Integrated Analysis of MicroRNA and Target Genes in Brachypodium distachyon Infected by Magnaporthe oryzae by Small RNA and Degradome Sequencing

Rice blast caused by Magnaporthe oryzae is one of the most important diseases that seriously threaten rice production. Brachypodium distachyon is a grass species closely related to grain crops, such as rice, barley, and wheat, and has become a new model plant of Gramineae. In this study, 15 small RNA samples were sequenced to examine the dynamic changes in microRNA (miRNA) expression in B. distachyon infected by M. oryzae at 0, 24, and 48 h after inoculation. We identified 432 conserved miRNAs and 288 predicted candidate miRNAs in B. distachyon. Additionally, there were 7 and 19 differentially expressed miRNAs at 24 and 48 h post-inoculation, respectively. Furthermore, using degradome sequencing, we identified 2,126 genes as targets for 308 miRNAs; using quantitative real-time PCR (qRT-PCR), we validated five miRNA/target regulatory units involved in B. distachyon–M. oryzae interactions. Moreover, using co-transformation technology, we demonstrated that BdNAC21 was negatively regulated by miR164c. This study provides a new approach for identifying resistance genes in B. distachyon by mining the miRNA regulatory network of host–pathogen interactions.