EXPLORING MECHANISM OF RESISTANCE TO ISOPROTHIOLANE IN MAGNAPORTHE ORYZAE THE CAUSAL AGENT OF RICE BLAST
M.J. Hu, Q.Y. Ma, K.B. Li, Y. Lin, C.X. Luo
The fungicide isoprothiolane (IPT) has widely been used to control the rice blast fungus Magnaporthe oryzae for decades. However, the molecular mechanism of resistance is still unexplained and was only believed to be associated with transmethylation in the biosynthesis of phosphatidylcholine. In this study we tested IPT sensitivity of hundreds of M. oryzae isolates collected from Yunnan and Hubei provinces of China. Three IPT-resistant mutants were generated by exposing the mycelium to increasing concentrations of IPT. No fitness penalty was observed in these resistant mutants. In consideration of the role on transmethylation in the biosynthesis of phosphatidylcholine, three candidate genes, PEAMT, CHO2, and OPI3, were sequenced, and their expression profile determined. There was no significant difference in the expression of these genes between resistant mutants and sensitive parental isolates. Additionally, Solexa sequencing was conducted to screen potential target genes. MGG_09793 was the most frequently changed gene between resistant mutant H08-1a_mut and sensitive parental isolate H08-1a after IPT treatment. After knockout, this gene in H08-1a_mut and H08-1a, resistance status did not change. This study indicates that the expected PEAMT, CHO2 and OPI3 genes were not responsible for IPT resistance. Interestingly, the DJ-1/PfpI family protein MGG_09793 was specifically and strongly induced by IPT treatment in sensitive isolates.