Norsolorinic acid is a red polyhydroxyanthraquinone. Mutants of Aspergillus parasiticus and Aspergillus flavus that accumulate norsolorinic acid, as well as making low levels of aflatoxin, have been used to study aflatoxin biosynthesis and aflatoxin genetics. In physiological studies the red color of norsolorinic acid serves as a visual screen for the putative presence of aflatoxin. In biosynthetic studies using ¹⁴C-radioisotope labeling, norsolorinic acid is the first stable intermediate detected in the pathway. By complementation of suitable marked strains, and selection for red pigment, the gene for the enzyme associated with norsolorinic acid became the first gene cloned from the aflatoxin pathway. Gene disruption confirmed the role of norsolorinic acid as an aflatoxin precursor. Several laboratories have partially purified an enzyme that catalyzes the transformation of norsolorinic acid to other pigments. It is proposed that double mutants of A. nidulans, lacking both norsolorinic acid production and another secondary metabolite, can be used to screen for regulatory genes of the aflatoxin/sterigmatocystin pathway.
Vaccaro G., Bennett J. W. (1999): Norsolorinic acid mutants and aflatoxin research. – Czech Mycology 51(2-3): 89–97.
