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.

scholarly journals Distinct Roles for Two Gα–Gβ Interfaces in Cell Polarity Control by a Yeast Heterotrimeric G Protein

2008 ◽  
Vol 19 (1) ◽  
pp. 181-197 ◽  
Author(s):  
Shelly C. Strickfaden ◽  
Peter M. Pryciak
Keyword(s):  
Map Kinase ◽  
G Protein ◽  
De Novo ◽  
Cell Polarization ◽  
Kinase Signaling ◽  
Directional Growth ◽  
Heterotrimeric G Protein ◽  
Map Kinase Signaling ◽  
Mitogen Activated Protein ◽  
Cell Asymmetry

Saccharomyces cerevisiae mating pheromones trigger dissociation of a heterotrimeric G protein (Gαβγ) into Gα-guanosine triphosphate (GTP) and Gβγ. The Gβγ dimer regulates both mitogen-activated protein (MAP) kinase cascade signaling and cell polarization. Here, by independently activating the MAP kinase pathway, we studied the polarity role of Gβγ in isolation from its signaling role. MAP kinase signaling alone could induce cell asymmetry but not directional growth. Surprisingly, active Gβγ, either alone or with Gα-GTP, could not organize a persistent polarization axis. Instead, following pheromone gradients (chemotropism) or directional growth without pheromone gradients (de novo polarization) required an intact receptor–Gαβγ module and GTP hydrolysis by Gα. Our results indicate that chemoattractant-induced cell polarization requires continuous receptor–Gαβγ communication but not modulation of MAP kinase signaling. To explore regulation of Gβγ by Gα, we mutated Gβ residues in two structurally distinct Gα–Gβ binding interfaces. Polarity control was disrupted only by mutations in the N-terminal interface, and not the Switch interface. Incorporation of these mutations into a Gβ–Gα fusion protein, which enforces subunit proximity, revealed that Switch interface dissociation regulates signaling, whereas the N-terminal interface may govern receptor–Gαβγ coupling. These findings raise the possibility that the Gαβγ heterotrimer can function in a partially dissociated state, tethered by the N-terminal interface.

scholarly journals Mating in Saccharomyces cerevisiae: The Role of the Pheromone Signal Transduction Pathway in the Chemotropic Response to Pheromone

Genetics ◽  
1997 ◽  
Vol 147 (1) ◽  
pp. 19-32 ◽  
Author(s):  
Kathrin Schrick ◽  
Barbara Garvik ◽  
Leland H Hartwell
Keyword(s):  
Signal Transduction ◽  
Map Kinase ◽  
Transcriptional Activation ◽  
Signal Transduction Pathway ◽  
Transduction Pathway ◽  
Wild Type ◽  
Mating Partner ◽  
Map Kinase Cascade ◽  
Kinase Cascade ◽  
Wild Type Control

Abstract The mating process in yeast has two distinct aspects. One is the induction and activation of proteins required for cell fusion in response to a pheromone signal; the other is chemotropism, i.e., detection of a pheromone gradient and construction of a fusion site available to the signaling cell. To determine whether components of the signal transduction pathway necessary for transcriptional activation also play a role in chemotropism, we examined strains with null mutations in components of the signal transduction pathway for diploid formation, prezygote formation and the chemotropic process of mating partner discrimination when transcription was induced downstream of the mutation. Cells mutant for components of the mitogen-activated protein (MAP) kinase cascade (ste5, ste20, ste11, ste7 or fus3 kss1) formed diploids at a frequency 1% that of the wild-type control, but formed prezygotes as efficiently as the wild-type control and showed good mating partner discrimination, suggesting that the MAP kinase cascade is not essential for chemotropism. In contrast, cells mutant for the receptor (ste2) or the β or γ subunit (ste4 and stel8) of the G protein were extremely defective in both diploid and prezygote formation and discriminated poorly between signaling and nonsignaling mating partners, implying that these components are important for chemotropism.

scholarly journals Sphingosine 1-phosphate signalling through the G-protein-coupled receptor Edg-1

1998 ◽  
Vol 330 (2) ◽  
pp. 605-609 ◽  
Author(s):  
C. M. Gerben ZONDAG ◽  
R. Friso POSTMA ◽  
Ingrid VAN ETTEN ◽  
Ingrid VERLAAN ◽  
H. Wouter MOOLENAAR
Keyword(s):  
Adenylate Cyclase ◽  
Map Kinase ◽  
G Protein ◽  
G Protein Coupled Receptors ◽  
Lpa Receptor ◽  
Kinase Activation ◽  
Protein Map ◽  
Mitogen Activated Protein ◽  
Sphingosine 1 Phosphate ◽  
G Protein Coupled

