Our ability to manipulate plant growth and development for beneficial purposes depends on understanding the genetic bases of these processes. Studies of the effects of external signals which disrupt development and cause abnormalities or disease have revealed many useful insights into the mechanisms controlling growth and development in plants and animals. Galls (abnormal growth structures) directed by signals from insects are an ideal model system to study how external signals manipulate plant growth. The insect, through unidentified chemical signals, hijacks the plant development to manipulate tissue growth into a gall that encloses, feeds and protects the larvae. Our approach utilizes functional genomics techniques to discover patterns and evolution of key features involved in this plant-insect interaction. Our model system utilizes two species of the plant genus Solidago, the fly Eurosta solidaginis and the moth Gnorimoschema gallaesolidaginis.

Project Goals

• Developmental Timing:
  What are the changes over time in host plant gene expression patterns that coordinate the growth of the highly structured and differentiated tissues of galls?
  
• Plant Genotype Effects:
  Are the plant gene expression patterns different when the galling insect invades a closely related plant species?
  
• Insect Galler Genotype Effects:
  Are the plant gene expression patterns different when infected separately by two different galling insect species that both produce stem galls?

The Solidago-Eurosta-Gnorimoschema interaction as a model system
Solidago altissima and S. gigantea are galled by both a fly, Eurosta solidagensis and a moth, Gnorimoschema gallaesolidaginis. These plant-animal interactions result in the formation of similar gall morphologies on the plant stem, each housing a single maturing insect larvae.

The Functional Genomics Approach
In order to determine the plant genes involved in the plant-animal interaction we are utilizing a functional genomics method that does not rely on availability of a whole genome sequence or EST libraries.. This methods utilizes reciprocally subtracted cDNA libraries for gall and stem tissues. Libraries are spotted on microarray slides and hybridized to evaluate the success of the subtraction (identify false positives) and to determine which clones requires further investigation by sequencing and real-time PCR.