Sexual reproduction and recombination in the aflatoxin-producing fungus Aspergillus parasiticus.
The fungal phylum Ascomycota comprises a large proportion of species with no known sexual stage, despite high genetic variability in field populations. One such asexual species, Aspergillus parasiticus, is a potent producer of carcinogenic and hepatotoxic aflatoxins, polyketide-derived secondary metabolites that contaminate a wide variety of agricultural crops. In this study, individuals of A. parasiticus from a population showing an evolutionary history of recombination were examined for sexual reproduction. Crosses between strains with opposite mating-type genes MAT1-1 and MAT1-2 resulted in the development of ascospore-bearing ascocarps embedded within stromata. Sexually compatible strains belonged to different vegetative compatibility groups. Recombination through the independent assortment of chromosomes 3 and 6 was detected using loci for mating type, aflatoxin gene cluster, and a protein-encoding gene. Our discovery of the sexual stage in A. parasiticus has important implications for current biological control strategies using nontoxigenic strains to reduce aflatoxin contamination in crops.
Horn
Bruce W
BW
National Peanut Research Laboratory, Agricultural Research Service, United States Department of Agriculture, Dawson, GA 39842, USA.
Ramirez-Prado
Jorge H
JH
Carbone
Ignazio
I
D000348:Aflatoxins / Q000096:biosynthesis*; D001230:Aspergillus / Q000235:genetics / Q000502:physiology*; D015825:Chromosomes, Fungal / Q000235:genetics; D049770:Genes, Mating Type, Fungal; D014644:Genetic Variation; D011995:Recombination, Genetic; D013172:Spores, Fungal / Q000235:genetics / Q000378:metabolism
D000348:Aflatoxins