TARGETED DIFFERENTIAL DISPLAY OF ABUNDANTLY EXPRESSED SEQUENCES FROM THE BASIDIOMYCETE PHANEROCHAETE-CHRYSOSPORIUM WHICH CONTAIN REGIONS CODING FOR FUNGAL CELLULOSE-BINDING DOMAINS

Cellulose-binding domains (CBDs) are present in the majority of fungal cellulases studied to-date. This work describes the use of targeted d ifferential display, employing degenerate primers designed to anneal t o variants of a region conserved in fungal CBDs, each in combination w ith an oligo-dT primer, to PCR-amplify cDNA sequences containing regio ns coding for such domains from Phanerochaete chrysosporium. After gro wth on either Avicel or carboxymethyl cellulose (CMC), five distinct. abundantly expressed cDNA sequences were obtained. Two of these origin ated from transcripts of the previously characterised cbhI.1 and cbhI. 2 genes, whereas three were from novel genes. One of the latter was is olated only after growth on CMC. No such sequences were obtained after growth on xylan. suggesting that the expression of sequences containi ng such regions is down-regulated on this substrate. The use of target ed differential display both for isolating novel sequences and for stu dying the expression of known genes within a family is discussed.