Ergot alkaloids (EA) are secondary metabolites synthesized by the phytopathogenic ascomycete Claviceps purpurea. The altogether 14 genes encoding the specific enzymes for the biosynthesis of EA are clustered. To date the molecular mechanisms of cluster regulation in C. purpurea are unknown. No transcription factor gene has been found within the cluster region involved in the synthesis of EA. It is only known to date that the EA in C. purpurea wild-type are produced during the ripening of the sclerotium and not in axenic cultures. Mutant strains producing alkaloids in submersed cultures require under specific conditions: (a) tryptophan as inducer and precursor, (b) a high osmotic value, (c) a low phosphate level. The alkaloid biosynthesis was speculated to be regulated by changes in the chromatin organization, a hypothesis checked by the cultivation of C. purpurea in the presence of either inhibitors of histone deacetylases (HDACis) or histone acetyltransferases (HATis). The production strain P1 of C. purpurea was cultivated under both alkaloid producing (T25N medium) and non-producing (BII medium) conditions. Unexpectedly, the alkaloid biosynthesis is repressed instead of induced by the addition of HDACis (euchromatin formation) and vice versa, indicating a complex regulation system (1). Another global regulatory system of secondary metabolism and development was discovered in Aspergillus nidulans, velvet (2). We are investigating if in C. purpurea the biosynthesis of ergot alkaloids could be regulated through velvet. We have identified and sequenced a velvet homologue in C. purpurea (cpvel1) and started a functional analysis. (1) Lorenz et al. (2009) Phytochemistry. 70:1822-1832. (2) Kim et al. (2002) Fungal Genet Biol. 37:72-80.
Full conference title:
10th EUROPEAN CONFERENCE ON FUNGAL GENETICS
- ECFG 10th (2010)