Botrytis cinerea cleaves a grapevine chitinase decreasing its enzymatic activity and impairing the detrimental effect on fungal growth

Chitin represents the main fibrillary component of the fungal cell wall. During plant infection, chitin apposition is counteracted by host chitinases. A chitinase class IV is constitutively contained in grapevine berries and it is expressed in leaves following Botrytis cinerea infection. Early, during fungal growth, the fungus proteolytically remove the chitin-binding domain (CBD). The chitinase without the CBD shows a reduction of activity by about 50% and louses the detrimental effects on conidia germination and fungal growth. Protease inhibition assays provided evidence that metalloprotease activity is involved in the chitinase cleavage. To ascertain whether the native and cleaved chitinase can differently affect the expression of genes involved in B. cinerea cell wall modeling, we analyzed by qPCR the expression of five fungal chitin synthase (Chs) and four chitin deacetylase (Cda) genes. Only one Chs gene decreased its expression in presence of the native chitinase. In conclusion, the removal of the CBD by B. cinerea proteases appears as a mechanism preserving fungal growth from plant chitinase activity. Further experiments will better clarify the type of B. cinerea protease activity capable to disarm the plant chitinases.