Using functional and applied genomics to identify genes that confer either resistance or susceptibility to fire blight

Fire blight, caused by the bacterium Erwinia amylovora, is a destructive disease of apple, pear and other plants of the Rosaceae. The goal of this project is to use functional genomics to characterize the response of apple to fire blight disease and, thereby, identify new opportunities for improving fire blight resistance. Fire blight-susceptible (M.26) and -resistant (G.41) apple rootstocks were challenged with E. amylovora and the transcriptome of the two cultivars is being characterized by cDNA subtractive/PCR-suppressive hybridization and cDNA-AFLP. In addition, bioinformatic approaches were used to identify publicly available apple ESTs uniquely associated with E. amylovora infected apple or similar to Pseudomonas syringae pv. tomato infected Arabidopsis ESTs. Gene silencing is being used to elucidate the role of specific candidate genes in resistance and susceptibility. Two types of RNAi plant transformation vectors designed to facilitate the evaluation of large EST populations are being evaluated: 1) those that use GATEWAY technology to facilitate the rapid generation of hairpin RNA-encoding constructs and 2) those that use a 3' untranslated region-inverted repeat to enhance sense-RNAi.