Plant & Animal Genome IX Conference

Workshop: Arabidopsis
W11_04.html

FUNCTIONAL GENOMICS OF NBS-LRR ENCODING GENES IN ARABIDOPSIS

¹ Deaprtment of Vegetable Crops, University of California, Davis, CA 95616

² Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI 53705

Genes encoding the NBS-LRR protein motifs are one of the most prevalent classes in plant genomes. A detailed functional analysis of NBS-LRR-encoding genes is being made in Arabidopsis. Our goal is to define the different classes of NBS-LRR-encoding genes, determine how many act as resistance genes and how many control processes unrelated to defense. There are more than 140 NBS-LRR-encoding genes in the Arabidopsis genome. Phylogenetic analysis showed that known resistance genes are present in most of the major clades. We are systematically studying these genes in a ligand-independent manner using transcriptional analysis, over-expression using a modified the dexamethasone-inducible system, gain-of-function variants, and gene-trap lines. 5' and 3' RACE analysis demonstrated that the majority of these genes are expressed in vegetative tissue. We will use microarrays to determine changes in global expression patterns caused by expression of NBS-LRR. This will provide an 'induced expression signature' for each gene that will indicate its function as well as allow us to assign them to functional classes. The expression signature of known resistance genes is being characterized and will be compared to the expression signatures of the unknown genes. The Affymetrix GeneChip Arabidopsis genome array was used to assay gene expression patterns induced by different avirulence genes. Wild-type Arabidopsis plants were inoculated with Pseudomonas syringae pv. glycinea Race 4 carrying avr genes avrRpt2, avrRpm1, avrRps4 or avrPphB. Initial analysis of this data set revealed genes that are induced or suppressed only for particular avr/R interactions, and revealed other genes that are regulated in common for multiple avr/R interactions.