scholarly journals Osmoregulation and Fungicide Resistance: the Neurospora crassa os-2 Gene Encodes a HOG1 Mitogen-Activated Protein Kinase Homologue

2002 ◽  
Vol 68 (2) ◽  
pp. 532-538 ◽  
Author(s):  
Yan Zhang ◽  
Randy Lamm ◽  
Christian Pillonel ◽  
Stephen Lam ◽  
Jin-Rong Xu
Keyword(s):  
Map Kinase ◽  
Neurospora Crassa ◽  
Fungicide Resistance ◽  
Point Mutations ◽  
Gene Replacement ◽  
Mitogen Activated Protein Kinase ◽  
Wild Type ◽  
High Osmolarity ◽  
Mitogen Activated Protein ◽  
Sib Selection

ABSTRACT Neurospora crassa osmosensitive (os) mutants are sensitive to high osmolarity and therefore are unable to grow on medium containing 4% NaCl. We found that os-2 and os-5 mutants were resistant to the phenylpyrrole fungicides fludioxonil and fenpiclonil. To understand the relationship between osmoregulation and fungicide resistance, we cloned the os-2 gene by using sib selection. os-2 encodes a putative mitogen-activated protein (MAP) kinase homologous to HOG1 and can complement the osmosensitive phenotype of a Saccharomyces cerevisiae hog1 mutant. We sequenced three os-2 alleles and found that all of them were null with either frameshift or nonsense point mutations. An os-2 gene replacement mutant also was generated and was sensitive to high osmolarity and resistant to phenylpyrrole fungicides. Conversely, os-2 mutants transformed with the wild-type os-2 gene could grow on media containing 4% NaCl and were sensitive to phenylpyrrole fungicides. Fludioxonil stimulated intracellular glycerol accumulation in wild-type strains but not in os-2 mutants. Fludioxonil also caused wild-type conidia and hyphal cells to swell and burst. These results suggest that the hyperosmotic stress response pathway of N. crassa is the target of phenylpyrrole fungicides and that fungicidal effects may result from a hyperactive os-2 MAP kinase pathway.

scholarly journals The Biotrophic, Non-Appressorium-Forming Grass Pathogen Claviceps purpurea Needs a Fus3/Pmk1 Homologous Mitogen-Activated Protein Kinase for Colonization of Rye Ovarian Tissue

2002 ◽  
Vol 15 (4) ◽  
pp. 303-312 ◽  
Author(s):  
G. Mey ◽  
B. Oeser ◽  
M. H. Lebrun ◽  
P. Tudzynski
Keyword(s):  
Map Kinase ◽  
Magnaporthe Grisea ◽  
Ovarian Tissue ◽  
Gene Replacement ◽  
Mitogen Activated Protein Kinase ◽  
Claviceps Purpurea ◽  
Obvious Effect ◽  
Wide Range ◽  
Mitogen Activated Protein ◽  
Detail Loss

Claviceps purpurea is a common pathogen of a wide range of grasses and cereals that is able to establish a stable, balanced interaction with its host plant and is considered a biotroph. It does not form special penetration structures such as appressoria. To study the signaling processes involved in this special host-pathogen interaction, we have cloned a gene, cpmk1, encoding a mitogen-activated protein (MAP) kinase that shows significant homology to Fus3 of Saccharomyces cerevisiae and to pmk1 of Magnaporthe grisea. Using a gene-replacement approach, we isolated a Δcpmk1 mutant and characterized it in detail. Loss of CPMK1 has no obvious effect on vegetative properties (such as growth rate, morphology, and conidia formation); however, infection tests on rye show that the mutant is unable to colonize rye tissue, i.e., it appears to be completely nonpathogenic. Complementation of the mutant with a wild-type copy of cpmk1 fully restores its pathogenicity, confirming that this MAP kinase is essential for infection of rye by C. purpurea. Transformation of the Δpmk1 mutant of M. grisea with a complete copy of cpmk1 (including the C. purpurea promoter) fully restored its ability to form appressoria and its pathogenicity on barley. Although both fungi drastically differ in their pathogenic strategies, this result indicates that the signal pathway involving CPMK1 is highly conserved.

