Ergot Alkaloid Synthesis Capacity of Penicillium camemberti.

Ergot alkaloids are specialized fungal metabolites with potent biological activities. They are encoded by well-characterized gene clusters in the genomes of producing fungi. plays a major role in the ripening of Brie and Camembert cheeses. The genome contains a cluster of five genes shown in other fungi to be required for synthesis of the important ergot alkaloid intermediate chanoclavine-I aldehyde and two additional genes ( and ) that may control modification of chanoclavine-I aldehyde into other ergot alkaloids. We analyzed samples of Brie and Camembert cheeses, as well as cultures of , and did not detect chanoclavine-I aldehyde or its derivatives. To create a functioning facsimile of the cluster, we expressed and in a chanoclavine-I aldehyde-accumulating knockout mutant of The -engineered strain accumulated a pair of compounds of 269.1288 in positive-mode liquid chromatography-mass spectrometry (LC-MS). The analytes fragmented in a manner typical of the stereoisomeric ergot alkaloids rugulovasine A and B, and the related rugulovasine producer accumulated the same isomeric pair of analytes. The genes were transcribed in culture, but comparison of the cluster with the functional cluster from indicated 11 polymorphisms. Whereas other genes functioned when expressed in , did not restore ergot alkaloids when expressed in an mutant. The data indicate that formerly had the capacity to produce the ergot alkaloids rugulovasine A and B. The presence of ergot alkaloid synthesis genes in the genome of is significant, because the fungus is widely consumed in Brie and Camembert cheeses. Our results show that, although the fungus has several functional genes from the ergot alkaloid pathway, it produces only an early pathway intermediate in culture and does not produce ergot alkaloids in cheese. , a close relative of , contains a similar but fully functional set of ergot alkaloid synthesis genes and produces ergot alkaloids chanoclavine-I, chanoclavine-I aldehyde, and rugulovasine A and B. Our reconstruction of the pathway in the model fungus indicated that formerly had the capacity to produce these same ergot alkaloids. Neither nor produced ergot alkaloids in cheese, indicating that nutritionally driven gene regulation prevents these fungi from producing ergot alkaloids in a dairy environment.