scholarly journals Peroxisome Function Is Required for Virulence and Survival of Fusarium graminearum

2012 ◽  
Vol 25 (12) ◽  
pp. 1617-1627 ◽  
Author(s):  
Kyunghun Min ◽  
Hokyoung Son ◽  
Jungkwan Lee ◽  
Gyung Ja Choi ◽  
Jin-Cheol Kim ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Fusarium Graminearum ◽  
Protein Import ◽  
Fluorescent Proteins ◽  
Deletion Mutants ◽  
In Planta ◽  
Peroxisomal Protein ◽  
Peroxisomal Targeting ◽  
Signal Type

Peroxisomes are organelles that are involved in a number of important cellular metabolic processes, including the β-oxidation of fatty acids, biosynthesis of secondary metabolites, and detoxification of reactive oxygen species (ROS). In this study, the role of peroxisomes was examined in Fusarium graminearum by targeted deletion of three genes (PEX5, PEX6, and PEX7) encoding peroxin (PEX) proteins required for peroxisomal protein import. PEX5 and PEX7 deletion mutants were unable to localize the fluorescently tagged peroxisomal targeting signal type 1 (PTS1)- and PTS2-containing proteins to peroxisomes, respectively, whereas the PEX6 mutant failed to localize both fluorescent proteins. Deletion of PEX5 and PEX6 resulted in retarded growth on long-chain fatty acids and butyrate, while the PEX7 deletion mutants utilized fatty acids other than butyrate. Virulence on wheat heads was greatly reduced in the PEX5 and PEX6 deletion mutants, and they were defective in spreading from inoculated florets to the adjacent spikelets through rachis. Deletion of PEX5 and PEX6 dropped survivability of aged cells in planta and in vitro due to the accumulation of ROS followed by necrotic cell death. These results demonstrate that PTS1-dependent peroxisomal protein import mediated by PEX5 and PEX6 are critical to virulence and survival of F. graminearum.

scholarly journals Functional Analyses of a Putative, Membrane-Bound, Peroxisomal Protein Import Mechanism from the Apicomplexan Protozoan Toxoplasma gondii

Genes ◽  
2018 ◽  
Vol 9 (9) ◽  
pp. 434
Author(s):  
Alison Mbekeani ◽  
Will Stanley ◽  
Vishal Kalel ◽  
Noa Dahan ◽  
Einat Zalckvar ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Protein Import ◽  
Fluorescent Protein ◽  
Metabolic Energy ◽  
Peroxisomal Protein ◽  
Genes Encoding ◽  
Peroxisomal Targeting ◽  
Membrane Bound ◽  
Green Fluorescent

Peroxisomes are central to eukaryotic metabolism, including the oxidation of fatty acids—which subsequently provide an important source of metabolic energy—and in the biosynthesis of cholesterol and plasmalogens. However, the presence and nature of peroxisomes in the parasitic apicomplexan protozoa remains controversial. A survey of the available genomes revealed that genes encoding peroxisome biogenesis factors, so-called peroxins (Pex), are only present in a subset of these parasites, the coccidia. The basic principle of peroxisomal protein import is evolutionarily conserved, proteins harbouring a peroxisomal-targeting signal 1 (PTS1) interact in the cytosol with the shuttling receptor Pex5 and are then imported into the peroxisome via the membrane-bound protein complex formed by Pex13 and Pex14. Surprisingly, whilst Pex5 is clearly identifiable, Pex13 and, perhaps, Pex14 are apparently absent from the coccidian genomes. To investigate the functionality of the PTS1 import mechanism in these parasites, expression of Pex5 from the model coccidian Toxoplasma gondii was shown to rescue the import defect of Pex5-deleted Saccharomyces cerevisiae. In support of these data, green fluorescent protein (GFP) bearing the enhanced (e)PTS1 known to efficiently localise to peroxisomes in yeast, localised to peroxisome-like bodies when expressed in Toxoplasma. Furthermore, the PTS1-binding domain of Pex5 and a PTS1 ligand from the putatively peroxisome-localised Toxoplasma sterol carrier protein (SCP2) were shown to interact in vitro. Taken together, these data demonstrate that the Pex5–PTS1 interaction is functional in the coccidia and indicate that a nonconventional peroxisomal import mechanism may operate in the absence of Pex13 and Pex14.

