Towards a molecular understanding of plant gall induction by aphids: the role of the huge, novel family of Bicycle effector proteins

Many species of arthropods produce effector molecules that induce abnormal plant organs, called galls, that the arthropods exploit for food and shelter. The identity of these effector molecules has long been mysterious. We have previously found that a large family of rapidly evolving genes that encode novel “Bicycle” proteins are secreted by aphids into plant tissue during gall development and that natural variation in one bicycle gene causes phenotypic variation in galls. I will present recent unpublished studies, in which we have found that bicycle genes are the major genetic determinants of plant gene expression variation in galls, suggesting that bicycle genes are a large and important class of gall effector proteins. We have also found that bicycle genes are present in the genomes of all aphid species examined, as well as those of phylloxerids and scale insects, suggesting that these non-gall forming taxa, which include myriad crop pests, also secrete Bicycle proteins into plants. I will also present new unpublished data on the structure and evolution of Bicycle proteins and on how Bicycle proteins carry out their molecular functions.