Complexity of fungal polyketide biosynthesis and function

Abstract

Where does one draw the line between primary and secondary metabolism? The answer depends on the perspective. Microbial secondary metabolites (SMs) were at first believed not to be very important for the producers because they are dispensable for growth under laboratory conditions. However, such compounds become important in natural niches of the organisms, and some are of prime importance for humanity. Polyketides are an important group of SMs with aflatoxin as a well‐known and well‐characterized example. In Aspergillus spp., all 34 afl genes encoding the enzymes for aflatoxin biosynthesis are located in close vicinity on chromosome III in a so‐called gene cluster. This led to the assumption that most genes required for polyketide biosynthesis are organized in gene clusters. Recent research, however, revealed an enormous complexity of the biosynthesis of different polyketides, ranging from individual polyketide synthases to a gene cluster producing several compounds, or to several clusters with additional genes scattered in the genome for the production of one compound. Research of the last decade furthermore revealed a huge potential for SM biosynthesis hidden in fungal genomes, and methods were developed to wake up such sleeping genes. The analysis of organismic interactions starts to reveal some of the ecological functions of polyketides for the producing fungi.

Different metabolite profiles acrossPenicillium roquefortipopulations associated with ecological niche specialisation and domestication

“…Fungi are known to produce a wide range of chemically diversified metabolites in nature, that are key for fungal development, interactions, survival and/or warfare with other microorganisms in complex ecosystems. These metabolites include toxins, antimicrobial compounds, bioactive compounds, e.g antibiotics, anti-cancer and immunosuppressants, as well as molecules involved in communication or protection from UV damage (Keller 2019; Stroe et al 2023). The role of metabolites is however still not fully understood and identifying different metabolite profiles in populations thriving in distinct niches may contribute to our understanding of their ecological role.…”