Sexual development of Aspergillus nidulans in tryptophan auxotrophic strains

The interplay between sexual development and amino acid biosynthesis in the ascomycete Aspergillus nidulans was studied. The growth and differentiatio n of four tryptophan auxotrophic strains that are unable to regulate their tryptophan biosynthesis, were examined. These strains are sterile an medium containing low tryptophan concentrations. Fruitbody formation was restored by supplementation with high concentrations of tryptophan and was promoted by supplementation with indole or auxin. Tryptophan supplementation result ed in auxin production of A. nidulans. Fertility of ascospores of the trypt ophan auxotrophic strains could only be partially re-established. trpC tran script levels and enzyme activities remained stable in cleistothecia and co nidiophore extracts as compared to those of mycelium, while levels of gene transcripts involved in glycolysis were lower in fruitbodies and conidiospo res. Auxotrophic strains unable to form fruitbodies at intermediate amino a cid supplementation levels turned on the cross-pathway regulatory system th at is induced by amino acid starvation. We conclude that there is a connect ion between the genetic network of cross-pathway control and sexual develop ment in A. nidulans.