Expanding molecular resources for the insect vector, Graminella nigrifrons

Rhabdoviruses are serious pathogens that infect humans, livestock and crops. Plant rhabdoviruses are often vectored Hemipterans, which themselves can be impacted during transmission. Maize fine streak virus (MFSV) is a recently described rhabdovirus that is transmitted in a persistent manner by the black-faced leafhopper, Graminella nigrifrons. G. nigrifrons individuals within the same population could be experimentally separated into three classes: ‘transmitters’, which can transmit MFSV to new plant hosts; ‘acquirers’ which become infected by but cannot transmit MFSV; and ‘non-acquirers’ which do not acquire MFSV despite feeding on infected plants. Although the biology of G. nigrifrons has been studied, no molecular information exists for this important vector. The lack of molecular resources is a significant barrier to understand the molecular basis of rhabdovirus transmission. We characterized G. nigrifrons transcripts by constructing two separate cDNA libraries of transmitters and acquirers, and sequencing on an Illumina GA-II. From these two libraries, 38,240 transcripts were obtained from the G. nigrifrons transcriptome, and 13,036 transcripts (34.1%) had matches in the Swissprot database. Quantitative reverse transcription PCR (qPCR) was used to test the expression of genes related to insect immune system among unexposed individuals and transmitters. Genes in the peptidoglycan recognition protein (PGRP) family, specifically SB1, SD, LA, LC, were significantly down regulated in the transmitters. These new genomic resources of G. nigrifrons will lead to a further understanding of the molecular interaction between rhabdoviruses and their insect hosts.