Salivary Proteins of Whitefly Bemisia tabaci Modulate Plant Defenses by Activating SA Signaling Pathway

The whitefly Bemisia tabaci is an infamous agricultural pest that inflicts significant harm on crops globally by directly feeding on them and indirectly transmitting viruses. Although it is believed that whiteflies inject saliva into their host plants to modulate plant defenses, however, due to their small size, study on the salivary proteome of whiteflies is still sparse and the roles of many salivary proteins remain elusive. This research employed four-dimensional data-independent acquisition (4D DIA) based proteomic techniques to analyze whitefly secreted saliva. In total, 2625 salivary proteins were identified. Bioinformatic analysis results showed that the secreted saliva proteins may play roles in hydrolysis, transport, protein binding and metabolism, and significantly increased the levels of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) activities as well as malondialdehyde (MDA), soluble sugars (SS), soluble protein (SP), and proline (PRO) in cucumbers. The expression of the salicylic acid (SA) response genes (PR1a, PR3, and PR5) were significantly induced. Additionally, exogenous methyl-salicylate (MeSA) treatment of cucumbers can significantly reduce the reproductive capacity and survival rate of whiteflies, and decrease the preference of whiteflies for host plants. This study's outcomes provide valuable insights into the interaction between plants and insects. It has been proved that the salivary proteins of whitefly participate in host plant defense responses by activating the SA signaling pathway, and provides basic data on the functional study of whitefly saliva elicitors and effectors, which can be used for development of novel strategies for pest management.