The candidate saliva proteins that might be involved in the host specialization process of the pea aphid (Acyrthosiphon pisum) complex

Aphids are sap feeding insects and inject numbers of saliva proteins into plants while they feed. Aphid saliva and the proteins contained in the saliva are reported to interfere or facilitate aphid feeding and progeny production. However, the protein components of aphid saliva and their functions are still largely unknown. The pea aphid (Acyrthosiphon pisum) forms multiple biotypes each of which is specialized to one or a few legume species. We hypothesize that saliva proteins are one of the factors that are involved in host plant specialization of the pea aphid complex and those genes have biotype specific sequences or expression patterns. We have resequenced the genomes of multiple pea aphid biotypes and identified several saliva gene candidates that show biotype specific polymorphisms. In addition, we are currently analyzing transcriptional profiles of multiple aphid biotypes. Based on these analyses, we are generating a list of candidate aphid saliva genes that might be involved in the host plant specialization. These candidate proteins will be subjected to functional analyses to examine their roles in plant-aphid interactions.