Isolation of differentially expressed transcripts after treatments in Platanus acerifolia with cerato-platanin, an unique multi-functional protein from Ceratocystis fimbriata f. sp. Platani

Cerato-platanin (CP) is a 12.4 kDa protein from the Ascomicete Ceratocystis fimbriata (Ell. And Halst.) Davidson f. sp. platani Walter, the causative agent of the canker stain of the plane trees. CP has been shown by our research group to have a high content of â-sheets and a high percentage (40%) of hydrophobic residues, and to contain 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 II class hydrophobin involved in Dutch elm disease. CP is able to self-assemby to give large, thioflavin T-positive molecular aggregates showing some similarities with those observed in the moderately hydrophobins. CP is located in the fungal cell walls, is early-secreted in culture filtrates, and interacts with the host plane leaves by eliciting phytoalexin synthesis, extended cell plasmolysis and crushing, and abundant starch accumulation in the chloroplasts. The cp gene was cloned in Pichia pastoris, and the recombinant protein is properly folded and maintains its biological activity. In the present paper the study of the expression of the host plane genes following the treatment with CP was approached by using the suppression subtractive hybridisation method (SSH). We constructed forward and reverse subtracted cDNA libraries for the isolation of differentially expressed transcripts, and identified some genes that are switched on/off after the treatment. The main feature of this technique is the peculiar effectiveness in isolating rarely expressed transcripts.