BIOLOGY, ETIOLOGY, GENETICS, AND CONTROL OF VIRUS DISEASES OF CORN AND SOYBEAN
Location: Corn, Soybean and Wheat Quality Research Unit
Title: Transcriptome of the plant virus vector Graminella nigrifrons, and the molecular interactions of Maize fine streak rhabdovirus transmission
Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 18, 2012
Publication Date: July 12, 2012
Citation: Chen, Y., Cassone, B.J., Bai, X., Redinbaugh, M.G., Michel, A. 2012. Transcriptome of the plant virus vector Graminella nigrifrons, and the molecular interactions of Maize fine streak rhabdovirus transmission. PLoS One. 7(7):e40613.
Interpretive Summary: Virus diseases can cause significant losses in crops, and most plant viruses are transmitted to new crop plants by insects. Aphids, whiteflies, planthoppers, and leafhoppers, are among the most important transmitters of viruses. Genome information on these virus transmitters, or vectors, is essential to understanding how these insects transmit viruses and for developing new ways of controlling the diseases they transmit. Some genomic information is available for aphids, whiteflies and planthoppers, but little or no genome information has been obtained for leafhoppers. The black-faced leafhopper, Graminella nigrifrons, is prevalent in the eastern U.S., and where it can transmit several different viruses to corn. In this study, we used a high throughput sequencing approach to identify over 38,000 G. nigrifrons genes. We could tentatively assign gene function to some of the genes by comparison to the genes of other insects, and identified some genes that may be involved in the insect’s innate immune system. Interestingly, five of the immunity genes were expressed at much lower levels in virus-infected leafhoppers than in uninfected leafhoppers. These results provide a sound framework for future studies aimed at understanding the interactions between the plant virus and insect vector that are important for virus transmission.
Background: Leafhoppers (Hemiptera:Cicadellidae) are plant-phloem feeders that are known for their ability to vector plant pathogens. The black-faced leafhopper (Graminella nigrifrons) has been identified as the only known vector for the Maize fine streak virus (MFSV), an emerging plant pathogen in the Rhabdoviridae. Within G. nigrifrons populations, individuals can be experimentally separated into three classes based on their capacity for viral transmission: transmitters, acquirers and non-acquirers. Understanding the molecular interactions between vector and virus can reveal important insights in virus immune defense and vector transmission.
Results: RNA sequencing (RNA-Seq) was performed to characterize the transcriptome of G. nigrifrons. A total of 38,240 ESTs of a minimum 100 bp were generated from two separate cDNA libraries consisting of virus transmitters and acquirers. More than 60% of known D. melanogaster, A. gambiae, T. castaneum immune response genes mapped to our G. nigrifrons EST database. Real time quantitative PCR (RT-qPCR) showed significant down-regulation of three genes for peptidoglycan recognition proteins (PGRP - SB1, SD, and LC) in G. nigrifrons transmitters versus control leafhoppers.
Conclusions: Our study is the first to characterize the transcriptome of a leafhopper vector species. Significant sequence similarity in immune defense genes existed between G. nigrifrons and other well characterized insects. The down-regulation of PGRPs in MFSV transmitters suggested a possible role in rhabdovirus transmission. The results provide a framework for future studies aimed at elucidating the molecular mechanisms of plant virus vector competence.