Plant & Animal Genomes XI Conference

January 11-15, 2003
Town & Country Convention Center
San Diego, CA

Poster: Functional Analysis
            

FUNCTIONAL AND COMPARATIVE GENOMICS OF DISEASE RESISTANCE GENE HOMOLOGS

¹ Department of Vegetable Crops, 148 Asmundson Hall, University of California, Davis, CA, 95616, USA.

² Department of Plant and Soil Science, University of Delaware, DE, 19711, USA.

³ Department of Plant Pathology, 1630 Linden Drive, University of Wisconsin, Madison, WI, 53706, USA.

Genes encoding NBS-LRR protein motifs are one of the most prevalent classes in plant genomes, with 148 genes in the Arabidopsis genome and over 500 in rice. Previous studies demonstrated that at least some of these genes are involved in disease resistance. We are performing bioinformatic and functional analyses of these genes in Arabidopsis to define functional classes. Approximately two-thirds of the 148 NBS-LRR encoding genes in Arabidopsis also encode a Toll-Interleukin homology (TIR) domain at the N-terminus; the remainder encode a coiled-coil (CC) motif at the N-terminus. In addition to these TIR-NBS-LRR (or “TNL”) and CC-NBS-LRR (or “CNL”) proteins, we identified genes encoding potential adapter proteins with a configuration of TIR-X (TX), TIR-NBS (TN), and CC-NBS (CN). Phylogenetic data and analyses of the rice genome indicate that the CNL family may be more ancient than the TNL family, and suggest a recent diversification of TN- and TNL-encoding genes. A variety of genetic events have occurred during the amplification of these gene families. We have been systematically studying these genes via transcriptional analysis and gene-trap lines. The majority of these genes are expressed in vegetative tissue. In addition, these genes are being characterized using a high-throughput, ligand-independent approach in which a dexamethasone-inducible expression system is used to overexpress the gene of interest. Microarrays are being used to determine changes in global expression patterns caused by over-expression of previously uncharacterized NBS-LRR-encoding genes. These induced expression patterns are being compared to changes in expression elicited by known resistance genes.