D-Galactose is present in hemicelluloses and pectin which are constituents of the plant cell wall. In pectin, β -1,4-linked D-galactose residues are present in galactan or in arabinogalactan side chains. In hemicelluloses, D-galactose residues are present in the form of side residues which are β -linked in to xyloglucan and xylan, but α -linked in to galactoglucomannan. For the degradation of these structures by filamentous fungi, several enzyme classes are required depending on the linkage. These classes are α - and β -galactosidases and endo- and exogalactanases. Aspergillus nidulans, a saprobic filamentous fungus, is able to use D-galactose efficiently as a carbon source. A. nidulans can convert D-galactose through two pathways: the common Leloir pathway as well as the recently described alternative D-galactose utilization pathway. Recently two regulators, GalR and GalX were identified that control D-galactose metabolism in A. nidulans. The interaction of these regulators, their control of the various genes of the two D-galactose utilization pathways as well as genes encoding extracellular galactose releasing enzymes will be discussed.
Full conference title:
10th EUROPEAN CONFERENCE ON FUNGAL GENETICS
- ECFG 10th (2010)