Search Results (30)

Precocious sexual inducer (psi)-producing oxygenases (Ppos) participate in the production of C8 moldy volatile compounds (MVOCs), and these compounds could act as signal molecules modulating G protein signaling cascades, which participates in the growth and development, secondary metabolisms and pathogenicity of filamentous fungi. In this study, PePpoA and PePpoC proteins were identified in Penicillium expansum. The deletion of ppoA decreased C8 MVOC production in P. expansum, while they were not detected in the ΔppoC strain (p < 0.05). In addition, down-regulated cAMP/PKA and PKC/PLC signaling showed in the two mutants (p < 0.05). The two mutants showed slow colony growth and down-regulated expression of genes regulating spore development (abaA, wetA, brlA and vosA) with broken morphology of spore and hyphae. In addition, the two mutants had decreased pathogenicity on apple fruit and less patulin production in vitro and in vivo. Compared with ΔppoA strain, the deletion of ppoC inhibited G protein signaling pathways more, and the ΔppoC strain had more defective growth and development as well as reduced pathogenicity and patulin production (p < 0.05). Therefore, PePpoC proteins affect more growth and development, patulin biosynthesis and pathogenicity of P. expansum by regulating C8 MVOC-mediated G protein signaling transduction. Full article

Rad6 is a canonical ubiquitin-conjugating enzyme known for its role in regulating chromosome-related cellular processes in yeast and has been proven to have multiple functions in Beauveria bassiana, including insect-pathogenic lifestyle, UV damage repair, and conidiation. However, previous studies have only reported the key role of Rad6 in regulating conidial production in a nutrient-rich medium, without any deep mechanism analyses. In this study, we found that the disruption of Rad6 leads to a profound reduction in conidial production, irrespective of whether the fungus is cultivated in nutrient-rich or nutrient-poor environments. The absence of rad6 exerts a suppressive effect on the transcription of essential genes in the central developmental pathway, namely, brlA, abaA, and wetA, resulting in a direct downregulation of conidiation capacity. Additionally, mutant strains exhibited a more pronounced decline in both conidial generation and hyphal development when cultured in nutrient-rich conditions. This observation correlates with the downregulation of the central developmental pathway (CDP) downstream gene vosA and the upregulation of flaA in nutrient-rich cultures. Moreover, single-transcriptomics analyses indicated that irregularities in biotin metabolism, DNA repair, and tryptophan metabolism are the underlying factors contributing to the reduced conidial production. Comprehensive dual transcriptomics analyses pinpointed abnormal biotin metabolism as the primary cause of conidial production decline. Subsequently, we successfully restored conidial production in the Rad6 mutant strain through the supplementation of biotin, further confirming the transcriptomic evidence. Altogether, our findings underscore the pivotal role of Rad6 in influencing biotin metabolism, subsequently impacting the expression of CDP genes and ultimately shaping the asexual life cycle of B. bassiana. Full article

About one-fourth of patients with pancreatic ductal adenocarcinoma (PDAC) are categorized as borderline resectable (BR) or locally advanced (LA). Chemotherapy and radiation therapy have not yielded the anticipated outcomes in curing patients with BR/LA PDAC. The surgical resection of these tumors presents challenges owing to the unpredictability of the resection margin, involvement of vasculature with the tumor, the likelihood of occult metastasis, a higher ratio of positive lymph nodes, and the relatively larger size of tumor nodules. Oncolytic virotherapy has shown promising activity in preclinical PDAC models. Unfortunately, the desmoplastic stroma within the PDAC tumor microenvironment establishes a barrier, hindering the infiltration of oncolytic viruses and various therapeutic drugs—such as antibodies, adoptive cell therapy agents, and chemotherapeutic agents—in reaching the tumor site. Recently, a growing emphasis has been placed on targeting major acellular components of tumor stroma, such as hyaluronic acid and collagen, to enhance drug penetration. Oncolytic viruses can be engineered to express proteolytic enzymes that cleave hyaluronic acid and collagen into smaller polypeptides, thereby softening the desmoplastic stroma, ultimately leading to increased viral distribution along with increased oncolysis and subsequent tumor size regression. This approach may offer new possibilities to improve the resectability of patients diagnosed with BR and LA PDAC. Full article

