scholarly journals Intra- and interspecific complementation of membrane-inexcitable mutants of Paramecium.

1983 ◽  
Vol 97 (2) ◽  
pp. 378-382 ◽  
Author(s):  
N Haga ◽  
Y Saimi ◽  
M Takahashi ◽  
C Kung
Keyword(s):  
Time Course ◽  
Paramecium Tetraurelia ◽  
Paramecium Caudatum ◽  
Mutant Clone ◽  
Wild Type ◽  
Genetic Tests ◽  
Membrane Excitation ◽  
Complementation Groups ◽  
Species Specific ◽  
Sister Cells

Membrane excitation was the basis for backward swimming of Paramecium facing stimulus. According to standard genetic tests, inexcitable mutants fell into three complementation groups for both Paramecium tetraurelia (pwA, pwB, and pwC) and Paramecium caudatum (cnrA, cnrB, and cnrC). Cytoplasm from a wild type transferred to a mutant through microinjection restored the excitability. Transfusions between genetically defined complementation groups of the same species effected curing, whereas transfusions between different mutants (alleles) of the same group or between sister cells of the same mutant clone did not. Cytoplasmic transfers of all combinations among the six groups of mutants of the two species showed that any cytoplasm, except those from the same group, was able to cure. Since the pawns and the caudatum nonreversals complement one another through transfusion, they appeared to belong to six different complementation groups. The extent of curing, the amount of transfer needed to cure, and the time course of curing were characteristic of the group that received the transfusion. Variations in these parameters further suggested that the six groups represented six different genes. Because the donor cytoplasms from either species were equally effective quantitatively in curing a given mutant, the curing factors were not species specific. These factors are discussed.

scholarly journals Phenotypic and Genetic Analysis of “Chameleon,” a Paramecium Mutant With an Enhanced Sensitivity to Magnesium

Genetics ◽  
1997 ◽  
Vol 146 (3) ◽  
pp. 871-880
Author(s):  
Robin R Preston ◽  
Jocelyn A Hammond
Keyword(s):  
Genetic Analysis ◽  
Single Locus ◽  
Behavioral Analysis ◽  
Paramecium Tetraurelia ◽  
Wild Type ◽  
Ion Conductance ◽  
Membrane Excitation ◽  
Enhanced Sensitivity ◽  
Electrophysiological Analysis ◽  
Mutant Strains

Three mutant strains of Paramecium tetraurelia with an enhanced sensitivity to magnesium have been isolated. These new “Chameleon” mutants result from partial- or codominant mutations at a single locus, Cha. Whereas the wild type responded to 5 mm Mg2+ by swimming backward for 10–15 sec, Cha mutants responded with ∼30 sec backward swimming. Electrophysiological analysis suggested that this behavior may be caused by slowing in the rate at which a Mg2+-specific ion conductance deactivates following membrane excitation. This would be consistent with an observed increase in the sensitivity of Cha mutants to nickel poisoning, since Ni2+ is also able to enter the cell via this pathway. More extensive behavioral analysis showed that Cha cells also overresponded to Na+, but there was no evidence for a defect in intracellular Ca2+ homeostasis that might account for a simultaneous enhancement of both the Mg2+ and Na+ conductances. The possibility that the Cha locus may encode a specific regulator of the Mg2+- and Na+-permeabilities is considered.

BEHAVIORAL MUTANTS IN PARAMECIUM CAUDATUM

Genetics ◽  
1979 ◽  
Vol 91 (3) ◽  
pp. 393-408
Author(s):  
Mihoko Takahashi
Keyword(s):  
Swimming Behavior ◽  
Paramecium Caudatum ◽  
Wild Type ◽  
Complementation Groups

ABSTRACT Mutants of Paramecium caudatum with abnormal swimming behavior or responses to cations were obtained by mutagenesis with N-methyl-N-nitro N-nitrosoguanidine. Some of the mutants, like pawn in P. tetraurelia, cannot swim backward and are called CNR. Seven independently obtained CNR mutants belonged to three complementation groups, designated as cnrA, cnrB and cnrC. Some characteristics of double homo- and heterozygotes were compared with single homo- and heterozygotes. Other behavioral mutants shown to have a genic basis included K+-sensitive, temperature-shack behavioral and slow swimmer. All those mutants except for slow swimmer had lesions in the membrane because Triton-extracted models of them show almost the same swimming behavior as wild type.

scholarly journals ATP keeps exocytosis sites in a primed state but is not required for membrane fusion: an analysis with Paramecium cells in vivo and in vitro.

