Research Progress on Fungal Sesterterpenoids Biosynthesis

Sesterterpenoids: sources, structural diversity, biological activity, and data management

Reviewing the literature published up to October 2024.Sesterterpenoids are one of the most chemically diverse and biologically promising subgroup of terpenoids, the largest family of secondary metabolites. The present review article summarizes more than seven decades of studies on isolation and characterization of more than 1600 structurally novel sesterterpenoids, supplemented by biological, pharmacological, ecological, and geographic distribution data. All the information have been implemented in eight tables available on the web and a relational database https://sesterterpenoids.unige.net/. The interface has two sections, one open to the public for reading only and the other, protected by an authentication mechanism, for timely updating of published results.

Terpestacin and Its Derivatives: Bioactivities and Syntheses

Terpestacin (1), fusaproliferin (2), and their derivatives are a class of sesterterpenes featured by a trans-fused 5/15-membered ring skeleton. There are 45 natural products (1, 2, 4-27, 65-83) isolated from various wild fungi (Fusarium sp., Bipolaris sorokiniana, Arthrinium sp., etc.) or from genetic mutants via biosynthetic gene clusters mining, and 37 derivatives (28-64) produced by semi-synthetic modifications. These compounds show a diverse range of important bioactivities such as antivirus, antimicrobial, cytotoxic, phytotoxic, anti-flammatory, and brine shrimp lethal activities. To date, two racemic and five enantioselective chemical total syntheses of 1 (including 2 and their isomers) have been developed. Over the past decade, a number of biosynthetic gene clusters or their mutants, along with their encoding enzymes responsible for producing sesterterpenes such as terpestacin and its derivatives, have also been identified. This review covers the literature from the year 1993, when 1 was firstly discovered, to May 2024, focusing on the bioactivities and syntheses of 1 and its derivatives or isomers.

Total Synthesis of an Immunosuppressive C25 Macrocyclic Terpenoid Produced by Terpene Synthase (LcTPS2)

Macrocyclic natural products, particularly those with no functionalities except unsaturation, are recognized for their therapeutic potential but are notoriously challenging to synthesize. In this study, we report the first total synthesis of an unconventional 18-membered, C25 macrocyclic terpenoid, which has demonstrated substantial immunosuppressive activity. This synthesis was achieved through strategic modifications and innovative reaction engineering, utilizing α-terpineol and geraniol as starting materials, highlighting a novel approach in macrocyclic terpenoid synthesis.

Review of the Structural Characteristics and Biological Activities of Tricholoma Secondary Metabolites (2018-2023)

Tricholoma are significant medicinal and edible mushrooms within Basidiomycota. Known for their various medicinal properties such as anti-tumor, immune regulation, and antioxidant effects, they are regarded worldwide as health foods of the 21st century. Tricholoma species produce various types of secondary metabolites, which have been extensively studied by the scientific community. In 2018, Clericuzio et al. summarized the structures, biosynthesis, and biological activities of over one hundred different secondary metabolites isolated from the fruiting bodies of 25 Tricholoma species. Building on this, the present article reviews the research progress on Tricholoma secondary metabolites from 2018 to 2023, identifying a total of 101 compounds, 46 of which were newly discovered. These secondary metabolites include a wide range of chemical categories such as terpenoids, steroids, and alkaloids, demonstrating broad biological activities. This article aims to provide in-depth scientific insights and guidance for researchers in this field by summarizing the chemical and biological properties of these secondary metabolites, promoting further applications and development of Tricholoma fungi in the pharmaceutical and food industries.

Serine 85 functions as a catalytic acid in the reprotonation process during EvAS-catalyzed astellifadiene biosynthesis

The deprotonation-reprotonation sequence introduces additional cyclization branches in terpene biosynthesis. However, the underlying mechanism remains poorly understood. In this study, we employed a combined approach of molecular dynamics (MD) simulations and site-directed mutagenesis on astellifadiene synthase EvAS from Emericella variecolor to investigate the role of a protonated S85 residue. This residue acts as a catalytic acid, previously unreported, that facilitates the reprotonation step in astellifadiene biosynthesis. Mutating S85 led to the production of a new tricyclic sesterterpene.

