Advances in aphid salivary protein research
Acta Entomologica Sinica
2019, 62 ( 12):
Aphids (Hemiptera: Aphididae), a group of important agricultural pests, ingest plant phloem sap and transmit plant viruses with piercing-sucking mouthparts. The outbreak of aphids often causes serious economic losses. In the long history of co-evolution, plants have established effective defense systems against the threat of aphids. In order to overcome these plant defenses, aphids also have developed sophisticated countermeasures. Among them, aphids secrete salivary proteins during the feeding process, which can modulate plant defenses and degrade plant secondary metabolites. Therefore, salivary proteins play a critical role in plant-aphid interactions. In this review, we summarized recent advances in the identification of aphid salivary proteins and the functional research of associated proteins, and brought forward the prospects about application of salivary proteins in aphid control and new directions for future research. Common methods used to identify and predict aphid salivary proteins include enzymatic activity assay of salivary proteins, proteomic analysis of aphid saliva, and transcriptomic and proteomic analysis of salivary glands. However, these methods all have their own advantages and disadvantages, and individual method may just reveal partial real information of the whole aphid secretome. The combination of different techniques can provide more realistic and detailed information. Aphid salivary proteins can be classified into various categories including detoxifying enzymes, protective enzymes, hydrolases, binding domain proteins, effector proteins of unknown function categories and so on. Aphid salivary proteins have multiple functions, such as participating in salivary sheath formation, inducing or repressing plant defenses, promoting aphid feeding and enhancing aphid fecundity. Silencing aphid salivary protein coding genes via RNAi technology can significantly affect feeding behaviors, and decrease aphid survival rate, fecundity and fitness. Therefore, aphid salivary proteins are ideal targets for manipulation in aphid control. Now, in several crops, some effective aphid-resistant lines, which can target salivary protein coding genes, have been established, via the HIGS (host-induced gene silencing) technique, and they have showed good application prospects. According to the present studies, it is urgent to analyze aphid secretomes with combination of multiple Omic techniques. There is still a serious lack of research on the specific functions of various salivary proteins. It is necessary to explore the functions and related molecular mechanisms of salivary proteins of aphids from multiple dimensions, such as aphids, plants and the interactions between them, so as to lay a foundation for the development of new aphid control strategies based on the regulation of salivary proteins in aphids.
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