1986 ◽  
Vol 103 (4) ◽  
pp. 1279-1288 ◽  
Author(s):  
J Vilmart-Seuwen ◽  
H Kersken ◽  
R Stürzl ◽  
H Plattner
Keyword(s):  
Membrane Fusion ◽  
Time Course ◽  
Paramecium Tetraurelia ◽  
Wild Type ◽  
Primed State ◽  
Different Strains ◽  
Exogenous Trigger ◽  
Free Media

We have tried to specify a widespread hypothesis on the requirement of ATP for exocytosis (membrane fusion). With Paramecium tetraurelia cells, synchronously (approximately 1 s) exocytosing trichocysts, ATP pools have been measured in different strains, including wild type cells, "non-discharge" (nd), "trichless" (tl), and other mutations. The occurrence of a considerable and rapid ATP consumption also in nd and tl mutations as well as its time course (with a maximum 3-5 s after exocytosis) in exocytosis-competent strains does not match the actual extent of exocytosis performance. However, from in vivo as well as from in vitro experiments, we came to the conclusion that ATP might be required to keep the system in a primed state and its removal might facilitate membrane fusion. (For the study of exocytosis in vitro we have developed a new system, consisting of isolated cortices). In vivo as well as in vitro exocytosis is inhibited by increased levels of ATP or by a nonhydrolyzable ATP analogue. In vitro exocytosis is facilitated in ATP-free media. In vivo-microinjected ATP retards exocytosis in response to chemical triggers, whereas microinjected apyrase triggers exocytosis without exogenous trigger. Experiments with this system also largely exclude any overlaps with other processes that normally accompany exocytosis. Our data also explain why it was frequently assumed that ATP would be required for exocytosis. We conclude that membrane fusion during exocytosis does not require the presence of ATP; the occurrence of membrane fusion might involve the elimination of ATP from primed fusogenic sites; most of the ATP consumption measured in the course of exocytosis may be due to other effects, probably to recovery phenomena.

scholarly journals A modifier gene involved in the expression of the dominant mating type allele in Paramecium caudatum

1976 ◽  
Vol 27 (2) ◽  
pp. 135-141 ◽  
Author(s):  
Koichi Hiwatashi ◽  
Koji Myohara
Keyword(s):  
Mating Type ◽  
Modifier Gene ◽  
Recessive Allele ◽  
Dominant Allele ◽  
Paramecium Caudatum ◽  
Mutant Clone ◽  
Wild Type ◽  
Type Allele ◽  
Type V

SUMMARYMating type in Paramecium caudatum, syngen 3 is determined by a pair of alleles with simple dominance; the recessive allele restricts homozygotes to mating type V and the dominant allele permits expression of mating type VI. Clones of mating type V never show natural selfing, but most clones of mating type VI self naturally. A mutant clone of mating type VI which never selfed over a period of more than 3 years was obtained by treatment with N-methyl-N′-nitro-N-nitrosoguanidine. When this mutant clone was crossed to a wild-type stock of mating type V, all F1 clones of mating type VI gave rise to selfers. From selfing of these F1 of mating type VI, clones of F2 were obtained. Nearly 3:1 segregation of selfer to non-selfer clones was observed among the F2 clones of mating type VI. The results were consistent with the interpretation that a dominant modifier gene, Su(+mtV), controls the instability in the expression of mating type VI.

scholarly journals GENETIC ANALYSES OF "PARANOIAC" MUTANTS OF PARAMECIUM TETRAURELIA

Genetics ◽  
1977 ◽  
Vol 86 (1) ◽  
pp. 113-120
Author(s):  
Judith Van Houten ◽  
Sheng-Yung Chang ◽  
Ching Kung
Keyword(s):  
Close Linkage ◽  
Paramecium Tetraurelia ◽  
Wild Type ◽  
Allelic Variants ◽  
Genetic Analyses ◽  
Behavioral Phenotypes ◽  
Membrane Excitation ◽  
The Future ◽  
In The Wild

ABSTRACT Six mutants of Paramecium tetraurelia with curious "Paranoiac" phenotypes have been isolated and examined. Instead of the normal transient avoiding reactions in Na+ solutions, these mutants show "violent avoidances"—backing continuously for 10 to over 60 sec. This behavior corresponds to prolonged membrane excitation.—Genetic analyses establish five genic loci at which mutations give the "Paranoiac" phenotype. Close linkage between two of these genes occurs. Allelic variants are found for two of the genes. In one case, the two alleles determine very different behavioral phenotypes ("Paranoiac" and "fast-2"). These results show that the mechanism(s) which shuts off excitation in the wild-type membrane is (are) complex, but in the future may be fruitfully pursued in mutants which are defective.

