Grapes are the world's most valuable fruit crop, and a small insect called phylloxera is one of the grapevine's worst enemies. In the past it has almost wiped out vineyards worldwide. Phylloxera causes the plant to create specialized structures in which it lives and reproduces, called galls. This way of attacking plants is widespread and has evolved numerous times, and many important plant pests are gall-makers. Still, no one has any idea how the insect instructs the plant to create a new organ that benefits the pest. This project will attempt to understand this remarkable ability by examining the plant genes that are turned on or off by the insect in creating a gall. Charles Darwin suggested that galls resemble fruits and this project will focus on genes the plant normally uses to create flowers and fruits. The hypothesis is that plant genes normally involved in fruit production are activated by the insect in roots and leaves. Preliminary evidence to date supports that view. Since plants normally regulate flower and fruit production using hormones, a second hypothesis to be tested is that phylloxera manipulates plant hormones to create galls. These ideas will be confirmed by producing genetically-modified grapevines with key genes blocked. It should be impossible for galls to form on these plants. Findings from this project will not only explain a long-held mystery of nature; they will also provide the genetic information necessary for developing insect-resistance grapevines. The project is a unique collaboration among ecologists, entomologists, plant biologists and biotechnologists. Its results will be extended to the public via a collaboration with the Missouri School of Journalism and to grapevine breeders. The PIs are very active supporters of McNair and EXPRESS program students and a substantial number of undergraduates and K-12 teachers will also participate.