scholarly journals SEX DETERMINATION IN THE NEMATODE C. ELEGANS: ANALYSIS OF tra-3 SUPPRESSORS AND CHARACTERIZATION OF fem GENES

Genetics ◽  
1986 ◽  
Vol 114 (1) ◽  
pp. 15-52
Author(s):  
Jonathan Hodgkin
Keyword(s):  
Sex Determination ◽  
Null Alleles ◽  
Temperature Sensitive ◽  
Female Development ◽  
C Elegans ◽  
Male Development ◽  
Maternal Contribution ◽  
New Gene ◽  
Extragenic Suppressors

ABSTRACT Mutations of the gene tra-3 result in partial masculinization of XX animals of C. elegans, which are normally hermaphrodites (males are XO). A total of 43 tra-3 revertants (one intragenic, 42 extragenic) have been isolated and analyzed, in the hope of identifying new sex-determination loci. Most (38) of the extragenic suppressors cause partial or complete feminization of XX and XO animals; the remaining four are weak suppressors. The feminizing suppressors are mostly alleles of known sex-determining genes: tra-1 (11 dominant alleles), tra-2 (one dominant allele), fem-1 (four alleles) and fem-2 (four alleles), but 18 are alleles of a new gene, fem-3. Additional alleles have been isolated for the fem-2 and fem-3 genes, as well as fem-3 deficiencies. Mutations in fem-3 resemble alleles of fem-1 (previously characterized): putative null alleles result in complete feminization of XX and XO animals, transforming them into fertile females. Severe alleles of fem-2 also cause complete feminization of XX animals at all temperatures, but feminization of fem-2 XO animals is temperature-sensitive: complete at 25°, incomplete at 20°. As with fem-1, severe mutations of fem-2 and fem-3 are wholly epistatic to masculinizing alleles of tra-2 and tra-3, and epistatic to tra-1 masculinizing alleles in the germline, but not in the soma. All three fem genes are essential for male development and appear to have a dual role in promoting spermatogenesis and repressing tra-1 activity. All three fem genes exhibit strong maternal effects; the maternal contribution of fem gene products may be inactivated in XX animals by a posttranscriptional mechanism. Maternal contributions of wild-type fem-3 product are necessary for normal XO male development and XX hermaphrodite (as opposed to female) development.

scholarly journals Null alleles of SAC7 suppress temperature-sensitive actin mutations in Saccharomyces cerevisiae.

1990 ◽  
Vol 10 (5) ◽  
pp. 2308-2314 ◽  
Author(s):  
T M Dunn ◽  
D Shortle
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Normal Growth ◽  
Null Alleles ◽  
Growth Defect ◽  
Temperature Sensitive ◽  
Actin Assembly ◽  
New Gene ◽  
Cold Sensitive ◽  
Sensitive Allele ◽  
Extragenic Suppressors

Extragenic suppressors of a new temperature-sensitive mutation (act1-4) in the actin gene of Saccharomyces cerevisiae were isolated in an attempt to identify genes whose products interact directly with actin. One suppressor with a cold-sensitive growth phenotype defined the new gene, SAC7, which was mapped, cloned, sequenced, and disrupted. Genetic analysis of strains that are disrupted for SAC7 demonstrated that the protein is required for normal growth and actin assembly at low temperatures. Surprisingly, null mutations in SAC7 also suppressed the temperature-sensitive growth defect caused by the act1-1 and act1-4 mutations, whereas they were lethal in combination with the temperature-sensitive allele act1-2. These results support the notion that the SAC7 gene product is involved in the normal assembly or function or both of actin.

Null alleles of SAC7 suppress temperature-sensitive actin mutations in Saccharomyces cerevisiae

1990 ◽  
Vol 10 (5) ◽  
pp. 2308-2314
Author(s):  
T M Dunn ◽  
D Shortle
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Normal Growth ◽  
Null Alleles ◽  
Growth Defect ◽  
Temperature Sensitive ◽  
Actin Assembly ◽  
New Gene ◽  
Cold Sensitive ◽  
Sensitive Allele ◽  
Extragenic Suppressors

Extragenic suppressors of a new temperature-sensitive mutation (act1-4) in the actin gene of Saccharomyces cerevisiae were isolated in an attempt to identify genes whose products interact directly with actin. One suppressor with a cold-sensitive growth phenotype defined the new gene, SAC7, which was mapped, cloned, sequenced, and disrupted. Genetic analysis of strains that are disrupted for SAC7 demonstrated that the protein is required for normal growth and actin assembly at low temperatures. Surprisingly, null mutations in SAC7 also suppressed the temperature-sensitive growth defect caused by the act1-1 and act1-4 mutations, whereas they were lethal in combination with the temperature-sensitive allele act1-2. These results support the notion that the SAC7 gene product is involved in the normal assembly or function or both of actin.

