Molecular characterization of the incompatible interaction of vitis vinifera leaves with Pseudomonas syringae pv. pisi:: Expression of genes coding for stilbene synthase and class 10 PR protein

The interaction between Vitis vinifera and Pseudomonas syringae pv. pisi was examined at the pathological and molecular levels. Leaves infiltrated with the bacterial suspension developed necrotic regions which remained restricted to the infiltrated areas. In the infiltrated zone the number of bacteria decreased around 24 h after inoculation whilst no bacteria could be isolated from the non-infiltrated zone. At the molecular level, two genes, stilbene synthase (SS) and a PR10 gene, encoding putative defense proteins, were analyzed. Expression of the SS gene, measured by the analysis of transcript accumulation, was shown to be highly induced and was followed by the accumulation of resveratrol (peaking at approximately 48 h post-inoculation), considered as one of the major nobreak phytolaexins in the Vitis species. We report for the first time the isolation of a genomic clone (VvPR10-1) coding for a PR10 protein from this plant. The accumulation of the corresponding mRNA (0.8 kb) was observed from 3 to 96 h post-inoculation, peaking at 24-48 h, and was followed by the accumulation (between 24 and, at least, 96 h after inoculation) of the encoded polypeptide as detected by immuno-blotting. These results indicate that our experimental system based on an interaction of the non-host plant V. vinifera leaves with P. s. pv. pisi, has to be considered as an HR-like response and is well suited for the analysis of the defense reaction of this economically important species.