naphthoquinones and bikaverin

We staged the transfer of the aurofusarin and bikaverin biosynthetic gene clusters (BGCs) to Aspergillus nidulans with the aim of gaining functional insights into dynamics immediately following a horizontal gene transfer (HGT) event. While the introduction of both BGCs resulted in the production of detectable pathway metabolites in A. nidulans, the transferred aurofusarin BGC formed dimeric shunt products instead of aurofusarin. This was linked to low transcription of the cluster activator and insufficient activity of tailoring enzymes, demonstrating how a shift of the pathway bottleneck after HGT can result in metabolic innovation. The transferred bikaverin BGC readily produced bikaverin, providing a model system for studying the conservation of regulatory responses to environmental cues. Conserved PacC-mediated pH regulation of the bikaverin BGC was observed between original host Fusarium fujikuroi and A. nidulans. Contrary to strong nitrogen responses described in other hosts, the BGC appeared unresponsive to environmental nitrogen in A. nidulans. While F. fujikuroi and A. nidulans both form chlamydospore-like structures when exposed to ralsolamycin, specific induction of the bikaverin BGC was not observed in A. nidulans. We propose that the presence of compatible cis-regulatory elements in BGCs facilitates regulatory conservation after transfer, without which the chromosomal context would dictate expression.

Topics: Aspergillus nidulans; Fungal Proteins; Fusarium; Gene Expression Regulation, Fungal; Gene Transfer Techniques; Multigene Family; Naphthoquinones; Xanthones

Filamentous fungi have gained growing interest as sources of diverse pigmented secondary metabolites. Some specific polyketides from Ascomycetous species have demonstrated a wide range of industrial applications in food, cosmetic, textile, and in the design of pharmaceutical products. The formulation of recipes containing fungal polyketides has increased over recent years. Fusarium strains were proven useful to mankind in a variety of technologies. Nevertheless, there is still need of new isolates of Fusarium for use in emerging and already existing fields. In this article, we report the concomitant production of the bioactive red bikaverin along with two novel purple pigments by the phytopathogenic Fusarium oxysporum LCP531 strain isolated from soil. In literature, the production of purple pigment had only been described in cultures of Fusarium Fujikuroi, Fusarium verticillioides, and Fusarium graminearum. The production of these naphthoquinonic pigments, their distribution (either produced in mycelia or excreted in liquid medium) and their chemical profiles were investigated with respect to nutrient composition. The pigments were extracted by using a pressurized liquid extraction method, monitored by colorimetric analysis and characterized by HPLC-DAD chromatography. To our knowledge, this is the first report of these two novel wild-type purple naphtoquinones pigments along with bikaverin, where additionally, the culture conditions were put into perspective to optimize fermentation cultures and extraction process accordingly to the pigment/biomolecule desired. These colored naphthoquinones should be promising fungal functional compounds which could be expected to have a place of choice, along with other antibacterial, antifungal, antiviral, anticancer, and antineoplastic derivatives. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2738, 2019.

Topics: Fungal Proteins; Fusarium; Naphthoquinones; Pigments, Biological; Polyketides; Xanthones

This study was conducted to characterize a novel Fusarium species that caused leaf and stem spot on Agapanthus praecox (Agapanthus, African lily) in northern Italy and leaf rot and spot on the same host in Melbourne, Australia. Formally described as Fusarium agapanthi, this pathogen was analyzed using phenotypic, phytopathogenic, secondary metabolite, molecular phylogenetic and genomic data. Five strains were characterized, including one isolated in 1999 from symptomatic A. praecox in Saluzzo, Italy, and four in 2010 from diseased leaf tissue from the same host exhibiting leaf rot and spot symptoms in the Melbourne Gardens, Royal Botanic Gardens Victoria, Australia. Maximum parsimony and maximum likelihood molecular phylogenetic analyses of portions of six individual genes and the combined dataset all strongly supported F. agapanthi either as the earliest diverging genealogically exclusive lineage in the American Clade of the F. fujikuroi species complex, or alternatively a novel monotypic lineage sister to the American Clade. Koch's postulates were completed on dwarf blue- and large white-flowering varieties of A. praecox, where two isolates of F. agapanthi produced slowly spreading necrotic lesions when inoculated onto leaves and flower stems. Fusarium agapanthi is distinguished from other fusaria by the production of densely branched aerial conidiophores with polyphialides throughout the aerial mycelium on synthetic nutrient-poor agar. BLASTn searches of the F. agapanthi NRRL 31653 and NRRL 54464 (= VPRI 41787) genome sequences were conducted to predict sexual reproductive mode and mycotoxin potential. Results indicated that they possessed MAT1-2 and MAT1-1 idiomorphs, respectively, indicating that this species might be heterothallic. Furthermore, based on the presence of homologs of the bikaverin and fusarubin biosynthetic gene clusters in the F. agapanthi genomes, liquid chromatography-mass spectrometry analysis was conducted and confirmed production of these secondary metabolites in rice and corn kernel cultures of the fungus.

Topics: Amaryllidaceae; Australia; Biosynthetic Pathways; Cluster Analysis; Fusarium; Genes, Mating Type, Fungal; Italy; Naphthoquinones; Phylogeny; Plant Diseases; Plant Leaves; Plant Stems; Sequence Analysis, DNA; Xanthones