Genetic control of sex determination in the germ line of Caenorhabditis elegans

1988 ◽  
Vol 322 (1208) ◽  
pp. 11-18 ◽  
Keyword(s):  
Caenorhabditis Elegans ◽  
Sex Determination ◽  
Genetic Control ◽  
Germ Line ◽  
Female Development ◽  
Tissue Specific ◽  
C Elegans ◽  
Male Development

The nematode Caenorhabditis elegans normally exists as one of two sexes: self-fertilizing hermaphrodite or male. Development as hermaphrodite or male requires the differentiation of each tissue in a sex-specific way. In this review, I discuss the genetic control of sex determination in a single tissue of C. elegans : the germ line. Sex determination in the germ line depends on the action of two types of genes: - those that act globally in all tissues to direct male or female development and those that act only in the germ line to specify either spermatogenesis or oogenesis. First, I consider a tissue-specific sex-determining gene, fog-1 , which promotes spermatogenesis in the germ line. Second, I consider the regulation of the hermaphrodite pattern of germ ­ line gametogenesis where first sperm and then oocytes are produced.

Characterization of Revertants of unc-93(e1500) in Caenorhabditis elegans Induced by N-ethyl-N-nitrosourea

Genetics ◽  
1997 ◽  
Vol 147 (2) ◽  
pp. 597-608 ◽  
Author(s):  
Elizabeth De Stasio ◽  
Catherine Lephoto ◽  
Lynn Azuma ◽  
Charles Holst ◽  
Dinesh Stanislaus ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Protein Function ◽  
Genetic Research ◽  
Rubber Band ◽  
Null Alleles ◽  
Suppressor Genes ◽  
C Elegans ◽  
Intragenic Deletions ◽  
New Gene

Phenotypic reversion of the rubber-band, muscle-defective phenotype conferred by unc-93(e1500) was used to determine the utility of N-ethyl-N-nitrosourea (ENU) as a mutagen for genetic research in Caenorhabditis elegans. In this system, ENU produces revertants at a frequency of 3 × 10–4, equivalent to that of the commonly used mutagen, EMS. The gene identity of 154 ENU-induced revertants shows that the distribution of alleles between three possible suppressor genes differs from that induced by EMS. A higher percentage of revertants are alleles of unc-93 and many fewer are alleles of sup-9 and sup-10. Three revertants complement the three known suppressor genes; they may therefore identify a new gene product(s) involved in this system of excitation-contraction coupling in C. elegans. Molecular characterization of putative unc-93 null alleles reveals that the base changes induced by ENU are quite different from those induced by EMS; specifically we see an increased frequency of A/T → G/C transitions. The frequency of ENU-induced intragenic deletions is found to be 13%. We suggest that ENU, at concentrations below 5 mm, will be a superior mutagen for studies of protein function in C. elegans.

scholarly journals Isolation and characterization of extragenic suppressors of mutations in the SSA hsp70 genes of Saccharomyces cerevisiae.

Genetics ◽  
1992 ◽  
Vol 131 (2) ◽  
pp. 277-285 ◽  
Author(s):  
R J Nelson ◽  
M F Heschl ◽  
E A Craig
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Stress Response ◽  
Regulatory Protein ◽  
Null Alleles ◽  
Temperature Sensitive ◽  
Gene Encoding ◽  
Isolation And Characterization ◽  
Transcriptional Regulatory ◽  
Extragenic Suppressors

Abstract Saccharomyces cerevisiae strains that contain null alleles of two hsp70 genes, SSA1 and SSA2, are temperature sensitive for growth. In this study, extragenic suppressors of ssa1 ssa2 have been isolated. Suppression is due to mutations at nuclear loci designated EXA1, EXA2 and EXA3 for EXtragenic suppressor hsp70 subfamily A. Two of the four EXA1 alleles are dominant as is EXA3-1. The other two EXA1 alleles as well as the sole EXA2 allele are recessive. EXA1 mutations lead to accumulation of a previously uncharacterized form of hsp70. EXA2 and EXA3 mutations affect the regulation of the stress response. In exa2-1 ssa1 ssa2 strains the gene products of the remaining SSA hsp70 genes, SSA3 and SSA4 (Ssa3/4p), accumulate to higher levels. The EXA3-1 mutation results in increased accumulation of both Ssa3/4p and the hsp70s encoded by the SSB1 and SSB2 genes (Ssb1/2p), suggesting that the EXA3 gene product plays a central role in the yeast stress response. Consistent with this hypothesis, EXA3-1 is tightly linked to HSF1, the gene encoding the transcriptional regulatory protein known as "heat shock factor." All of the genes identified in this study seem to be involved in regulating the expression of SSA3 and SSA4 or the activity of their protein products.

scholarly journals Characterization of mutations that suppress the temperature-sensitive growth of the hpr1 delta mutant of Saccharomyces cerevisiae.

