A characteristic hallmark of Aspergillus niger is the formation of black conidiospores. In this study, we report the characterization of a color mutant, colA, which was isolated because of a complete loss of pigmentation resulting in white conidia. Pigmentation of the colA mutant was restored by a gene that encodes the A. niger ortholog of the 4’-phosphopantetheinyl transferase protein (PptA). 4’phosphopantetheinyl transferase activity is required for the activation of Polyketide synthases (PKSs) and Non-Ribosomal Peptide Synthases (NRPSs) (1). Complementation analysis showed that the colA mutant is allelic to a previously isolated color mutant, gryA. Sequencing of the colA and gryA loci and the targeted deletion of the pptA gene further confirmed that the colA /gryA mutants are mutated in the pptA gene. Spores from the 8710;pptA deletion are paler in color that spores of an A. niger strain disrupted in the pksA gene. PksA encodes the polyketide synthase required for melanin biosynthesis (2) and spores from the pksA disruption strain become fawn colored. Spores from both the 8710;pksA and the 8710;pptA were hypersensitive to UV-radiation indicating that melanin is required for resistance against UV-radiation. The 8710;pksA strain was equally sensitive to hydrogen peroxide as the parental strain, but spores from the 8710;pptA strain showed increased sensitivity. The results suggest the involvement of PKS or NRPS-derived metabolites that confer resistance towards oxidative stress conditions.
Full conference title:
10th EUROPEAN CONFERENCE ON FUNGAL GENETICS
- ECFG 10th (2010)