The Rice LRR-Like1 Protein YELLOW AND PREMATURE DWARF 1 is Involved in High Light-Induced Leaf Senescence.

Senescence is induced by endogenous physiological changes or exogenous stresses in plants. Here, we isolated two alleles of a novel rice (Oryza sativa L.) mutant, yellow and premature dwarf 1 (ypd1). The ypd1 mutants exhibited a yellow and dwarf phenotype from germination, and premature senescence starting at tillering. Moreover, the ypd1 mutants were sensitive to high light, which accelerated cell death and senescence. Consistent with their yellow phenotype, the ypd1 mutants had abnormal chloroplasts and lower levels of photosynthetic pigments. Trypan blue staining, TUNEL experiments, NBT staining, and DAB staining demonstrated that the ypd1 mutants showed cell death and accumulated reactive oxygen species. Moreover, the ypd1 mutants showed increased expression of senescence-associated genes. Map-based cloning revealed a substitution (G→A) in exon 6 (ypd1-1) and 13 (ypd1-2) of LOC_Os06g13050 that affected splicing and caused premature termination of the encoded protein. YPD1 was preferentially expressed in the leaf and encodes an LRR-Like1 (LRRL1) protein. Complementation, overexpression, and targeted deletion experiments confirmed that the mutations in YPD1 cause the ypd1 phenotype. YPD1 localized on the chloroplast membrane. These findings revealed that the novel rice LRRL1 protein YPD1 affects rice chloroplast development and leaf senescence.