scholarly journals The G alpha i homologue gna-1 controls multiple differentiation pathways in Neurospora crassa.

1996 ◽  
Vol 7 (8) ◽  
pp. 1283-1297 ◽  
Author(s):  
F D Ivey ◽  
P N Hodge ◽  
G E Turner ◽  
K A Borkovich
Keyword(s):  
Neurospora Crassa ◽  
G Proteins ◽  
Solid Medium ◽  
Sexual Cycle ◽  
Heterotrimeric G Proteins ◽  
Wild Type ◽  
Multiple Phenotypes ◽  
Multiple Differentiation ◽  
Differentiation Pathways ◽  
Type Strains

Heterotrimeric G proteins are components of principal signaling pathways in eukaryotes. In higher organisms, alpha subunits of G proteins have been divided into four families, Gi, Gs, Gq, and G12. We previously identified a G alpha i homologue gna-1 in the filamentous fungus Neurospora crassa. Now we report that deletion of gna-1 leads to multiple phenotypes during the vegetative and sexual cycles in N. crassa. On solid medium, delta gna-1 strains have a slower rate of hyphal apical extension than wild type, a rate that is more pronounced under hyperosmotic conditions or in the presence of a cellophane overlay. delta gna-1 mutants accumulate less mass than wild-type strains, and their mass accumulation is not affected in the same way by exposure to light. delta gna-1 strains are defective in macroconidiation, possessing aerial hyphae that are shorter, contain abnormal swellings, and differentiate adherent macroconidia. During the sexual cycle, delta gna-1 strains are fertile as males. However, the mutants are female-sterile, producing small, aberrant female reproductive structures. After fertilization, delta gna-1 female structures do not enlarge and develop normally, and no sexual spores are produced. Thus, mutation of gna-1 results in sex-specific loss of fertility.

scholarly journals Mutational Activation of a Gαi Causes Uncontrolled Proliferation of Aerial Hyphae and Increased Sensitivity to Heat and Oxidative Stress in Neurospora crassa

Genetics ◽  
1999 ◽  
Vol 151 (1) ◽  
pp. 107-117
Author(s):  
Qi Yang ◽  
Katherine A Borkovich
Keyword(s):  
Signal Transduction ◽  
Neurospora Crassa ◽  
Signal Transduction Pathway ◽  
Sexual Cycle ◽  
Intracellular Camp ◽  
Wild Type ◽  
Independent Functions ◽  
Aerial Hyphae ◽  
Mutational Activation ◽  
Camp Levels

Abstract Heterotrimeric G proteins, consisting of α, β, and γ subunits, transduce environmental signals through coupling to plasma membrane-localized receptors. We previously reported that the filamentous fungus Neurospora crassa possesses a Gα protein, GNA-1, that is a member of the Gαi superfamily. Deletion of gna-1 leads to defects in apical extension, differentiation of asexual spores, sensitivity to hyperosmotic media, and female fertility. In addition, Δgna-1 strains have lower intracellular cAMP levels under conditions that promote morphological abnormalities. To further define the function of GNA-1 in signal transduction in N. crassa, we examined properties of strains with mutationally activated gna-1 alleles (R178C or Q204L) as the only source of GNA-1 protein. These mutations are predicted to inhibit the GTPase activity of GNA-1 and lead to constitutive signaling. In the sexual cycle, gna-1R178C and gna-1Q204L strains are female-fertile, but produce fewer and larger perithecia than wild type. During asexual development, gna-1R178C and gna-1Q204L strains elaborate abundant, long aerial hyphae, produce less conidia, and possess lower levels of carotenoid pigments in comparison to wild-type controls. Furthermore, gna-1R178C and gna-1Q204L strains are more sensitive to heat shock and exposure to hydrogen peroxide than wild-type strains, while Δgna-1 mutants are more resistant. In contrast to Δgna-1 mutants, gna-1R178C and gna-1Q204L strains have higher steady-state levels of cAMP than wild type. The results suggest that GNA-1 possesses several Gβγ-independent functions in N. crassa. We propose that GNA-1 mediates signal transduction pathway(s) that regulate aerial hyphae development and sensitivity to heat and oxidative stresses, possibly through modulation of cAMP levels.

scholarly journals Genetic Analysis of the Sinorhizobium meliloti BacA Protein: Differential Effects of Mutations on Phenotypes

