scholarly journals Trichoderma atroviride G-Protein α-Subunit Gene tga1 Is Involved in Mycoparasitic Coiling and Conidiation

2002 ◽  
Vol 1 (4) ◽  
pp. 594-605 ◽  
Author(s):  
Víctor Rocha-Ramírez ◽  
Carmi Omero ◽  
Ilan Chet ◽  
Benjamin A. Horwitz ◽  
Alfredo Herrera-Estrella
Keyword(s):  
G Protein ◽  
Intracellular Camp ◽  
Protein Kinase Activity ◽  
Gtpase Activity ◽  
Trichoderma Atroviride ◽  
Α Subunit ◽  
Transgenic Lines ◽  
G Protein Α Subunit ◽  
Host Signals ◽  
Camp Levels

ABSTRACT The soil fungus Trichoderma atroviride, a mycoparasite, responds to a number of external stimuli. In the presence of a fungal host, T. atroviride produces hydrolytic enzymes and coils around the host hyphae. In response to light or nutrient depletion, asexual sporulation is induced. In a biomimetic assay, different lectins induce coiling around nylon fibers; coiling in the absence of lectins can be induced by applying cyclic AMP (cAMP) or the heterotrimeric G-protein activator mastoparan. We isolated a T. atroviride G-protein α-subunit (Gα) gene (tga1) belonging to the fungal subfamily with the highest similarity to the Gαi class. Generated transgenic lines that overexpress Gα show very delayed sporulation and coil at a higher frequency. Furthermore, transgenic lines that express an activated mutant protein with no GTPase activity do not sporulate and coil at a higher frequency. Lines that express an antisense version of the gene are hypersporulating and coil at a much lower frequency in the biomimetic assay. The loss of Tga1 in these mutants correlates with the loss of GTPase activity stimulated by the peptide toxin Mas-7. The application of Mas-7 to growing mycelial colonies raises intracellular cAMP levels, suggesting that Tga1 can activate adenylyl cyclase. In contrast, cAMP levels and cAMP-dependent protein kinase activity drop when diffusible host signals are encountered and the mycoparasitism-related genes ech42 and prb1 are highly expressed. Mycoparasitic signaling is unlikely to be a linear pathway from host signals to increased cAMP levels. Our results demonstrate that the product of the tga1 gene is involved in both coiling and conidiation.

Isolation of a gene encoding a G protein α subunit involved in the regulation of cAMP levels in the yeastKluyveromyces lactis

Yeast ◽  
1996 ◽  
Vol 12 (11) ◽  
pp. 1125-1133 ◽  
Author(s):  
Alma L. Saviñón-Tejeda ◽  
Laura Ongay-Larios ◽  
Jorge RamíRez ◽  
Roberto Coria
Keyword(s):  
G Protein ◽  
Gene Encoding ◽  
Α Subunit ◽  
G Protein Α Subunit ◽  
Camp Levels

The G protein α subunit Tga1 of Trichoderma atroviride is involved in chitinase formation and differential production of antifungal metabolites

2005 ◽  
Vol 42 (9) ◽  
pp. 749-760 ◽  
Author(s):  
Barbara Reithner ◽  
Kurt Brunner ◽  
Rainer Schuhmacher ◽  
Isabel Peissl ◽  
Verena Seidl ◽  
...  
Keyword(s):  
G Protein ◽  
Trichoderma Atroviride ◽  
Α Subunit ◽  
Antifungal Metabolites ◽  
G Protein Α Subunit

scholarly journals Signal Transduction by Tga3, a Novel G Protein α Subunit of Trichoderma atroviride

2005 ◽  
Vol 71 (3) ◽  
pp. 1591-1597 ◽  
Author(s):  
Susanne Zeilinger ◽  
Barbara Reithner ◽  
Valeria Scala ◽  
Isabel Peissl ◽  
Matteo Lorito ◽  
...  
Keyword(s):  
Cyclic Amp ◽  
G Protein ◽  
Vegetative Growth ◽  
Chitinase Activity ◽  
Phytopathogenic Fungi ◽  
Trichoderma Atroviride ◽  
Α Subunit ◽  
General Role ◽  
Infection Structures ◽  
G Protein Α Subunit

