A B-type histone acetyltransferase Hat1 regulates secondary metabolism, conidiation, and cell wall integrity in the taxol-producing fungus Pestalotiopsis microspora

Comparative Transcriptome Analysis of the Hypothalamic-Pituitary-Gonadal Axis of Jinhu Grouper (Epinephelus fuscoguttatus ♀ × Epinephelus tukula ♂) and Tiger Grouper (Epinephelus fuscoguttatus)

Jinhu groupers, the hybrid offspring of tiger groupers (Epinephelus fuscoguttatus) and potato groupers (Epinephelus tukula), have excellent heterosis in fast growth and strong stress resistance. However, compared with the maternal tiger grouper, Jinhu groupers show delayed gonadal development. To explore the interspecific difference in gonadal development, we compared the transcriptomes of brain, pituitary, and gonadal tissues between Jinhu groupers and tiger groupers at 24-months old. In total, 3034 differentially expressed genes (DEGs) were obtained. KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analyses showed that the osteoclast differentiation, oocyte meiosis, and ovarian steroidogenesis may be involved in the difference in gonadal development. Trend analysis showed that the DEGs were mainly related to signal transduction and cell growth and death. Additionally, differences in expression levels of nr4a1, pgr, dmrta2, tbx19, and cyp19a1 may be related to gonadal retardation in Jinhu groupers. A weighted gene co-expression network analysis revealed three modules (i.e., saddlebrown, paleturquoise, and greenyellow) that were significantly related to gonadal development in the brain, pituitary, and gonadal tissues, respectively, of Jinhu groupers and tiger groupers. Network diagrams of the target modules were constructed and the respective hub genes were determined (i.e., cdh6, col18a1, and hat1). This study provides additional insight into the molecular mechanism underlying ovarian stunting in grouper hybrids.

Pestalotiopsis Diversity: Species, Dispositions, Secondary Metabolites, and Bioactivities

Pestalotiopsis species have gained attention thanks to their structurally complex and biologically active secondary metabolites. In past decades, several new secondary metabolites were isolated and identified. Their bioactivities were tested, including anticancer, antifungal, antibacterial, and nematicidal activity. Since the previous review published in 2014, new secondary metabolites were isolated and identified from Pestalotiopsis species and unidentified strains. This review gathered published articles from 2014 to 2021 and focused on 239 new secondary metabolites and their bioactivities. To date, 384 Pestalotiopsis species have been discovered in diverse ecological habitats, with the majority of them unstudied. Some may contain secondary metabolites with unique bioactivities that might benefit pharmacology.

A Fungal Diterpene Synthase Is Responsible for Sterol Biosynthesis for Growth

A conserved open reading frame, dps, is described in Pestalotiopsis microspora, sharing a remarkable similarity with fungal diterpene synthases whose function is less studied. Loss-of-function approach manifested that dps was necessary for the growth and the development of the fungus. A deletion strain, dpsΔ, showed a fundamental retardation in growth, which could deliberately be restored by the addition of exogenous sterols to the media. Gas chromatography-mass spectrometry analysis confirmed the loss of the ability to produce certain sterols. Thus, the tolerance and the resistance of dpsΔ to several stress conditions were impaired. Secondary metabolites, such as the polyketide derivative dibenzodioxocinones, were significantly diminished. At the molecular level, the deletion of dps even affected the expression of genes in the mevalonate pathway. This report adds knowledge about fungal diterpene synthases in Pestalitiopsis microspora.

Epigenetic manipulation of filamentous fungi for biotechnological applications: a systematic review

The study of the epigenetic regulation of gene function has reached pivotal importance in life sciences in the last decades. The mechanisms and effects of processes such as DNA methylation, histone posttranslational modifications and non-coding RNAs, as well as their impact on chromatin structure and dynamics, are clearly involved in physiology homeostasis in plants, animals and microorganisms. In the fungal kingdom, studies on the model yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe contributed enormously to the elucidation of the eukaryote epigenetic landscape. Epigenetic regulation plays a central role in the expression of virulence attributes of human pathogens such as Candida albicans. In this article, we review the most recent studies on the effects of drugs capable of altering epigenetic states and on the impact of chromatin structure-related genes deletion in filamentous fungi. Emphasis is given on plant and insect pathogens, endophytes, secondary metabolites and cellulases/xylanases producing species.

