A novel role of ammonia in appressorium formation of Alternaria alternata (Fries) Keissler, a tobacco pathogenic fungus

2010 ◽  
Vol 117 (3) ◽  
pp. 112-116 ◽  
Author(s):  
W. J. Duan ◽  
X. Q. Zhang ◽  
T. Z. Yang ◽  
X. W. Dou ◽  
T. G. Chen ◽  
...  
Keyword(s):  
Alternaria Alternata ◽  
Pathogenic Fungus ◽  
Appressorium Formation

Role of Glucan-Derived Polymers in the Pathogenic Fungus Candida albicans

2019 ◽  
pp. 393-407
Author(s):  
Daniel Prieto ◽  
Elvira Román ◽  
Rebeca Alonso-Monge ◽  
Jesús Pla
Keyword(s):  
Candida Albicans ◽  
Pathogenic Fungus

scholarly journals The Role of Dimorphism Regulating Histidine Kinase (Drk1) in the Pathogenic Fungus Paracoccidioides brasiliensis Cell Wall

2021 ◽  
Vol 7 (12) ◽  
pp. 1014
Author(s):  
Marina Valente Navarro ◽  
Yasmin Nascimento de Barros ◽  
Wilson Dias Segura ◽  
Alison Felipe Alencar Chaves ◽  
Grasielle Pereira Jannuzzi ◽  
...  
Keyword(s):  
Cell Wall ◽  
Histidine Kinase ◽  
Mammalian Cells ◽  
Paracoccidioides Brasiliensis ◽  
Pathogenic Fungus ◽  
Fungal Resistance ◽  
Phagocytic Index ◽  
Mammalian Host ◽  
Control Group

Dimorphic fungi of the Paracoccidioides genus are the causative agents of paracoccidioidomycosis (PCM), an endemic disease in Latin America with a high incidence in Brazil. This pathogen presents as infective mycelium at 25 °C in the soil, reverting to its pathogenic form when inhaled by the mammalian host (37 °C). Among these dimorphic fungal species, dimorphism regulating histidine kinase (Drk1) plays an essential role in the morphological transition. These kinases are present in bacteria and fungi but absent in mammalian cells and are important virulence and cellular survival regulators. Hence, the purpose of this study was to investigate the role of PbDrk1 in the cell wall modulation of P. brasiliensis. We observed that PbDrk1 participates in fungal resistance to different cell wall-disturbing agents by reducing viability after treatment with iDrk1. To verify the role of PbDRK1 in cell wall morphogenesis, qPCR results showed that samples previously exposed to iDrk1 presented higher expression levels of several genes related to cell wall modulation. One of them was FKS1, a β-glucan synthase that showed a 3.6-fold increase. Furthermore, confocal microscopy analysis and flow cytometry showed higher β-glucan exposure on the cell surface of P. brasiliensis after incubation with iDrk1. Accordingly, through phagocytosis assays, a significantly higher phagocytic index was observed in yeasts treated with iDrk1 than the control group, demonstrating the role of PbDrk1 in cell wall modulation, which then becomes a relevant target to be investigated. In parallel, the immune response profile showed increased levels of proinflammatory cytokines. Finally, our data strongly suggest that PbDrk1 modulates cell wall component expression, among which we can identify β-glucan. Understanding this signalling pathway may be of great value for identifying targets of antifungal molecular activity since HKs are not present in mammals.

Dipeptidase PEPDA is required for the conidiation pattern shift in Metarhizium acridum

2021 ◽  
Author(s):  
Juan Li ◽  
Xueling Su ◽  
Yueqing Cao ◽  
Yuxian Xia
Keyword(s):  
Amino Acids ◽  
Filamentous Fungi ◽  
Pathogenic Fungus ◽  
Digital Gene Expression ◽  
Hyphal Growth ◽  
Metarhizium Acridum ◽  
Key Enzyme ◽  
Hydrolysis Of ◽  
Microcycle Conidiation