Membrane currents of pawn mutants of the pwA group in Paramecium tetraurelia

1980 ◽  
Vol 84 (1) ◽  
pp. 57-71 ◽  
Author(s):  
Y. Satow ◽  
C. Kung
Keyword(s):  
Time Course ◽  
Membrane Currents ◽  
Voltage Sensitivity ◽  
Paramecium Tetraurelia ◽  
Ca Channels ◽  
Wild Type ◽  
Outward Currents ◽  
In The Wild ◽  
Inward Currents ◽  
K Current

Membrane currents were recorded from the wild type and two pawn mutants of the pwA complementation group in Paramecium tetraurelia under a voltage clamp. Most currents are not changed by the mutations. Transient inward currents of a leaky mutant, pwA132, upon step depolarizations are less than those in the wild type. The inward transient is completely lacking in a non-leaky mutant, pwA500. The time course of the residual inward currents in the leaky mutant is not significantly different from that of wild type. The voltage sensitivity of the Ca channels in the leaky mutant is also similar to that of wild type. The inward currents upon membrane hyperpolarizations in the mutants show normal characteristics in the presence or absence of external K+. With sufficiently large, prolonged depolarization, outward currents progressively develop in the wild type but decay in the mutants. The simplest conclusion we can draw is that the pwA mutations reduce the number of functional Ca channels but do not change the channel characteristics. From the conductance measurements, 45% of the Ca channels remain in the leaky mutant pwA132, and none remain in the non-leaky mutant pwA500. By subtracting the outward currents of pwA500 from the slow and prolonged outward currents of the wild type, we have tentatively separated a Ca-induced K+ current from the voltage-dependent K+ current. The time courses of these two currents differ by two orders of magnitude.

scholarly journals Regulation of macronuclear DNA content in Paramecium tetraurelia.

1978 ◽  
Vol 76 (1) ◽  
pp. 116-126 ◽  
Author(s):  
J D Berger ◽  
H J Schmidt
Keyword(s):  
Cell Cycle ◽  
Dna Content ◽  
Regulatory Mechanism ◽  
Paramecium Tetraurelia ◽  
Wild Type ◽  
Constant Variance ◽  
Dna Contents ◽  
The Mean ◽  
Macronuclear Division ◽  
Sister Cells

The macronucleus of Paramecium divides amitotically, and daughter macronuclei with different DNA contents are frequently produced. If no regulatory mechanism were present, the variance of macronuclear DNA content would increase continuously. Analysis of variance within cell lines shows that macronuclear DNA content is regulated so that a constant variance is maintained from one cell generation to the next. Variation in macronuclear DNA content is removed from the cell population by the regulatory mechanism at the same rate at which it is introduced through inequality of macronuclear division. Half of the variation in macronuclear DNA content introduced into the population at a particular fission by inequality of division is compensated for during the subsequent period of DNA synthesis. Half of the remaining variation is removed during each subsequent cell cycle. The amount of variation removed in one cell cycle is proportional to the postfission variation. The cell's power to regulate DNA content is substantially greater than that required to compensate for the small differences that arise during division of wild-type cells. For example, a constant variance was still maintained when the mean difference between sister cells was increased to ten times its normal level in a mutant strain. The observations are consistent with a replication model that assumes that each cell synthesizes an approximately constant amount of DNA which is independent of the initial DNA content of the macronucleus. It is suggested that the amount of DNA synthesized may be largely determined by the mass of the cell.

Arabidopsis 4-COUMAROYL-COA LIGASE 8 contributes to the biosynthesis of the benzenoid ring of coenzyme Q in peroxisomes

2019 ◽  
Vol 476 (22) ◽  
pp. 3521-3532
Author(s):  
Eric Soubeyrand ◽  
Megan Kelly ◽  
Shea A. Keene ◽  
Ann C. Bernert ◽  
Scott Latimer ◽  
...  
Keyword(s):  
Oxidative Metabolism ◽  
Time Course ◽  
Reverse Genetics ◽  
De Novo ◽  
Coenzyme Q ◽  
Control Level ◽  
Wild Type ◽  
Fluorescent Reporters ◽  
Coa Ligase ◽  
Peroxisomal Targeting