Histone acetyltransferase MoHat1 acetylates autophagy-related proteins MoAtg3 and MoAtg9 to orchestrate functional appressorium formation and pathogenicity in Magnaporthe oryzae

Macroautophagy/autophagy is critical for normal appressorium formation and pathogenicity of the rice blast fungus Magnaporthe oryzae, but the molecular base of autophagy linked to pathogenicity remains elusive in this or other pathogenic fungi. We found that MoHat1, a histone acetyltransferase (HAT) homolog, had a role in the regulation of autophagy through the acetylation of autophagy related proteins MoAtg3 and MoAtg9. We also found that MoHat1 was subject to regulation by the protein kinase MoGsk1 that modulated the translocation of MoHat1 from the nucleus to the cytoplasm with the assistance of MoSsb1, a protein chaperone. The alternation of intracellular location affected MoHat1 in the modification of cytosolic autophagy proteins that maintained normal autophagy. Furthermore, we provided evidence linking acetylation of MoAtg3 and MoAtg9 by MoHat1 to functional appressorium development and pathogenicity. Together with the first report of MoAtg9 being subject to acetylation regulation by MoHat1, our studies depicted how MoHat1 regulated autophagy in conjunction with MoGsk1 and how normal autophagy was linked to appressorium formation and function and pathogenicity of M. oryzae. Abbreviations: A/Ala: alanine; AP: autophagosome; Atg genes/proteins: autophagy-related genes/proteins; BiFC: bimolecular fluorescence complementation; co-IP: co-immunoprecipitation; DAPI: 4', 6-diamidino-2-phenylindole; D/Asp: aspartic acid; GFP: green fluorescent protein; GSK3: glycogen synthase kinase 3; HAT: histone acetyltransferase; Hsp70: heat-shock protein 70; IH: invasive hyphae; K/Lys: lysine; MMS: methyl methanesulfonate; Mo: Magnaporthe oryzae; PAS: phagophore assembly site; PE: phosphatidylethanolamine; PtdIns3K: phosphatidylinositol 3-kinase; R/Arg: arginine; S/Ser: serine; T/Thr: threonine; TOR: target of rapamycin; WT: wild type; YFP: yellow fluorescent protein.

On top of biosynthetic gene clusters: How epigenetic machinery influences secondary metabolism in fungi

Fungi produce an abundance of bioactive secondary metabolites which can be utilized as antibiotics and pharmaceutical drugs. The genes encoding secondary metabolites are contiguously arranged in biosynthetic gene clusters (BGCs), which supports co-regulation of all genes required for any one metabolite. However, an ongoing challenge to harvest this fungal wealth is the finding that many of the BGCs are 'silent' in laboratory settings and lie in heterochromatic regions of the genome. Successful approaches allowing access to these regions - in essence converting the heterochromatin covering BGCs to euchromatin - include use of epigenetic stimulants and genetic manipulation of histone modifying proteins. This review provides a comprehensive look at the chromatin remodeling proteins which have been shown to regulate secondary metabolism, the use of chemical inhibitors used to induce BGCs, and provides future perspectives on expansion of epigenetic tools and concepts to mine the fungal metabolome.

Distinct Roles of Velvet Complex in the Development, Stress Tolerance, and Secondary Metabolism in Pestalotiopsis microspora, a Taxol Producer

The velvet family proteins have been shown to play critical roles in fungal secondary metabolism and development. However, variations of the roles have been observed in different fungi. We report here the observation on the role of three velvet complex components VeA, VelB, and LaeA in Pestalotiopsis microspora, a formerly reported taxol-producing fungus. Deletion of individual members led to the retardation of vegetative growth and sporulation and pigmentation, suggesting critical roles in these processes. The mutant strain △velB appeared hypersensitive to osmotic stress and the dye Congo red, whereas △veA and △laeA were little affected by the pressures, suggesting only velB was required for the integrity of the cell wall. Importantly, we found that the genes played distinct roles in the biosynthesis of secondary metabolites in P. microspora. For instance, the production of pestalotiollide B, a previously characterized polyketide, required velB and laeA. In contrast, the veA gene appeared to inhibit the pestalotiollide B (PB) role in its biosynthesis. This study suggests that the three components of the velvet complex are important global regulators, but with distinct roles in hyphal growth, asexual production, and secondary metabolism in P. microspora. This work provides information for further understanding the biosynthesis of secondary metabolism in the fungus.

