State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
J Integr Plant Biol. 2016 Aug;58(8):724-36. doi: 10.1111/jipb.12465. Epub 2016 Feb 24.
Leaf senescence is the final leaf developmental process that is regulated by both intracellular factors and environmental conditions. The mitogen-activated protein kinase (MAPK) signaling cascades have been shown to play important roles in regulating leaf senescence; however, the component(s) downstream of the MAPK cascades in regulating leaf senescence are not fully understood. Here we showed that the transcriptions of ZmMEK1, ZmSIMK1, and ZmMPK3 were induced during dark-induced maize leaf senescence. Furthermore, in-gel kinase analysis revealed the 42 kDa MAPK was activated. ZmMEK1 interacted with ZmSIMK1 in yeast and maize mesophyll protoplasts and ZmSIMK1 was activated by ZmMEK1 in vitro. Expression of a dominant negative mutant of ZmMEK1 in Arabidopsis transgenic plants induced salicylic acid (SA) accumulation and SA-dependent leaf senescence. ZmMEK1 interacted with Arabidopsis MPK4 in yeast and activated MPK4 in vitro. SA treatment accelerated dark-induced maize leaf senescence. Moreover, blockage of MAPK signaling increased endogenous SA accumulation in maize leaves. These findings suggest that ZmMEK1-ZmSIMK1 cascade and its modulating SA levels play important roles in regulating leaf senescence.
叶片衰老是一个由细胞内因素和环境条件共同调控的最终叶片发育过程。有研究表明，丝裂原活化蛋白激酶（MAPK）信号级联在调控叶片衰老中起着重要作用；然而，MAPK 级联下游调控叶片衰老的组分尚未完全阐明。本研究表明，在黑暗诱导的玉米叶片衰老过程中，ZmMEK1、ZmSIMK1 和 ZmMPK3 的转录被诱导。此外，凝胶激酶分析显示 42kDa 的 MAPK 被激活。ZmMEK1 在酵母和玉米叶肉原生质体中与 ZmSIMK1 相互作用，并且 ZmSIMK1 在体外被 ZmMEK1 激活。在拟南芥转基因植物中表达一个显性负突变体的 ZmMEK1 诱导水杨酸（SA）积累和 SA 依赖性叶片衰老。ZmMEK1 在酵母中与拟南芥 MPK4 相互作用，并在体外激活 MPK4。SA 处理加速了黑暗诱导的玉米叶片衰老。此外，阻断 MAPK 信号通路增加了玉米叶片中的内源 SA 积累。这些发现表明，ZmMEK1-ZmSIMK1 级联及其对 SA 水平的调节在调控叶片衰老中起着重要作用。
