The lesion mimic mutant g303 and g342 were isolated by treating the seeds of indica varieties 9311 and R8015 with γray radiation, respectively. The yellow spots initially appear on g303 leaves at 4leaf stage. With the growth and development of the plant, the lesions almost occupied the whole plant till the maturity stage. Compared with the wild type, the plant height, seed setting rate and 1000grain weight of g303 significantly dropped, the chlorophyll and photosynthetic rate obviously decreased. Genetic analysis showed that the mutant phenotype was controlled by a single recessive gene. Using F2 mapping population of g303/ Nipponbare, the g303 mutant gene was mapped between marker InD10 and InD12 on rice chromosome 12, with genetic distances of 0.19 cM and 0.76 cM, respectively. Sequence analysis revealed that the mutated gene was allelic to SL, g303 and g342 mutated gene had a single nucleotide deletion (T572 and G1206, respectively), leading to a premature termination codon. Realtime PCR analysis showed that the expression level of defenserelated genes upregulated significantly, these results demonstrated that the mutation may activate the defense response.
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