Maize fine streak virus (MFSV) is a newly discovered member of the genus Nucleorhabdovirus. Insect transmission of rhabdoviruses is highly specific; a given rhabdovirus is transmitted only by one or a few closely related insect species. The goal of this study is to identify and characterize factors essential for insect vector competence.
Immunolocalization-confocal microscopy results showed that MFSV and maize mosaic virus (MMV) infection were observed in the virion-fed and injected vectors Graminella nigrifrons (Forbes) and Peregrinus maidis (Ashmead), respectively. The virus was detected in muscle, nerve, salivary gland, and/or midgut cells. However, MFSV was not detected in P. maidis and MMV was not detected in G. nigrifrons. The results support the hypothesis that there are multiple barriers to rhabdovirus replication and movement in nonvector insects.
Sequence analysis of MFSV cDNA clones indicated three genomic sequences with similarity to the nucleocapsid (N), glycoprotein (G) and RNA polymerase (L) genes of Sonchus yellow net virus (SYNV). The L protein sequence of MFSV had 51-55% identity with that of two nucleorhabdoviruses, SYNV and Rice transitory yellowing virus (RTYV), and the cytorhabdovirus Northern cereal mosaic virus (NCMV). In phylogenetic analyses, the plant-infecting viruses grouped together, with the nucleorhabdoviruses (MFSV, RTYV and SYNV) forming a strongly supported group. Interestingly, leafhopper-transmitted MFSV is more related to the aphid-transmitted SYNV than to the leafhopper-transmitted RTYV. Rhabdoviruses may adapt easily to different insect vectors. The non-conserved surface-exposed G protein recognizes cellular receptors and is likely to determine vector specificity.
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