|CASSONE, BRYAN - The Ohio State University|
|CISNEROS-CARTER, F - The Ohio State University|
|MICHEL, A - The Ohio State University|
|Redinbaugh, Margaret - Peg|
Submitted to: PLoS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2014
Publication Date: 11/24/2015
Publication URL: http://handle.nal.usda.gov/10113/61399
Citation: Cassone, B.J., Cisneros-Carter, F.M., Michel, A.P., Stewart, L.R., Redinbaugh, M.G. 2015. Genetic insights into Graminella nigrifrons competence for Maize fine streak virus infection and transmission. PLoS One. 9(11):e113529. DOI:10.1371/journal.pone.0113529.
Interpretive Summary: Most plant-infecting rhabdoviruses are transmitted by one or a few closely related insect species. Additionally, intraspecific differences in transmission efficacy exist among races/biotypes within vector species and among strains within a virus species. The black-faced leafhopper, Graminella nigrifrons, is the only known vector of the persistent propagative rhabdovirus Maize fine streak virus (MFSV). Only a small percentage of leafhoppers are capable of transmitting the virus, although the mechanisms underlying vector competence are not well understood. In this study, we used RNA-Seq to explore transcript expression changes and sequence variation in G. nigrifrons and MFSV that may be associated with the capability of the vector to acquire and transmit the virus. Feeding on MFSV-infected maize elicited a considerable transcriptional response in G. nigrifrons, with increased expression of cytoskeleton organization and immunity transcripts in infected leafhoppers. Differences between leafhoppers capable of transmitting MFSV, relative to non-transmitting but infected leafhoppers were more limited, which may reflect the difficulties discerning between the two groups and/or the strong possibility that the transmitter phenotype results from one or a few genetic differences. The ability of infected leafhoppers to transmit MFSV did not appear associated with virus transcript accumulation in the infected leafhoppers or sequence polymorphisms in the viral genome. However, the non-structural MFSV 3 gene was expressed at unexpectedly high levels infected leafhoppers, suggesting it plays an active role in the infection of the insect host. The results of this study begin to define the functional roles of specific G. nigrifrons and MFSV genes in the viral transmission process.
Technical Abstract: Insects are critical for the spread of most plant virus diseases, with >75% of plant viruses depending on an insects for transmission to new, uninfected hosts. However, little is known about the molecular and cellular factors in the insect that are important for virus transmission. The black-faced leafhopper (Graminella nigrifrons) is the vector of two corn-infecting viruses that use different strategies for host transmission: Maize chlorotic dwarf virus, which stays in the insect gut and is transmitted quickly by the leafhopper; and, Maize fine streak virus (MFSV), which multiplies in leafhopper cells and requires a long incubation period before it can be transmitted by the leafhopper. In our lab population of leafhoppers we can identify three types of individuals: those that are able to acquire and transmit MFSV; those that acquire MFSV but do not transmit it; and, those that do not acquire the virus (non-acquirers). In this study, we used next generation sequencing to characterize gene expression in these three types of leafhoppers. Gene expression was affected in all leafhoppers feeding on MFSV-infected corn, especially expression of genes associated with the insect's immune response and systems for intracellular movement of proteins. There were also significant differences in gene expression between leafhoppers in which MFSV multiplies and the non-acquirers. However, gene expression in the leafhoppers that could acquire and transmit MFSV or just acquire the virus was quite similar, which would be expected if our hypothesis that there are only one or a few factors that distinguish these two types of leafhoppers is correct. The ability of leafhoppers to transmit MFSV was not associated with virus transcript accumulation in the infected leafhoppers or with sequence differences within the viral genome. However, high levels of expression for one of the viral genes with an unknown function (MFSV 3) suggest it plays a role in virus multiplication in the leafhopper. This study provides clues for researchers to identify and test specific genes for their roles in making a leafhopper a vector and to develop a better understanding of the function of the MFSV genes, both of which can provide targets for disease control.