CORRELATION BETWEEN THE REGULATION OF STERIGMATOCYSTIN BIOSYNTHESIS AND ASEXUAL AND SEXUAL SPORULATION IN EMERICELLA NIDULANS

We analyzed the regulation of sterigmatocystin biosynthesis in wild ty pe and mutant strains of Emericella nidulans (= Aspergillus nidulans). A positive correlation between both asexual and sexual sporulation an d synthesis of the mycotoxin was observed. Those conditions which favo red sporulation stimulated sterigmatocystin formation, and vice versa. Both processes were stimulated by light in a veA(+) genetic backgroun d. In contrast, they were inhibited by idaminobutanone, an inhibitor o f ornithine decarboxylase. The effect of this inhibitor was partially reverted by putrescine addition. Partial supplementation of specific r equirements to auxotrophic mutants allowed normal vegetative growth, b ut interfered with asexual sporulation and sterigmatocystin biosynthes is. Synthesis of the mycotoxin was neither affected in a brlA mutant o r in developmental mutants blocked at later steps in sporulation. As i n wild type strain, diaminobutanone inhibited sterigmatocystin biosynt hesis and cleisthotecia formation in the bl-IA mutant, and its effect was reverted by addition of putrescine. The inhibitor also affected th e transcription of brlA. Our results indicate that sporulation and the synthesis of sterigmatocystin are co-regulated at a step previous to the brlA execution point.