Fine-mapping Of Rice Lesion Mimic Mutant T₃₄and Physiological Character Analysis Of T₃₉

Rice lesion mimic mutants can spontaneously form programmed cell death in the absence of pathogen and stress attack.These mutants have similar physiological and biochemical characterisitics with hypersensitive response and some of them show enhanced resistance to pathogens.Both T34 and 39mutant were obtained by EMS mutagenesis.In this paper,the mutational gene of T34 was fine mapped,and physiological character of T39mutant was analyzed.The results from our experiments are summarized as follows:(1)The results of histochemical staining showed that cell necrotic-like phenotype was similar to hypersensitive response in T34 mutant.Bronzing lesion mimicry formed on rice leaves at seedling stage,and then spread all of the leaves and resulted in the senescence of leaves.The resistance of T34 mutant to bacterial blight races P3 and P6 was increased,but not for races P2,P4,P5,P 7 and P8.(2)Genetic analysis revealed that T34 mutant is controlled by a single recessive gene.The gene was fine-mapped to 360kb region adjacent to centromere on chromosome 12.(3)According to the phenotype of T34 and the region of mutational gene,OsSL was selected as the candidate gene.Single nucleotide mutantion was discovered in this gene by sequence analysis.It showed that an aspartic acid residue to tyrosine residue.However,the aspartic acid residue was consistent in different plant species.So we supposed that single nucleotide mutation maybe result in the mutant phenotype of T34.(4)The results of histochemical staining indicated that T39 mutant is a lesion mimic mutant.Lesion mimicry formed on rice leaves at seedling stage.The shading experiment showed that the lesion mimic phenotype of T39 mutant was caused by light.These phenomena indicate that T39 mutant belongs to starting,environmentally-sensitive mutant.(5)The expression level of disease-resistant gene was detected by quantative real-time PCR.PR1a,PR 10,NH1 were higher in T39 mutant than in wild-type.Resistance test showed that T39 mutant has high resistance to all races of bacterial blight.(6)Genetic analysis revealed that 39mutant is controlled by a single recessive gene.These results provide the basis for the cloning T39 mutational gene.