MicroRNA response in insect salivary glands to plant virus infection

Most arboviruses rely on insect vectors for transmission, with salivary glands serving as a critical gateway for viral spread to new hosts. MicroRNAs (miRNAs) are key regulators of gene expression, yet their roles in salivary glands during virus infection remain poorly understood. Using the small brown planthopper (SBPH)-rice stripe virus (RSV) system, we sequenced small RNAs from salivary glands of nonviruliferous and viruliferous insects and identified 5,909 known miRNAs from 201 families. Of these, 1,143 miRNAs were differentially expressed upon RSV infection, including 1,090 upregulated from 36 families and 53 downregulated from 11 families. These differentially expressed miRNAs were predicted to target 2,876 genes. Gene Ontology analysis showed that targets of upregulated miRNA were enriched in "protein binding," while those of downregulated miRNAs were associated with "cytoskeleton" and "regulation of dephosphorylation." The neurotrophin signaling pathway was the top-enriched KEGG pathway for the upregulated miRNA targets. Two miRNAs, miR-276-5p and miR-13a-3p, were specifically modulated by RSV in the salivary glands but not in the guts. miR-276-5p was found to enhance RSV secretion from the salivary glands into rice without altering viral load in insects, whereas miR-13a-3p could play a negative role in viral accumulation in insects. Taken together, our findings highlight tissue-specific miRNA responses in vector-virus interactions and uncover distinct roles of salivary gland miRNAs in regulating viral transmission.

Most plant viruses depend on insect vectors for transmission. The salivary glands of insect vectors are the last barrier for these viruses to overcome before being transmitted to plant hosts. In this work, we dissected the microRNA (miRNA) response to plant virus infection in insect salivary glands using the model of the small brown planthopper and rice stripe virus (RSV). The abundance of hundreds of miRNAs changes in the salivary glands after RSV infection. Two specific miRNAs play distinct roles. One enhances the release of RSV from salivary glands into rice plants, and the other regulates viral accumulation within the insects. These findings deepen our understanding of small RNA reactions and potential functions of miRNAs to viral infection in the salivary glands of insect vectors.