Analysis of aphid (Hemiptera: Aphididae) salivary proteins

We evaluated the salivary constituents of the Russian wheat aphid (Diuraphis noxia, Hemiptera: Aphididae). Protein phosphatase was putatively identified in D. noxia saliva using Orbitrap MS, and alkaline phosphatase activity confirmed using biochemical assays. Alkaline phosphatase was only detected in probed 15% sucrose diet, and was not detected in probed diet consisting of amino acids (100-mM serine, 100-mM methionine, 100-mM aspartic acid, and 15% sucrose). Other peptides in sucrose diet weakly but significantly showed similarities to putative dehydrogenase and RNA helicase ESTs described from other aphids. We also compared salivary constituents between two D. noxia biotypes (RWA-1 and RWA-2) that differ in their responses to wheat resistance conferred by Dn-4 using gel electrophoresis and MALDI-TOF-MS. We did not detect substantial differences, but analyses are ongoing. Lastly, we compared the salivary constituents between several grain aphids (D. noxia, D. tritici, D. mexicana, and Schizaphis graminum), and the pea aphid (Acyrthosiphon pisum) using protein electrophoresis and biochemical assays. Banding patterns were similar for the three Diuraphis species, but were variable across genera. However, all five species shared common protein products (~125-kDa) detected on SDS-PAGE, and alkaline phosphatase activity was detected in the saliva of each species.