2001 ◽  
Vol 183 (21) ◽  
pp. 6444-6453 ◽  
Author(s):  
Kristin LeVier ◽  
Graham C. Walker
Keyword(s):  
Amino Acids ◽  
Genetic Analysis ◽  
Protein Function ◽  
Sinorhizobium Meliloti ◽  
Null Allele ◽  
Biological Function ◽  
Wild Type ◽  
Phenotypic Characteristics ◽  
Multiple Phenotypes ◽  
Type Strains

ABSTRACT Sinorhizobium meliloti strains lacking BacA function are impaired in symbiosis with alfalfa host plants and display altered sensitivities to a number of compounds relative to wild-type strains. With the goal of finding clues to the currently unknown biological function(s) of BacA, we carried out a genetic analysis to determine which amino acids are critical for protein function and to attempt to ascertain whether the multiple phenotypes that result from abacA-null allele were the result of a common cause or whether BacA has multiple functions. We have created a set of 20 site-directed mutants in which selected individual amino acids inbacA were replaced with glycine residues. The resulting mutants were characterized to determine how the various amino acid changes affected a number of phenotypes associated with loss of BacA function. Mutants H165G, W182G, D198G, and R284G had null phenotypes for all functions assayed, while mutants W57G, S83G, S231G, and K350G were indistinguishable from wild-type strains. The remaining 12 site-directed mutants demonstrate mixed phenotypic characteristics and fall into a number of distinctly different groups. These observations may be consistent with a role for BacA in multiple, nonoverlapping functions.

Characterization of mat A-2, mat A-3 and ΔmatA Mating-Type Mutants of Neurospora crassa

Genetics ◽  
1998 ◽  
Vol 148 (3) ◽  
pp. 1069-1079 ◽  
Author(s):  
Adlane V-B Ferreira ◽  
Zhiqiang An ◽  
Robert L Metzenberg ◽  
N Louise Glass
Keyword(s):  
Neurospora Crassa ◽  
Mating Type ◽  
Sexual Development ◽  
Vegetative Growth ◽  
Double Mutant ◽  
Sexual Cycle ◽  
Wild Type ◽  
Type Locus ◽  
Isolation And Characterization

AbstractThe mating-type locus of Neurospora crassa regulates mating identity and entry into the sexual cycle. The mat A idiomorph encodes three genes, mat A-1, mat A-2, and mat A-3. Mutations in mat A-1 result in strains that have lost mating identity and vegetative incompatibility with mat a strains. A strain containing mutations in both mat A-2 and mat A-3 is able to mate, but forms few ascospores. In this study, we describe the isolation and characterization of a mutant deleted for mat (ΔmatA), as well as mutants in either mat A-2 or mat A-3. The ΔmatA strain is morphologically wild type during vegetative growth, but it is sterile and heterokaryon compatible with both mat A and mat a strains. The mat A-2 and mat A-3 mutants are also normal during vegetative growth, mate as a mat A strain, and produce abundant biparental asci in crosses with mat a, and are thus indistinguishable from a wild-type mat A strain. These data and the fact that the mat A-2 mat A-3 double mutant makes few asci with ascospores indicate that MAT A-2 and MAT A-3 are redundant and may function in the same pathway. Analysis of the expression of two genes (sdv-1 and sdv-4) in the various mat mutants suggests that the mat A polypeptides function in concert to regulate the expression of some sexual development genes.

scholarly journals Overlapping Functions for Two G Protein α Subunits in Neurospora crassa

Genetics ◽  
1997 ◽  
Vol 147 (1) ◽  
pp. 137-145 ◽  
Author(s):  
Rudeina A Baasiri ◽  
Xiaohui Lu ◽  
Patricia S Rowley ◽  
Gloria E Turner ◽  
Katherine A Borkovich
Keyword(s):  
Neurospora Crassa ◽  
G Protein ◽  
Sexual Cycle ◽  
Fusion Activity ◽  
Heterotrimeric G Proteins ◽  
Phenotypic Analysis ◽  
Activating Mutations ◽  
Eukaryotic Microbes ◽  
Α Subunits ◽  
G Protein Α Subunits

