Characterisation of a xylanase gene from Cochliobolus sativus and its expression

A xylanase gene, XYL2, was identified and characterised in Cochliobolus sat ivus (anamorph Bipolaris sorokiniana), a necrotrophic cereal pathogen that attacks both shoots and roots. The fungus was grown on a xylanase inducing medium containing mineral salts, oat spelt xylan, cellulose, and peptone, R NA was isolated, and a complementary DNA (cDNA) library constructed. The li brary was screened with a xylanase (XYLI) cDNA clone from the maize pathoge n Cochliobolus carbonum. Xylanase cDNA clones, all representing a single ge ne, were identified. Corresponding genomic DNA was amplified by PCR. Sequen cing of the cDNA and the PCR products gave a nucleotide sequence of 2211 bp containing two introns in an open reading frame of 693 bp that codes for a xylanase from glycosyl hydrolase family II. The most similar sequences to this gene in nucleotide sequence databases are the XYL2 gene of C, carbonum and a xylanase (XYLI) cDNA from a saprophytic fungus, Humicola insolens. N orthern blot analysis and reverse transcription PCR (RT-PCR) showed express ion of the gene when the fungus was grown on xylan or cellulose, but not wh en peptone or sucrose was the only carbon source. Expression of XYLI in ino culated barley seedlings was detected by RT-PCR.