Hyperproduction of some glycosidases in Neurospora crassa

Abstract

Results of a cross between a hyperderepressed strain (89601 a) and a normal strain (74A) of Neurospora crassa suggest that there is a single gene difference in this trait. The evidence is clearest with amylase although a similar segregation pattern is suggested for invertase and, perhaps, trehalase. On the other hand, phosphatase activity is not affected by this gene. The gene for hyperderepression does not appear to be widespread in wild-type strains of this organism for, in the seven tested, only 89601 a was hyperderepressed for amylase. The action of the hyperderepression gene probably is not due to diminished sensitivity to catabolite repression because the synthesis of amylase begins at roughly the same point in glucose depletion in both the hyperderepressed and normal strains. Furthermore, growth of these strains on constant but low levels of a carbon source causes derepression to the degree expected in both strains. Nor does hyperderepression appear to be due to achange in sensitivity to induction, according to experiments with cellobiase, which is inducible. Increases in enzyme activity due to the gene for hyperderepression are in the order, amylase-cellobiase>invertase>trehalase. Thus, the gene exhibits polarity as well as being pleiotropic. An explanation for its effect is proposed, based upon changes in the cell surface.