Revealing The Mechanism Of The Transcription Factor OsMYB3 Regulating Blast Resistance And Evaluating Its Breeding Application

Rice blast caused by Magnaporthe oryzae(M.oryzae),is one of the devastating diseases of rice.It occurs in various areas of rice production in China,which seriously affects rice yield and quality,and even threatens food security.Developing rice with resistance genes or resistance-related genes for breeding is the most effective way to protect rice from this severe disease.Developing resistance-related genes and analyzing their mechanism can lay an important theoretical foundation for breeding disease-resistant varieties.The evaluation of breeding application of resistance-related genes can effectively promote the progress of disease-resistant breeding.We has identified that a R2R3-MYB transcription Factor of OsMYB3 that positively regulates blast resistance by analyzing transcriptome and testing blast resistance.In order to deeply reveal blast resistance mechanism mediated byOsMYB3.We tested the resistance spectrum,observed cellular process of blast fugus growing in leaf sheath,screened and identified the up-regulating genes and target genes of OsMYB3,and determined the agronomic characters.The main results are as follows:1.The plants with overexpressing OsMYB3(OsMYB3ox)have weaker susceptibility than the control plants using spraying inoculation of M.oryzae.The result suggests that the resistance mediated by OsMYB3 is not race-specific.2.The PR genes can be induced by Chitin and Flg22 in the plants with overexpessing OsMYB3.The results indicated that OsMYB3 might regulat basic immunization of rice.3.After observing dynamic process of blast fugus in leaf sheathand stained tissues ofleaf,we found that overexpressing OsMYB3 can increase the accumulation of lignin in leaves,which might result into the lowinfection efficiency of M.oryzae.4.The lignin content in OsMYB3 ox increased using AcBr method.It was indicated that the increasing lignin contents in OsMYB3 ox might enhance blast resistance.5.On the basis of results of yeast one-hybrid,EMSA and ChIP-qPCR,we found that that OsMYB3 can directly bond the promoter of OsMTG3.And OsTRM3 belonging to WRKY family can bond the promoter of OsMYB3.The results suggest that OsMTG3 is a target gene of OsMYB3 and OsTRM3 is a up-regulated protein of OsMTG3.6.The lignin contents in OsMTG3 ox increased by comparing to the control.And overexpressing OsMTG3 enhanced blast resistance.7.In order to evaluate the application of OsMYB3 in breeding,We determined agronomic traits includingthe number of grains per ear,seed setting rate,1000-grain weight and plant hight.Comparing to control plants,there were no significant differences in agronomic characters except for plant height.It is suggested that OsMYB3 has potential application value in rice breeding for blast resistance.In this study,we elucidated the mechanism of blast resistance mediated by OsMYB3 and evaluated the application value of OsMYB3 in rice breeding.It enriches the resistance mechanism of rice blast and lays an important theoretical foundation for rice breeding of blast resistance.