CHARACTERIZATION OF BOTRYTIS CINEREA POLYGALACTURONASES AND LACCASES DURING GRAPE BERRIES INFECTION

Botrytis cinerea, the causal agent of grey mould disease on grapevine, when infects the grape berries encounters an environment rich in polyphenols and proteins with potential anti-fungal activity. In particular, the stilbenic phytoalexin trans-resveratrol and proteins structurally and functionally related to plant pathogenesis-related (PR) proteins, including mostly thaumatin-like proteins and chitinase. B. cinerea is thought to infect the host tissue by producing cell-wall degrading enzymes, such as polygalacturonases (PGs), and detoxification enzymes, for example laccase which is likely to be involved in trans-resveratrol detoxification. The combination of trans-resveratrol and grape polyphenols or proteins induce in vitro a strong release of B. cinerea laccase activity which, in turn, neutralizes the toxicity of grape stilbenic phytoalexins and, by oxidizing grape polyphenols, causes the insolubilization of grape proteins. This mechanism could favour berry infection by the fungus and is in accordance to the observation that grape berries infected with B. cinerea show a strong reduction of the protein content in comparison to healthy ones. Grape polyphenols have been also shown to inhibit B. cinerea PG activity in vitro. Nevertheless, the importance of B. cinerea PGs in grape berries infection cannot be ruled out since the fungus could have evolved an avoidance mechanism in order to escape the inhibitory effect of polyphenols. To better understand the role played by B. cinerea PG and laccase activities during grape berries infection, we are analyzing the enzyme activities secreted by the fungus in the infected berry and the expression of the corresponding encoding genes.