scholarly journals Role of a Mitogen-Activated Protein Kinase Cascade in Ion Flux-Mediated Turgor Regulation in Fungi

2006 ◽  
Vol 5 (3) ◽  
pp. 480-487 ◽  
Author(s):  
Roger R. Lew ◽  
Natalia N. Levina ◽  
Lana Shabala ◽  
Marinela I. Anderca ◽  
Sergey N. Shabala
Keyword(s):  
Map Kinase ◽  
Mitogen Activated Protein Kinase ◽  
Wild Type ◽  
Turgor Regulation ◽  
Map Kinase Cascade ◽  
Protein Map ◽  
Mitogen Activated Protein ◽  
Kinase Cascade ◽  
Protein Kinase Cascade

ABSTRACT Fungi normally maintain a high internal hydrostatic pressure (turgor) of about 500 kPa. In response to hyperosmotic shock, there are immediate electrical changes: a transient depolarization (1 to 2 min) followed by a sustained hyperpolarization (5 to 10 min) prior to turgor recovery (10 to 60 min). Using ion-selective vibrating probes, we established that the transient depolarization is due to Ca2+ influx and the sustained hyperpolarization is due to H+ efflux by activation of the plasma membrane H+-ATPase. Protein synthesis is not required for H+-ATPase activation. Net K+ and Cl− uptake occurs at the same time as turgor recovery. The magnitude of the ion uptake is more than sufficient to account for the osmotic gradients required for turgor to return to its original level. Two osmotic mutants, os-1 and os-2, homologs of a two-component histidine kinase sensor and the yeast high osmotic glycerol mitogen-activated protein (MAP) kinase, respectively, have lower turgor than the wild type and do not exhibit the sustained hyperpolarization after hyperosmotic treatment. The os-1 mutant does not exhibit all of the wild-type turgor-adaptive ion fluxes (Cl− uptake increases, but net K+ flux barely changes and net H+ efflux declines) (os-2 was not examined). Both os mutants are able to regulate turgor but at a lower level than the wild type. Our results demonstrate that a MAP kinase cascade regulates ion transport, activation of the H+-ATPase, and net K+ and Cl− uptake during turgor regulation. Other pathways regulating turgor must also exist.

scholarly journals TRAF6-Dependent Mitogen-Activated Protein Kinase Activation Differentially Regulates the Production of Interleukin-12 by Macrophages in Response to Toxoplasma gondii

2004 ◽  
Vol 72 (10) ◽  
pp. 5662-5667 ◽  
Author(s):  
Nicola J. Mason ◽  
Jim Fiore ◽  
Takashi Kobayashi ◽  
Katherine S. Masek ◽  
Yongwon Choi ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Toxoplasma Gondii ◽  
Signaling Pathways ◽  
Intracellular Signaling ◽  
Mitogen Activated Protein Kinase ◽  
Interleukin 12 ◽  
Wild Type ◽  
Kinase Activation ◽  
Extracellular Signal ◽  
Mitogen Activated Protein

ABSTRACT The production of interleukin-12 (IL-12) is critical to the development of innate and adaptive immune responses required for the control of intracellular pathogens. Many microbial products signal through Toll-like receptors (TLR) and activate NF-κB family members that are required for the production of IL-12. Recent studies suggest that components of the TLR pathway are required for the production of IL-12 in response to the parasite Toxoplasma gondii; however, the production of IL-12 in response to this parasite is independent of NF-κB activation. The adaptor molecule TRAF6 is involved in TLR signaling pathways and associates with serine/threonine kinases involved in the activation of both NF-κB and mitogen-activated protein kinase (MAPK). To elucidate the intracellular signaling pathways involved in the production of IL-12 in response to soluble toxoplasma antigen (STAg), wild-type and TRAF6−/− mice were inoculated with STAg, and the production of IL-12(p40) was determined. TRAF6−/− mice failed to produce IL-12(p40) in response to STAg, and TRAF6−/− macrophages stimulated with STAg also failed to produce IL-12(p40). Studies using Western blot analysis of wild-type and TRAF6−/− macrophages revealed that stimulation with STAg resulted in the rapid TRAF6-dependent phosphorylation of p38 and extracellular signal-related kinase, which differentially regulated the production of IL-12(p40). The studies presented here demonstrate for the first time that the production of IL-12(p40) in response to toxoplasma is dependent upon TRAF6 and p38 MAPK.

scholarly journals Signaling through mitogen-activated protein kinase and Rac/Rho does not duplicate the effects of activated Ras on skeletal myogenesis.

