Identification of candidate virus response and vector competence genes in the virus-transmitting leafhopper, Graminella nigrifrons

Leafhoppers are important transmitters of bacterial and viral plant pathogens.  The black-faced leafhopper (Graminella nigrifrons Forbes) semi-persistently transmits Maize chlorotic dwarf virus (MCDV) which is transiently foregut-associated, and persistently transmits Maize fine streak virus (MFSV) which infects and circulates in the leafhopper.  To compare leafhopper responses to these two viruses with very different transmission modes, transcriptional changes were measured in leafhoppers fed on MCDV- and MFSV- infected maize.  Common immune induction responses were observed when leafhoppers were exposed to either virus, but most transcriptional changes were virus-specific.  These changes may reflect differences in the virus-vector biology as well as changes to the infected feeding source plants.  The interaction between black-faced leafhoppers and MFSV was further examined, based on observations that only a subset of insects exposed to virus are infected with MFSV, and a subset of those experimentally transmit the virus.  No major genetic or transcriptional differences were observed between MFSV-infected leafhoppers that experimentally transmitted virus and those that did not.  However, the MFSV 3 gene was expressed at unexpectedly high levels, indicating a possible role in leafhoppers.  In summary, transcriptome analyses have identified genes involved in leafhopper responses to plant viruses, including candidates that may be important in vectoring pathogens.