The Identification Of Two Rice Lesion Mimic Mutants And Their Interaction With Magnaporthe Oryzae

Rice blast,caused by the fungus Magnaporthe oryzae,is one of the factors that influences the production of rice.Once Magnaporthe oryzae infected rice,its partial tissues would be recognized by rice immune system,which activate the PAMPs triggered immunity.In order to avoid recognition by the immune system of rice,Magnaporthe oryzae will secrete effectors to block the immune response,leading to effector triggered susceptibility.Resistance proteins in rice can sense the effector and activate the plant’s effector triggered immunity.Two rice lesion mimic mutants,which named lm8015-2 and lm8015-3,were identified in this study.The expression level of defense genes in those two lesion mimic mutants,inoculated with Magnaporthe oryzae,was analyzed to substantiate the interaction between rice and Magnaporthe oryzae,the research results were as follows:1.The red rust-like spots of lm8015-2 were first observed on the tips of the three-week-old mutant leaves after sowing,then spread gradually to cover the leaves at tillering stage,causing the death of whole leaf at harvest stage.The lesions on the leaves of lm8015-2 were induced by natural light.Meanwhile,the photosynthetic pigments content of lm8015-2 were decreased significantly.The histochemical staining showed the excessive H₂O₂ deposition and cell death of lm8015-2.Genetic analysis suggested that the phenotype of lm8015-2 was controlled by a single nuclear recessive gene,which was localized between the markers W32-85 and C32-8 on chromosome 5.2.The qRT-PCR results showed the expression level of partial defense genes of lm8015-2 were higher than ZH8015.The spray inoculation result indicated the enhanced resistance of lm8015-2 to Magnaporthe oryzae.With the inoculation of Magnaporthe oryzae,the qRT-PCR results showed the expression level of defense genes of lm8015-2 and ZH8015 were decreased within 48 h and nearly equaled at 48 h,while the level of lm8015-2 was higher than ZH8015 significantly after 48 h.3.The orange-yellow spots of lm8015-3 were first observed on the lower leaves of the three-week-old mutant after sowing,and covered most leaves of the whole plant at tillering stage,fusing to cause the death of whole leaf at harvest stage.The appearance of lesions of lm8015-3 was induced by natural light.Meanwhile,the photosynthetic pigments content of lm8015-3 were decreased significantly.Histochemical staining showed the excessive H₂O₂ deposition in lm8015-3.Genetic analysis suggested that the phenotype of lm8015-3 was controlled by a single nuclear recessive gene,which was localized between the markers C35-16 and W35-6 on chromosome 12.4.The qRT-PCR results showed the expression level of partial defense genes were down-regulated obviously in lm8015-3.The spray inoculation result indicated the reduced resistance of lm8015-3 to rice blast.The appearance of infected lesion of lm8015-3 was 2 days earlier than ZH8015.With the inoculation of Magnaporthe oryzae,the qRT-PCR results showed the expression level of defense genes of lm8015-3 and ZH8015 were decreased within 48 h and nearly equaled at 48 h,while the expression level of lm8015-3 was lower than ZH8015 significantly within 48-72 h.The leaf sheath inoculation result showed more accumulated spores in lm8015-3,which was majorly constituted of germinating spores.The qRT-PCR results showed the expression level of defense genes of lm8015-3,from 48 h to72 h after inoculation,are lower than ZH8015 significantly.All the proofs indicated the activating of immune system of lm8015-3 was defective.