Asexual development is the main propagation and transmission mode of Beauveria bassiana and the basis of its pathogenicity. The regulation mechanism of conidiation and the key gene resources for utilization are key links to improving the conidia yield and quality of Beauveria bassiana. Their clarification may promote the industrialization of fungal pesticides. Here, we compared the regulation of morphology, resistance to external stress, virulence, and nutrient utilization capacity between the upstream developmental regulatory gene fluG and the key genes brlA, abaA, and wetA in the central growth and development pathway. The results showed that the ΔbrlA and ΔabaA mutants completely lost the capacity to conidiate and that the ΔwetA mutant had seriously reduced conidiation capacity. Although the deletion of fluG did not reduce the conidiation ability as much as deletions of brlA, abaA, and wetA, it significantly reduced the fungal response to external stress, virulence, and nutrient utilization, while the deletion of the three other genes had little effect. Via transcriptome analysis and screening the yeast nuclear system library, we found that the differentially expressed genes in the ΔfluG mutants were concentrated in the signaling pathways of ABC transporters, propionate metabolism, tryptophan metabolism, DNA replication, mismatch repair, and fatty acid metabolism. FluG directly acted on 40 proteins that were involved in various signaling pathways such as metabolism, oxidative stress, and cell homeostasis. The analysis indicated that the regulatory function of fluG was mainly involved in DNA replication, cell homeostasis, fungal growth and metabolism, and the response to external stress. Our results revealed the biological function of fluG in asexual development and the responses to several environmental stresses as well as its influence on the asexual development regulatory network in B. bassiana. Full article

Aspergillus fumigatus is the leading cause of aspergillosis, associated with high mortality rates, particularly in immunocompromised individuals. In search of novel genetic targets against aspergillosis, we studied the WOPR transcription factor OsaA. The deletion of the osaA gene resulted in colony growth reduction. Conidiation is also influenced by osaA; both osaA deletion and overexpression resulted in a decrease in spore production. Wild-type expression levels of osaA are necessary for the expression of the conidiation regulatory genes brlA, abaA, and wetA. In addition, osaA is necessary for normal cell wall integrity. Furthermore, the deletion of osaA resulted in a reduction in the ability of A. fumigatus to adhere to surfaces, decreased thermotolerance, as well as increased sensitivity to oxidative stress. Metabolomics analysis indicated that osaA deletion or overexpression led to alterations in the production of multiple secondary metabolites, including gliotoxin. This was accompanied by changes in the expression of genes in the corresponding secondary metabolite gene clusters. These effects could be, at least in part, due to the observed reduction in the expression levels of the veA and laeA global regulators when the osaA locus was altered. Importantly, our study shows that osaA is indispensable for virulence in both neutropenic and corticosteroid-immunosuppressed mouse models. Full article

Signaling pathways play a crucial role in regulating cellulase production. The pathway mediated by signaling proteins plays a crucial role in understanding how cellulase expression is regulated. In this study, using affinity purification of ClrB, we have identified sixteen proteins that potentially interact with ClrB. One of the proteins, the catalytic subunit of cAMP-dependent protein kinase A (PoPKA-C), is an important component of the cAMP/PKA signaling pathway. Knocking out PoPKA-C resulted in significant decreases in the growth, glucose utilization, and cellulose hydrolysis ability of the mutant strain. Furthermore, the cellulase activity and gene transcription levels were significantly reduced in the ΔPoPKA-C mutant, while the expression activity of CreA, a transcriptional regulator of carbon metabolism repression, was notably increased. Additionally, deletion of PoPKA-C also led to earlier timing of conidia production. The expression levels of key transcription factor genes stuA and brlA, which are involved in the production of the conidia, showed significant enhancement in the ΔPoPKA-C mutant. These findings highlight the involvement of PoPKA-C in mycelial development, conidiation, and the regulation of cellulase expression. The functional analysis of PoPKA-C provides insights into the mechanism of the cAMP/PKA signaling pathway in cellulase expression in filamentous fungi and has significant implications for the development of high-yielding cellulase strains. Full article