scholarly journals The peroxisomal protein import machinery displays a preference for monomeric substrates

Open Biology ◽  
2015 ◽  
Vol 5 (4) ◽  
pp. 140236 ◽  
Author(s):  
Marta O. Freitas ◽  
Tânia Francisco ◽  
Tony A. Rodrigues ◽  
Celien Lismont ◽  
Pedro Domingues ◽  
...  
Keyword(s):  
Protein Import ◽  
Urate Oxidase ◽  
Experimental Conditions ◽  
Peroxisomal Membrane ◽  
Oligomeric Proteins ◽  
Peroxisomal Protein ◽  
Peroxisomal Targeting ◽  
Targeting Signal ◽  
Monomeric Proteins

Peroxisomal matrix proteins are synthesized on cytosolic ribosomes and transported by the shuttling receptor PEX5 to the peroxisomal membrane docking/translocation machinery, where they are translocated into the organelle matrix. Under certain experimental conditions this protein import machinery has the remarkable capacity to accept already oligomerized proteins, a property that has heavily influenced current models on the mechanism of peroxisomal protein import. However, whether or not oligomeric proteins are really the best and most frequent clients of this machinery remain unclear. In this work, we present three lines of evidence suggesting that the peroxisomal import machinery displays a preference for monomeric proteins. First, in agreement with previous findings on catalase, we show that PEX5 binds newly synthesized (monomeric) acyl-CoA oxidase 1 (ACOX1) and urate oxidase (UOX), potently inhibiting their oligomerization. Second, in vitro import experiments suggest that monomeric ACOX1 and UOX are better peroxisomal import substrates than the corresponding oligomeric forms. Finally, we provide data strongly suggesting that although ACOX1 lacking a peroxisomal targeting signal can be imported into peroxisomes when co-expressed with ACOX1 containing its targeting signal, this import pathway is inefficient.

scholarly journals Human peroxisomal targeting signal-1 receptor restores peroxisomal protein import in cells from patients with fatal peroxisomal disorders.

1995 ◽  
Vol 130 (1) ◽  
pp. 51-65 ◽  
Author(s):  
E A Wiemer ◽  
W M Nuttley ◽  
B L Bertolaet ◽  
X Li ◽  
U Francke ◽  
...  
Keyword(s):  
Protein Import ◽  
Zellweger Syndrome ◽  
Complementation Group ◽  
Cell System ◽  
Peroxisomal Disorders ◽  
Peroxisomal Membrane ◽  
Peroxisomal Protein ◽  
Peroxisomal Targeting ◽  
Targeting Signal

Two peroxisomal targeting signals, PTS1 and PTS2, are involved in the import of proteins into the peroxisome matrix. Human patients with fatal generalized peroxisomal deficiency disorders fall into at least nine genetic complementation groups. Cells from many of these patients are deficient in the import of PTS1-containing proteins, but the causes of the protein-import defect in these patients are unknown. We have cloned and sequenced the human cDNA homologue (PTS1R) of the Pichia pastoris PAS8 gene, the PTS1 receptor (McCollum, D., E. Monosov, and S. Subramani. 1993. J. Cell Biol. 121:761-774). The PTS1R mRNA is expressed in all human tissues examined. Antibodies to the human PTS1R recognize this protein in human, monkey, rat, and hamster cells. The protein is localized mainly in the cytosol but is also found to be associated with peroxisomes. Part of the peroxisomal PTS1R protein is tightly bound to the peroxisomal membrane. Antibodies to PTS1R inhibit peroxisomal protein-import of PTS1-containing proteins in a permeabilized CHO cell system. In vitro-translated PTS1R protein specifically binds a serine-lysine-leucine-peptide. A PAS8-PTS1R fusion protein complements the P. pastoris pas8 mutant. The PTS1R cDNA also complements the PTS1 protein-import defect in skin fibroblasts from patients--belonging to complementation group two--diagnosed as having neonatal adrenoleukodystrophy or Zellweger syndrome. The PTS1R gene has been localized to a chromosomal location where no other peroxisomal disorder genes are known to map. Our findings represent the only case in which the molecular basis of the protein-import deficiency in human peroxisomal disorders is understood.

