scholarly journals Isolation and Characterization of a Temperature-Sensitive Circadian Clock Mutant of Neurospora crassa

Genetics ◽  
1997 ◽  
Vol 146 (2) ◽  
pp. 525-530 ◽  
Author(s):  
Louis W Morgan ◽  
Jerry F Feldman
Keyword(s):  
Circadian Clock ◽  
Neurospora Crassa ◽  
Mutant Strain ◽  
Double Mutant ◽  
Period Length ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Isolation And Characterization ◽  
Double Mutant Strain ◽  
Clock Mutant

A new circadian clock mutant has been isolated in Neurospora crassa. This new mutation, called period-6 (pd-6), has two features novel to known clock mutations. First, the mutation is temperature sensitive. At restrictive temperatures (above 21°) the mutation shortens circadian period length from a wild-type value of 21.5 hr to 18 hr. At permissive temperatures (below 21°) the mutant has a 20.5-hr period length close to that of the wild-type strain. Second, the prd-6 mutation is epistatic to the previously isolated clock mutation period-2 (prd-2). This epistasis is unusual in that the prd-2 prd-6 double mutant strain has an 18-hr period length at both the restrictive and permissive temperatures. That is, the temperature-sensitive aspect of the phenotype of the prd-6 strain is lost in the prd-2 prd-6 double mutant strain. This suggests that the gene products of the prd-2 and prd-6 loci may interact physically and that the presence of a normal prd-2+ protein is required for low temperature to “rescue” the prd-6 mutant phenotype. These results, combined with our recent finding that prd-2 and some alleles of the frq gene show genetic synergy, suggest that it may be possible to establish a more comprehensive model of the Neurospora circadian clock.

scholarly journals GENETIC AND PHYSIOLOGICAL CHARACTERISTICS OF A SLOW-GROWING CIRCADIAN CLOCK MUTANT OF NEUROSPORA CRASSA

Genetics ◽  
1978 ◽  
Vol 88 (2) ◽  
pp. 255-265
Author(s):  
Jerry F Feldman ◽  
Cheryl A Atkinson
Keyword(s):  
Linkage Group ◽  
Circadian Clock ◽  
Neurospora Crassa ◽  
Double Mutant ◽  
Slow Growth ◽  
Period Length ◽  
The Other ◽  
Wild Type ◽  
Long Period ◽  
Clock Mutant

ABSTRACT A circadian clock mutant of Neurospora crassa with a period length of about 25.8 hours (4 hr longer than wild type) has been isolated after mutagenesis of the band strain. This mutant, called frq-5, segregates as a single nuclear gene, maps near the centromere on linkage group III, and is unlinked to four previously described clock mutants clustered on linkage group VII R (Feldman and Hoyle 1973, 1976). frq-5 differs from the other clock mutants in at least two other respects: (1) it is recessive in heterokaryons, and (2) it grows at about 60% the rate of the parent band strain on both minimal and complete media. Double mutants between frq-5 and each of the other clock mutants show additivity of period length-two long period mutants produce a double mutant whose period length is longer than either of the two single mutants, while a long and a short period double mutant has an intermediate period length. Although slow growth and long periodicity of frq-5 have segregated together among more than 300 progeny, slow growth per se is not responsible for the long period, since all the double mutants have the slow growth characteristic of frq-5, but have period lengths both shorter and longer than wild type.

scholarly journals Epistatic and Synergistic Interactions Between Circadian Clock Mutations in Neurospora crassa

Genetics ◽  
2001 ◽  
Vol 159 (2) ◽  
pp. 537-543
Author(s):  
Louis W Morgan ◽  
Jerry F Feldman
Keyword(s):  
Circadian Clock ◽  
Neurospora Crassa ◽  
Mutant Strain ◽  
Temperature Compensation ◽  
Double Mutant ◽  
Synergistic Interactions ◽  
Long Period ◽  
Double Mutant Strain ◽  
Short Period ◽  
Compensation Mechanisms

Abstract We identified a series of epistatic and synergistic interactions among the circadian clock mutations of Neurospora crassa that indicate possible physical interactions among the various clock components encoded by these genes. The period-6 (prd-6) mutation, a short-period temperature-sensitive clock mutation, is epistatic to both the prd-2 and prd-3 mutations. The prd-2 and prd-3 long-period mutations show a synergistic interaction in that the period length of the double mutant strain is considerably longer than predicted. In addition, the prd-2 prd-3 double mutant strain also exhibits overcompensation to changes in ambient temperature, suggesting a role in the temperature compensation machinery of the clock. The prd-2, prd-3, and prd-6 mutations also show significant interactions with the frq7 long-period mutation. These results suggest that the gene products of prd-2, prd-3, and prd-6 play an important role in both the timing and temperature compensation mechanisms of the circadian clock and may interact with the FRQ protein.

