Identification of the antiphagocytic trypacidin gene cluster in the human-pathogenic fungus Aspergillus fumigatus

Abstract

The opportunistic human pathogen Aspergillus fumigatus produces numerous different natural products. The genetic basis for the biosynthesis of a number of known metabolites has remained unknown. The gene cluster encoding for the biosynthesis of the conidia-bound metabolite trypacidin is of particular interest because of its antiprotozoal activity and possible role in the infection process. Here, we show that the genes encoding the biosynthesis enzymes of trypacidin reside within an orphan gene cluster in A. fumigatus. Genome mining identified tynC as an uncharacterized polyketide synthase with high similarity to known enzymes, whose products are structurally related to trypacidin including endocrocin and fumicycline. Gene deletion of tynC resulted in the complete absence of trypacidin production, which was fully restored when the mutant strain was complemented with the wild-type gene. When confronted with macrophages, the tynC deletion mutant conidia were more frequently phagocytosed than those of the parental wild-type strain. This was also found for phagocytic amoebae of the species Dictyostelium discoideum, which showed increased phagocytosis of ΔtynC conidia. Both macrophages and amoebae were also sensitive to trypacidin. Therefore, our results suggest that the conidium-bound trypacidin could have a protective function against phagocytes both in the environment and during the infection process.

Temperature during conidiation affects stress tolerance, pigmentation, and trypacidin accumulation in the conidia of the airborne pathogen Aspergillus fumigatus

“…AFUA_8G01640 was more highly expressed in the conidia that were grown at 45°C, whereas pksP and tpcC/tynC , which are responsible for DHN-melanin and trypacidin biosynthesis, respectively, were more highly expressed at 25°C. The trypacidin biosynthesis ( tpc/tyn ) gene cluster was recently reported to comprise 13 contiguous genes ( tpcA/tynA to tpcM/tynM ) [26,27]. Indeed, the present RNA sequencing analysis showed that the expression of the tpc genes was coordinately regulated in a temperature-dependent manner, with clear borders on both ends of the gene cluster (Fig 4A).…”

“…Trypacidin also affects the interaction between A . fumigatus conidia and amoebae [27]. Indeed, tpcC deletion mutant conidia were more sensitive to an amoebae challenge, which suggests that trypacidin is responsible for predation avoidance.…”

Secondary metabolite arsenal of an opportunistic pathogenic fungus

“…BGC 14 (Trypacidin). Another spore pigment, this compound is produced by a 13-gene BGC [32,64]. The endocrocin and trypacidin BGCs show redundancy as both synthesize the spore pigment endocrocin [32].…”

Oxidative Cyclization in Natural Product Biosynthesis

“…140,141 The gene clusters of 150 and 154 are highly homologous and a side by side comparison suggests TynJ is the responsible copper oxidase for C-O bond formation. 141 …”