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《Fungal biology》2021,125(8):596-608
Fungal dimorphism is the ability of certain fungi to switch between two different cellular forms, yeast and mycelial forms, in response to external environmental factors. The pacC/Pal signal transduction pathway responds to neutral and alkaline environments and is also involved in the fungal dimorphic transition. In this study, we investigated the function of the pacC homolog, MripacC, which regulates the dimorphic transition and modulates virulence of the insect pathogenic fungus Metarhizium rileyi. MripacC expression was upregulated under alkaline condition, with increased number of yeast-like cells compared to the number of hyphae cells. A MripacC deletion mutant (ΔMripacC) was obtained by homologous replacement and exhibited decreased blastospore budding, with direct development of conidia into hyphae without entering the yeast-like stage when cultured on alkaline medium. Observation of host hemolymph morphology and analysis of samples to detect the main immune factors revealed a decreased ability of ΔMripacC to evade the host immune system. The results of insect bioassays showed that ΔMripacC had decreased virulence with extended median lethality time. Together, the results suggested that MripacC not only regulated adaptation to acidic and alkaline environments, but also influenced virulence by budding blastospores. This elucidation of the function of MripacC adds to our understanding of blastospore budding and virulence of this fungal pathogen. 相似文献
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Mi-Kyung Lee Nak-Jung Kwon Jae Min Choi Im-Soon Lee Seunho Jung Jae-Hyuk Yu 《Genetics》2014,197(1):159-173
Asexual development (conidiation) of the filamentous fungus Aspergillus nidulans occurs via balanced activities of multiple positive and negative regulators. For instance, FluG (+) and SfgA (−) govern upstream regulation of the developmental switch, and BrlA (+) and VosA (−) control the progression and completion of conidiation. To identify negative regulators of conidiation downstream of FluG-SfgA, we carried out multicopy genetic screens using sfgA deletion strains. After visually screening >100,000 colonies, we isolated 61 transformants exhibiting reduced conidiation. Responsible genes were identified as AN3152 (nsdD), AN7507, AN2009, AN1652, AN5833, and AN9141. Importantly, nsdD, a key activator of sexual reproduction, was present in 10 independent transformants. Furthermore, deletion, overexpression, and double-mutant analyses of individual genes have led to the conclusion that, of the six genes, only nsdD functions in the FluG-activated conidiation pathway. The deletion of nsdD bypassed the need for fluG and flbA∼flbE, but not brlA or abaA, in conidiation, and partially restored production of the mycotoxin sterigmatocystin (ST) in the ΔfluG, ΔflbA, and ΔflbB mutants, suggesting that NsdD is positioned between FLBs and BrlA in A. nidulans. Nullifying nsdD caused formation of conidiophores in liquid submerged cultures, where wild-type strains do not develop. Moreover, the removal of both nsdD and vosA resulted in even more abundant development of conidiophores in liquid submerged cultures and high-level accumulation of brlA messenger (m)RNA even at 16 hr of vegetative growth. Collectively, NsdD is a key negative regulator of conidiation and likely exerts its repressive role via downregulating brlA. 相似文献
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Fabrice N. Gravelat Daniele E. Ejzykowicz Lisa Y. Chiang Josée C. Chabot Mirjam Urb K. Denyese Macdonald Nadia Al‐Bader Scott G. Filler Donald C. Sheppard 《Cellular microbiology》2010,12(4):473-488
In medically important fungi, regulatory elements that control development and asexual reproduction often govern the expression of virulence traits. We therefore cloned the Aspergillus fumigatus developmental modifier MedA and characterized its role in conidiation, host cell interactions and virulence. As in the model organism Aspergillus nidulans, disruption of medA in A. fumigatus dramatically reduced conidiation. However, the conidiophore morphology was markedly different between the two species. Further, gene expression analysis suggested that MedA governs conidiation through different pathways in A. fumigatus compared with A. nidulans. The A. fumigatusΔmedA strain was impaired in biofilm production and adherence to plastic, as well as adherence to pulmonary epithelial cells, endothelial cells and fibronectin in vitro. The ΔmedA strain also had reduced capacity to damage pulmonary epithelial cells, and stimulate pro‐inflammatory cytokine mRNA and protein expression. Consistent with these results, the A. fumigatusΔmedA strain also exhibited reduced virulence in both an invertebrate and a mammalian model of invasive aspergillosis. Collectively, these results suggest that the downstream targets of A. fumigatus MedA mediate virulence, and may provide novel therapeutic targets for invasive aspergillosis. 相似文献
