The primary biochemical effect of a morphological mutation in Neurospora crassa.

Abstract

A mutation in a particular gene in Neurospora crassa which leads to a morphologically distinct colonial growth pattern causes a decrease in the affinity of glucose-6-phosphate [glucose-6-P] dehydrogenase for both glucose-6-P and TPN. This decreased glucose-6-P affinity can be consistently correlated with an increased in vivo glucose-6-P level in the colonial strain under a variety of conditions. The altered enzyme and higher glucose-6-P level segregate with the col-2 marker, and both are changed back to the normal wild-type state by mutations which restore a wild-type morphology. The evidence indicates that the col-2 locus is the structural gene for the glucose-6-P dehydrogenase and that the primary effect of the col-2 mutation in Neurospora is to change the structure of this enzyme, producing the pleiotropic effects which ultimately lead to the change in morphology.