Sphingosine 1-phosphate (S1P) and lysophosphatidic acid (LPA) are structurally related lipid mediators that act on distinct G-protein-coupled receptors to evoke similar responses, including Ca2+ mobilization, adenylate cyclase inhibition, and mitogen-activated protein (MAP) kinase activation. However, little is still known about the respective receptors. A recently cloned putative LPA receptor (Vzg-1/Edg-2) is similar to an orphan Gi-coupled receptor termed Edg-1. Here we show that expression of Edg-1 in Sf9 and COS-7 cells results in inhibition of adenylate cyclase and activation of MAP kinase (Gi-mediated), but not Ca2+ mobilization, in response to S1P. These responses are specific in that (i) S1P action is not mimicked by LPA, and (ii) Vzg-1/Edg-2 cannot substitute for Edg-1. Thus the Edg-1 receptor is capable of mediating a subset of the cellular responses to S1P.

scholarly journals Distinct and Combined Roles of the MAP Kinases of Cochliobolus heterostrophus in Virulence and Stress Responses

2008 ◽  
Vol 21 (6) ◽  
pp. 769-780 ◽  
Author(s):  
Aeid Igbaria ◽  
Sophie Lev ◽  
Mark S. Rose ◽  
Bee Na Lee ◽  
Ruthi Hadar ◽  
...  
Keyword(s):  
Stress Responses ◽  
Map Kinases ◽  
Cochliobolus Heterostrophus ◽  
Wild Type ◽  
Necrotrophic Pathogen ◽  
Disease Symptoms ◽  
Monosaccharide Transporter ◽  
Maize Leaves ◽  
Mitogen Activated Protein ◽  
Corn Leaf Blight

Pathogenicity mitogen-activated protein kinases (MAPKs), related to yeast FUS3/KSS1, are essential for virulence in fungi, including Cochliobolus heterostrophus, a necrotrophic pathogen causing Southern corn leaf blight. We compared the phenotypes of mutants in three MAPK genes: HOG1, MPS1, and CHK1. The chk1 and mps1 mutants show autolytic appearance, light pigmentation, and dramatic reduction in virulence and conidiation. Similarity of mps1 and chk1 mutants is reflected by coregulation by these two MAPKs of several genes. Unlike chk1, mps1 mutants are female-fertile and form normal-looking appressoria. HOG1 mediates resistance to hyperosmotic and, to a lesser extent, oxidative stress, and is required for stress upregulation of glycerol-3-phosphate phosphatase, transaldolase, and a monosaccharide transporter. Hog1, but not Mps1 or Chk1, was rapidly phosphorylated in response to increased osmolarity. The hog1 mutants have smaller appressoria and cause decreased disease symptoms on maize leaves. Surprisingly, loss of MPS1 in a wild-type or hog1 background improved resistance to some stresses. All three MAPKs contribute to the regulation of central developmental functions under normal and stress conditions, and full virulence cannot be achieved without appropriate input from all three pathways.

scholarly journals A Sphingolipid Elicitor-Inducible Mitogen-Activated Protein Kinase Is Regulated by the Small GTPase OsRac1 and Heterotrimeric G-Protein in Rice

2005 ◽  
Vol 138 (3) ◽  
pp. 1644-1652 ◽  
Author(s):  
Damien Lieberherr ◽  
Nguyen Phuong Thao ◽  
Ayako Nakashima ◽  
Kenji Umemura ◽  
Tsutomu Kawasaki ◽  
...  
Keyword(s):  
Protein Kinase ◽  
G Protein ◽  
Small Gtpase ◽  
Mitogen Activated Protein Kinase ◽  
Heterotrimeric G Protein ◽  
Mitogen Activated Protein

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.

Heterotrimeric G protein β subunit GPB1 and MAP kinase MPK1 regulate hyphal growth and female fertility in Fusarium sacchari

Mycoscience ◽  
2013 ◽  
Vol 54 (2) ◽  
pp. 148-157 ◽  
Author(s):  
Isao Kaneko ◽  
Makoto Iyama-Kadono ◽  
Kana Togashi-Nishigata ◽  
Isamu Yamaguchi ◽  
Tohru Teraoka ◽  
...  
Keyword(s):  
Map Kinase ◽  
G Protein ◽  
Hyphal Growth ◽  
Female Fertility ◽  
Β Subunit ◽  
Heterotrimeric G Protein ◽  
Fusarium Sacchari

scholarly journals A role for autophosphorylation revealed by activated alleles of FUS3, the yeast MAP kinase homolog.

