Expression Alteration of Candidate Rice MiRNAs in Response to Sheath Blight Disease

Background: MicroRNAs, as small non-coding RNAs, are recently reported to be involved in plant defense system against pathogens including fungi. Objective: In this research, it was intended to investigate candidate susceptible rice (Oryza Sativa) Osa-miRNA expression alteration following the infection by Rhizoctonia solani. Materials and Methods: To this aim, literature review suggested eight conserved plant miRNAs that are involved in other plant-pathogen interactions. Then, sixty days old rice plants (Hashemi, susceptible cultivar) were inoculated with R. solani and candidate miRNA expression alterations were investigated 2 hpi (hours post inoculation), 2 dpi (days post inoculation) and 6 dpi. Results: RT-qPCR analysis suggested four subgroups of candidate miRNAs based on the time of their responses to the pathogenesis of R. solani. While Osa-miR-156 was early-responsive, Osa-miR159 was the last-responsive and Osa-miR167, Osa-miR171, Osa-miR408, and Osa-miR444 were late responsive to R. solani infection. Osa-miR166 and Osa-miR393 were non-responsive to this infection, compared to the mock-inoculated control group. Consistently, Os-SPL3 and Os-MADS known target genes were expressed in reverse correlation to Osa-miR156 and Osa-miR444, respectively. Conclusions: From these data, it is suggested that both early (Osa-miR-156) and late (Osa-miR167, Osa-miR171, OsamiR408, Osa-miR444) responsive miRNAs might be involved in R. solani infection in rice plants.