Plants have evolved the ability to derive the benzenoid moiety of the respiratory cofactor and antioxidant, ubiquinone (coenzyme Q), either from the β-oxidative metabolism of p-coumarate or from the peroxidative cleavage of kaempferol. Here, isotopic feeding assays, gene co-expression analysis and reverse genetics identified Arabidopsis 4-COUMARATE-COA LIGASE 8 (4-CL8; At5g38120) as a contributor to the β-oxidation of p-coumarate for ubiquinone biosynthesis. The enzyme is part of the same clade (V) of acyl-activating enzymes than At4g19010, a p-coumarate CoA ligase known to play a central role in the conversion of p-coumarate into 4-hydroxybenzoate. A 4-cl8 T-DNA knockout displayed a 20% decrease in ubiquinone content compared with wild-type plants, while 4-CL8 overexpression boosted ubiquinone content up to 150% of the control level. Similarly, the isotopic enrichment of ubiquinone's ring was decreased by 28% in the 4-cl8 knockout as compared with wild-type controls when Phe-[Ring-13C6] was fed to the plants. This metabolic blockage could be bypassed via the exogenous supply of 4-hydroxybenzoate, the product of p-coumarate β-oxidation. Arabidopsis 4-CL8 displays a canonical peroxisomal targeting sequence type 1, and confocal microscopy experiments using fused fluorescent reporters demonstrated that this enzyme is imported into peroxisomes. Time course feeding assays using Phe-[Ring-13C6] in a series of Arabidopsis single and double knockouts blocked in the β-oxidative metabolism of p-coumarate (4-cl8; at4g19010; at4g19010 × 4-cl8), flavonol biosynthesis (flavanone-3-hydroxylase), or both (at4g19010 × flavanone-3-hydroxylase) indicated that continuous high light treatments (500 µE m−2 s−1; 24 h) markedly stimulated the de novo biosynthesis of ubiquinone independently of kaempferol catabolism.

Postnatal growth rate and gonadal development in circadian tau mutant hamsters reared in constant dim red light

Reproduction ◽  
2000 ◽  
pp. 327-330 ◽  
Author(s):  
RJ Lucas ◽  
JA Stirland ◽  
YN Mohammad ◽  
AS Loudon
Keyword(s):  
Time Course ◽  
Red Light ◽  
Somatic Growth ◽  
Postnatal Growth ◽  
Gonadal Development ◽  
Testicular Development ◽  
Wild Type ◽  
Similar Time ◽  
Syrian Hamsters ◽  
Body Weights

The role of the circadian clock in the reproductive development of Syrian hamsters (Mesocricetus auratus was examined in wild type and circadian tau mutant hamsters reared from birth to 26 weeks of age under constant dim red light. Testis diameter and body weights were determined at weekly intervals in male hamsters from 4 weeks of age. In both genotypes, testicular development, subsequent regression and recrudescence exhibited a similar time course. The age at which animals displayed reproductive photosensitivity, as exhibited by testicular regression, was unrelated to circadian genotype (mean +/- SEM: 54 +/- 3 days for wild type and 59 +/- 5 days for tau mutants). In contrast, our studies revealed a significant impact of the mutation on somatic growth, such that tau mutants weighed 18% less than wild types at the end of the experiment. Our study reveals that the juvenile onset of reproductive photoperiodism in Syrian hamsters is not timed by the circadian system.

scholarly journals The Cloning and Molecular Analysis of pawn-B in Paramecium tetraurelia

Genetics ◽  
2000 ◽  
Vol 155 (3) ◽  
pp. 1105-1117 ◽  
Author(s):  
W John Haynes ◽  
Kit-Yin Ling ◽  
Robin R Preston ◽  
Yoshiro Saimi ◽  
Ching Kung
Keyword(s):  
Genomic Library ◽  
Open Reading Frame ◽  
Paramecium Tetraurelia ◽  
Wild Type ◽  
Rt Pcr ◽  
Reading Frame ◽  
Close Proximity ◽  
In The Wild ◽  
Dna Fragment ◽  
Alternative Sites

Abstract Pawn mutants of Paramecium tetraurelia lack a depolarization-activated Ca2+ current and do not swim backward. Using the method of microinjection and sorting a genomic library, we have cloned a DNA fragment that complements pawn-B (pwB/pwB). The minimal complementing fragment is a 798-bp open reading frame (ORF) that restores the Ca2+ current and the backward swimming when expressed. This ORF contains a 29-bp intron and is transcribed and translated. The translated product has two putative transmembrane domains but no clear matches in current databases. Mutations in the available pwB alleles were found within this ORF. The d4-95 and d4-96 alleles are single base substitutions, while d4-662 (previously pawn-D) harbors a 44-bp insertion that matches an internal eliminated sequence (IES) found in the wild-type germline DNA except for a single C-to-T transition. Northern hybridizations and RT-PCR indicate that d4-662 transcripts are rapidly degraded or not produced. A second 155-bp IES in the wild-type germline ORF excises at two alternative sites spanning three asparagine codons. The pwB ORF appears to be separated from a 5′ neighboring ORF by only 36 bp. The close proximity of the two ORFs and the location of the pwB protein as indicated by GFP-fusion constructs are discussed.

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