Filamentous fungi conduct two types of conidiation, typical conidiation from mycelia and microcycle conidiation (MC). Fungal conidiation can shift between the two patterns, which involved a large number of genes in the regulation of this process. In this study, we investigated the role of a dipeptidase gene pepdA in conidiation pattern shift in Metarhizium acridum , which is upregulated in MC pattern compared to typical conidiation. Results showed that disruption of the pepdA resulted in a shift of conidiation pattern from MC to typical conidiation. Metabolomic analyses of amino acids showed that the levels of 19 amino acids significantly changed in Δ pepdA mutant. The defect of MC in Δ pepdA can be rescued when nonpolar amino acids, α-alanine, β-alanine or proline, were added into s ucrose y east extract a gar (SYA) medium. Digital gene expression profiling analysis revealed that PEPDA mediated transcription of sets of genes which were involved in hyphal growth and development, sporulation, cell division, and amino acid metabolism. Our results demonstrated that PEPDA played important roles in the regulation of MC by manipulating the levels of amino acids in M. acridum . IMPORTANCE Conidia, as the asexual propagules in many fungi, are start and end of fungal lifecycle. In entomopathogenic fungi, conidia are the infective form essential for their pathogenicity. Filamentous fungi conduct two types of conidiation, typical conidiation from mycelia and microcycle conidiation. The mechanisms of the shift between the two conidiation patterns remain to be elucidated. In this study, we demonstrated that the dipeptidase PEPDA, a key enzyme from the insect-pathogenic fungus Metarhizium acridum for the hydrolysis of dipeptides, is associated with a shift of conidiation pattern. The conidiation pattern of the Δ pepdA mutant was restored when supplemented with the nonpolar amino acids rather than polar amino acids. Therefore, this report highlights that the dipeptidase PEPDA regulates MC by manipulating the levels of amino acids in M. acridum.

scholarly journals Functional characterization of the AGL1 aegerolysin in the mycoparasitic fungus Trichoderma atroviride reveals a role in conidiation and antagonism

2020 ◽  
Author(s):  
Mukesh Dubey ◽  
Dan Funck Jensen ◽  
Magnus Karlsson
Keyword(s):  
Pathogenic Fungus ◽  
Functional Characterization ◽  
Fruit Body ◽  
Cellular Membrane ◽  
Plant Diseases ◽  
Wall Material ◽  
Trichoderma Atroviride ◽  
Phenotypic Analysis ◽  
Mycoparasitic Fungus

Abstract Aegerolysins are small secreted pore-forming proteins that are found in both prokaryotes and eukaryotes. The role of aegerolysins in sporulation, fruit body formation, and in lysis of cellular membrane is suggested in fungi. The aim of the present study was to characterize the biological function of the aegerolysin gene agl1 in the mycoparasitic fungus Trichoderma atroviride, used for biological control of plant diseases. Gene expression analysis showed higher expression of agl1 during conidiation and during growth in medium supplemented with cell wall material from the plant pathogenic fungus Rhizoctonia solani as the sole carbon source. Expression of agl1 was supressed under iron-limiting condition, while agl1 transcript was not detected during T. atroviride interactions with the prey fungi Botrytis cinerea or R. solani. Phenotypic analysis of agl1 deletion strains (Δagl1) showed reduced conidiation compared to T. atroviride wild type, thus suggesting the involvement of AGL1 in conidiation. Furthermore, the Δagl1 strains display reduced antagonism towards B. cinerea and R. solani based on a secretion assay, although no difference was detected during direct interactions. These data demonstrate the role of AGL1 in conidiation and antagonism in the mycoparasitic fungus T. atroviride.

scholarly journals Glycerol-3-Phosphate Acyltransferase Contributes to Triacylglycerol Biosynthesis, Lipid Droplet Formation, and Host Invasion in Metarhizium robertsii

2013 ◽  
Vol 79 (24) ◽  
pp. 7646-7653 ◽  
Author(s):  
Qiang Gao ◽  
Yanfang Shang ◽  
Wei Huang ◽  
Chengshu Wang
Keyword(s):  
Pathogenic Fungus ◽  
Single Copy ◽  
Fungal Genome ◽  
Model Organisms ◽  
Glycerol Phosphate ◽  
Fungal Virulence ◽  
Metarhizium Robertsii ◽  
Content Type ◽  
Rate Limiting Step

ABSTRACTEnzymes involved in the triacylglycerol (TAG) biosynthesis have been well studied in the model organisms of yeasts and animals. Among these, the isoforms of glycerol-3-phosphate acyltransferase (GPAT) redundantly catalyze the first and rate-limiting step in glycerolipid synthesis. Here, we report the functions of mrGAT, a GPAT ortholog, in an insect-pathogenic fungus,Metarhizium robertsii. Unlike in yeasts and animals, a single copy of the mrGAT gene is present in the fungal genome and the gene deletion mutant is viable. Compared to the wild type and the gene-rescued mutant, the ΔmrGATmutant demonstrated reduced abilities to produce conidia and synthesize TAG, glycerol, and total lipids. More importantly, we found that mrGAT is localized to the endoplasmic reticulum and directly linked to the formation of lipid droplets (LDs) in fungal cells. Insect bioassay results showed thatmrGATis required for full fungal virulence by aiding fungal penetration of host cuticles. Data from this study not only advance our understanding of GPAT functions in fungi but also suggest that filamentous fungi such asM. robertsiican serve as a good model to elucidate the role of the glycerol phosphate pathway in fungal physiology, particularly to determine the mechanistic connection of GPAT to LD formation.

