Regulation of endopolygalacturonase gene expression in Botrytis cinerea by galacturonic acid, ambient pH and carbon catabolite repression

The phytopathogenic fungus Botrytis cinerea produces a set of endopolygalacturonases (endoPGs) which are involved in the enzymatic degradation of pectin in plant cell walls. The endoPG-encoding genes of B, cinerea are differentially expressed when the fungus is grown in liquid culture on different carbon sources. A basic constitutive expression level was observed for two genes, Bcpg1 and Bcpg2, which encode basic isozymes, Galacturonic acid was shown to induce the expression of Bcpg4 and Bcpg6. Low pH of the culture medium resulted in induced expression of the Bepg3 gene. Expression of the Bcpg5 gene was inducible, however the inducing factors could not be identified. Finally, galacturonic acid-induced expression of the Bcpg4 gene was repressed by the presence of more-favourable carbon sources, such as glucose.