Disruption of LEAF LESION MIMIC 4 affects ABA synthesis and ROS accumulation in rice
Hao Wu,
Gaoxing Dai,
Rao Yuchun,
Kaixiong Wu,
Junge Wang,
Peng Hu,
Yi Wen,
Yueying Wang,
Lixin Zhu,
Bingze Chai,
Jialong Liu,
Guofu Deng,
Qian Qian,
Jiang Hu
Affiliations
Hao Wu
Department of Agronomy, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou 310058, Zhejiang, China; State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou 310006, Zhejiang, China; Guangxi Crop Genetic Improvement and Biotechnology Laboratory, Guangxi Academy of Agricultural Sciences, Nanning 530007, Guangxi, China
Gaoxing Dai
Guangxi Crop Genetic Improvement and Biotechnology Laboratory, Guangxi Academy of Agricultural Sciences, Nanning 530007, Guangxi, China
Rao Yuchun
College of Life Sciences, Zhejiang Normal University, Jinhua 321004, Zhejiang, China
Kaixiong Wu
State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou 310006, Zhejiang, China
Junge Wang
State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou 310006, Zhejiang, China
Peng Hu
State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou 310006, Zhejiang, China
Yi Wen
State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou 310006, Zhejiang, China
Yueying Wang
State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou 310006, Zhejiang, China
Lixin Zhu
State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou 310006, Zhejiang, China
Bingze Chai
State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou 310006, Zhejiang, China
Jialong Liu
State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou 310006, Zhejiang, China
Guofu Deng
Guangxi Crop Genetic Improvement and Biotechnology Laboratory, Guangxi Academy of Agricultural Sciences, Nanning 530007, Guangxi, China; Corresponding authors.
Qian Qian
Department of Agronomy, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou 310058, Zhejiang, China; State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou 310006, Zhejiang, China; Corresponding authors.
Jiang Hu
State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou 310006, Zhejiang, China; Corresponding authors.
Lesion mimic mutants (LMMs) are advantageous materials for studying programmed cell death (PCD). Although some rice LMM genes have been cloned, the diversity of functions of these genes indicates that the mechanism of cell death regulation in LMMs needs further study. In this study, we identified a rice light-dependent leaf lesion mimic mutant 4 (llm4) that showed abnormal chloroplast structure, photoinhibition, reduced photosynthetic protein levels, massive accumulation of reactive oxygen species (ROS), and PCD. Map-based cloning and complementation testing revealed that LLM4 encodes zeaxanthin epoxidase (ZEP), an enzyme involved in the xanthophyll cycle, which functions in plant photoprotection, ROS scavenging, and carotenoid and abscisic acid (ABA) biosynthesis. The ABA content was decreased, and the contents of 24 carotenoids differed between the llm4 mutant and the wild type (WT). The llm4 mutant showed reduced dormancy and greater sensitive to ABA than the WT. We concluded that the mutation of LLM4 resulted in the failure of xanthophyll cycle, in turn causing ROS accumulation. The excessive ROS accumulation damaged chloroplast structure and induced PCD, leading eventually to the formation of lesion mimics.
