A salivary effector enables whitefly to feed on host plants by eliciting salicylic acid-signaling pathway

Phloem-feeding insects feed on plant phloem using their stylets. While ingesting phloem sap, these insects secrete saliva to circumvent plant defenses. Previous studies have shown that, to facilitate their feeding, many phloem-feeding insects can elicit the salicylic acid- (SA-) signaling pathway an...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2019-01, Vol.116 (2), p.490-495
Main Authors: Xu, Hong-Xing, Qian, Li-Xin, Wang, Xing-Wei, Shao, Ruo-Xuan, Hong, Yue, Liu, Shu-Sheng, Wang, Xiao-Wei
Format: Article
Language:English
Subjects:
Animals
Biological Sciences
Hemiptera - metabolism
Herbivory - physiology
Homeodomain Proteins - metabolism
Plant Proteins - metabolism
Salicylic Acid - metabolism
Saliva - metabolism
Signal Transduction - physiology
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Summary:Phloem-feeding insects feed on plant phloem using their stylets. While ingesting phloem sap, these insects secrete saliva to circumvent plant defenses. Previous studies have shown that, to facilitate their feeding, many phloem-feeding insects can elicit the salicylic acid- (SA-) signaling pathway and thus suppress effective jasmonic acid defenses. However, the molecular basis for the regulation of the plant’s defense by phloem-feeding insects remains largely unknown. Here, we show that Bt56, a whitefly-secreted low molecular weight salivary protein, is highly expressed in the whitefly primary salivary gland and is delivered into host plants during feeding. Overexpression of the Bt56 gene in planta promotes susceptibility of tobacco to the whitefly and elicits the SA-signaling pathway. In contrast, silencing the whitefly Bt56 gene significantly decreases whitefly performance on host plants and interrupts whitefly phloem feeding with whiteflies losing the ability to activate the SA pathway. Protein-protein interaction assays show that the Bt56 protein directly interacts with a tobacco KNOTTED 1-like homeobox transcription factor that decreases whitefly performance and suppresses whitefly-induced SA accumulation. The Bt56 orthologous genes are highly conserved but differentially expressed in different species of whiteflies. In conclusion, Bt56 is a key salivary effector that promotes whitefly performance by eliciting salicylic acid-signaling pathway.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1714990116