scholarly journals The Stress-Activated Protein Kinase FgOS-2 Is a Key Regulator in the Life Cycle of the Cereal Pathogen Fusarium graminearum

2012 ◽  
Vol 25 (9) ◽  
pp. 1142-1156 ◽  
Author(s):  
Thuat Van Nguyen ◽  
Wilhelm Schäfer ◽  
Jörg Bormann
Keyword(s):  
Protein Kinase ◽  
Fusarium Graminearum ◽  
Fluorescent Protein ◽  
Microscopic Analysis ◽  
Deletion Mutants ◽  
Wild Type ◽  
In Planta ◽  
Head Blight ◽  
Food And Feed

Fusarium graminearum is one of the most destructive pathogens of cereals and a threat to food and feed production worldwide. It is an ascomycetous plant pathogen and the causal agent of Fusarium head blight disease in small grain cereals and of cob rot disease in maize. Infection with F. graminearum leads to yield losses and mycotoxin contamination. Zearalenone (ZEA) and deoxynivalenol (DON) are hazardous mycotoxins; the latter is necessary for virulence toward wheat. Deletion mutants of the F. graminearum orthologue of the Saccharomyces cerevisiae Hog1 stress-activated protein kinase, FgOS-2 (ΔFgOS-2), showed drastically reduced in planta DON and ZEA production. However, ΔFgOS-2 produced even more DON than the wild type under in vitro conditions, whereas ZEA production was similar to that of the wild type. These deletion strains are dramatically reduced in pathogenicity toward maize and wheat. We constitutively expressed the fluorescent protein dsRed in the deletion strains and the wild type. Microscopic analysis revealed that ΔFgOS-2 is unable to reach the rachis node at the base of wheat spikelets. During vegetative growth, ΔFgOS-2 strains exhibit increased resistance against the phenylpyrrole fludioxonil. Growth of mutant colonies on agar plates supplemented with NaCl is reduced but conidia formation remained unchanged. However, germination of mutant conidia on osmotic media is severely impaired. Germ tubes are swollen and contain multiple nuclei. The deletion mutants completely fail to produce perithecia and ascospores. Furthermore, FgOS-2 also plays a role in reactive oxygen species (ROS)-related signaling. The transcription and activity of fungal catalases is modulated by FgOS-2. Among the genes regulated by FgOS-2, we found a putative calcium-dependent NADPH-oxidase (noxC) and the transcriptional regulator of ROS metabolism, atf1. The present study describes new aspects of stress-activated protein kinase signaling in F. graminearum.

Import of microinjected proteins bearing the SKL peroxisomal targeting sequence into the peroxisomes of a human fibroblast cell line: evidence that virtually all peroxisomes are import-competent

1995 ◽  
Vol 108 (4) ◽  
pp. 1469-1476
Author(s):  
P.E. Hill ◽  
P.A. Walton
Keyword(s):  
Cell Line ◽  
Human Fibroblast ◽  
Mammalian Cells ◽  
Protein Import ◽  
Fibroblast Cell ◽  
Matrix Proteins ◽  
Fibroblast Cell Line ◽  
Peroxisomal Protein ◽  
Human Fibroblast Cell ◽  
Peroxisomal Targeting