The histone acetyltransferase Mst2 sustains the biological control potential of a fungal insect pathogen through transcriptional regulation

Histone lysine acetylation orchestrates transcriptional activity essential for diverse cellular events across organisms, but it remains poorly understood how an acetylated lysine affects cellular functions in filamentous fungal pathogens. Here, we show the functions of a histone acetyltransferase that is phylogenetically close to Mst2 in fission yeast and specifically acetylates histone H3K14 in Beauveria bassiana, a fungal insect pathogen widely applied in arthropod pest management. Deletion of mst2 in B. bassiana resulted in moderate growth defects on rich and minimal media, delayed conidiation, and drastic reduction (75%) in conidiation capacity under normal culture conditions. The Δmst2 conidia suffered slower germination, decreased hydrophobicity, attenuated virulence, and reduced thermotolerance and UV-B resistance. The Δmst2 mutant also displayed increased sensitivities to DNA damaging, oxidative, cell wall perturbing, and osmotic stresses during conidial germination and colony growth at optimal 25 °C. Intriguingly, the phenotypic changes were accompanied with transcriptional repression of related gene sets, which are required for asexual development and conidial hydrophobicity or cascaded for CWI and HOG pathways, and encode the families of superoxide dismutases (SOD), catalases, heat-shock proteins, and trehalose or mannitol-metabolizing enzymes. Consequently, total SOD and catalase activities, trehalose and mannitol contents, and hydrophobicity were remarkably lowered in the hyphal cells or conidia of Δmst2. All of these changes were well restored by targeted mst2 complementation. Our results indicate that Mst2 enables to mediate global gene transcription and/or post-translation through H3K14 acetylation and plays an essential role in sustaining the biological control potential of B. bassiana against arthropod pests.

Analysis of the global regulator Lae1 uncovers a connection between Lae1 and the histone acetyltransferase HAT1 in Fusarium fujikuroi

The fungus Fusarium fujikuroi causes "bakanae" disease of rice due to its ability to produce gibberellins (GAs), a family of plant hormones. Recent genome sequencing revealed the genetic capacity for the biosynthesis of 46 additional secondary metabolites besides the industrially produced GAs. Among them are the pigments bikaverin and fusarubins, as well as mycotoxins, such as fumonisins, fusarin C, beauvericin, and fusaric acid. However, half of the potential secondary metabolite gene clusters are silent. In recent years, it has been shown that the fungal specific velvet complex is involved in global regulation of secondary metabolism in several filamentous fungi. We have previously shown that deletion of the three components of the F. fujikuroi velvet complex, vel1, vel2, and lae1, almost totally abolished biosynthesis of GAs, fumonisins and fusarin C. Here, we present a deeper insight into the genome-wide regulatory impact of Lae1 on secondary metabolism. Over-expression of lae1 resulted in de-repression of GA biosynthetic genes under otherwise repressing high nitrogen conditions demonstrating that the nitrogen repression is overcome. In addition, over-expression of one of five tested histone acetyltransferase genes, HAT1, was capable of returning GA gene expression and GA production to the GA-deficient Δlae1 mutant. Deletion and over-expression of HAT1 in the wild type resulted in downregulation and upregulation of GA gene expression, respectively, indicating that HAT1 together with Lae1 plays an essential role in the regulation of GA biosynthesis.

Amino Acid Sensor Kinase Gcn2 Is Required for Conidiation, Secondary Metabolism, and Cell Wall Integrity in the Taxol-Producer Pestalotiopsis microspora

The canonical Gcn2/Cpc1 kinase in fungi coordinates the expression of target genes in response to amino acid starvation. To investigate its possible role in secondary metabolism, we characterized a gcn2 homolog in the taxol-producing fungus Pestalotiopsis microspora. Deletion of the gene led to severe physiological defects under amino acid starvation, suggesting a conserved function of gcn2 in amino acid sensing. The mutant strain Δgcn2 displayed retardation in vegetative growth. It generated dramatically fewer conidia, suggesting a connection between amino acid metabolism and conidiation in this fungus. Importantly, disruption of the gene altered the production of secondary metabolites by HPLC profiling. For instance, under amino acid starvation, the deletion strain Δgcn2 barely produced secondary metabolites including the known natural product pestalotiollide B. Even more, we showed that gcn2 played critical roles in the tolerance to several stress conditions. Δgcn2 exhibited a hypersensitivity to Calcofluor white and Congo red, implying a role of Gcn2 in maintaining the integrity of the cell wall. This study suggests that Gcn2 kinase is an important global regulator in the growth and development of filamentous fungi and will provide knowledge for the manipulation of secondary metabolism in P. microspora.