Genetics ◽  
1994 ◽  
Vol 137 (4) ◽  
pp. 945-956 ◽  
Author(s):  
H Y Fan ◽  
H L Klein
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Synthetic Lethality ◽  
Direct Repeat ◽  
Fold Increase ◽  
Temperature Sensitive ◽  
Rad Genes ◽  
Complementation Groups ◽  
Rad Mutants ◽  
Extragenic Suppressors

Abstract The hpr1 delta 3 mutant of Saccharomyces cerevisiae is temperature-sensitive for growth at 37 degrees and has a 1000-fold increase in deletion of tandem direct repeats. The hyperrecombination phenotype, measured by deletion of a leu2 direct repeat, is partially dependent on the RAD1 and RAD52 gene products, but mutations in these RAD genes do not suppress the temperature-sensitive growth phenotype. Extragenic suppressors of the temperature-sensitive growth have been isolated and characterized. The 14 soh (suppressor of hpr1) mutants recovered represent eight complementation groups, with both dominant and recessive soh alleles. Some of the soh mutants suppress hpr1 hyperrecombination and are distinct from the rad mutants that suppress hpr1 hyperrecombination. Comparisons between the SOH genes and the RAD genes are presented as well as the requirement of RAD genes for the Soh phenotypes. Double soh mutants have been analyzed and reveal three classes of interactions: epistatic suppression of hpr1 hyperrecombination, synergistic suppression of hpr1 hyperrecombination and synthetic lethality. The SOH1 gene has been cloned and sequenced. The null allele is 10-fold increased for recombination as measured by deletion of a leu2 direct repeat.

scholarly journals The TRANSFORMER Genes of the Fern Ceratopteris Simultaneously Promote Meristem and Archegonia Development and Repress Antheridia Development in the Developing Gametophyte

Genetics ◽  
1997 ◽  
Vol 147 (4) ◽  
pp. 1885-1897 ◽  
Author(s):  
Jo Ann Banks
Keyword(s):  
Sex Determination ◽  
Sex Expression ◽  
The Other ◽  
Female Development ◽  
Epistatic Interactions ◽  
Male Development ◽  
Sporophyte Development

Abstract The sex of the haploid gametophyte of the fern Ceratopteris is determined by the presence or absence of the pheromone antheridiogen, which, when present, promotes male development and represses female development of the gametophyte. Several genes involved in sex determination in Ceratopteris have been identified by mutation. In this study, the epistatic interactions among new and previously described sex-determining mutants have been characterized. These results show that sex expression is regulated by two sets of genes defined by the FEM1 and TRA loci. Each promotes the expression of either male or female traits and simultaneously represses the expression of the other. A model describing how antheridiogen regulates the expression of these genes and the sex of the gametophyte is described. The observation that some gametophytic sexdetermining mutants have phenotypic effects on the spore phyte plant indicates that sex determination in the Ceratopteris gametophyte is regulated by a mechanism that also regulates sporophyte development.

scholarly journals ACTIVITY OF THE SEX-DETERMINING GENE tra-2 IS MODULATED TO ALLOW SPERMATOGENESIS IN THE C. ELEGANS HERMAPHRODITE

Genetics ◽  
1986 ◽  
Vol 114 (1) ◽  
pp. 53-76
Author(s):  
Tabitha Doniach
Keyword(s):  
Sex Determination ◽  
Regulatory Genes ◽  
The State ◽  
The Self ◽  
Wild Type ◽  
Gain Of Function ◽  
C Elegans ◽  
Male Development ◽  
In The Wild ◽  
Mode Of Regulation

