PI: James H. Westwood (Virginia Polytechnic Institute and State University)
CoPIs: Claude dePamphilis (Pennsylvania State University; subawardee), John Yoder (University of California-Davis; subawardee), and Michael Timko (University of Virginia; subawardee)
The evolutionary transition from autotrophism to heterotrophism by parasitic plants is an extraordinary example of adaptive plant biology. The central example of this is the haustorium, an organ unique to parasitic plants that penetrates the host and forms a physiological bridge between parasite and host. In parasites of the Orobanchaceae, the haustorium is believed to have evolved from root tissue, but nothing is known about the origins of the genes responsible for haustorium development. Furthermore, a parasitic plant species free of the constraints of autotrophy may show substantial changes in morphology and physiology such as reductions in root and leaves mass and loss of photosynthetic machinery, but little is known about the consequences of such changes on their genomes. The project will address these issues using a comparative genomic analysis of three related genera that span the spectrum of parasitism: a facultative parasite (Triphysaria versicolor), a photosynthetically competent obligate parasite (Striga hermonthica), and an obligate holoparasite (Orobanche ramosa). The availability of a sequenced genome for the closely related non-parasite Mimulus provides a fully autotrophic outgroup to further enhance this approach. The project will sequence cDNAs representing transcripts from key life stages of each parasitic species, conduct cursory comparative analysis of expression patterns based on sequence diversity and abundance. Sequences can be accessed through the project website, GenBank and the Plant Genome Network (PGN) (http://pgn.cornell.edu/help/about.shtml) which serves as a public repository for trace files and sequences from ongoing EST sequencing projects.
Expected broader impacts of the proposed research: These studies establish a starting point for future detailed comparative gene expression analysis aimed at identifying potential genetic changes associated with the evolutionary transition from autotrophy to heterotrophy. In addition, the research is expected to produce new insights into management of weedy parasitic species such as Striga and Orobanche spp., which are devastating agricultural pests in much of the world. A major impact of this project will be the public release of an extensive set of gene sequences from a group of related plants that encompass an enormous breadth of morphological and physiological diversity. This project will reach out to the parasitic plant research communities through a project website, and will seek to establish exchanges between US personnel and researchers from developing nations who need opportunities for training in genomics or bioinformatics. It is hoped that data from this project will contribute to the development of effective control strategies.
