According to molecular biology, genomic and proteo- mic data, the phytopathogenic gamma-proteobacte- rium Pseudomonas syringae pv. tomato DC3000 pro-duces a number of proteins that may promote infec- tion and draw nutrients from plants. Remarkably, P. syringae DC3000 strain possesses three paralogous gap genes encoding glyceraldehyde-3-phosphate dehy- drogenase (GAPDH) enzymes with different predic- ted molecular sizes and metabolic functions. As GAPDH was shown to be a virulence factor in other microbial pathogens, in the current study, we analyzed the ex-pression levels of each paralogous gap gene by real- time PCR to understand the actual impact of their protein products on P. syringae virulence. We found that all of them were strongly induced during the in-fection process. Nevertheless, proteomic analysis of cul- ture supernatants revealed that only Class I GAPDH1 encoded by the gap1 gene was identified as an extra-cellular protein in infective cells. These results strongly suggest that this GAPDH should play a role in the infective process, including its well-know en-zymatic function in the glycolytic metabolic pathway.

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