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Members of the APSES protein group are basic helix-loop-helix (bHLH) proteins that regulate processes such as mating, asexual sporulation and dimorphic growth in fungi. Penicillium marneffei is a human pathogen and is the only member of its genus to display a dimorphic growth transition. At 25 degrees C, P. marneffei grows with a filamentous morphology and produces asexual spores from multicellular con-idiophores. At 37 degrees C, the filamentous morphology is replaced by yeast cells that reproduce by fission. We have cloned and characterized an APSES protein-encoding gene from P. marneffei that has a high degree of similarity to Aspergillus nidulans stuA. Deletion of stuA in P. marneffei showed that it is required for metula and phialide formation during conidiation but is not required for dimorphic growth. This suggests that APSES proteins may control processes that require budding (formation of the metulae and phialides, pseudohyphal growth in Saccharomyces cerevisiae and dimorphic growth in Candida albicans) but not those that require fission (dimorphic growth in P. marneffei). The A. nidulans DeltastuA mutant has defects in both conidiation and mating. The P. marneffei stuA gene was capable of complementing the conidiation defect but could only inefficiently complement the sexual defects of the A. nidulans mutant. This suggests that the P. marneffei gene, which comes from an asexual species, has diverged significantly from the A. nidulans gene with respect to sexual but not asexual development. 相似文献
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Sporotrichosis is a common cutaneous mycosis caused by the dimorphic fungus Sporothrix schenckii, which exhibits a temperature-dependent dimorphic switch. At 25°C, it grows in a mycelial phase, while at 37°C, it forms unicellular
yeast cells. The formation of yeast cells was thought to be a requisite for the pathogenicity of S. schenckii. To identify fragments that might be related to morphogenesis, whole-cell proteins from the mold and early yeast stages of
S. schenckii were analyzed using 2DE. Among thousands of protein molecules displayed, more than 300 showed a differential expression between
the two phases. In particular, 24 yeast-specific proteins were identified using MALDI-TOF/MS. One of the most interesting
proteins was a hybrid histidine kinase, DRK1, a global regulator of dimorphism and virulence in Blastomyces dermatitidis and Histoplasma capsulatum that was abundant in the yeast phase. Our study introduced a new approach to study dimorphism in S. schenckii, and the data may help us better understand the molecular mechanisms of phase transition. 相似文献
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Calcineurin orchestrates dimorphic transitions,antifungal drug responses and host–pathogen interactions of the pathogenic mucoralean fungus Mucor circinelloides
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Soo Chan Lee Alicia Li Silvia Calo Makoto Inoue Nam K. Tonthat Judith M. Bain Johanna Louw Mari L. Shinohara Lars P. Erwig Maria A. Schumacher Dennis C. Ko Joseph Heitman 《Molecular microbiology》2015,97(5):844-865
Calcineurin plays essential roles in virulence and growth of pathogenic fungi and is a target of the natural products FK506 and Cyclosporine A. In the pathogenic mucoralean fungus Mucor circinelloides, calcineurin mutation or inhibition confers a yeast‐locked phenotype indicating that calcineurin governs the dimorphic transition. Genetic analysis in this study reveals that two calcineurin A catalytic subunits (out of three) are functionally diverged. Homology modeling illustrates modes of resistance resulting from amino substitutions in the interface between each calcineurin subunit and the inhibitory drugs. In addition, we show how the dimorphic transition orchestrated by calcineurin programs different outcomes during host–pathogen interactions. For example, when macrophages phagocytose Mucor yeast, subsequent phagosomal maturation occurs, indicating host cells respond appropriately to control the pathogen. On the other hand, upon phagocytosis of spores, macrophages fail to form mature phagosomes. Cytokine production from immune cells differs following exposure to yeast versus spores (which germinate into hyphae). Thus, the morphogenic transition can be targeted as an efficient treatment option against Mucor infection. In addition, genetic analysis (including gene disruption and mutational studies) further strengthens the understanding of calcineurin and provides a foundation to develop antifungal agents targeting calcineurin to deploy against Mucor and other pathogenic fungi. 相似文献
