A novel family of secreted proteins linked to plant gall development

In an elaborate form of inter-species exploitation, many insects hijack plant development to induce galls--novel plant organs resulting from dramatic reprograming of plant cell biology. Insects induce galls by introducing unidentified molecules into plants. Here we identify an aphid gene, determinant of gall color (dgc), that is genetically associated with variation in a gall phenotype, providing the first example of an insect gene implicated in gall development. Dgc encodes a BICYCLE protein, a new family of secreted proteins. Bicycle genes are strongly expressed specifically in galling aphid salivary glands, suggesting they control many aspects of gall development. Bicycle genes have experienced unusually strong diversifying selection, consistent with their potential role controlling gall development in a molecular arms race between aphids and their host plants. One Sentence SummaryAphid bicycle genes, which encode diverse secreted proteins, contribute to plant gall development.