Abstract Heterotrimeric G proteins, consisting of α, β and γ subunits, mediate a variety of signaling pathways in eukaryotes. We have previously identified two genes, gna-1 and gna-2, that encode G protein α subunits in the filamentous fungus Neurospora crassa. Mutation of gna-1 results in female infertility and sensitivity to hyperosmotic media. In this study, we investigate the expression and functions of gna-2. Results from Western analysis and measurements of gna-2 promoter-lacZ fusion activity indicate that gna-2 is expressed during the vegetative and sexual cycle of N. crassa in both A and a mating types. Activating mutations predicted to abolish the GTPase activity of GNA-2 cause subtle defects in aerial hyphae formation and conidial germination. Extensive phenotypic analysis of Δgna-2 strains did not reveal abnormalities during vegetative or sexual development. In contrast, deletion of gna-2 in a Δgna-1 strain accentuates the Δgna-1 phenotypes. Δgna-1 Δgna-2 strains have a slower rate of hyphal apical extension than Δgna-1 strains on hyperosmotic media. Moreover, Δgna-1 Δgna-2 mutants have more pronounced defects in female fertility than Δgna-1 strains. We propose that gna-1 and gna-2 have overlapping functions and may constitute a gene family. This is the first report of G protein α subunits with overlapping functions in eukaryotic microbes.

scholarly journals G-Alpha Subunit Abundance and Activity Differentially Regulate β-Catenin Signaling

2018 ◽  
Vol 39 (5) ◽  
Author(s):  
Arshiya Banu ◽  
Karen J. Liu ◽  
Alistair J. Lax ◽  
Agamemnon E. Grigoriadis
Keyword(s):  
G Proteins ◽  
Pasteurella Multocida ◽  
Alpha Subunit ◽  
Dependent Manner ◽  
Heterotrimeric G Proteins ◽  
Wild Type ◽  
Content Type ◽  
Alpha Subunits ◽  
Licl Treatment ◽  
Signal Transduction Proteins

ABSTRACT Heterotrimeric G proteins are signal transduction proteins involved in regulating numerous signaling events. In particular, previous studies have demonstrated a role for G-proteins in regulating β-catenin signaling. However, the link between G-proteins and β-catenin signaling is controversial and appears to depend on G-protein specificity. We describe a detailed analysis of a link between specific G-alpha subunits and β-catenin using G-alpha subunit genetic knockout and knockdown approaches. The Pasteurella multocida toxin was utilized as a unique tool to activate G-proteins, with LiCl treatment serving as a β-catenin signaling agonist. The results show that Pasteurella multocida toxin (PMT) significantly enhanced LiCl-induced active β-catenin levels in HEK293T cells and mouse embryo fibroblasts. Evaluation of the effect of specific G-alpha proteins on the regulation of β-catenin showed that Gq/11 and G12/13 knockout cells had significantly higher levels of active and total β-catenin than wild-type cells. The stimulation of active β-catenin by PMT and LiCl was lost upon both constitutive and transient knockdown of G12 and G13 but not Gq. Based on our results, we conclude that endogenous G-alpha proteins are negative regulators of active β-catenin; however, PMT-activated G-alpha subunits positively regulate LiCl-induced β-catenin expression in a G12/13-dependent manner. Hence, G-alpha subunit regulation of β-catenin is context dependent.

scholarly journals Induction of Nad-Specific Glutamate Dehydrogenase In Neurospora Crassa by Addition of Glutamate to The Media

1969 ◽  
Vol 22 (2) ◽  
pp. 425 ◽  
Author(s):  
WN Strickland
Keyword(s):  
Neurospora Crassa ◽  
Nitrogen Source ◽  
Glutamate Dehydrogenase ◽  
Inorganic Nitrogen ◽  
The Other ◽  
Wild Type ◽  
Carbon And Nitrogen ◽  
The Media ◽  
Type Strains

There are two glutamate dehydrogenases (GDH) produced by wild-type strains of N. cra88a, one of which is specific for the coenzyme NADP and the other for the coenzyme NAD. The latter enzyme (NAD-GDH) is induced if glutamate is used as the sole carbon and nitrogen source and is induced to a lesser extent if inorganic nitrogen is added. Addition of sucrose to the medium prevents uptake of glutamate and there is no induction of the enzyme.

scholarly journals Cantil: a previously unreported organ in wild-type Arabidopsis regulated by FT, ERECTA and heterotrimeric G proteins

Development ◽  
2021 ◽  
Vol 148 (11) ◽  
Author(s):  
Timothy E. Gookin ◽  
Sarah M. Assmann
Keyword(s):  
G Proteins ◽  
Heterotrimeric G Proteins ◽  
Wild Type ◽  
Flowering Locus T ◽  
Long Day ◽  
Receptor Like Kinase ◽  
Per Se ◽  
Delayed Flowering ◽  
Delayed Phase ◽  
Short Days