Antrodia cinnamomea is a valuable edible and medicinal mushroom with antitumor, hepatoprotective, and antiviral effects that play a role in intestinal flora regulation. Spore-inoculation submerged fermentation has become the most efficient and well-known artificial culture process for A. cinnamomea. In this study, a specific low-molecular compound named 1,8-cineole (cineole) from Cinnamomum kanehirae Hay was first reported to have remarkably promoted the asexual sporulation of A. cinnamomea in submerged fermentation (AcSmF). Then, RNA sequencing, real-time quantitative PCR, and a literature review were performed to predict the molecular regulatory mechanisms underlying the cineole-promoted sporulation of AcSmF. The available evidence supports the hypothesis that after receiving the signal of cineole through cell receptors Wsc1 and Mid2, Pkc1 promoted the expression levels of rlm1 and wetA and facilitated their transfer to the cell wall integrity (CWI) signal pathway, and wetA in turn promoted the sporulation of AcSmF. Moreover, cineole changed the membrane functional state of the A. cinnamomea cell and thus activated the heat stress response by the CWI pathway. Then, heat shock protein 90 and its chaperone Cdc37 promoted the expression of stuA and brlA, thus promoting sporulation of AcSmF. In addition, cineole promoted the expression of areA, flbA, and flbD through the transcription factor NCP1 and inhibited the expression of pkaA through the ammonium permease of MEP, finally promoting the sporulation of AcSmF. This study may improve the efficiency of the inoculum (spores) preparation of AcSmF and thereby enhance the production benefits of A. cinnamomea. Full article

The genus Aspergillus, one of the most abundant airborne fungi, is classified into hundreds of species that affect humans, animals, and plants. Among these, Aspergillus nidulans, as a key model organism, has been extensively studied to understand the mechanisms governing growth and development, physiology, and gene regulation in fungi. A. nidulans primarily reproduces by forming millions of asexual spores known as conidia. The asexual life cycle of A. nidulans can be simply divided into growth and asexual development (conidiation). After a certain period of vegetative growth, some vegetative cells (hyphae) develop into specialized asexual structures called conidiophores. Each A. nidulans conidiophore is composed of a foot cell, stalk, vesicle, metulae, phialides, and 12,000 conidia. This vegetative-to-developmental transition requires the activity of various regulators including FLB proteins, BrlA, and AbaA. Asymmetric repetitive mitotic cell division of phialides results in the formation of immature conidia. Subsequent conidial maturation requires multiple regulators such as WetA, VosA, and VelB. Matured conidia maintain cellular integrity and long-term viability against various stresses and desiccation. Under appropriate conditions, the resting conidia germinate and form new colonies, and this process is governed by a myriad of regulators, such as CreA and SocA. To date, a plethora of regulators for each asexual developmental stage have been identified and investigated. This review summarizes our current understanding of the regulators of conidial formation, maturation, dormancy, and germination in A. nidulans. Full article

The contamination of peanuts, with Aspergillus flavus and subsequent aflatoxins (AFs) is considered to be one of the most serious, safety problems in the world. Water activity (a_w) and temperature are limiting, factors for fungal growth and aflatoxin production during storage. The objectives of this study were to integrate data on the effects of temperature (34, 37, and 42 °C) and water activity (a_w; 0.85, 0.90, and 0.95) on growth rate aflatoxin B1 (AFB1) production and up- or-downregulation of the molecular expression of biosynthetic AFB1 genes divided into three types based on their A. flavus isolate composition and AFB1 capacity in vitro: A. flavus KSU114 (high producer), A. flavus KSU114 (low producer), and A. flavus KSU121 (non-producer). The A. flavus isolates were shown to be resilient in terms of growth on yeast extract sucrose agar media when exposed to temperature and water activity as pivotal environmental factors. The optimal conditions for the fungal growth of three isolates were a temperature of 34 °C and water activity of 0.95 a_w; there was very slow fungal growth at the highest temperature of 42 °C, with different a_w values causing inhibited fungal growth. The AFB1 production for the three isolates followed the same pattern with one exception: A. flavus KSU114 failed to produce any AFB1 at 42 °C with different a_w values. All tested genes of A. flavus were significantly up- or downregulated under three levels of interaction between temperature and a_w. The late structural genes of the pathway were significantly upregulated at 34 °C under a_w 0.95, although aflR, aflS and most of the early structural genes were upregulated. Compared to 34 °C with an a_w value of 0.95, most of the expressed genes were significantly downregulated at 37 and 42 °C with a_w values of 0.85 and 0.90. Additionally, two regulatory genes were downregulated under the same conditions. The expression level of laeA was also completely associated with AFB1 production, while the expression level of brlA was linked to A. flavus colonization. This information is required to forecast the actual effects of climate change on A. flavus. The findings can be applied to improve specific food technology processes and create prevention strategies to limit the concentrations of potential carcinogenic substances in peanuts and their derivatives. Full article

