Zhang Hui, Xiang Yanli, He Neng, Liu Xiangguo, Liu Hongbo, Fang Liping, Zhang Fei, Sun Xiaopeng, Zhang Delin, Li Xingwang, Terzaghi William, Yan Jianbing, Dai Mingqiu
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.
Jilin Provincial Key Laboratory of Agricultural Biotechnology, Agro-Biotechnology Institute, Jilin Academy of Agricultural Sciences, Changchun 130124, China.
Mol Plant. 2020 May 4;13(5):760-776. doi: 10.1016/j.molp.2020.02.005. Epub 2020 Feb 14.
Abscisic acid (ABA) is a key phytohormone that mediates environmental stress responses. Vitamin C, or L-ascorbic acid (AsA), is the most abundant antioxidant protecting against stress damage in plants. How the ABA and AsA signaling pathways interact in stress responses remains elusive. In this study, we characterized the role of a previously unidentified gene, PTPN (PTP-like Nucleotidase) in plant drought tolerance. In Arabidopsis, (AtPTPN was expressed in multiple tissues and upregulated by ABA and drought treatments. Loss-of-function mutants of AtPTPN were hyposensitive to ABA but hypersensitive to drought stresses, whereas plants with enhanced expression of AtPTPN showed opposite phenotypes to . Overexpression of maize PTPN (ZmPTPN) promoted, while knockdown of ZmPTPN inhibited plant drought tolerance, indicating conserved and positive roles of PTPN in plant drought tolerance. We found that both AtPTPN and ZmPTPN release Pi by hydrolyzing GDP/GMP/dGMP/IMP/dIMP, and that AtPTPN positively regulated AsA production via endogenous Pi content control. Consistently, overexpression of VTC2, the rate-limiting synthetic enzyme in AsA biosynthesis, promoted AsA production and plant drought tolerance, and these effects were largely dependent on AtPTPN activity. Furthermore, we demonstrated that the heat shock transcription factor HSFA6a directly binds the AtPTPN promoter and activates AtPTPN expression. Genetic analyses showed that AtPTPN is required for HSFA6a to regulate ABA and drought responses. Taken together, our data indicate that PTPN-mediated crosstalk between the ABA signaling and AsA biosynthesis pathways positively controls plant drought tolerance.
脱落酸（ABA）是一种介导环境胁迫响应的关键植物激素。维生素C，即L-抗坏血酸（AsA），是植物中含量最丰富的抗氧化剂，可保护植物免受胁迫损伤。ABA和AsA信号通路在胁迫响应中如何相互作用仍不清楚。在本研究中，我们对一个先前未鉴定的基因PTPN（类PTP核苷酸酶）在植物耐旱性中的作用进行了表征。在拟南芥中，AtPTPN在多个组织中表达，并受ABA和干旱处理上调。AtPTPN功能缺失突变体对ABA不敏感，但对干旱胁迫敏感，而AtPTPN表达增强的植物表现出相反的表型。玉米PTPN（ZmPTPN）的过表达促进了植物耐旱性，而ZmPTPN的敲低则抑制了植物耐旱性，表明PTPN在植物耐旱性中具有保守的正向作用。我们发现AtPTPN和ZmPTPN都通过水解GDP/GMP/dGMP/IMP/dIMP释放无机磷酸盐（Pi），并且AtPTPN通过控制内源Pi含量正向调节AsA的产生。一致地，AsA生物合成中的限速合成酶VTC2的过表达促进了AsA的产生和植物耐旱性，并且这些效应在很大程度上依赖于AtPTPN的活性。此外，我们证明热激转录因子HSFA6a直接结合AtPTPN启动子并激活AtPTPN表达。遗传分析表明，HSFA6a调节ABA和干旱响应需要AtPTPN。综上所述，我们的数据表明PTPN介导的ABA信号通路和AsA生物合成途径之间的串扰正向控制植物耐旱性。
