Plant resistance-related responses are elicited by cerato-platanin, a small protein from C. fimbriata f. sp. platani

Abstract

Cerato-platanin (CP) is a 12.4 kDa protein from the Ascomycete Ceratocystis fimbriata (Ell. and Halst.) Davidson f. sp. platani Walter, the causative agent of the canker stain of the plane trees. CP has the 40% percentage of hydrophobic residues, and contains 4 cysteines forming two S-S bridges at Cys20-57 and Cys60-115. CP is the founder member of the cerato-platanin family, and its N-terminal region presents a high similarity with that of cerato-ulmin, an Ophiostoma class II hydrophobin involved in Dutch elm disease. CP is able to self-assembly to give large, thioflavin T-positive molecular aggregates showing some similarities with those observed in the moderately hydrophobic hydrophobins. CP is located in the fungal cell walls, and is early-secreted in culture filtrates. The cp gene was cloned in Pichia pastoris, and the recombinant protein is properly folded and maintains its biological activity. CP interacts with the plane leaves by eliciting phytoalexin synthesis, extended cell plasmolysis and crushing, and abundant starch accumulation in the chloroplasts. Various plane genes induced by CP treatments have been identified by the suppression subtractive hybridisation method