The VosA-VelB hetero-dimeric complex plays a pivotal role in regulating development and secondary metabolism in Aspergillus nidulans. In this work, we characterize a new VosA/VelB-activated gene called vadH, which is predicted to encode a 457-amino acid length protein containing four adjacent C₂H₂ zinc-finger domains. Mutational inactivation of vosA or velB led to reduced mRNA levels of vadH throughout the lifecycle, suggesting that VosA and VelB have a positive regulatory effect on the expression of vadH. The deletion of vadH resulted in decreased asexual development (conidiation) but elevated production of sexual fruiting bodies (cleistothecia), indicating that VadH balances asexual and sexual development in A. nidulans. Moreover, the vadH deletion mutant exhibited elevated susceptibility to hyperosmotic stress compared to wild type and showed elevated production of the mycotoxin sterigmatocystin (ST). Genome-wide expression analyses employing RNA-Seq have revealed that VadH is likely involved in regulating more genes and biological pathways in the developmental stages than those in the vegetative growth stage. The brlA, abaA, and wetA genes of the central regulatory pathway for conidiation are downregulated significantly in the vadH null mutant during asexual development. VadH also participates in regulating the genes, mat2, ppgA and lsdA, etc., related to sexual development, and some of the genes in the ST biosynthetic gene cluster. In summary, VadH is a putative transcription factor with four C₂H₂ finger domains and is involved in regulating asexual/sexual development, osmotic stress response, and ST production in A. nidulans. Full article

The basic biological function of glutamine synthetase (Gs) is to catalyze the conversion of ammonium and glutamate to glutamine. This synthetase also performs other biological functions. However, the roles of Gs in fungi, especially in filamentous fungi, are not fully understood. Here, we found that conditional disruption of glutamine synthetase (AflGsA) gene expression in Aspergillus flavus by using a xylose promoter leads to a complete glutamine deficiency. Supplementation of glutamine could restore the nutritional deficiency caused by AflGsA expression deficiency. Additionally, by using the xylose promoter for the downregulation of AflgsA expression, we found that AflGsA regulates spore and sclerotic development by regulating the transcriptional levels of sporulation genes abaA and brlA and the sclerotic generation genes nsdC and nsdD, respectively. In addition, AflGsA was found to maintain the balance of reactive oxygen species (ROS) and to aid in resisting oxidative stress. AflGsA is also involved in the regulation of light signals through the production of glutamine. The results also showed that the recombinant AflGsA had glutamine synthetase activity in vitro and required the assistance of metal ions. The inhibitor molecule L-α-aminoadipic acid suppressed the activity of rAflGsA in vitro and disrupted the morphogenesis of spores, sclerotia, and colonies in A. flavus. These results provide a mechanistic link between nutrition metabolism and glutamine synthetase in A. flavus and suggest a strategy for the prevention of fungal infection. Full article

BrlA and AbaA are key activators of the central developmental pathway (CDP) that controls asexual development in Aspergillus but their roles remain insufficiently understood in hypocerealean insect pathogens. Here, regulatory roles of BrlA and AbaA orthologs in Metarhizium robertsii (Clavicipitaceae) were characterized for comparison to those elucidated previously in Beauveria bassiana (Cordycipitaceae) at phenotypic and transcriptomic levels. Time-course transcription profiles of brlA, abaA, and the other CDP activator gene wetA revealed that they were not so sequentially activated in M. robertsii as learned in Aspergillus. Aerial conidiation essential for fungal infection and dispersal, submerged blastospore production mimicking yeast-like budding proliferation in insect hemocoel, and insect pathogenicity via cuticular penetration were all abolished as a consequence of brlA or abaA disruption, which had little impact on normal hyphal growth. The disruptants were severely compromised in virulence via cuticle-bypassing infection (intrahemocoel injection) and differentially impaired in cellular tolerance to oxidative and cell wall-perturbing stresses. The ΔbrlA and ΔabaA mutant shad 255 and 233 dysregulated genes (up/down ratios: 52:203 and 101:122) respectively, including 108 genes co-dysregulated. These counts were small compared with 1513 and 2869 dysregulated genes (up/down ratios: 707:806 and 1513:1356) identified in ΔbrlA and ΔabaA mutants of B. bassiana. Results revealed not only conserved roles for BrlA and AbaA in asexual developmental control but also their indispensable roles in fungal adaptation to the insect-pathogenic lifecycle and host habitats. Intriguingly, BrlA- or AbaA-controlled gene expression networks are largely different between the two insect pathogens, in which similar phenotypes were compromised in the absence of either brlA or abaA. Full article

