EXPRESSION PATTERNS OF 10 HEMICELLULASE GENES OF THE FILAMENTOUS FUNGUS TRICHODERMA-REESEI ON VARIOUS CARBON-SOURCES

The filamentous fungus Trichoderma reesei produces a multitude of cell ulolytic and hemicellulolytic enzymes. The expression of ten hemicellu lase-encoding genes was studied by Northern analyses in various cultur e conditions including polymeric and di-and monomeric sugars. The stud y included genes encoding two beta-xylanases (xyn1 and xyn2) and a bet a-mannanase (man1) which hydrolyze the main chain of hemicellulose pol ymers by endo fashion, and the acetyl xylan esterase (axe1), the alpha -glucuronidase (glr1), the alpha-L-arabinofuranosidase (abf1), and thr ee alpha-galactosidases (agl1, agl2 and agl3), which attack the side g roups of hemicellulosic substrates. The genes encoding the oligosaccha ride-hydrolysing enzymes beta-glucosidase (bgl1) and beta-xylosidase ( bxl1) were also studied and as a reference the cellulase encoding gene cbh1. A general picture of their relative expression patterns and rel ative expression levels in particular conditions was obtained. Growth in the presence of cellulose, sophorose, xylobiose, xylan and L-arabit ol gave rise to abundant expression of most genes studied. alpha-galac tosidase I and II, beta-xylosidase and alpha-L-arabinofuranosidase enc oding genes were the ones most frequently expressed in the conditions studied, whereas expression of the mannanase and alpha-galactosidase I II was rarely seen. Expression of the genes was not detected in the pr esence of glucose in the strain QM9414 but derepressed expression of m ost of them occurred after glucose depletion. Expression of at least x yn1, bxl1, agl1, agl2, agl3 and axel is under control of the glucose r epressor cre1 as studied in the cre1-1 mutant Rut-C30 and Rut-C30 tran sformed with the wild type cre1 allele. (C) 1997 Elsevier Science B.V.