Peroxisomes import virtually all of their membrane and matrix proteins post-translationally. It is presently unknown whether, in mammalian cells, their exists a pool of mature peroxisomes which have received their complement of proteins and are import-incompetent. Previous work has shown that fibroblasts are capable of importing microinjected peroxisomal proteins into peroxisomes. This report describes the import of a hybrid peroxisomal protein into virtually all peroxisomes of the microinjected cell. The peroxisomal import was uniform in both short and long incubations. Pretreatment of the cells with cycloheximide did not affect the import of the peroxisomal protein, nor was there any difference in the distribution of the imported protein. Sequential microinjection experiments demonstrated that peroxisomes that had imported luciferase were capable of importing another peroxisomal protein injected 24 hours later. These results suggest that, in fibroblasts, all peroxisomes have associated protein-import machinery; this evidence does not support the hypothesis that there exists a pool of import-incompetent peroxisomes.

scholarly journals Cinnamic-Derived Acids Significantly Affect Fusarium graminearum Growth and In Vitro Synthesis of Type B Trichothecenes

2011 ◽  
Vol 101 (8) ◽  
pp. 929-934 ◽  
Author(s):  
Nadia Ponts ◽  
Laetitia Pinson-Gadais ◽  
Anne-Laure Boutigny ◽  
Christian Barreau ◽  
Florence Richard-Forget
Keyword(s):  
Fusarium Graminearum ◽  
Phenolic Acids ◽  
Antioxidant Properties ◽  
Fungal Growth ◽  
Type B ◽  
In Planta ◽  
In Vitro Synthesis ◽  
The Impact ◽  
Toxin Accumulation

The impact of five phenolic acids (ferulic, coumaric, caffeic, syringic, and p-hydroxybenzoic acids) on fungal growth and type B trichothecene production by four strains of Fusarium graminearum was investigated. All five phenolic acids inhibited growth but the degree of inhibition varied between strains. Our results suggested that the more lipophilic phenolic acids are, the higher is the effect they have on growth. Toxin accumulation in phenolic acid-supplemented liquid glucose, yeast extract, and peptone cultures was enhanced in the presence of ferulic and coumaric acids but was reduced in the presence of p-hydroxybenzoic acid. This modulation was shown to correlate with a regulation of TRI5 transcription. In this study, addition of phenolic acids with greater antioxidant properties resulted in a higher toxin accumulation, indicating that the modulation of toxin accumulation may be linked to the antioxidant properties of the phenolic acids. These data suggest that, in planta, different compositions in phenolic acids of kernels from various cultivars may reflect different degrees of sensitivity to “mycotoxinogenesis.”

scholarly journals Pex7p and Pex20p ofNeurospora crassaFunction Together in PTS2-dependent Protein Import into Peroxisomes

2003 ◽  
Vol 14 (2) ◽  
pp. 810-821 ◽  
Author(s):  
Martin Sichting ◽  
Annette Schell-Steven ◽  
Holger Prokisch ◽  
Ralf Erdmann ◽  
Hanspeter Rottensteiner
Keyword(s):  
Protein Import ◽  
Peroxisomal Membrane ◽  
Peroxisomal Targeting ◽  
Signal Type ◽  
Dependent Protein ◽  
Docking Proteins ◽  
Targeting Signal ◽  
Specific Factors ◽  
Species Specific

Recruiting matrix proteins with a peroxisomal targeting signal type 2 (PTS2) to the peroxisomal membrane requires species-specific factors. In Saccharomyces cerevisiae, the PTS2 receptor Pex7p acts in concert with the redundant Pex18p/Pex21p, whereas inYarrowia lipolytica, Pex20p might unite the function of both S. cerevisiae peroxins. Herein, the genome of the filamentous fungus Neurospora crassa was analyzed for peroxin-encoding genes. We identified a set of 18 peroxins that resembles that of Y. lipolytica rather than that ofS. cerevisiae. Interestingly, proteins homologous to both S. cerevisiae Pex7p and Y. lipolytica Pex20p exist in N. crassa. We report on the isolation of these PTS2-specific peroxins and demonstrate thatNcPex20p can substitute for S. cerevisiaePex18p/Pex21p, but not for ScPex7p. Like Pex18p,NcPex20p did not bind PTS2 protein or the docking proteins in the absence of ScPex7p. Rather,NcPex20p was required before docking to form an import-competent complex of cargo-loaded PTS2 receptors.NcPex7p did not functionally replace yeast Pex7p, probably because the N. crassa PTS2 receptor failed to associate with Pex18p/Pex21p. However, once NcPex7p andNcPex20p had been coexpressed, it proved possible to replace yeast Pex7p. Pex20p and Pex18p/Pex21p are therefore true orthologues, both of which are in need of Pex7p for PTS2 protein import.

