Identification and analysis of miRNAs in IR56 rice in response to BPH infestations of different virulence levels

Rice production and sustainability are challenged by its most dreadful pest, the brown planthopper (Nilaparvata lugens Stål, BPH). Therefore, the studies on rice-BPH interactions and their underlying mechanisms are of high interest. The rice ontogenetic defense, such as the role of microRNAs (miRNAs) has mostly been investigated against the pathogens, with only a few reports existing against the insect infestations. Thus, revealing the involvement of rice miRNAs in response to BPH infestations will be beneficial in understanding these complex interactions. In this study, the small RNA profiling of the IR56 rice in response to separate BPH infestations of varied virulence levels identified the BPH-responsive miRNAs and revealed the differential transcript abundance of several miRNAs during a compatible and incompatible rice-BPH interaction. The miRNA sequence analysis identified 218 known and 28 novel miRNAs distributed in 54 miRNA families. Additionally, 138 and 140 numbers of differentially expressed (DE) miRNAs were identified during the compatible and incompatible interaction, respectively. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed the target gene candidates of DE miRNAs (including osa-miR2871a-3p, osa-miR172a, osa-miR166a-5p, osa-miR2120, and osa-miR1859) that might be involved in the IR56 rice defense responses against BPH infestation. Conversely, osa-miR530-5p, osa-miR812s, osa-miR2118g, osa-miR156l-5p, osa-miR435 and two of the novel miRNAs, including novel_16 and novel_52 might negatively modulate the IR56 rice defense. The expressional validation of the selected miRNAs and their targets further supported the IR56 rice defense regulatory network. Based on our results, we have proposed a conceptual model depicting the miRNA defense regulatory network in the IR56 rice against BPH infestation. The findings from the study add further insights into the molecular mechanisms of rice-BPH interactions and will be helpful for the future researches.