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Abstract: Guzman-de-Pena, D., and Ruiz-Herrera, J. 1997. Relationship between aflatoxin biosynthesis and sporulation in Aspergillus parasiticus. Fungal Genetics and Biology21.198-205. Regulation of aflatoxin biosynthesic during differentiation of Aspergillus parasiticus was analyzed by using a drug that inhibits the development of the fungus and mutants affected in sporulation. Diaminobutanone, a competitive inhibitor of ornithine decarboxylase, repressed spore germination. If added after spore germination had occurred, it blocked sporulation completely and suppressed aflatoxin biosynthesic, but was only partially inhibitory of mycelial growth. Putrescine partially counteracted the inhibitory effect of the drug on both sporulation and aflatoxin biosynthesis. Analysis of mutants affected in sporulation confirmed the existence of a relationship between sporulation and aflatoxin formation. A nonsporulating mutant was unable to synthesize aflatoxins. In a sectorial

mutant, the sporulating sector synthesized aflatoxins normally, whereas the asporogenous sector was unable to do so. It is suggested that regulation of aflatoxin biosynthesis is correlated with the sporulation PrOCeSS.