1997 ◽  
Vol 17 (7) ◽  
pp. 3547-3555 ◽  
Author(s):  
M B Ramocki ◽  
S E Johnson ◽  
M A White ◽  
C L Ashendel ◽  
S F Konieczny ◽  
...  
Keyword(s):  
Map Kinase ◽  
Signaling Pathways ◽  
Transcriptional Activation ◽  
Intracellular Signaling ◽  
Mitogen Activated Protein Kinase ◽  
Ras Signaling ◽  
Negative Effects ◽  
Intracellular Signaling Pathway ◽  
Helix Loop Helix ◽  
Mitogen Activated Protein

The ability of basic helix-loop-helix muscle regulatory factors (MRFs), such as MyoD, to convert nonmuscle cells to a myogenic lineage is regulated by numerous growth factor and oncoprotein signaling pathways. Previous studies have shown that H-Ras 12V inhibits differentiation to a skeletal muscle lineage by disrupting MRF function via a mechanism that is independent of the dimerization, DNA binding, and inherent transcriptional activation properties of the proteins. To investigate the intracellular signaling pathway(s) that mediates the inhibition of MRF-induced myogenesis by oncogenic Ras, we tested two transformation-defective H-Ras 12V effector domain variants for their ability to alter terminal differentiation. H-Ras 12V,35S retains the ability to activate the Raf/MEK/mitogen-activated protein (MAP) kinase cascade, whereas H-Ras 12V,40C is unable to interact directly with Raf-1 yet still influences other signaling intermediates, including Rac and Rho. Expression of each H-Ras 12V variant in C3H10T1/2 cells abrogates MyoD-induced activation of the complete myogenic program, suggesting that MAP kinase-dependent and -independent Ras signaling pathways individually block myogenesis in this model system. However, additional studies with constitutively activated Rac1 and RhoA proteins revealed no negative effects on MyoD-induced myogenesis. Similarly, treatment of Ras-inhibited myoblasts with the MEK1 inhibitor PD98059 revealed that elevated MAP kinase activity is not a significant contributor to the H-Ras 12V effect. These data suggest that an additional Ras pathway, distinct from the well-characterized MAP kinase and Rac/Rho pathways known to be important for the transforming function of activated Ras, is primarily responsible for the inhibition of myogenesis by H-Ras 12V.

scholarly journals G-Protein β Subunit of Cochliobolus heterostrophus Involved in Virulence, Asexual and Sexual Reproductive Ability, and Morphogenesis

2004 ◽  
Vol 3 (6) ◽  
pp. 1653-1663 ◽  
Author(s):  
Sherif Ganem ◽  
Shun-Wen Lu ◽  
Bee-Na Lee ◽  
David Yu-Te Chou ◽  
Ruthi Hadar ◽  
...  
Keyword(s):  
Map Kinase ◽  
G Protein ◽  
Signal Transduction Pathway ◽  
Cochliobolus Heterostrophus ◽  
Wild Type ◽  
Heterotrimeric G Protein ◽  
Reproductive Ability ◽  
Pathway Gene ◽  
Mitogen Activated Protein ◽  
Nuclear Degradation