1994 ◽  
Vol 5 (3) ◽  
pp. 297-312 ◽  
Author(s):  
J A Brill ◽  
E A Elion ◽  
G R Fink
Keyword(s):  
Escherichia Coli ◽  
Signal Transduction ◽  
Map Kinase ◽  
Signal Transduction Pathway ◽  
Transduction Pathway ◽  
Phosphorylated Form ◽  
Protein Map ◽  
Mitogen Activated Protein ◽  
Mating Signal

We have isolated dominant gain-of-function (gf) mutations in FUS3, a Saccharomyces cerevisiae mitogen-activated protein (MAP) kinase homolog, that constitutively activate the yeast mating signal transduction pathway and confer hypersensitivity to mating pheromone. Surprisingly, the phenotypes of dominant FUS3gf mutations require the two protein kinases, STE7 and STE11. FUS3gf kinases are hyperphosphorylated in yeast independently of STE7. Consistent with this, FUS3gf kinases expressed in Escherichia coli exhibit an increased ability to autophosphorylate on tyrosine in vivo. FUS3gf mutations suppress the signal transduction defect of a severely catalytically impaired allele of STE7. This finding suggests that the tyrosine-phosphorylated form of FUS3 is a better substrate for activation by STE7. Furthermore, these results imply that the degree of autophosphorylation of a MAP kinase determines its threshold of sensitivity to upstream signals.

scholarly journals p38 MAP kinase regulates IL-1β responses in cultured airway smooth muscle cells

2000 ◽  
Vol 279 (5) ◽  
pp. L932-L941 ◽  
Author(s):  
Johanne D. Laporte ◽  
Paul E. Moore ◽  
Thomas Lahiri ◽  
Igor N. Schwartzman ◽  
Reynold A. Panettieri ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Map Kinase ◽  
Airway Smooth Muscle ◽  
Signal Transduction Pathway ◽  
P38 Map Kinase ◽  
Airway Smooth Muscle Cells ◽  
P38 Inhibitor ◽  
Mitogen Activated Protein ◽  
Cox 2 ◽  
Sb 203580

We have previously reported that interleukin (IL)-1β causes β-adrenergic hyporesponsiveness in cultured human airway smooth muscle (HASM) cells by increasing cyclooxygenase (COX)-2 expression. The purpose of this study was to determine whether p38 mitogen-activated protein (MAP) kinase is involved in these events. IL-1β (2 ng/ml for 15 min) increased p38 phosphorylation fourfold. The p38 inhibitor SB-203580 (3 μM) decreased IL-1β-induced COX-2 by 70 ± 7% ( P < 0.01). SB-203580 had no effect on PGE2 release in control cells but caused a significant (70–80%) reduction in PGE2 release in IL-1β-treated cells. IL-1β increased the binding of nuclear proteins to the oligonucleotides encoding the consensus sequences for activator protein (AP)-1 and nuclear factor (NF)-κB, but SB-203580 did not affect this binding, suggesting that the mechanism of action of p38 was not through AP-1 or NF-κB activation. The NF-κB inhibitor MG-132 did not alter IL-1β-induced COX-2 expression, indicating that NF-κB activation is not required for IL-1β-induced COX-2 expression in HASM cells. IL-1β attenuated isoproterenol-induced decreases in HASM stiffness as measured by magnetic twisting cytometry, and SB-203580 abolished this effect. These results are consistent with the hypothesis that p38 is involved in the signal transduction pathway through which IL-1β induces COX-2 expression, PGE2 release, and β-adrenergic hyporesponsiveness.

NO inhibits signal transduction pathway for ATP release from erythrocytes via its action on heterotrimeric G protein Gi

2004 ◽  
Vol 287 (2) ◽  
pp. H748-H754 ◽  
Author(s):  
Jeffrey J. Olearczyk ◽  
Alan H. Stephenson ◽  
Andrew J. Lonigro ◽  
Randy S. Sprague
Keyword(s):  
Signal Transduction ◽  
G Protein ◽  
Atp Release ◽  
Signal Transduction Pathway ◽  
Transduction Pathway ◽  
Heterotrimeric G Protein
Sign in / Sign up

Export Citation Format

Share Document