ABSTRACT Trichoderma species are used commercially as biocontrol agents against a number of phytopathogenic fungi due to their mycoparasitic characterisitics. The mycoparasitic response is induced when Trichoderma specifically recognizes the presence of the host fungus and transduces the host-derived signals to their respective regulatory targets. We made deletion mutants of the tga3 gene of Trichoderma atroviride, which encodes a novel G protein α subunit that belongs to subgroup III of fungal Gα proteins. Δtga3 mutants had changes in vegetative growth, conidiation, and conidial germination and reduced intracellular cyclic AMP levels. These mutants were avirulent in direct confrontation assays with Rhizoctonia solani or Botrytis cinerea, and mycoparasitism-related infection structures were not formed. When induced with colloidal chitin or N-acetylglucosamine in liquid culture, the mutants had reduced extracellular chitinase activity even though the chitinase-encoding genes ech42 and nag1 were transcribed at a significantly higher rate than they were in the wild type. Addition of exogenous cyclic AMP did not suppress the altered phenotype or restore mycoparasitic overgrowth, although it did restore the ability to produce the infection structures. Thus, T. atroviride Tga3 has a general role in vegetative growth and can alter mycoparasitism-related characteristics, such as infection structure formation and chitinase gene expression.

scholarly journals G Protein Signaling Mediates Developmental Processes and Pathogenesis of Alternaria alternata

2006 ◽  
Vol 19 (11) ◽  
pp. 1280-1288 ◽  
Author(s):  
Daisuke Yamagishi ◽  
Hiroshi Otani ◽  
Motoichiro Kodama
Keyword(s):  
G Protein ◽  
Alternaria Alternata ◽  
Signal Transduction Pathway ◽  
Intracellular Camp ◽  
Protein Signaling ◽  
Wild Type ◽  
Targeted Disruption ◽  
Α Subunit ◽  
Cellulose Membranes ◽  
Camp Levels

A G protein α subunit gene (AGA1) has been cloned and characterized from a toxigenic and necrotrophic Alternaria alternata pathogen. Targeted disruption of AGA1 in the apple pathotype of A. alternata gave rise to mutants that differed in colony and conidial morphology as well as sporulation. The conidia of wild type and ΔAGA1 mutants showed equal germination on cellulose membranes. However, wild-type germ tubes formed readily from different points around the conidia, grew randomly, and were often branched, whereas those of the mutants formed only at one or both ends of the conidia and tended to grow in straight paths. Targeted disruption of AGA1 also resulted in reduction of pathogenicity on apple leaves, although the mutant produced host-specific AM-toxin, a fungal secondary metabolite associated with pathogenicity of the pathogen, at levels similar to the wild-type strain. Measurement of the intracellular cAMP levels of the mutant revealed that it was consistently higher than that of the wild type, indicating that AGA1 negatively regulates cAMP levels similar to mammalian Gαi systems. These results indicate that the signal transduction pathway represented by AGA1 appears to be involved in developmental pathways leading to sporulation and pathogenesis of A. alternata.

scholarly journals The G-Protein α-Subunit GasC Plays a Major Role in Germination in the Dimorphic FungusPenicillium marneffei

Genetics ◽  
2003 ◽  
Vol 164 (2) ◽  
pp. 487-499 ◽  
Author(s):  
Sophie Zuber ◽  
Michael J Hynes ◽  
Alex Andrianopoulos
Keyword(s):  
G Protein ◽  
Germination Rate ◽  
Yeast Cells ◽  
Class Iii ◽  
Temperature Dependent ◽  
Gene Encoding ◽  
Α Subunit ◽  
G Protein Α Subunit ◽  
Opportunistic Human Pathogen

