东北地理所解析MAX2在介导植物抗旱及ABA反应中重要调节功能

中科院东北地理与农业生态研究所卜庆云实验室发现，MAX2能正调控植物的抗旱反应，表现为max2突变体对干旱非常敏感，失水速度快。另外，MAX2负调控植物在萌发及萌发后的早期生长阶段对ABA的反应。相关文章发表于2013年11月06日的《plant Physiology》杂志上。

MAX2(More AXillary growth 2)是植物激素-独脚金内酯(Strigolacton)信号途径的重要组分，其功能在拟南芥、水稻、矮牵牛中都被报道，除了影响独脚金内酯调控的植物分蘖表型外，还影响着植物的光形态建成、衰老等生长发育的多个方面。但其在植物对非生物胁迫反应中的功能还未见报道。

研究人员发现，MAX2能正调控植物的抗旱反应，表现为max2突变体对干旱非常敏感，失水速度快。深入研究表明，max2突变体在干旱条件下气孔关闭慢;表面蜡质层较薄;ABA 合成、代谢、运输、信号传导等途径的基因在max2突变体表达量下降;植物对逆境胁迫反应的基因等在max2突变体也下降。

此外，MAX2负调控植物在萌发及萌发后的早期生长阶段对ABA的反应，max2突变体在种子萌发、萌发后的子叶生长、根的伸长等对ABA超敏感，而且ABA调控的萌发阶段基因在max2突变体表达量也增加。进一步的研究表明，独脚金内酯途径中，只有MAX2基因参与了植物对干旱及对ABA的反应，其他组分MAX1、MAX3、MAX4都和野生型类似。说明MAX2蛋白除了参与独脚金内酯信号途径的传导，还特异的在植物逆境胁迫反应中起重要作用。

该文章得到了国家自然科学基金、中科院“百人计划”启动经费及“中科院大豆分子设计育种重点实验室”开放课题的资助。中科院东北地理与农业生态研究所为第一研究单位。卜庆云为第一作者和共同通讯作者，2012级博士生吕天晓是并列第一作者，助理研究员王臻昱参与了部分工作。其他合作单位有美国德克萨斯州立大学、加州大学圣地亚哥分校及湖南农业大学等。Plant Physiology为国际植物学领域经典期刊，近五年影响因子是7.084。

作者简介：

卜庆云，男，1976 年生。博士，研究员，博士生导师。主要从事植物激素的信号传导，和植物的光形态建成，在ABA和JA的信号传导、PIF1蛋白的磷酸化和泛素化修饰等方面有突出研究成果。以第一作者在Journal of Biological Chemistry, Plant Journal, Plant Physiology, Plant molecular Biology, Cell research等国际主流刊物发表论文多篇。

原文摘要：

Regulation of drought tolerance by the F-box protein MAX2 inArabidopsis

Qingyun Bu,Tianxiao Lv, Hui Shen, Phi Luong, Jimmy Wang, Zhenyu Wang,Zhigang Huang, Langtao Xiao, Cawas Engineer, Tae Houn Kim,Julian I. Schroeder, and Enamul Huq

MAX2 (More AXillary growth 2) has been shown to regulate diverse biological processes, including plant architecture, photomorphogenesis, senescence and karrikin signaling. Although karrikin is a smoke-derived abiotic signal, a role forMAX2 in abiotic stress response pathways is least investigated. Here, we show that the max2 mutant is strongly hypersensitive to drought stress compared to wild type. Stomatal closure of max2 was less sensitive to ABA than that of wild type. Cuticle thickness of max2 is significantly thinner than that of wild type. Both of these phenotypes of max2 mutant plants correlate with the increased water loss and drought sensitive phenotype. qRT-PCR analyses showed that theexpression of stress responsive genes and ABA biosynthesis, catabolism, transport and signaling genes was impaired in max2 compared to wild type seedlings in response to drought stress. Double mutant analysis of max2 with ABA-insensitive mutants abi3 and abi5 indicated that MAX2 may function upstream of these genes. The expression of ABA-regulated genes was enhancedin imbibed max2 seeds. In addition, max2 mutant seedlings are hypersensitive to ABA and osmotic stress including NaCl, Mannitol and Glucose. Interestingly, ABA, osmotic stress and drought sensitive phenotypes were restricted to max2, and the strigolactone biosynthetic pathway mutants, max1, max3 and max4, did not display any defects in these responses. Taken together, these results uncover an important role for MAX2 in plant responses to abiotic stress conditions.