Characterization of a putative Peregrinus maidis antimicrobial peptide and its interaction with a rhabdovirus

Peregrinus maidis (Ashmead), the corn planthopper, is a hemipteran insect pest on maize found in tropical and subtropical regions, and it is the sole insect vector of maize mosaic virus (MMV), a plant and animal-infecting rhabdovirus. Insect transmission of MMV occurs in a persistent-propagative manner, and MMV infection on maize causes severe stunting, resulting in significant economic losses. The insect antiviral response to MMV is not known, and we aim to fill that knowledge gap. Since the MMV glycoprotein is crucial for initiating viral infections, a membrane-based yeast two-hybrid system was used to identify glycoprotein-interacting insect proteins. The results from that screen together with in silico analyses led us to discover a putative ortholog of lugensin (PMLgs), a newly found antimicrobial peptide (AMP) from Nilaparvata lugens (Stål), the brown planthopper. Because some AMPs have antiviral activity, and PMLgs binds to the viral surface glycoprotein, we hypothesized that PMLgs has antiviral activity against MMV. Additionally, we hypothesized that PMLgs is an antibacterial peptide as N. lugens lugensin was demonstrated to have antibacterial properties. Preliminary functional analysis studies show that dsRNA-mediated RNAi is highly efficient in P. maidis, and that knocking down PMLgs transcript levels did not significantly affect MMV accumulation. PMLgs was prokaryotically expressed, and the purified peptide was shown to inhibit E. coli growth in bacterial growth inhibition assays. Characterization of the role of PMLgs will contribute towards our understanding of insect immunity and the vector-host interactions between P. maidis, MMV, and its associated bacterial microbiome.