Wang Wen-Hua, He En-Ming, Chen Juan, Guo Ying, Chen Juan, Liu Xiang, Zheng Hai-Lei
Fujian Key Laboratory of Subtropical Plant Physiology and Biochemistry, Fujian Institute of Subtropical Botany, Xiamen, Fujian, 361006, China.
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling, Shaanxi, 712100, China.
Plant J. 2016 Apr;86(2):132-44. doi: 10.1111/tpj.13154.
Besides their participation in photosynthesis, leaf chloroplasts function in plant responses to stimuli, yet how they direct stimulus-induced stomatal movement remains elusive. Here, we showed that over-reduction of the plastoquinone (PQ) pool by dibromothymoquinone (DBMIB) was closely associated with stomatal closure in plants which required chloroplastic H2O2 generation in the mesophyll. External application of H2 O2 reduced the PQ pool, whereas the cell-permeable reactive oxygen species (ROS) scavenger N-acetylcysteine (NAC) reversed the DBMIB-induced over-reduction of the PQ pool and stomatal closure. Mesophyll chloroplasts are key players of extracellular Ca(2+) (Ca(2+)o)-induced stomatal closure, but when treated with either 3-(3',4'-dichlorophenyl)-1,1-dimethylurea (DCMU) or NAC they failed to facilitate Ca(2+)o-induced stomatal closure due to the inhibition of chloroplastic H2 O2 synthesis in mesophyll. Similarly, the Arabidopsis electron transfer chain-related mutants npq4-1, stn7 and cas-1 exhibited diverse responses to Ca(2+)o or DBMIB. Transcriptome analysis also demonstrated that the PQ pool signaling pathway shared common responsive genes with the H2 O2 signaling pathway. These results implicated a mechanism for chloroplast-mediated stomatal closure involving the generation of mesophyll chloroplastic H2O2 based on the reduced state of the PQ pool, which is calcium-sensing receptor (CAS) and LHCII phosphorylation dependent.
除了参与光合作用外，叶片叶绿体还在植物对刺激的反应中发挥作用，然而它们如何指导刺激诱导的气孔运动仍不清楚。在这里，我们表明，二溴百里香醌（DBMIB）使质体醌（PQ）库过度还原与植物气孔关闭密切相关，这需要叶肉中叶绿体产生H2O2。外源施加H2O2可降低PQ库，而细胞可渗透的活性氧（ROS）清除剂N-乙酰半胱氨酸（NAC）可逆转DBMIB诱导的PQ库过度还原和气孔关闭。叶肉叶绿体是细胞外Ca2+（Ca2+o）诱导气孔关闭的关键因素，但用3-（3'，4'-二氯苯基）-1，1-二甲基脲（DCMU）或NAC处理时，由于叶肉中叶绿体H2O2合成受到抑制，它们无法促进Ca2+o诱导的气孔关闭。同样，拟南芥电子传递链相关突变体npq4-1、stn7和cas-1对Ca2+o或DBMIB表现出不同的反应。转录组分析还表明，PQ库信号通路与H2O2信号通路共享共同的响应基因。这些结果暗示了一种叶绿体介导的气孔关闭机制，该机制涉及基于PQ库还原状态产生叶肉叶绿体H2O2，这依赖于钙传感受体（CAS）和LHCII磷酸化。
