Regulatory elements in aflatoxin biosynthesis.

This review provides a synopsis of factors involved in the regulation of aflatoxin inAspergillus species at the molecular level. Much of the knowledge available today on the regulation of secondary metabolite production in fungi has been gleaned from studies of the aflatoxin gene cluster inA. flavus andA. parasiticus and the sterigmatocystin gene cluster inA. nidulans. Regulation of these two gene clusters is under the control of both pathway-specific transcription factors such as AflR and AflJ and global or broad-domain transcription factors such as AreA and PacC. Study of secondary metabolite (sec-) mutants inA. parasiticus first identified an association between mycotoxin production and fungal development. This linkage has been extended at the molecular level by the characterization of a G-protein/cAMP/Protein kinase A signaling pathway that regulates sporulation via the transcription factor BrlA and aflatoxin/sterigmatocystin production via AflR. Another global regulator of mycotoxin production, VeA, mediates a developmental light-response inA. nidulans andA. flavus. Though not similar to any known fungal transcriptional regulators, VeA controls aflatoxin/sterigmatocystin production via transcriptional control of AflR and it also regulates development of sexual structures such as cleistothecia inA. nidulans and sclerotia inA. flavus.