scholarly journals COMPLEMENTATION ANALYSIS OF LINKED CIRCADIAN CLOCK MUTANTS OF NEUROSPORA CRASSA

Genetics ◽  
1976 ◽  
Vol 82 (1) ◽  
pp. 9-17 ◽  
Author(s):  
Jerry F Feldman ◽  
Marian N Hoyle
Keyword(s):  
Linkage Group ◽  
Circadian Clock ◽  
Neurospora Crassa ◽  
Period Length ◽  
Complementation Analysis ◽  
Wild Type ◽  
The Right

ABSTRACT A fourth mutant of Neurospora crassa, designated frq-4, has been isolated in which the period length of the circadian conidiation rhythm is shortened to 19.3 ± 0.3 hours. This mutant is tightly linked to the three previously isolated frq mutants, and all four map to the right arm of linkage group VII about 10 map units from the centromere. Complementation tests suggest, but do not prove, that all four mutations are allelic, since each of the four mutants is co-dominant with the frq  + allele—i.e., heterokaryons have period lengths intermediate between the mutant and wild-type—and since heterokaryons between pairs of mutants also have period lengths intermediate between those of the two mutants.

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 Disruption of the cpsE and endA Genes Attenuates Streptococcus pneumoniae Virulence: Towards the Development of a Live Attenuated Vaccine Candidate

Vaccines ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 187 ◽  
Author(s):  
Malik Amonov ◽  
Nordin Simbak ◽  
Wan Mohd. Razin Wan Hassan ◽  
Salwani Ismail ◽  
Nor Iza A. Rahman ◽  
...  
Keyword(s):  
Developing Countries ◽  
Streptococcus Pneumoniae ◽  
Mutant Strain ◽  
Double Mutant ◽  
Gene Knockout ◽  
High Serum ◽  
High Dose ◽  
Wild Type ◽  
Knockout Mutant ◽  
Double Mutant Strain

The majority of deaths due to Streptococcus pneumoniae infections are in developing countries. Although polysaccharide-based pneumococcal vaccines are available, newer types of vaccines are needed to increase vaccine affordability, particularly in developing countries, and to provide broader protection across all pneumococcal serotypes. To attenuate pneumococcal virulence with the aim of engineering candidate live attenuated vaccines (LAVs), we constructed knockouts in S. pneumoniae D39 of one of the capsular biosynthetic genes, cpsE that encodes glycosyltransferase, and the endonuclease gene, endA, that had been implicated in the uptake of DNA from the environment as well as bacterial escape from neutrophil-mediated killing. The cpsE gene knockout significantly lowered peak bacterial density, BALB/c mice nasopharyngeal (NP) colonisation but increased biofilm formation when compared to the wild-type D39 strain as well as the endA gene knockout mutant. All constructed mutant strains were able to induce significantly high serum and mucosal antibody response in BALB/c mice. However, the cpsE-endA double mutant strain, designated SPEC, was able to protect mice from high dose mucosal challenge of the D39 wild-type. Furthermore, SPEC showed 23-fold attenuation of virulence compared to the wild-type. Thus, the cpsE-endA double-mutant strain could be a promising candidate for further development of a LAV for S. pneumoniae.

scholarly journals An msbB Homologue Carried in Plasmid pO157 Encodes an Acyltransferase Involved in Lipid A Biosynthesis in Escherichia coli O157:H7

2004 ◽  
Vol 72 (2) ◽  
pp. 1174-1180 ◽  
Author(s):  
Sang-Hyun Kim ◽  
Wenyi Jia ◽  
Russell E. Bishop ◽  
Carlton Gyles
Keyword(s):  
Escherichia Coli ◽  
Mutant Strain ◽  
Double Mutant ◽  
Lipid A ◽  
Escherichia Coli O157 ◽  
Wild Type ◽  
Single Mutant ◽  
Double Mutant Strain ◽  
Mutant Strains ◽  
Lipid A Biosynthesis

ABSTRACT Escherichia coli O157:H7 carries a chromosomal msbB1 and a plasmid-encoded msbB2 gene. We characterized msbB2 function as a homologue of msbB1 by examination of wild-type organisms and mutant strains that lacked functional msbB1, msbB2, and both msbB1 and msbB2. The msbB double-mutant strain generated pentaacyl lipid A, while the single-mutant strains synthesized hexaacyl lipid A. Complementation with overexpressed msbB2 converted pentaacyl into hexaacyl lipid A in the double-mutant strain. The transcription of both msbB genes occurred simultaneously. Lack of MsbB2 activity slightly increased the microheterogeneity of the lipid A species. These results suggest that the msbB2 gene plays a role not only in the routine generation of fully hexaacylated lipid A but also in suppressing the microheterogeneity of lipid A species, the endotoxic determinant of the organism.

scholarly journals A RECESSIVE CIRCADIAN CLOCK MUTATION AT THE frq LOCUS OF NEUROSPORA CRASSA

