You Jun, Zong Wei, Hu Honghong, Li Xianghua, Xiao Jinghua, Xiong Lizhong
National Key Laboratory of Crop Genetic Improvement and National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan 430070, China.
National Key Laboratory of Crop Genetic Improvement and National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan 430070, China
Plant Physiol. 2014 Dec;166(4):2100-14. doi: 10.1104/pp.114.251116. Epub 2014 Oct 15.
Plants respond to abiotic stresses through a complexity of signaling pathways, and the dephosphorylation mediated by protein phosphatase (PP) is an important event in this process. We identified a rice (Oryza sativa) PP2C gene, OsPP18, as a STRESS-RESPONSIVE NAC1 (SNAC1)-regulated downstream gene. The ospp18 mutant was more sensitive than wild-type plants to drought stress at both the seedling and panicle development stages. Rice plants with OsPP18 suppressed through artificial microRNA were also hypersensitive to drought stress. Microarray analysis of the mutant revealed that genes encoding reactive oxygen species (ROS) scavenging enzymes were down-regulated in the ospp18 mutant, and the mutant exhibited reduced activities of ROS scavenging enzymes and increased sensitivity to oxidative stresses. Overexpression of OsPP18 in rice led to enhanced osmotic and oxidative stress tolerance. The expression of OsPP18 was induced by drought stress but not induced by abscisic acid (ABA). Although OsPP18 is a typical PP2C with enzymatic activity, it did not interact with SNF1-RELATED PROTEIN KINASE2 protein kinases, which function in ABA signaling. Meanwhile, the expression of ABA-responsive genes was not affected in the ospp18 mutant, and the ABA sensitivities of the ospp18 mutant and OsPP18-overexpressing plants were also not altered. Together, these findings suggest that OsPP18 is a unique PP2C gene that is regulated by SNAC1 and confers drought and oxidative stress tolerance by regulating ROS homeostasis through ABA-independent pathways.
植物通过复杂的信号通路对非生物胁迫作出反应，而蛋白磷酸酶（PP）介导的去磷酸化是这一过程中的重要事件。我们鉴定出一个水稻（Oryza sativa）PP2C基因OsPP18，它是受胁迫响应NAC1（SNAC1）调控的下游基因。ospp18突变体在幼苗期和穗发育阶段比野生型植物对干旱胁迫更敏感。通过人工miRNA抑制OsPP18表达的水稻植株对干旱胁迫也表现出超敏反应。对该突变体的微阵列分析表明，编码活性氧（ROS）清除酶的基因在ospp18突变体中表达下调，且该突变体的ROS清除酶活性降低，对氧化胁迫的敏感性增加。在水稻中过表达OsPP18可增强其对渗透胁迫和氧化胁迫的耐受性。OsPP18的表达受干旱胁迫诱导，但不受脱落酸（ABA）诱导。尽管OsPP18是一个具有酶活性的典型PP2C，但它不与在ABA信号传导中起作用的SNF1相关蛋白激酶2相互作用。同时，ospp18突变体中ABA响应基因的表达不受影响，ospp18突变体和过表达OsPP18植株的ABA敏感性也未改变。综上所述，这些发现表明OsPP18是一个独特的PP2C基因，受SNAC1调控，通过不依赖ABA的途径调节ROS稳态，从而赋予植物干旱和氧化胁迫耐受性。
