于茉莉酸调控基因表达对干旱胁迫的初始反应，构成水稻中的 OsbHLH148-OsJAZ-OsCOI1 信号模块。
