A study on the interplay between sexual development and tryptophan biosynthesis in the ascomycete Aspergillus nidulans was initiated. To elucidate the connection, strains were examined which are unable to regulate their tryptophan biosynthesis and are dependent on external supply. Therefore, the auxotrophic mutants trpA, trpB, trpC and trpD were tested for growth and differentiation. These strains which carry mutations in the structural genes for the biosynthetic enzymes of each step in the formation of tryptophan from chorismate, are unable to form fruitbodies on medium containing low tryptophan concentrations. We show that cleistothecia formation can be restored by high tryptophan supplementation. Cleistothecia formation of the trpA and trpD strains can also be restored by high concentrations of either the tryptophan precursors anthranilate and indole or auxin. Fertilty of ascospores of the strains can only be restored to about one hundredth of the wild-type fertility. Oversupplementation with tryptophan inhibits cleistothecia formation, but not conidiation. Tryptophan supplementation was found to result in auxin production of A. nidulans. trpC transcript levels and enzyme activities remain stable during development whereas transcript levels and enzyme activities of another biosynthetic gene as control are reduced. We conclude an extensive connection between a balanced tryptophan biosynthesis and sexual development in Aspergillus nidulans .
Fungal Genet. Newsl. 46 (Supl):
Full conference title:
Fungal Genetics Conference 20th
- Fungal Genetics Conference 20th (1999)