Glyceraldehyde-3-phosphate dehydrogenase is required for fire blight disease establishment in apple fruitlets

Host sugar resource utilization is an essential aspect of parasitism by Erwinia amylovora, the bacterium that causes fire blight disease of pome fruits. We assessed the virulence of E. amylovora glyceraldehyde-3-phosphate dehydrogenase (gapA) mutants, which are predicted to be defective in sugar utilization through both glycolysis and the phosphogluconate pathway. A plasmid insertion mutant and an allelic exchange mutant of gapA were generated and found to be avirulent in apple fruitlets. The gapA insertion mutant was unstable, with insertion element excision resulting in restoration of pathogenicity. The results indicate that gapA is essential for E. amylovora virulence on apple fruitlets.