Identification And Gene Mapping Of A Rice Lesion Mimic Mutant G340

The lesion mimic mutant g340was isolated by treating the seeds of indica variety9311with γ-rayradiation. In this study, the mutant g340and its wild type9311were used to conduct research on thephenotype, physiological characters, morphological structure, disease resistance and expression ofdefense related gene. The results showed as follows:1. The brown necrotic spots began to appear about2months after sowing. The number of spots didnot change after one week. The white spots intiation after the brown necrotic spots appeared andengulf the whole leaf. The colour of lesion changed from white to tawny. Compared with wild type,the plant height, total grain number per spike and1000-grain-weight dropped significantly.2. The results show the content of photosynthetic pigment decreased and the photosynthetic rate of themutant g340was lower than wild type. Spherical chloroplasts and abnormal shape and stackingparallel distribution of chloroplasts, degraded grana, the plastoglobuli residue and the destroyedchloroplast membrane could be detected in g340.3. The active oxygen metabolism studies have shown the SOD activity of g340was higher than thewild-type. While the CAT activity was lower than the wild type. A large number of ROSaccumulation in g340mutant may induce the SOD expression.4. To determine whether the lesion mimic mutant confer enhanced disease resistance, the g340mutantwas inoculated with three X. o. pv. oryzae strains CR2, CR4, and CR7. The results suggested g340show significant reductions in lesion lengths g340showed enhanced resistance only to CR2.Real-time PCR analysis show that the expression level of defense-related genes PR1a、PR10、PBZ1、PAL1、POX22.3increase significantly.5. Genetic analysis showed that the mutant phenotype was controlled by a single gene. Using F2:3population of g340×Nipponbare, the g340mutant gene was mapped to rice chromosome9in a55.6kb region. There were9candidates gene in the targeted region by querying The Rice AnnotationProject Database. Sequencing results further revealed that ORF1gene have5base deletion in thefirst exons which caused a premature termination. Therefore, we suggest the ORF1is the targetedg340gene.