Genetics ◽  
1986 ◽  
Vol 114 (4) ◽  
pp. 1095-1110
Author(s):  
Jennifer J Loros ◽  
Adam Richman ◽  
Jerry F Feldman
Keyword(s):  
Circadian Clock ◽  
Neurospora Crassa ◽  
Temperature Compensation ◽  
Single Gene ◽  
Complete Loss ◽  
The Other ◽  
Compensation Mechanism ◽  
Wild Type ◽  
Structure Mapping ◽  
Clock Mutant

ABSTRACT A circadian clock mutant of Neurospora crassa, the most distinctive characteristic of which is the complete loss of temperature compensation of its period length, maps to the frq locus where seven other clock mutants have previously been mapped. This mutant, designated frq-9, is recessive to the wild-type allele and to each of the other frq mutants; thus, it differs from the other mutants, which show incomplete dominance to wild type and to each other. Complementation analysis suggests either that the frq locus is a single gene or that frq-9 is a deletion that overlaps adjacent genes. Preliminary efforts at fine structure mapping have indicated that recombination between certain pairs of frq mutations is less than 0.005%, a distance consistent with the locus being a single gene. The recessive nature of frq-9, coupled with complete loss of temperature compensation, suggests that this mutant may represent the null phenotype of the locus and that the frq gene is involved in the temperature compensation mechanism of the clock.—Genetic mapping studies have placed the frq locus on linkage group VIIR, midway between oli (oligomycin resistance) and for (formate auxotrophy), about 2 map units from each, and clearly indicate that frq and oli are separate genes.

scholarly journals THE frq LOCUS IN NEUROSPORA CRASSA: A KEY ELEMENT IN CIRCADIAN CLOCK ORGANIZATION

Genetics ◽  
1980 ◽  
Vol 96 (4) ◽  
pp. 877-886 ◽  
Author(s):  
George F Gardner ◽  
Jerry F Feldman
Keyword(s):  
Linkage Group ◽  
Circadian Clock ◽  
Neurospora Crassa ◽  
Single Gene ◽  
Gene Interaction ◽  
Period Length ◽  
Additive Effects ◽  
Wild Type ◽  
Incomplete Dominance ◽  
Significant Gene

ABSTRACT Four new circadian clock mutants of Neurospora crassa have been isolated that alter the period length of the circadian conidiation rhythm. Three of these are at the frq locus on linkage group VIIR, where four other clock mutants are located. In contrast to wild type, which has a period length of 21.6 hr, frq-6 has a period length of 19 hr, while frq-7 and frq-8 have period lengths of 29 hr and represent the largest effects of any single gene mutants on circadian periodicity. Thus, seven mutants have now been isolated that map to the frq locus, with period lengths ranging from 16.5 to 29 hr, and each mutant alters clock periodicity by an integral multiple of 2.5 hr. In addition, all frq mutants show incomplete dominance in heterokaryons. The large percentage of clock mutants that map to this locus, coupled with their unique properties, suggests that the frq locus plays an important role in clock organization.—The fourth mutant, designated chrono (chr), has a period length of 23.5 hr, shows incomplete dominance and is unlinked to either of the previously identified clock loci, frq or prd (formerly called frq-5). Double mutants between various combinations of clock mutants show additive effects and indicate no significant gene interaction among mutants at these three loci.

scholarly journals COMPLEMENTATION ANALYSIS OF METABOLITE-RESISTANT MUTATIONS WITH FORCED HETEROKARYONS OF NEUROSPORA CRASSA

Genetics ◽  
1973 ◽  
Vol 74 (4) ◽  
pp. 581-593
Author(s):  
W M Thwaites ◽  
F K Knauert ◽  
S S Carney
Keyword(s):  
Positive Result ◽  
Neurospora Crassa ◽  
Mutant Strain ◽  
Uptake Rate ◽  
Double Mutant ◽  
Complementation Test ◽  
Gene Products ◽  
Double Mutant Strain ◽  
Common Precursor ◽  
Resistant Mutants

ABSTRACT The double mutant strain pyr-3  arg-12s is a prototroph because a common precursor of arginine and pyrimidine is supplied by the arginine pathway. Growth of this strain is inhibited by exogenous citrulline or arginine. Citrulline-resistant mutants of this strain were selected, and they resulted from modifier mutations at other loci. Forced heterokaryons were used to study complementation among these modifiers. Since the complementation test requires the scoring of non-growth as the positive result, there was concern that variations in nuclear ratios could give erroneous results. This possibility does not seem significant, since groups of mutants established by complementation correspond with groups established by physiological, enzymatic, and recombinational measurements.—The technique has revealed that the most frequently mutated loci are arg-1 and what is probably un-3. Arg-1 mutations affect the conversion of citrulline to argininosuccinate, while un-3 mutations reduce the citrulline uptake rate. Since most of these mutations are of the intracistronic complementing type, a complementation map was constructed for most of the affected loci. The high proportion of complementors in each map can be explained by assuming that partially functioning gene products are more likely to complement with each other than are those which are nonfunctional.

Sign in / Sign up

Export Citation Format

Share Document