Generation And Identification Of Rice Mutants In EDR1-mediated Disease Resistenctace Pathway And Preliminary Study Of Related Gene Function In Rice Disease Resistance

Rice is an important food crop in China.However,disease can cause serious damage to the yield and quality of rice.For a long time,farmers use pesticides to control disease,which not only cause great pollution to the environment,but also increase the economic burden for the peasants.In contrast,using disease resistance genes can markedly increase crop's resistance to disease and it is thought to be both economic and environment friendly.OsEDR1 encodes a MAPKKK(mitogen-activated protein kinase kinase kinase)kinase,osedrl shows enhanced resistance towards Xanthomonas oryzae pv.oryzae strain PX0347 at adult stage compared to the wild type plant,in the meanwhile,this mutant has lesion mimic on its leaves at adult stage.In this study,we used methyl sulfonic acid ethyl ester(ethylmethylsulfone,EMS)to treat osedrl plants,for the purpose to obtain those plants without lesion mimic and are susceptible to PX0347.Now,we have got those plants that possess the traits after three generations of screening.Next,in order to remove unrelated background,these plants will be backcrossed with osedrl.This study will certainly facilitate next step of gene cloning.Xa4,a major disease resistance gene conferring resistance to rice bacterial blight,encodes a cell wall associated protein kinase.Dr.Hu Kerning found Xa4 may mediated resistance signaling through regulating the cellulose synthase genes OsCesA4,OsCesA7 and OsCesA9.To test this hypothesis,we artificially suppressed the expression of OsCesA4,OsCesA7 and OsCesA9 in rice variety Zhonghua 11.We found that repressing of OsCesA4,OsCesA7 or OsCesA9 expression reduced their resistance to rice bacterial blight.Those result suggested that these three cellulose synthase gene are indispensable for rice to defend pathogen infection.Dr.Hu Kerning found Xa4 was highly expressed in rice root,and we know rice blast fungus can infect rice through the root.In order to understand the function of Xa4 in rice root defense towards blast,IRBB4(having Xa4)and its nearly isogenic line IR24(without Xa4)were inoculated with blast fungus through roots or leaf.It showed that under both inoculation condition,IRBB4 was more resistant to the pathogen than IR24.In addition,the expression of Xa4 was obviously induced in leaf after fungal infection through leaf.However,when blast fungus infected rice through the roots,the expression of Xa4 in leaf was not significantly induced.These results suggest that Xa4's tissue specific expression may be important for its function in rice defense to blast fungus.