Emerindanols A and B: Two Bipolyhydroindenol Sesterterpenes with 5/6-6/5 Coupled Ring System Discovered by Genome Mining

Genome mining of Emericella sp. XL-029 achieved a new type E sesterterpene synthase, EmES, which affored a novel bipolyhydroindenol sesterterpene, emerindanol A. Heterologous coexpression with the upstream P450 oxidase revealed C-4 hydroxylated product, emerindanol B. Notably, emerindanols A and B represented the first sesterterpenes featuring a unique 5/6-6/5 coupled ring system. EmES was postulated to initiate through C1-IV-V pathway and convert the fused ring intermediate into the final coupled ring product through a spiro skeleton.

Biosynthesis of fungal terpenoids

Covering: up to August 2023Terpenoids, which are widely distributed in animals, plants, and microorganisms, are a large group of natural products with diverse structures and various biological activities. They have made great contributions to human health as therapeutic agents, such as the anti-cancer drug paclitaxel and anti-malarial agent artemisinin. Accordingly, the biosynthesis of this important class of natural products has been extensively studied, which generally involves two major steps: hydrocarbon skeleton construction by terpenoid cyclases and skeleton modification by tailoring enzymes. Additionally, fungi (Ascomycota and Basidiomycota) serve as an important source for the discovery of terpenoids. With the rapid development of sequencing technology and bioinformatics approaches, genome mining has emerged as one of the most effective strategies to discover novel terpenoids from fungi. To date, numerous terpenoid cyclases, including typical class I and class II terpenoid cyclases as well as emerging UbiA-type terpenoid cyclases, have been identified, together with a variety of tailoring enzymes, including cytochrome P450 enzymes, flavin-dependent monooxygenases, and acyltransferases. In this review, our aim is to comprehensively present all fungal terpenoid cyclases identified up to August 2023, with a focus on newly discovered terpenoid cyclases, especially the emerging UbiA-type terpenoid cyclases, and their related tailoring enzymes from 2015 to August 2023.

Chemical structures, biological activities, and biosynthetic analysis of secondary metabolites of the Diatrypaceae family: A comprehensive review

The family Diatrypaceae is a less well-known group within the order Xylariales (Ascomycota). Initially, the focus on its metabolites was related to the pathogenicity of one of its members, Eutypa lata. To date, a total of 254 natural products have been identified from Diatrypaceae strains. These compounds include terpenoids, sterols, polyketones, phenols, and acetylene aromatic compounds, which have shown anticancer, cytotoxic, anti-inflammatory, antimicrobial, and antiviral activities. The complex and diverse structural types, along with the diverse bioactivities, highlight the potential of Diatrypaceae as a valuable source of bioactive natural products. In this review, a deep analysis of the biosynthesis of pimarane diterpenes and scoparasin-type cytochalasins is provided, coupled with a compilation of the biosynthetic pathways of aromatic acetylene compounds in filamentous fungi. This comprehensive review not only enhances our understanding of the natural product chemistry, biological activities, and biosynthesis of secondary metabolites from the Diatrypaceae family but also promotes the exploitation and development of important bioactive compounds and potential strains.

Developing Ganoderma lucidum as a next-generation cell factory for food and nutraceuticals

Ganoderma lucidum holds a colossal reservoir of hydrolytic enzymes and therapeutic compounds and can be a sustainable source of proteins and bioactive compounds. Its metabolic versatility, propelled by its rich genome content, provides excellent biosynthetic machinery for innovation-driven pathway engineering. However, robust regulatory networks and low frequency of homologous recombination are critical bottlenecks that limit the development of molecular tools and precise genetic markers for biomanufacturing innovations in this organism. Modern synthetic biology provides tools that could help to accelerate precise multiple gene targeting and editing and untangling the biosynthetic machinery of G. lucidum. This review provides insight into molecular strategies to unwind the regulatory bottlenecks and transform G. lucidum into efficient cell factories for food and nutraceuticals.

