| Lesion mimic mutants exhibit spontaneous cell death spots on leaves or other tissues in the absence of pathogen attack or environmental stess. Studies on these mutants have promoted the understanding of plant disease resistance and plant programmed cell death. In the present study, a runaway cell death mutant, designated as rcd1, was screened from the tissue culture progeny of indica rice restorer line Minghui 86. We investigated the phenotype, pathogenesis-related gene expression pattern of the rcd1 mutant, and performed gene mapping of the rcd1 mutated gene. Using map-based cloning approach, the rcd1 mutated gene was mapped to a 428 kb region on the centromere region of chromosome 12, and was further identified as allelic to SL. Our results laid a foundation for illuminating the function of the rcd1/SL gene. The main results are as follows:1. rcd1 started appear orange mimic lesions on the leaves at late seedling stage, and the mimic lesions developed more serious in whole leaves and sheaths after tillering stage. With the growth of the plants to flowering stage, rcd1 displayed a runaway necrosis phenotype.2. RT-PCR analysis showed that the expressions of pathogenesis-related genes OsPR1b, OsNAC4, OsPAL1, OsCHT1, OsCHT3, and OsPOC1 were induced in rcd1 leaf tissues. Field investigation revealed that rcd1 plants displayed enhanced resistance to Bipolaris oryzae.3. Genetic analysis revealed that the mutant phenotype was controlled by a single recessive gene. F2 population derived from a cross between 93-11 and rcd1 was used for gene mapping, and the rcd1 mutated gene was mapped to a 428 kb region between InDel markers ID7909 and ID8337 on the centromere region of chromosome 12.4. Sequencing and co-segregation analyses revealed that rcdl mutated gene was allelic to SL. In rcdl, a G1205T point mutation was identified in SL coding region, leading to an Arg to Leu mutation at amino acid 370. SL gene encodes CYP71P1 in a cytochrome P450 monooxy genase family. |
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