Genetics Coupled to Quantitative Intact Proteomics Links Heritable Aphid and Endosymbiont Protein Expression to Circulative Polerovirus Transmission

Abstract

Yellow dwarf viruses in the family Luteoviridae, which are the causal agents of yellow dwarf disease in cereal crops, are each transmitted most efficiently by different species of aphids in a circulative manner that requires the virus to interact with a multitude of aphid proteins. Aphid proteins differentially expressed in F2 Schizaphis graminum genotypes segregating for the ability to transmit Cereal yellow dwarf virus-RPV (CYDV-RPV) were identified using two-dimensional difference gel electrophoresis (DIGE) coupled to either matrix-assisted laser desorption ionization-tandem mass spectrometry or online nanoscale liquid chromatography coupled to electrospray tandem mass spectrometry. A total of 50 protein spots, containing aphid proteins and proteins from the aphid's obligate and maternally inherited bacterial endosymbiont, Buchnera, were identified as differentially expressed between transmission-competent and refractive aphids. Surprisingly, in virus transmission-competent F2 genotypes, the isoelectric points of the Buchnera proteins did not match those in the maternal Buchnera proteome as expected, but instead they aligned with the Buchnera proteome of the transmission-competent paternal parent. Among the aphid proteins identified, many were involved in energy metabolism, membrane trafficking, lipid signaling, and the cytoskeleton. At least eight aphid proteins were expressed as heritable, isoelectric point isoform pairs, one derived from each parental lineage. In the F2 genotypes, the expression of aphid protein isoforms derived from the competent parental lineage aligned with the virus transmission phenotype with high precision. Thus, these isoforms are candidate biomarkers for CYDV-RPV transmission in S. graminum. Our combined genetic and DIGE approach also made it possible to predict where several of the proteins may be expressed in refractive aphids with different barriers to transmission. Twelve proteins were predicted to act in the hindgut of the aphid, while six proteins were predicted to be associated with the accessory salivary glands or hemolymph. Knowledge of the proteins that regulate virus transmission and their predicted locations will aid in understanding the biochemical mechanisms regulating circulative virus transmission in aphids, as well as in identifying new targets to block transmission.

Proteomic Analysis of Frankliniella occidentalis and Differentially Expressed Proteins in Response toTomato Spotted Wilt VirusInfection

“…A glyceraldehyde-3-phosphate dehydrogenase (G3PDH) was identified in spot 182 and within spot 196 as being downregulated by TSWV infection in both spots. In contrast, this protein was consistently found upregulated in three different vector-competent genotypes of the greenbug (16), and G3PDH has been found to be potentially involved in the transcytosis of beet western yellows virus in the green peach aphid (Myzus persicae) (68). G3PDH has been found to be important in the infection process of other plant-and animalinfecting viruses.…”

“…To identify proteins that are differentially expressed in the first-instar larvae of F. occidentalis during TSWV infection, we subjected proteins extracted from virus-exposed and nonexposed L1 thrips by the trichloroacetic acid-acetone (TCA-A) extraction method used by Cilia et al (15,16) to 2-D electrophoresis. To standardize the relative abundance of proteins across treatments and biological replications, we used 375 g of protein extract per sample.…”

Implication of the Bacterial Endosymbiont Rickettsia spp. in Interactions of the Whitefly Bemisia tabaci with Tomato yellow leaf curl virus

“…Circulative plant virus transmission is a very specific and regulated process controlled by both insect and virus proteins (15)(16)(17)(18), with the crucial participation of a third player-bacterial endosymbionts. Evidence points to the direct involvement of whitefly bacterial endosymbiont proteins in begomovirus-whitefly circulative transmission (4,7).…”

Analysis of Intact Protein Isoforms by Mass Spectrometry

“…4) (97). Cilia et al (97) used DIGE to phenotype sister aphid F2 genotypes that segregated in their ability to transmit plant viruses. The study revealed phenotyping and virus transmission information.…”