Genomics-driven derivatization of the bioactive fungal sesterterpenoid variecolin: Creation of an unnatural analogue with improved anticancer properties

A biosynthetic gene cluster for the bioactive fungal sesterterpenoids variecolin (1) and variecolactone (2) was identified in Aspergillus aculeatus ATCC 16872. Heterologous production of 1 and 2 was achieved in Aspergillus oryzae by expressing the sesterterpene synthase VrcA and the cytochrome P450 VrcB. Intriguingly, the replacement of VrcB with homologous P450s from other fungal terpenoid pathways yielded three new variecolin analogues (5-7). Analysis of the compounds' anticancer activity in vitro and in vivo revealed that although 5 and 1 had comparable activities, 5 was associated with significantly reduced toxic side effects in cancer-bearing mice, indicating its potentially broader therapeutic window. Our study describes the first tests of variecolin and its analogues in animals and demonstrates the utility of synthetic biology for creating molecules with improved biological activities.

H3K27me3 is vital for fungal development and secondary metabolite gene silencing, and substitutes for the loss of H3K9me3 in the plant pathogen Fusarium proliferatum

Facultative heterochromatin marked by histone H3 lysine 27 trimethylation (H3K27me3) is an important regulatory layer involved in secondary metabolite (SM) gene silencing and crucial for fungal development in the genus Fusarium. While this histone mark is essential in some (e.g., the rice pathogen Fusarium fujikuroi), it appears dispensable in other fusaria. Here, we show that deletion of FpKMT6 is detrimental but not lethal in the plant pathogen Fusarium proliferatum, a member of the Fusarium fujikuroi species complex (FFSC). Loss of FpKmt6 results in aberrant growth, and expression of a large set of previously H3K27me3-silenced genes is accompanied by increased H3K27 acetylation (H3K27ac) and an altered H3K36me3 pattern. Next, H3K9me3 patterns are affected in Δfpkmt6, indicating crosstalk between both heterochromatic marks that became even more obvious in a strain deleted for FpKMT1 encoding the H3K9-specific histone methyltransferase. In Δfpkmt1, all H3K9me3 marks present in the wild-type strain are replaced by H3K27me3, a finding that may explain the subtle phenotype of the Δfpkmt1 strain which stands in marked contrast to other filamentous fungi. A large proportion of SM-encoding genes is allocated with H3K27me3 in the wild-type strain and loss of H3K27me3 results in elevated expression of 49% of them. Interestingly, genes involved in the biosynthesis of the phytohormones gibberellins (GA) are among the most upregulated genes in Δfpkmt6. Although several FFSC members harbor GA biosynthetic genes, its production is largely restricted to F. fujikuroi, possibly outlining the distinct lifestyles of these notorious plant pathogens. We show that H3K27me3 is involved in GA gene silencing in F. proliferatum and at least one additional FFSC member, and thus, may serve as a regulatory layer for gene silencing under non-favoring conditions.

Arthproliferins A-D, Four New Sesterterpenes from the Mangrove-Sediment-Derived Fungus Arthrinium sp. SCSIO41221

Four new sesterterpenes, arthproliferins A-D (1-4), together with four known derivatives, were isolated and characterized from the mangrove-sediment-derived fungus Arthrinium sp. SCSIO41221. Their structures were determined using detailed nuclear magnetic resonance (NMR) and mass spectroscopic (MS) analyses. Some of the isolated compounds were evaluated for their cytotoxicity in vitro. The results revealed that terpestacin (6) exhibited significant activity with an IC50 value of 20.3 μM, and compounds 2 and 5 were found to show weak inhibitory effects against U87MG-derived GSCs.