Proteomic insights into the saliva and salivary glands of the cotton aphid, Aphis gossypii (Hemiptera: Aphididae)

The cotton aphid or melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is a rising threat to cotton production. Aphids use needle-like stylets to puncture the plant epidermis, access the sieve tube, and ingest the plant phloem. Aphids release salivary proteins while feeding, allowing them to colonize host plants successfully. Aphid saliva consists of many constituents that facilitate the consumption of phloem sap upon partial digestion and modulate plant defense systems. The salivary proteomes of A. gossypii were studied using liquid chromatography-tandem mass spectrometry (LC–MS/MS), which resulted in the identification of 189 proteins in excised salivary glands and 95 proteins in artificial diet-fed aphid saliva, with 25 proteins commonly noticed in both proteomes. Several proteins, including CAH1711662.1, CAH1735943.1, PFF0380w, XP_027839681.2, CAH1714583.1, CAH1713131.1 and XP_027840117.2 remained unique and uncharacterized. Previously identified salivary proteins of insects, such as glucose dehydrogenase, Mp1, Mp58, peroxidase, heat shock protein (HSP), elongation factor, and aminopeptidases, were also found. The identified proteins were categorized into seven groups, viz., enzymes, cytoskeletal proteins, sheath proteins, calcium-binding proteins, transporter proteins, chromatin-, RNA-, and DNA-binding proteins, and miscellaneous proteins. Twenty-five proteins from diet-fed aphid saliva and 17 proteins in the salivary gland possessed signal peptides. This study's results offer a more detailed understanding of the salivary proteins of A. gossypii and provide the foundation for future functional studies on aphid-cotton interactions to develop new aphid control methods.