scholarly journals The YAP1 Homolog–Mediated Oxidative Stress Tolerance Is Crucial for Pathogenicity of the Necrotrophic Fungus Alternaria alternata in Citrus

2009 ◽  
Vol 22 (8) ◽  
pp. 942-952 ◽  
Author(s):  
Ching-Hsuan Lin ◽  
Siwy Ling Yang ◽  
Kuang-Ren Chung
Keyword(s):  
Oxidative Stress ◽  
Alternaria Alternata ◽  
Critical Role ◽  
Disease Process ◽  
Brown Spot ◽  
Null Mutant ◽  
Wild Type ◽  
Protein Fusion ◽  
Fungal Pathogenicity

Citrus brown spot disease is caused by the necrotrophic fungus Alternaria alternata. Its pathogenic capability has been thought to depend exclusively on the production of host-selective ACT toxin. However, circumvention of plant defenses is also likely to be important for the disease process. To investigate the fungal response to host-generated reactive oxygen species (ROS), we cloned and characterized the AaAP1 gene of A. alternata, which encodes a polypeptide resembling yeast YAP1-like transcriptional activators implicated in cellular responses to stress. Expression of the AaAP1 gene in a wild-type strain was primarily induced by H2O2 or ROS-generating oxidants. Using a loss-of-function mutation in the AaAP1 gene, we demonstrated an essential requirement for oxidative tolerance during the host invasion step. Mutants lacking AaAP1 showed increased sensitivity to H2O2 and loss of fungal pathogenicity. The ΔAaAP1 null mutant did not cause any visible necrotic lesions on wounded or unwounded leaves of citrus cv. Minneola. Compared with the wild type, the null mutant displayed lower catalase, peroxidase, and superoxide dismutase activities. All mutant phenotypes were restored to the wild type in fungal strains expressing a functional copy of AaAP1. Upon exposure to H2O2, the AaAP1::sGFP (synthetic green fluorescent protein) fusion protein became localized in the nucleus. Inoculation of the mutant with NADPH oxidase inhibitors partially restored fungal pathogenicity. Our results highlight the global regulatory role of a YAP1 homolog in response to oxidative stress in A. alternata and provide insights into the critical role of ROS detoxification in the pathogenicity of A. alternata.

scholarly journals Flotillin-dependent lipid-raft microdomains are required for functional phagolysosomes against fungal infections

2019 ◽  
Author(s):  
Franziska Schmidt ◽  
Andreas Thywißen ◽  
Marie Röcker ◽  
Cristina Cunha ◽  
Zoltán Cseresnyés ◽  
...  
Keyword(s):  
Lipid Rafts ◽  
Lipid Raft ◽  
Fungal Infections ◽  
Pathogenic Fungus ◽  
Cell Transplant ◽  
Hematopoietic Stem ◽  
Essential Components ◽  
Human Pathogenic Fungus ◽  
Lipid Raft Microdomains

SUMMARYLipid rafts form signaling platforms on biological membranes with incompletely characterized role in immune response to infection. Here we report that lipid raft microdomains are essential components of the phagolysosomal membrane of macrophages. Genetic deletion of the lipidraft chaperons flotillin-1 and flotillin-2 demonstrate that the assembly of both major defense complexes vATPase and NADPH oxidase on the phagolysosomal membrane requires lipid rafts. Furthermore, we discovered a new virulence mechanism leading to the dysregulation of lipid-raft formation by melanized wild-type conidia of the important human-pathogenic fungusAspergillus fumigatus. This results in reduced phagolysosomal acidification. Phagolysosomes with ingested melanized conidia contain a reduced amount of free Ca2+ions as compared to phagolysosomes with melanin-free conidia. In agreement with a role of Ca2+for generation of functional lipid rafts, we show that Ca2+-dependent calmodulin activity is required for lipid-raft formation on the phagolysosome. We identified a single nucleotide polymorphism in the humanFLOT1gene that results in heightened susceptibility for invasive aspergillosis in hematopoietic stem-cell transplant recipients. Collectively, flotillin-dependent lipid rafts on the phagolysosomal membrane play an essential role in protective antifungal immunity in humans.

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