MicroRNAs And RPW8.1 Are Involved In Rice Resistance Against Magnaporthe Oryzae

Rice blast fungus posed a threat to rice production and rice security in the world. The interaction mechanism between rice and rice blast fungus is one of the most hot spots in this research field. MiRNAs act as important regulate factors, they can regulate plant growth and development, disease or stress defense. Our lab had vaccinated rice blast fungus on susceptible accession LTH and resistant line IRBLkm-Ts and detect the accumulation of miRNAs before and after the inoculation by deep sequencing in the previous study. In this study, we have constructed three miRNAs over-expression transgenic lines, then identified the disease resistance to rice blast fungus and the resistance pathway they may be involved. The main results are described as follows:The expression level of miR169a is significant increased both in susceptible line LTH and resistant line IRBLkm-Ts after infected by blast fungus. The over-expression of miR 169a transgenic lines compromise rice blast fungus resistance after dropping or spray the fungus. The transcription level of OsRP10 is lower in miR169OE lines than that in WT. The mRNA level of OsKS4 (a marker gene of base defense) are not significant expressed after induced by flg22 or chitin in miR169aOE lines,and the mRNA level of OsNAC4 doesn’t reach to a high level until 8hr. We hypothesis that miR169a has little effect on the early resistance of rice. In summary,miR169a inhibit the rice resistance to blast fungus via negatively the late defense responses.In summary,miR169a negatively regulate the rice resistance to blast fungus,but don’t significantly inhibit the early resistance of rice.The accumulation of miR827a in 48hr is approximately 10 times of that in Ohr or 12hr after infected by blast fungus on LTH. After be infected 12hr in IRBLkm-Ts, the accumulation of miR827a is increased almost 3 times compared with pre-infection. The miR827aOE lines enhanced resistance responses after be infected blast fungus. The mRNA level of OsPR10 is significant higher in miR827aOE lines than that in WT after be vaccinated 48hr. The expression level of OsNAC4 and OsKS4 (two base defense marker genes) is higher in miR827aOE lines than that in TP309 after induced by flg22.The expression level of OsNAC4 is also increased in miR827aOE lines after induced 8hr by chitin. The data indicate that miR827a enhanced the rice resistance to blast fungus by positively regulates PTI responses.The expression of miR167d is induced to a higher level in LTH compared in IRBLkm-Ts. The miR167dOE lines are more susceptible to blast fungus and the mRNA level of OsPR10 is lower in miR167dOE lines than that in WT after vaccinated rice blast fungus. There are no significant differences of OsKS4 expression in miR167dOE lines and WT after induced by flg22 or chitin. But the mRNA level of OsNAC4 is higher in miR167dOE lines than that in WT. Therefore, we speculated that miR167d negatively regulates the rice resistance to blast fungus and partly promotes PTI response.AtRPW8.1 is a broad spectrum resistance protein. We test the effects of RPW8.1 to rice blast fungus resistance after ectopic expression of AtRPW8.1 in rice. We found that both the mRNA level and the protein accumulation of RPW8.1 are increased through the identification of T3 generation of transgenic lines. The data demonstrates that ectopic protein RPW8.1 can be induced by rice blast fungus in rice. The transgenic rice lines enhanced the rice resistance to blast fungus. The mRNA level of OsPBZ1 and OsPR10 are significant higher than that in WT. The data indicate that RPW8.1 positively regulates the rice resistance to blast fungus. The mRNA level and the protein accumulation of RPW8.1 are significant increased in RPW8.1 transgenic lines after be treated with flg22 or chitin. The mRNA level of OsNAC4 is also higher in transgenic lines than WT. Taken together, we speculated that RPW8.1 can ectopic express in rice and enhance the rice resistance to blast fungus.