ABSTRACT Previous work established that mutations in mitogen-activated protein (MAP) kinase (CHK1) and heterotrimeric G-protein α (Gα) subunit (CGA1) genes affect the development of several stages of the life cycle of the maize pathogen Cochliobolus heterostrophus. The effects of mutating a third signal transduction pathway gene, CGB1, encoding the Gβ subunit, are reported here. CGB1 is the sole Gβ subunit-encoding gene in the genome of this organism. cgb1 mutants are nearly wild type in vegetative growth rate; however, Cgb1 is required for appressorium formation, female fertility, conidiation, regulation of hyphal pigmentation, and wild-type virulence on maize. Young hyphae of cgb1 mutants grow in a straight path, in contrast to those of the wild type, which grow in a wavy pattern. Some of the phenotypes conferred by mutations in CGA1 are found in cgb1 mutants, suggesting that Cgb1 functions in a heterotrimeric G protein; however, there are also differences. In contrast to the deletion of CGA1, the loss of CGB1 is not lethal for ascospores, evidence that there is a Gβ subunit-independent signaling role for Cga1 in mating. Furthermore, not all of the phenotypes conferred by mutations in the MAP kinase CHK1 gene are found in cgb1 mutants, implying that the Gβ heterodimer is not the only conduit for signals to the MAP kinase CHK1 module. The additional phenotypes of cgb1 mutants, including severe loss of virulence on maize and of the ability to produce conidia, are consistent with CGB1 being unique in the genome. Fluorescent DNA staining showed that there is often nuclear degradation in mature hyphae of cgb1 mutants, while comparable wild-type cells have intact nuclei. These data may be genetic evidence for a novel cell death-related function of the Gβ subunit in filamentous fungi.

Functional Role of p38 Mitogen Activated Protein Kinase in Platelet Activation induced by a Thromboxane A2 Analogue and by 8-iso-prostaglandin F2 α

2002 ◽  
Vol 87 (05) ◽  
pp. 888-898 ◽  
Author(s):  
Stefania Gaino ◽  
Valeria Zuliani ◽  
Rosa Tommasoli ◽  
Donatella Benati ◽  
Riccardo Ortolani ◽  
...  
Keyword(s):  
Map Kinase ◽  
Platelet Activation ◽  
Tyrosine Kinases ◽  
Actin Polymerization ◽  
Shape Change ◽  
Specific Inhibitor ◽  
P38 Map Kinase ◽  
Mitogen Activated Protein Kinase ◽  
Mitogen Activated Protein ◽  
Kinase Phosphorylation

SummaryWe investigated similarities in the signaling pathways elicited by the F2 isoprostane 8-iso-PGF2α and by low doses of U46619 to induce platelet activation. Both 0.01-0.1 µmol/L U46619 and 0.01-1 µmol/L 8-isoPGF2α triggered shape change and filopodia extension, as well as adhesion to immobilized fibrinogen of washed platelets. At these doses the two platelet agonists failed to trigger secretion and aggregation, which were however induced by higher doses of U46619 (0.1-1 µmol/L). SB203580 (1-10 µmol/L), a specific inhibitor of the p38 mitogen activated protein (MAP) kinase blunted platelet shape change and adhesion induced by 0.05-1 µmol/L 8-iso-PGF2α and by 0.01 µmol/L U46619. These platelet responses were also inhibited by 20 µmol/L cytochalasin D, an inhibitor of actin polymerization, and 50 µmol/L piceatannol, an inhibitor of the Syk tyrosine kinases. Both 8-iso-PGF2α and U46619-induced p38 MAP kinase phosphorylation in suspended platelets and this was inhibited by piceatannol, indicating that Syk activation occurs upstream p38 MAP kinase phosphorylation. These findings suggest that the signaling pathway triggered by both 8-iso-PGF2α and low concentrations of U46619 to induce platelet adhesion and shape change implicates Syk, the p38 MAP kinase, and actin polymerization.

scholarly journals Cell Biology of Conidial Anastomosis Tubes in Neurospora crassa

2005 ◽  
Vol 4 (5) ◽  
pp. 911-919 ◽  
Author(s):  
M. Gabriela Roca ◽  
Jochen Arlt ◽  
Chris E. Jeffree ◽  
Nick D. Read
Keyword(s):  
Neurospora Crassa ◽  
Optical Tweezers ◽  
Cell Biology ◽  
Transmembrane Protein ◽  
Mitogen Activated Protein Kinase ◽  
Cellular Element ◽  
Hyphal Fusion ◽  
Self Recognition ◽  
Mitogen Activated Protein ◽  
Germ Tubes