ABSTRACT In the nematode C. elegans, there are two sexes, the self-fertilizing hermaphrodite (XX) and the male (XO). The hermaphrodite is essentially a female that makes sperm for a brief period before oogenesis. Sex determination in C. elegans is controlled by a pathway of autosomal regulatory genes, the state of which is determined by the X:A ratio. One of these genes, tra-2, is required for hermaphrodite development, but not for male development, because null mutations in tra-2 masculinize XX animals but have no effect on XO males. Dominant, gain-of-function tra-2 mutations have now been isolated that completely feminize the germline of XX animals so that they make only oocytes and no sperm and, thus, are female. Most of the tra-2(dom) mutations do not correspondingly feminize XO animals, so they do not appear to interfere with control by her-1, a gene thought to negatively regulate tra-2 in XO animals. Thus, these mutations appear to cause gain of tra-2 function in the XX animal only. Dosage studies indicate that 5 of 7 tra-2(dom) alleles are hypomorphic, so they do not simply elevate XX tra-2 activity overall. These properties suggest that in the wild type, tra-2 activity is under two types of control: (1) in males, it is inactivated by her-1 to allow male development to occur, and (2) in hermaphrodites, tra-2 is active but transiently inactivated by another, unknown, regulator to allow hermaphrodite spermatogenesis; this mode of regulation is hindered by the tra-2(dom) mutations, thereby resulting in XX females.

scholarly journals A General Method for Identifying Recessive Diploid-Specific Mutations in Saccharomyces cerevisiae, Its Application to the Isolation of Mutants Blocked at Intermediate Stages of Meiotic Prophase and Characterization of a New Gene SAE2

Genetics ◽  
1997 ◽  
Vol 146 (3) ◽  
pp. 797-816 ◽  
Author(s):  
Andrew H Z McKee ◽  
Nancy Kleckner
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Meiotic Prophase ◽  
Temperature Sensitive ◽  
Yeast Saccharomyces Cerevisiae ◽  
New Approach ◽  
Strand Breaks ◽  
Recessive Mutations ◽  
New Genes ◽  
New Gene

We describe a general new approach for identifying recessive mutations that affect diploid strains of yeast Saccharomyces cerevisiae and the application of this method to the identification of mutations that confer an intermediate block in meiotic prophase chromosome metabolism. The method uses a temperature-sensitive conjugation mutation ste7-1 in combination with homothallism. The mutations of interest confer a defect in spore formation that is dependent upon a gene required for initiation of meiotic recombination and development of meiosis-specific chromosome structure (SPO11). Identified in this screen were null mutations of the DMC1 gene, nonnull mutations of RAD50 (rad50S, and mutations in three new genes designated SAE1, SAE2 and SAE3 (Sporulation in the Absence of Spo Eleven). Molecular characterization of the SAE2 gene and characterization of meiotic and mitotic phenotypes of sae2 mutants are also presented. The phenotypes conferred by a sae2 null mutation are virtually indistinguishable from those conferred by the previously identified nonnull mutations of RAD50 (rad50S). Most notably, both mutations confer only weak sensitivity to the radiomimetic agent methyl methane sulfonate (MMS) but completely block resection and turnover of meiosis-specific double-strand breaks. These observations provide further evidence that this constellation of phenotypes identifies a specific molecular function.

scholarly journals ISOLATION AND CHARACTERIZATION OF CONDITIONAL ALLELES OF BACTERIOPHAGE T4 GENES uvsX AND uvsY

Genetics ◽  
1984 ◽  
Vol 107 (4) ◽  
pp. 505-523
Author(s):  
Mark A Conkling ◽  
John W Drake
Keyword(s):  
Bacteriophage T4 ◽  
Null Alleles ◽  
Chain Elongation ◽  
Complementation Test ◽  
Temperature Sensitive ◽  
Isolation And Characterization ◽  
Defect Sensitivity ◽  
Dna Chain ◽  
Ionizing Radiations

ABSTRACT The bacteriophage T4 uvsW, uvsX and uvsY gene functions are required for wild-type levels of recombination and for normal survival and mutagenesis after treatments with ultraviolet (UV) and ionizing radiations. The ability of uvsX and uvsY mutations to suppress the lethality of gene 49 mutations was used to select temperature-sensitive and amber alleles of these two genes. (uvsW mutations do not suppress gene 49 mutations.) A simple and powerful complementation test was developed to assist in assigning uvs mutations to genes. The amber alleles of uvsX and uvsY behave as simple null alleles, fully suppressing a gene 49 defect, enhancing UV killing and abolishing UV mutagenesis. However, the properties of the ts alleles of uvsX and uvsY demonstrated that suppression of a gene 49 defect, sensitivity to UV-induced inactivation and UV mutability can be partially uncoupled. These results prompt the hypothesis that radiation mutagenesis occurs during DNA chain elongation past template damage within a recombinational intermediate rather than within a conventional replication fork.

Sign in / Sign up

Export Citation Format

Share Document