Identification and Gene Fine Mapping of Starch Accumulation and Early Senescent Leaf Mutant esl10 in Rice

A novel starch accumulation and early senescent leaf mutant esl10 was identified among progenies of the rice (Oryza sativa L.) indica maintainer line Xinong 1B raised from seeds treated with ethyl methane sulfonate (EMS). Under paddy field conditions, leaf starch accumulation commenced at the three-leaf stage in the mutant esl10 and the leaves began to yellow at the four-leaf stage, gradually extending from the tip to the middle of the leaf. The yellowing phenotype was most obvious at the tillering stage and persisted until maturity. Compared with the wild type, photosynthetic pigment concentrations and net photosynthetic rate of esl10 were significantly lower, whereas the concentrations of reactive oxygen species and malondialdehyde (MDA) were higher. Moreover, catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) activities decreased in leaves at the tillering stage. Quantitative real-time polymerase chain reaction showed that the expression of genes associated with starch metabolism pathway changed. Excessive accumulation of leaf starch may have caused the leaf premature senescence, finally influencing grain yield and quality of esl10. Genetic analysis showed that esl10 was controlled by a dominant nuclear gene (tentatively called ESL10). ESL10 was mapped between the single-nucleotide polymorphism markers SNP585 and SNP498 on chromosome 7 with a physical distance of 416.29 kb including 56 annotated genes. The results provide a foundation for gene cloning and functional analysis of ESL10.