Sporogenic effect of polyunsaturated fatty acids on development of Aspergillus spp.

Aspergillus spp. are frequently occurring seed-colonizing fungi that comple te their disease cycles through the development of asexual spores, which fu nction as inocula, and through the formation of cleistothecia and sclerotia . We found that development of all three of these structures in Aspergillus nidulans, Aspergillus flavus, and aspergillus parasiticus is affected by l inoleic acid and light. The specific morphological effects of linoleic acid include induction of precocious and increased asexual spore development in A. flavus and A. parasiticus strains and altered sclerotium production in some A. flavus strains in which sclerotium production decreases in the ligh t but increases in the dark In A. nidulans, both asexual spore production a nd sexual spore production were altered by linoleic acid. Spore development was induced in all three species by hydroperoxylinoleic acids, which are l inoleic acid derivatives that are produced during fungal colonization of se eds. The sporogenic effects of these linoleic compounds on A. nidulans are similar to the sporogenic effects of A. nidulans psi factor, an endogenous mixture of hydroxylinoleic acid moieties. Light treatments also significant ly increased asexual spore production in all three species. The sporogenic effects of light, linoleic acid, and linoleic acid derivatives on A. nidula ns required an intact veA gene. The sporogenic effects of light and linolei c acid on Aspergillus spp., as well as members of other fungal genera, sugg est that these factors may be significant environmental signals for fungal development.