microbiology, Vol 143, 2991-2998, Copyright © 1997 by Society for General Microbiology

ARTICLES

Isolation of Aspergillus niger creA mutants and effects of the mutations on expression of arabinases and L-arabinose catabolic enzymes

GJ Ruijter, SA Vanhanen, MM Gielkens, PJ van de Vondervoort and J Visser
Section Molecular Genetics of Industrial Microorganisms, Wageningen Agricultural University, The Netherlands.

Aspergillus niger mutants relieved of carbon repression were isolated from an areA parental strain by selection of colonies that exhibited improved growth on a combination of 4-aminobutanoic acid (GABA) and D- glucose. In addition to derepression of the utilization of GABA as a nitrogen source in the presence of D-glucose, three of the four mutants also showed derepression of L-alanine and L-proline utilization. Transformation of the mutants with the A. niger creA gene, encoding the repressor protein CREA, re-established the areA phenotype on GABA/D- glucose, identifying the mutations as creAd. The creA gene mapped on chromosome IV by linkage analysis and contour-clamped homogeneous electric field hybridization. The creA mutants obtained were used to study the involvement of CREA in repression by D-glucose of arabinases and L-arabinose catabolism in A. niger. In wild-type A. niger, alpha-L- arabinofuranosidase A, alpha-L-arabinofuranosidase B, endo-arabinase, L- arabinose reductase and L-arabitol dehydrogenase were induced on L- arabinose, but addition of D-glucose prevented this induction. Repression was relieved to varying degrees in the creA mutants, showing that biosynthesis of arabinases and L-arabinose catabolic enzymes is under control of CREA.

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