scholarly journals The SH3 domain of the Saccharomyces cerevisiae peroxisomal membrane protein Pex13p functions as a docking site for Pex5p, a mobile receptor for the import PTS1-containing proteins.

1996 ◽  
Vol 135 (1) ◽  
pp. 97-109 ◽  
Author(s):  
Y Elgersma ◽  
L Kwast ◽  
A Klein ◽  
T Voorn-Brouwer ◽  
M van den Berg ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Membrane Protein ◽  
Protein Import ◽  
Sh3 Domain ◽  
Type I ◽  
Peroxisomal Membrane ◽  
Peroxisomal Membrane Protein ◽  
Peroxisomal Targeting ◽  
Src Homology

We identified a Saccharomyces cerevisiae peroxisomal membrane protein, Pex13p, that is essential for protein import. A point mutation in the COOH-terminal Src homology 3 (SH3) domain of Pex13p inactivated the protein but did not affect its membrane targeting. A two-hybrid screen with the SH3 domain of Pex13p identified Pex5p, a receptor for proteins with a type I peroxisomal targeting signal (PTS1), as its ligand. Pex13p SH3 interacted specifically with Pex5p in vitro. We determined, furthermore, that Pex5p was mainly present in the cytosol and only a small fraction was associated with peroxisomes. We therefore propose that Pex13p is a component of the peroxisomal protein import machinery onto which the mobile Pex5p receptor docks for the delivery of the selected PTS1 protein.

scholarly journals The Multifunctional β-Oxidation Enzyme Is Required for Full Symptom Development by the Biotrophic Maize Pathogen Ustilago maydis

2006 ◽  
Vol 5 (12) ◽  
pp. 2047-2061 ◽  
Author(s):  
Jana Klose ◽  
James W. Kronstad
Keyword(s):  
Fatty Acids ◽  
Ustilago Maydis ◽  
Long Chain Fatty Acids ◽  
In Planta ◽  
Gene Encoding ◽  
Metabolic Role ◽  
Fungal Phytopathogen ◽  
Long Chain ◽  
Chain Fatty Acids

ABSTRACT The transition from yeast-like to filamentous growth in the biotrophic fungal phytopathogen Ustilago maydis is a crucial event for pathogenesis. Previously, we showed that fatty acids induce filamentation in U. maydis and that the resulting hyphal cells resemble the infectious filaments observed in planta. To explore the potential metabolic role of lipids in the morphological transition and in pathogenic development in host tissue, we deleted the mfe2 gene encoding the multifunctional enzyme that catalyzes the second and third reactions in β-oxidation of fatty acids in peroxisomes. The growth of the strains defective in mfe2 was attenuated on long-chain fatty acids and abolished on very-long-chain fatty acids. The mfe2 gene was not generally required for the production of filaments during mating in vitro, but loss of the gene blocked extensive proliferation of fungal filaments in planta. Consistent with this observation, mfe2 mutants exhibited significantly reduced virulence in that only 27% of infected seedlings produced tumors compared to 88% tumor production upon infection by wild-type strains. Similarly, a defect in virulence was observed in developing ears upon infection of mature maize plants. Specifically, the absence of the mfe2 gene delayed the development of teliospores within mature tumor tissue. Overall, these results indicate that the ability to utilize host lipids contributes to the pathogenic development of U. maydis.

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