Magnaporthe oryzae infection triggers rice resistance to brown planthopper through the influence of jasmonic acid on the flavonoid biosynthesis pathway.

In agroecosystems, plants are constantly exposed to attack from diverse herbivorous insects and microbes, and infestation with one species may change the plant defense response to other species. In our investigation of the relationships among rice plants, the brown planthopper Nilaparvata lugens (Stål) and the rice blast fungus Magnaporthe oryzae, we observed a significant increase in the resistance of rice treated with rice blast to N. lugens, as evidenced by improved plant survival rates in a small population resistance study. Subsequent transcriptome data analysis revealed that the rice blast fungus can induce the expression of genes in the jasmonic acid (JA) and flavonoid pathways. Similar to the flavonoid pathway, the JA pathway also contains 2 types of genes that exhibit similar and opposite trends in response to N. lugens and rice blast. Among these genes, the osjaz1 mutant and the osmyc2 mutant were phenotypically confirmed to positively and negatively regulate rice resistance to N. lugens and rice blast, respectively. Subsequent mass spectrometry and quantification experiments showed that the exogenous application of methyl jasmonate (MeJA) can induce the accumulation of eriodictyol, naringenin and quercetin, as well as the expression of OsF3H, Os4CL5 and OsCHI in the flavonoid pathway. This suggests a close connection between the JA pathway and the flavonoid pathway. However, OsF3'H, which negatively regulates rice resistance to N. lugens and rice blast, did not show increased expression. Phenotypic and molecular experiments confirmed that OsMYC2 can bind to and inhibit the expression of OsF3'H, thus revealing the mechanism of rice resistance to N. lugens after treatment with rice blast. These findings will deepen our understanding of the interactions among rice, N. lugens and rice blast.