AbstractThe opportunistic human pathogen Penicillium marneffei exhibits a temperature-dependent dimorphic switch. At 25°, multinucleate, septate hyphae that can undergo differentiation to produce asexual spores (conidia) are produced. At 37° hyphae undergo arthroconidiation to produce uninucleate yeast cells that divide by fission. This work describes the cloning of the P. marneffei gasC gene encoding a G-protein α-subunit that shows high homology to members of the class III fungal Gα-subunits. Characterization of a ΔgasC mutant and strains carrying a dominant-activating gasCG45R or a dominant-interfering gasCG207R allele show that GasC is a crucial regulator of germination. A ΔgasC mutant is severely delayed in germination, whereas strains carrying a dominant-activating gasCG45R allele show a significantly accelerated germination rate. Additionally, GasC signaling positively affects the production of the red pigment by P. marneffei at 25° and negatively affects the onset of conidiation and the conidial yield, showing that GasC function overlaps with functions of the previously described Gα-subunit GasA. In contrast to the S. cerevisiae ortholog Gpa2, our data indicate that GasC is not involved in carbon or nitrogen source sensing and plays no major role in either hyphal or yeast growth or in the switch between these two forms.

Analysis by mRNA levels of the expression of six G protein α-subunit genes in mammalian cells and tissues

1991 ◽  
Vol 1094 (2) ◽  
pp. 193-199 ◽  
Author(s):  
Jermelina Linor R. Garibay ◽  
Tohru Kozasa ◽  
Hiroshi Itoh ◽  
Toshihiko Tsukamoto ◽  
Masaaki Matsuoka ◽  
...  
Keyword(s):  
G Protein ◽  
Mammalian Cells ◽  
Mrna Levels ◽  
Α Subunit ◽  
G Protein Α Subunit

scholarly journals Large G protein α-subunit XLαs limits clathrin-mediated endocytosis and regulates tissue iron levels in vivo

2017 ◽  
Vol 114 (45) ◽  
pp. E9559-E9568 ◽  
Author(s):  
Qing He ◽  
Richard Bouley ◽  
Zun Liu ◽  
Marc N. Wein ◽  
Yan Zhu ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
G Protein ◽  
Critical Role ◽  
Hek293 Cells ◽  
Activity Levels ◽  
Α Subunit ◽  
Proteomic Screen ◽  
Protein Levels ◽  
G Protein Α Subunit

Alterations in the activity/levels of the extralarge G protein α-subunit (XLαs) are implicated in various human disorders, such as perinatal growth retardation. Encoded by GNAS, XLαs is partly identical to the α-subunit of the stimulatory G protein (Gsα), but the cellular actions of XLαs remain poorly defined. Following an initial proteomic screen, we identified sorting nexin-9 (SNX9) and dynamins, key components of clathrin-mediated endocytosis, as binding partners of XLαs. Overexpression of XLαs in HEK293 cells inhibited internalization of transferrin, a process that depends on clathrin-mediated endocytosis, while its ablation by CRISPR/Cas9 in an osteocyte-like cell line (Ocy454) enhanced it. Similarly, primary cardiomyocytes derived from XLαs knockout (XLKO) pups showed enhanced transferrin internalization. Early postnatal XLKO mice showed a significantly higher degree of cardiac iron uptake than wild-type littermates following iron dextran injection. In XLKO neonates, iron and ferritin levels were elevated in heart and skeletal muscle, where XLαs is normally expressed abundantly. XLKO heart and skeletal muscle, as well as XLKO Ocy454 cells, showed elevated SNX9 protein levels, and siRNA-mediated knockdown of SNX9 in XLKO Ocy454 cells prevented enhanced transferrin internalization. In transfected cells, XLαs also inhibited internalization of the parathyroid hormone and type 2 vasopressin receptors. Internalization of transferrin and these G protein-coupled receptors was also inhibited in cells expressing an XLαs mutant missing the Gα portion, but not Gsα or an N-terminally truncated XLαs mutant unable to interact with SNX9 or dynamin. Thus, XLαs restricts clathrin-mediated endocytosis and plays a critical role in iron/transferrin uptake in vivo.

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