Aspergillus species, especially A. fumigatus, and to a lesser extent others (A. flavus, A. niger, A. terreus), although rarely pathogenic to healthy humans, can be very aggressive to immunocompromised patients (they are opportunistic pathogens). Although survival rates for such infections have improved in recent decades following the introduction of azole derivatives, they remain a clinical challenge. The fact that current antifungals act as fungistatic rather than fungicide, that they have limited safety, and that resistance is becoming increasingly common make the need for new, more effective, and safer therapies to become more acute. Over the last decades, knowledge about the molecular biology of A. fumigatus and other Aspergillus species, and particularly of calcineurin, Hsp90, and their signaling pathway proteins, has progressed remarkably. Although calcineurin has attracted much interest, its adverse effects, particularly its immunosuppressive effects, make it less attractive than it might at first appear. The situation is not very different for Hsp90. Other proteins from their signaling pathways, such as protein kinases phosphorylating the four SPRR serine residues, CrzA, rcnA, pmcA-pmcC (particularly pmcC), rfeF, BAR adapter protein(s), the phkB histidine kinase, sskB MAP kinase kinase, zfpA, htfA, ctfA, SwoH (nucleoside diphosphate kinase), CchA, MidA, FKBP12, the K27 lysine position from Hsp90, PkcA, MpkA, RlmA, brlA, abaA, wetA, other heat shock proteins (Hsp70, Hsp40, Hsp12) currently appear promising and deserve further investigation as potential targets for antifungal drug development. Full article

Aspergillus flavus is a representative fungal species in the Aspergillus section Flavi and has been used as a model system to gain insights into fungal development and toxin production. A. flavus has several adverse effects on humans, including the production of the most carcinogenic mycotoxin aflatoxins and causing aspergillosis in immune-compromised patients. In addition, A. flavus infection of crops results in economic losses due to yield loss and aflatoxin contamination. A. flavus is a saprophytic fungus that disperses in the ecosystem mainly by producing asexual spores (conidia), which also provide long-term survival in the harsh environmental conditions. Conidia are composed of the rodlet layer, cell wall, and melanin and are produced from an asexual specialized structure called the conidiophore. The production of conidiophores is tightly regulated by various regulators, including the central regulatory cascade composed of BrlA-AbaA-WetA, the fungi-specific velvet regulators, upstream regulators, and developmental repressors. In this review, we summarize the findings of a series of recent studies related to asexual development in A. flavus and provide insights for a better understanding of other fungal species in the section Flavi. Full article

Antrodia cinnamomea is a precious edible and medicinal mushroom with various biological activities, such as hepatoprotection, antitumor, antivirus, immunoregulation, and intestinal flora regulation. However, the wild fruiting bodies of A. cinnamomea are scarce and expensive. Submerged fermentation based on spore inoculation has become the most efficient and popular artificial culture method for A. cinnamomea. In order to complement the mechanism of asexual sporulation of A. cinnamomea in submerged fermentation, and provide a theoretical basis to further improve the sporulation, comparative transcriptomics analysis using RNA-seq and RT-qPCR were conducted on A. cinnamomea mycelia cultured under different nutritional conditions to reveal the regulatory mechanism underlying the asexual sporulation induced by nutrient limitation. The obtained mechanism is as follows: under nitrogen starvation, the corresponding sensors transmit signals to genes, such as areA and tmpA, and promote their expression. Among these genes, AreA has a direct or indirect effect on flbD and promotes its expression, further enhancing the expression of brlA. Meanwhile, TmpA has a direct or indirect effect on brlA and promotes its expression; under carbon starvation, transport protein Rco-3, as a glucose sensor, directly or indirectly transmits signals to brlA and promotes its expression. BrlA promotes the expression of abaA gene, which further enhances the expression of wetA gene, and wetA then directly leads to asexual sporulation and promotes spore maturation; meanwhile, gulC can also promote cell autolysis, which provides energy and raw materials for sporulation. Full article