Fine Mapping of a New Lesion Mimic and Early Senescence 2 (lmes2) Mutant in Rice

A novel lesion mimic and early senescence 2 (lmes2) mutant was identified from Jinhui10, an indica restorer line in rice (Oryza sativa L.), which was treated with ethyl methane sulfonate (EMS). Lmes2 began to develop disease-like lesions on leaves at the seedling stage and aged leaves that had the maximum distribution of such lesions began to senesce. Compared with the wild-type, a low content of chlorophylls was observed, while the proline content increased in proportion to the development of lesion mimics. In addition, the photosynthetic rate and superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities fell very significantly, which indicates that lmes2 develops early senescence. Excessive hydrogen peroxide (H2O2) deposition and trypan blue staining imply that lmes2 goes through programmed cell death. A population of F-2 was used to fine map LMES2 to a 66-kb region on chromosome 10, which harbors 10 open reading frames. Quantitative real-time polymerase chain reaction results show the activation of two disease resistance indicator genes, PAL and PBZ1, in the process of lesion formation; this finding indicates that resistance activity may have activated. Our results provide a foundation for finding and functional analysis of the novel lesion mimic mutant (LMM) gene, LMES2.