ABSTRACT We describe a previously unreported macroscopic Arabidopsis organ, the cantil, named for its ‘cantilever’ function of holding the pedicel at a distance from the stem. Cantil development is strongest at the first nodes after the vegetative to reproductive inflorescence transition; cantil magnitude and frequency decrease acropetally. Cantils develop in wild-type Arabidopsis accessions (e.g. Col-0, Ws and Di-G) as a consequence of delayed flowering in short days; cantil formation is observed in long days when flowering is delayed by null mutation of the floral regulator FLOWERING LOCUS T. The receptor-like kinase ERECTA is a global positive regulator of cantil formation; therefore, cantils never form in the Arabidopsis strain Ler. ERECTA functions genetically upstream of heterotrimeric G proteins. Cantil expressivity is repressed by the specific heterotrimeric complex subunits GPA1, AGB1 and AGG3, which also play independent roles: GPA1 suppresses distal spurs at cantil termini, while AGB1 and AGG3 suppress ectopic epidermal rippling. These G protein mutant traits are recapitulated in long-day flowering gpa1-3 ft-10 plants, demonstrating that cantils, spurs and ectopic rippling occur as a function of delayed phase transition, rather than as a function of photoperiod per se.

scholarly journals Regulation of Conidiation and Adenylyl Cyclase Levels by the Gα Protein GNA-3 in Neurospora crassa

2000 ◽  
Vol 20 (20) ◽  
pp. 7693-7705 ◽  
Author(s):  
Ann M. Kays ◽  
Patricia S. Rowley ◽  
Rudeina A. Baasiri ◽  
Katherine A. Borkovich
Keyword(s):  
Neurospora Crassa ◽  
Adenylyl Cyclase ◽  
Submerged Culture ◽  
Solid Medium ◽  
Predicted Amino Acid Sequence ◽  
Aerial Hypha ◽  
Wild Type ◽  
Α Subunit ◽  
Liquid Cultures ◽  
Camp Levels

ABSTRACT We have identified a new gene encoding the G protein α subunit,gna-3, from the filamentous fungusNeurospora crassa. The predicted amino acid sequence of GNA-3 is most similar to the Gα proteins MOD-D, MAGA, and CPG-2 from the saprophytic fungus Podospora anserina and the pathogenic fungi Magnaporthe grisea and Cryphonectria parasitica, respectively. Deletion of gna-3 leads to shorter aerial hyphae and premature, dense conidiation during growth on solid medium or in standing liquid cultures and to inappropriate conidiation in submerged culture. The conidiation and aerial hypha defects of the Δgna-3 strain are similar to those of a previously characterized adenylyl cyclase mutant, cr-1. Supplementation with cyclic AMP (cAMP) restores wild-type morphology to Δgna-3 strains in standing liquid cultures. Solid medium augmented with exogenous cAMP suppresses the premature conidiation defect, but aerial hypha formation is still reduced. Submerged-culture conidiation is refractory to cAMP but is suppressed by peptone. In addition, Δgna-3 submerged cultures express the glucose-repressible gene, qa-2, to levels greatly exceeding those observed in the wild type under carbon-starved conditions. Δgna-3 strains exhibit reduced fertility in homozygous crosses during the sexual cycle; exogenous cAMP has no effect on this phenotype. Intracellular steady-state cAMP levels of Δgna-3 strains are decreased 90% relative to the wild type under a variety of growth conditions. Reduced intracellular cAMP levels in the Δgna-3 strain correlate with lower adenylyl cyclase activity and protein levels. These results demonstrate that GNA-3 modulates conidiation and adenylyl cyclase levels in N. crassa.

THE OCCURRENCE OF TWO DIFFERENT GLUTAMIC DEHYDROGENASES IN NEUROSPORA

1961 ◽  
Vol 7 (3) ◽  
pp. 319-328 ◽  
Author(s):  
B. D. Sanwal ◽  
Madhu Lata
Keyword(s):  
Neurospora Crassa ◽  
Wild Type ◽  
Michaelis Constants ◽  
Type Strains

Many wild-type strains of Neurospora crassa produce two glutamic dehydrogenases, one specific for triphosphopyridine nucleotide and another for diphosphopyridine nucleotide. The enzymes have been separated from one another and purified about 50-fold. Michaelis constants have been reported for various substrates. The pH optima of the DPN- and TPN-specific enzymes are 8.3 and 7.5 respectively.The possible reasons for the presence of two different enzymes catalyzing the same reaction are discussed.

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