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

Abstract

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 Lalanine 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 GABND-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, a-L-arabinofuranosidase A, a+ arabinof uranosidase 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 arabinaoes and L-arabinose catabolic enzymes is under control of CREA.1

The abfB gene encoding the major α-L-arabinofuranosidase of Aspergillus nidulans: nucleotide sequence, regulation and construction of a disrupted strain

“…This protein is likely to be the A. nidulans equivalent of AxhA from A. tubingensis. AxhA was found to release Larabinose residues from ara binoxylans only (Kormelink et al, 1991), and its expression was induced by Larabitol (Gielkens et al, 1997). The A. tubingensis…”

“…In A. niger, the synthesis of these enzymes is induced by both L-arabinose, the final product of L-arabinan degradation, and by L-arabitol, an intermediate in the catabolic pathway of L-arabinose, though the latter is a stronger inducer ( Van der Veen et al, 1993). Furthermore, the expression of the L-arabinanase system is under carbon-catabolite repression when more preferable carbon sources like D-glucose are present in the medium Ruijter et al, 1997).…”

Organic acid production in Aspergillus niger and other filamentous fungi

“…While this result suggests a role of CreA in controlling the expression of rhtA and rhaB, as reported before for other sugar utilisation systems (Ademark et al, 2001;de Vries et al, 1999;Niu et al, 2015;Ruijter et al, 1997a), a different glucose-repression mechanism seems to have a major role in the transcriptional regulation of these genes. The existence of CreA-independent glucose repression mechanisms controlling the regulation of α-L-rhamnosidase genes (Tamayo- Ramos et al, 2012), and the phenylacetic acid uptake system (Cubero et al, 2000), has been previously reported in A. nidulans.…”

“…This complements the pyrA6 transformation marker and restores the uridine prototrophy. In addition, we measured citrate production under low iron stress (no iron added to the medium, see Supplementary file 1) in A. niger NW129 (cspA1, goxC17, pyrA1) (Ruijter et al, 1997a).…”

“…The Aspergillus niger strains used in this study were N400 (NRRL3, ATCC9029, CBS120.49), N402 (cspA1) (Bos et al, 1988), NW283 (fwnA1; cspA1; lysA7; pyrA6; creAd4) (Ruijter et al, 1997a), MA169.4 (cspA1, kusA::DR-amdS-DR, pyrG -) (Carvalho et al, 2010), and its derivatives JS14, (∆rhaR), JS16 (∆rhtA) and JS19…”