Isolation and identification of the Aspergillus nidulans gdhA gene encoding NADP-linked glutamate dehydrogenase

The Neurospora crassa am gene was used as a heterologous probe to identify clones from two independently constructed Aspergillus nidulans gene libraries. These clones have a common HindIII 1.85 kb fragment. This A. nidulans nucleotide stretch hybridises to a N. crassa 2.7 kb BamHI fragment of wild type DNA but not to a co-migrating fragment from the DNA of the N. crassa am132 deletion mutant. One A. nidulans clone was shown to complement the N. crasse am132 deletion strain. The N. crassa transformants show low levels (approximately 5%) of heterologous glutamate dehydrogenase activity. The A. nidulans gdhA gene was found to locate in N. crassa at both the "homologous" (i.e. am) site as well as non-homologous sites. Partial nucleotide analysis of the fragment has revealed the 5' end of the locus and considerable homology with the N. crassa am gene. We concluded that we have cloned the A. nidulans gdhA gene.