Physiological Characteristics and Gene Mapping of a Precocious Leaf Senes-cence Mutant ospls3 in Rice

Abstract

Leaf senescence is the final stage of leaf development. However, premature aging of functional leaves leads to yield reduction and quality decline. Thus, it is very important for developing novel crop germplasms with delayed leaf-senescence characteristics through investigating the molecular mechanism of leaf senescence. In this study, an ospls3 (Oryza sativa preco- cious leaf senescence 3) mutant, produced by 60 Co γ-radiation treatment of indica cultivar N142, was identified. The symptoms of the premature senescence mutant presented firstly at tillering stage showing brown leaf tip and brown spots in top part of leaf blade, then spread rapidly to basal part of leaf blade and led leaf to die. The physiological analysis indicated that, in the ospls3 mutant, the content of chlorophyll was the highest in the flag leaf, the following was in second-top and third-top leaves, but all of them were significantly lower than those in the wild type. The contents of MDA, O2܋ , and H2O2 and the activities of SOD and POD among the top three leaves in the wild type maintained similar levels, which were significantly lower than those in the mu- tant. The soluble protein contents and the activity of CAT had no significant difference among top three leaves in the wild type while significantly decreased in the mutant. Genetic analysis verified that the ospls3 is a recessive mutant and was mapped in a 294 kb interval between RM6953 and RM28753 on the long arm of chromosome 12, which establishes a solid foundation for further cloning and functional studies of this gene.