Boyce Thompson Institute for Plant Research Ithaca, New York
Plant-aphid interactions involve a wide array of mostly uninvestigated small molecules, proteins, and signaling pathways, which together constitute a dynamic co-evolutionary battle between these insect pests and their host plants. We used mass spectrometry to identify Myzus persicae (green peach aphid) salivary proteins that were secreted into artificial diet. Genes encoding sixty of these salivary proteins were cloned into Agrobacterium tumefaciens vectors for transient expression in Nicotiana benthamiana. Four of the proteins elicited severe hypersensitive responses, reminiscent of those induced by some bacterial effectors. We determined the subcellular localization of the sixty aphid salivary proteins in N. benthamiana leaves using GFP fusions and confocal microscopy. This showed that two of the aphid proteins were transported into plant cell nuclei, indicating that they may regulate transcription during plant-aphid interactions. Co-immunoprecipitation of Sp15 (salivary protein 15) with its putative plant partners led to identification of two transcription factors and one RNA-dependent RNA polymerase by mass spectrometry. By contrast, co-immunoprecipitation of Sp11, an aphid salivary protein that elicits plant hypersensitive responses, identified several plant peroxisomal proteins, including catalase and glycolate oxidase, as putative interacting partners. On N. benthamiana plants that were transiently expressing Sp11, M. persicae were able to produce more progeny than on Agrobacterium-infiltrated control plants. Ongoing functional characterization of Sp11, Sp15, and other aphid salivary proteins will identify mechanisms by which aphids manipulate host plant metabolism and defense responses for their own benefit.
