PLANT-CELL WALL DEGRADING ENZYMES OF SEPTORIA-NODORUM

Septoria nodorum, a fungal pathogen of wheat, secretes a variety of enzymes that can potentially degrade cell walls of monocotyledonous plants. When grown in media containing wheat cell walls as the sole carbon source, the fungus secreted glycanases, xylanase, polygalacturonase, β-1,3- and β-1,4-glucanase together with glycosidases, α-arabinosidase, acetylesterase, β-galactosidase and β-xylosidase. Most of the secreted enzyme activities were also associated with fungal cells. The fungus also produced polygalacturonase, β-1,3-glucanase, β-glucosidase and acetylesterase activities when grown in a glucose medium. The enzyme activities were resolved by isoelectric focusing into a number of apparent isoenzymes: 13 xylanase isoenzymes, 16 polygalacturonases, 13 β-1,4-glucanases, 2 β-1,3-glucanases, 4 β-xylosidases, 2 β-glucosidases and 1 β-galactosidase. Growth in the presence of wheat cell wall preparation selectively induced the expression of certain isoenzymes. © 1993 Academic Press Limited.