W361R mutation in GaaR, the regulator of D-galacturonic acid-responsive genes, leads to constitutive production of pectinases in Aspergillus niger.

ABSTRACT: Polysaccharides present in plant biomass, such as pectin, are the main carbon source for filamentous fungi. Aspergillus niger naturally secretes pectinases to degrade pectin and utilize the released monomers, mainly D-galacturonic acid. The transcriptional activator GaaR, the repressor of D-galacturonic acid utilization GaaX, and the physiological inducer 2-keto-3-deoxy-L-galactonate play important roles in the transcriptional regulation of D-galacturonic acid-responsive genes, which include the genes encoding pectinases. In this study, we described the mutations found in gaaX and gaaR that enabled constitutive (i.e., inducer-independent) expression of pectinases by A. niger. Using promoter-reporter strains (PpgaX-amdS) and polygalacturonic acid plate assays, we showed that W361R mutation in GaaR results in constitutive production of pectinases. Analysis of subcellular localization of C-terminally eGFP-tagged GaaR/GaaR^{W 361R} revealed important differences in nuclear accumulation of N- versus C-terminally eGFP-tagged GaaR.

SUBMITTER: Alazi E 

PROVIDER: S-EPMC6528562 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature