Characterization and fine mapping of a light-dependent leaf lesion mimic mutant 1 in rice

• Published in: Plant physiology and biochemistry 2015-12, Vol.97, p.44-51
• Main Authors: Wang, Jing, Ye, Bangquan, Yin, Junjie, Yuan, Can, Zhou, Xiaogang, Li, Weitao, He, Min, Wang, Jichun, Chen, Weilan, Qin, Peng, Ma, Bintian, Wang, Yuping, Li, Shigui, Chen, Xuewei
• Format: Article
• Language: English
• Subjects: Chloroplast; Chloroplasts - ultrastructure; Chromosome Mapping; Coproporphyrinogen Oxidase - genetics; Coproporphyrinogen Oxidase - metabolism; Disease Resistance; Gene mapping; Genetic Loci - genetics; Lesion mimic; Light; Mutation; Oryza - enzymology; Oryza - genetics; Oryza - immunology; Oryza - radiation effects; Phenotype; Plant Diseases - immunology; Plant Leaves - enzymology; Plant Leaves - genetics; Plant Leaves - immunology; Plant Leaves - radiation effects; Plant Proteins - genetics; Plant Proteins - metabolism; Reactive Oxygen Species - metabolism; Rice; Seeds - enzymology; Seeds - genetics; Seeds - immunology; Seeds - radiation effects
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/j.plaphy.2015.09.001

Plants that spontaneously produce lesion mimics or spots, without any signs of obvious adversity, such as pesticide and mechanical damage, or pathogen infection, are so-called lesion mimic mutants (lmms). In rice, many lmms exhibit enhanced resistance to pathogens, which provides a unique opportunity to uncover the molecular mechanism underlying lmms. We isolated a rice light-dependent leaf lesion mimic mutant 1 (llm1). Lesion spots appeared in the leaves of the llm1 mutant at the tillering stage. Furthermore, the mutant llm1 had similar agronomic traits to wild type rice. Trypan blue and diamiobenzidine staining analyses revealed that the lesion spot formation on the llm1 mutant was due to programmed cell death and reactive oxygen species. The chloroplasts were severely damaged in the llm1 mutant, suggesting that chloroplast damage was associated with the formation of lesion spots in llm1. More importantly, llm1 exhibited enhanced resistance to bacterial blight pathogens within increased expression of pathogenesis related genes (PRs). Using a map-based cloning approach, we delimited the LLM1 locus to a 121-kb interval between two simple sequence repeat markers, RM17470 and RM17473, on chromosome 4. We sequenced the candidate genes on the interval and found that a base mutation had substituted adenine phosphate for thymine in the last exon of LOC_Os04g52130, which led to an amino acid change (Asp388 to Val) in the llm1 mutant. Our investigation showed that the putative coproporphyrinogen III oxidase (CPOX) encoded by LOC_Os04g52130 was produced by LLM1 and that amino acid Asp388 was essential for CPOX function. Our study provides the basis for further investigations into the mechanism underlying lesion mimic initiation associated with LLM1. •We identified a light-dependent leaf lesion mimic mutant 1, llm1, in rice.•PCD accompanied with ROS occurred in the llm1 mutant.•The llm1 plants displayed enhanced resistance to various Xoo pathogens without obvious effects on seed yield.•Asp388 to Vla in the putative coproporphyrinogen III oxidase encoded by LOC_Os04g52130 resulted in the phenotype of the llm1.