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Shengan Zhu Xueyao Feng Nemat O. Keyhani Yu Liu Dan Jin Sheng Tong Yan Pei Yanhua Fan 《Environmental microbiology》2021,23(9):5087-5101
Entomopathogenic fungi such as Metarhizium rileyi and Beauveria bassiana are widely used insect biological control agents. Little, however, is known concerning genetic or enzymatic factors that differentiate the mechanisms employed by these two fungal pathogens to infect target hosts. Infection by either of these organisms is known to increase levels of the growth and molting hormone, ecdysone, which also regulates the expression of a number of innate immune pathways. M. rileyi, but not B. bassiana, has apparently evolved an ecdysteroid-22-oxidase (MrE22O) that inactivate ecdysone. We show that deletion of MrE22O impaired virulence compared with the wild-type strain, with an increase in ecdysone titer seen in hosts that was coupled to an increase in the expression of antimicrobial genes. An M. rileyi strain engineered to overexpress MrE22O (MrE22OOE), as well as trans-expression in B. bassiana (Bb::MrE220OE) resulted, in strains displaying enhanced virulence and dampening of host immune responses compared with their respective wild-type parental strains. These results indicate that ecdysone plays an important role in mediating responses to fungal infection and that some insect pathogenic fungi have evolved mechanisms for targeting this hormone as a means for facilitating infection. 相似文献
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《Autophagy》2013,9(4):455-461
Nutrient limitation acts as a trigger for the synthesis of glycogen, which serves as a carbon and energy reserve during starvation. Recently, we reported that an autophagy-deficient mutant (atg8Δ) shows severe reduction in aerial hyphal growth and conidiation in the rice-blast fungus Magnaporthe oryzae, and proposed that autophagy plays an important role in facilitating glycogen homeostasis to ensure proper asexual differentiation in Magnaporthe. Here, we identify and characterize a vacuolar glucoamylase function (Sga1) that hydrolyses glycogen to meet the energy requirements during asexual development in Magnaporthe. Loss of SGA1 resulted in significant reduction in conidiation compared to the wild-type Magnaporthe strain. More importantly, an sga1Δ atg8Δ double deletion mutant showed further reduction in conidiation compared to the atg8Δ mutant in Magnaporthe. Forced localization of GFP-Sga1 to the cytoplasm (through removal of the predicted signal peptide) led to increased conidiation in wild type and the sga1Δ, but more interestingly, significantly restored conidiation in the atg8Δ mutant. Our results indicate that autophagy and Sga1 act cooperatively in vacuolar glycogen breakdown, which is essential for conidia formation but dispensable for pathogenicity in Magnaporthe. 相似文献
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为研究冬虫夏草菌(Ophiocordyceps sinensis)微循环产孢过程中的分子机理,采用高通量测序技术,对微循环产孢前后冬虫夏草菌的转录组进行研究。筛选获得差异表达基因6 902个。Gene Ontology(GO)功能聚类分析表明,差异表达基因主要参与分子功能、胞内运输、核糖核蛋白复合体等生物学通路。京都基因与基因组百科全书(Kyoto Encyclopedia of Genes and Genomes,KEGG)功能富集分析结果表明,差异表达基因参与了核糖体、嘧啶代谢、蛋白酶体、嘌呤代谢、甘氨酸代谢等过程。Mmc、Mcb、MaH1、MaPP5、MaAGA、Pyk等候选基因不同程度的参与了冬虫夏草菌微循环产孢过程,其中Mcb家族基因可能起到关键作用。通过qRT PCR验证差异表达基因,定量结果与转录组测序结果一致。本研究为进一步揭示冬虫夏草菌微循环产孢分子机制以及关键基因的调控提供了重要信息。 相似文献
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Levi G. Cleare Daniel Zamith Heino M. Heyman Sneha P. Couvillion Leonardo Nimrichter Marcio L. Rodrigues Ernesto S. Nakayasu Joshua D. Nosanchuk 《Cellular microbiology》2020,22(9)
Histoplasma capsulatum is a dimorphic fungus that most frequently causes pneumonia, but can also disseminate and proliferate in diverse tissues. Histoplasma capsulatum has a complex secretion system that mediates the release of macromolecule‐degrading enzymes and virulence factors. The formation and release of extracellular vesicles (EVs) are an important mechanism for non‐conventional secretion in both ascomycetes and basidiomycetes. Histoplasma capsulatum EVs contain diverse proteins associated with virulence and are immunologically active. Despite the growing knowledge of EVs from H. capsulatum and other pathogenic fungi, the extent that changes in the environment impact the sorting of organic molecules in EVs has not been investigated. In this study, we cultivated H. capsulatum with distinct culture media to investigate the potential plasticity in EV loading in response to differences in nutrition. Our findings reveal that nutrition plays an important role in EV loading and formation, which may translate into differences in biological activities of these fungi in various fluids and tissues. 相似文献