USE OF GENE REPLACEMENT TRANSFORMATION TO ELUCIDATE GENE-FUNCTION IN THE QA GENE-CLUSTER OF NEUROSPORA-CRASSA

Gene replacement by transformation, employing selective genetic recomb ination techniques, has been used to delete or disrupt the qa-x, qa-y and qa-1S genes of the qa gene cluster of Neurospora crassa. The growt h characteristics of the strain carrying the deletion of the qa-y gene support earlier evidence that this gene encodes a quinic acid permeas e. The strain containing the deletion of the qa-1S gene (DELTA-qa-1S) was examined with respect to quinic acid induction and carbon cataboli te repression. The DELTA-qa-1S strain exhibits constitutive expression of the qa genes supporting earlier evidence that the qa-1S gene codes for a repressor. Several of the qa genes continued to be expressed at high levels even in the presence of glucose in the DELTA-qa-1S strain , which indicates that transcription of these genes is not being affec ted directly by a repressor molecule in the presence of glucose.