Total Heterologous Biosynthesis of Fungal Natural Products in Aspergillus nidulans

Abstract

Fungal natural products comprise a wide range of bioactive compounds including important drugs and agrochemicals. Intriguingly, bioinformatic analyses of fungal genomes have revealed that fungi have the potential to produce significantly more natural products than what have been discovered so far. It has thus become widely accepted that most biosynthesis pathways of fungal natural products are silent or expressed at very low levels under laboratory cultivation conditions. To tap into this vast chemical reservoir, the reconstitution of entire biosynthetic pathways in genetically tractable fungal hosts (total heterologous biosynthesis) has become increasingly employed in recent years. This review summarizes total heterologous biosynthesis of fungal natural products accomplished before 2020 using Aspergillus nidulans as heterologous hosts. We review here Aspergillus transformation, A. nidulans hosts, shuttle vectors for episomal expression, and chromosomal integration expression. These tools, collectively, not only facilitate the discovery of cryptic natural products but can also be used to generate high-yield strains with clean metabolite backgrounds. In comparison with total synthesis, total heterologous biosynthesis offers a simplified strategy to construct complex molecules and holds potential for commercial application.

Advances in Synthetic Biology of Fungi and Contributions to the Discovery of New Molecules

“…However, many fungal NPs require PKSs and NRPSs, multimodular enzymes containing acyl‐carrier protein binding domains, which need to be activated by specific phosphopantetheinyl transferases (PPTs), not present in yeast [61] . For this reason, the question of whether a model filamentous fungus with a clean metabolite background should be developed to facilitate the identification of cryptic metabolites has been raised for many years, with examples already available [54b,62] . However, the heterologous expression of exogenous PPT genes in S. cerevisiae enabled the biosynthesis of 6‐methylsalicylic acid, using a PKS‐encoding gene from Penicillium patulum , [63] and the complete biosynthesis of penicillin, by expressing cDNAs isolated from Penicillium chrysogenum [64] .…”

Terpenoid balance inAspergillus nidulansunveiled by heterologous squalene synthase expression

“…Of the ca. 35 terpene synthesis related genes including terpene synthases, terpene cyclases, and/or prenyl transferases, found in the sequenced A. nidulans FGSC A4 genome (the isolate used in this study), only nine have been genetically linked to their product: AN1592 and AN1594 (PbcA) to ent -pimara-8(14),15-diene, AN9259 (AusN) and AN9257 (AusL) to austinol, AN3228 (PkfE) to aspernidines, AN8514 (tidB) to terrequinone, AN11080 (nptA) to nidulanin A, and AN6784 (xptA) and AN12402 (xptB) to prenylated xanthones (Fig. 2).…”

“…A. nidulans is a renowned heterologous expression host due to the ease of genetic manipulation first established in the late 1940s ( 13 ) and easily adapted to new genetic tools in the subsequent decades ( 14 ). Further, studies in this fungus in the last 30 years have linked over 30 BGCs to specific NPs ( 15 ) which simplifies the identification of heterologous NPs such as those expressed from FACs.…”

Complexity of fungal polyketide biosynthesis and function

“…It has been used to decipher the alternariol biosynthesis (Wenderoth et al., 2019) and more recently for the production of basidiomycete polyketides (Han et al., 2023). Another host organism is A. nidulans , which has been engineered by deletion of eight entire native BGCs from its genome for a cleaner background and less crosstalk between native and heterologous genes (Chiang et al., 2022). Expression systems have also been developed for Aspergillus niger , for instance, the terrein‐based system (Gressler et al., 2015), the ATNT‐system (Geib & Brock, 2017), or a system suitable for the expression of very long PKSs derived from mushroom‐forming fungi and early diverging fungi (Kirchgaessner et al., 2023).…”