ABSTRACT Although hyphal fusion has been well documented in mature colonies of filamentous fungi, it has been little studied during colony establishment. Here we show that specialized hyphae, called conidial anastomosis tubes (CATs), are produced by all types of conidia and by conidial germ tubes of Neurospora crassa. The CAT is shown to be a cellular element that is morphologically and physiologically distinct from a germ tube and under separate genetic control. In contrast to germ tubes, CATs are thinner, shorter, lack branches, exhibit determinate growth, and home toward each other. Evidence for an extracellular CAT inducer derived from conidia was obtained because CAT formation was reduced at low conidial concentrations. A cr-1 mutant lacking cyclic AMP (cAMP) produced CATs, indicating that the inducer is not cAMP. Evidence that the transduction of the CAT inducer signal involves a putative transmembrane protein (HAM-2) and the MAK-2 and NRC-1 proteins of a mitogen-activated protein kinase signaling pathway was obtained because ham-2, mak-2, and nrc-1 mutants lacked CATs. Optical tweezers were used in a novel experimental assay to micromanipulate whole conidia and germlings to analyze chemoattraction between CATs during homing. Strains of the same and opposite mating type were shown to home toward each other. The cr-1 mutant also underwent normal homing, indicating that cAMP is not the chemoattractant. ham-2, mak-2, and nrc-1 macroconidia did not attract CATs of the wild type. Fusion between CATs of opposite mating types was partially inhibited, providing evidence of non-self-recognition prior to fusion. Microtubules and nuclei passed through fused CATs.

Involvement of Ras/MAP Kinase in the Regulation of Ca2+ Channels in Adult Bullfrog Sympathetic Neurons by Nerve Growth Factor

1998 ◽  
Vol 80 (3) ◽  
pp. 1352-1361 ◽  
Author(s):  
Saobo Lei ◽  
William F. Dryden ◽  
Peter A. Smith
Keyword(s):  
Nerve Growth Factor ◽  
Growth Factor ◽  
Protein Kinase ◽  
Map Kinase ◽  
Kinase Inhibitors ◽  
Sympathetic Neurons ◽  
Mitogen Activated Protein Kinase ◽  
Nerve Growth ◽  
Channel Current ◽  
Mitogen Activated Protein

Lei, Saobo, William F. Dryden, and Peter A. Smith. Involvement of Ras/MAP kinase in the regulation of Ca2+ channels in adult bullfrog sympathetic neurons by nerve growth factor. J. Neurophysiol. 80: 1352–1361, 1998. The cellular mechanisms that underlie nerve growth factor (NGF) induced increase in Ca2+-channel current in adult bullfrog sympathetic B-neurons were examined by whole cell recording techniques. Cells were maintained at low density in neuron-enriched, defined-medium, serum-free tissue culture for 6 days in the presence or absence of NGF (200 ng/ml). The increase in Ba2+ current ( I Ba) density induced by NGF was attenuated by the RNA synthesis inhibitor cordycepin (20 μM), by the DNA transcription inhibitor actinomycin D (0.01 μg/ml), by inhibitors of Ras isoprenylation (perillic acid 0.1–1.0 mM or α-hydroxyfarnesylphosphonic acid 10–100 μM), by tyrosine kinase inhibitors genistein (20 μM) or lavendustin A (1 μM), and by PD98059 (10–100 μM), an inhibitor of mitogen-activated protein kinase kinase. Inhibitors of the phosphatidylinositol 3-kinase (PI3K) pathway (wortmannin, 100 nM, or LY29400, 100 μM) were ineffective as were inhibitors of phospholipase Cγ (U73122 or neomycin, both 100 μM). The effect of NGF persisted in Ca2+-free medium that contained 1.8 mM Mg2+ and 2 mM ethylene glycol-bis(β-aminoethyl ether)- N, N, N′, N′-tetraacetic acid. It was mimicked by a Trk antibody that was capable of inducing neurite outgrowth in explant cultures of bullfrog sympathetic ganglion. Antibodies raised against the low-affinity p75 neurotrophin receptor were ineffective in blocking the effect of NGF on I Ba. These results suggest that NGF-induced increase in Ca2+ channel current in adult sympathetic neurons results, at least in part, from new channel synthesis after Trk activation of Ras and mitogen activated protein kinase by a mechanism that is independent of extracellular Ca2+.

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