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1

Genetic and epigenetic factors affecting meiosis induction in eukaryotes revealed in Paramecium research

100%
Prajer M.
Folia Biologica
|
2008
|
vol. 56
|
issue 1-2
1-11
EN
This review presents studies of the induction of meiosis undertaken on the ciliate Paramecium, a unicellular model eukaryotic organism. Meiosis in Paramecium, preceding the process of fertilization, appears in starved cells after passing a defined number of divisions (cell generations), starting from the last fertilization. Investigations were performed on clones of cells entering autogamy, a self-fertilization process. Genetic as well as epigenetic factors, i.e. endo- and exogenous factors, affecting the induction of meiosis and changing the duration of the interautogamous interval (IAI), were analyzed. The results show that: (1) Meiosis induction is controlled genetically by the somatic macronucleus. However, besides the nuclear factors, the cytoplasmic protein immaturin also affects this process (HAGA & HIWATASHI 1981); (2) Epigenetic factors, such as non-genetically disturbed cytoskeleton structures and changes in the cell architecture observed in doublet Paramecium cells, exert internal mechanical stress (INGBER 2003), which constitutes the endogenous impulse accelerating meiosis; (3) Mild osmotic stress, acting as an exogenous factor, can initiate the specific MAP kinases signaling pathway resulting in earlier meiosis induction, as in other unicellular eukaryotes (SEET & PAWSON 2004).
2

Effect of wild-type macronucleoplasm transplantation into trichocyst mutant cells of Paramecium tetraurelia

63%
Prajer M., Kosciuszko H.
Folia Biologica
|
2001
|
vol. 49
|
issue 3-4
125-128
EN
Approximately 1/2 of the macronucleoplasm of wild-type cells of Paramecium tetraurelia was transplanted into d4-84 mutant recipient homozygous for mutations nd3a (non-discharging trichocysts) and ts401 (temperature sensitive). After injection, 30% of surviving cells shifted from mutant to wild-type phenotype. Among the remaining cell lines 29% were unable to eject any trichocysts, and 41% discharged less than 10 of them per cell, when tested with picric acid. Observations were made through two successive vegetative fissions. These results showed that 30% of d4-84 cells contained foreign gene responsible for trichocyst discharge and produced cell lines of the wild-type phenotype, in which the expression as well as replication of this gene appeared normal.
3

Transplantation of Paramecium tetraurelia cytoplasm committed irreversibly to autogamy, into cells immature for this process. Absence of evidence for a cytoplasmic autogamy inducing factor in Paramecium tetraurelia

63%
Kosciuszko H., Prajer M.
Folia Biologica
|
1997
|
vol. 45
11-14
EN
The onset of autogamy is preceded by a 'critical fission', final, irreversible commitment to autogamy occurring at the G1 phase, about 1 h after this fission. In order to ascertain whether cytoplasm from cells committed to autogamy can induce this process in young cells, cytoplasm from P. tetraurelia cells, being 1,5 to 2 h after the critical fission, was transplanted into cells immature for autogamy. None of the 92 experimental cells entered autogamy, while most of the donor sister cells were autogamous. This result indicates that cytoplasm at this stage is ineffective in inducing autogamy, which may be caused either by the lack of the responsible component, or by too small a volume of transplanted cytoplasm, insufficient to overrule the action of autogamous immaturity factor/s. or/s.
4

The role of nuclear and cytoplasmic factors in the regulation of the interautogamous interval (IAI) in the Paramecium aurelia species complex

63%
Prajer M., Kosciuszko H.
Folia Biologica
|
1998
|
vol. 46
1-6
EN
This paper reviews recent investigations on nuclear and cytoplasmic factors affecting the interautogamous interval. It is concluded that although its length is essentially determined by the macronucleus, cytoplasmic factors also play an important role in its regulation. Apart from immaturin, the authors summarize observations indicating the possible presence of an 'autogamous immaturity factor' and 'autogamy accelerating factor'.
5

Anomalies of autogamy in Paramecium tetraurelia temperature sensitive mutant induced by heat treatment

63%
Prajer M., Iftode F.
Folia Biologica
|
2001
|
vol. 49
|
issue 1-2
13-27
EN
The run of autogamy in temperature sensitive mutant ts401, carrying also the mutation of trichocysts nd3a, at permissive (26oC) and non-permissive temperature (35oC) was studied and compared with this process in wild d4-2 stock of Paramecium tetraurelia. The effect of heat treatment on programmed nuclear and cortical events was investigated using cytological silver impregnation Fernandez-Galiano method and immunofluorescence technique with the application of two anti-a-tubulin antibodies. The appearance of cells with some large macronuclear fragments and an excess number of micronuclei suggests that nuclear differentiation is inhibited at restrictive temperature and that macronuclear regeneration takes place in this thermosensitive mutant. In such cells impaired oral reorganization was observed. After slight refeeding at the late autogamy, cells stopped at first postautogamous division were induced by heat treatment. The most striking feature of these abnormal divisions was the lack of a basal body duplication wave, which suggests that production of g-tubulin, structural protein being the essential component of the microtubule organizing centres, is disturbed at high temperature.
6

Length of the interautogamous interval (IAI) in wild and mutant stocks of Paramecium tetraurelia

63%
Prajer M., Kosciuszko H.
Folia Biologica
|
1999
|
vol. 47
|
issue 3-4
85-90
EN
Duration of the interautogamous interval (IAI) was studied in wild and mutant stocks of Paramecium tetraurelia. The investigations revealed slight but statistically significant differences in IAI duration in complementary mating types of some stocks of P. tetraurelia. A certain range of variability characterized the duration of this period in particular stocks. The greatest variability observed in mutant stock d4-108 may result from abnormal, unequal macronuclear divisions frequent in these mutant cells. In none of the investigated stocks is parental age of relatively young, mature for autogamy cells related to the IAI duration in progeny generation.
7

Effect of cytoplasm containing immaturin - a protein controlling mating immaturity - on the occurence of autogamy in Paramecium tetraurelia

63%
Kosciuszko H., Prajer M.
Folia Biologica
|
1995
|
vol. 43
|
issue 1-2
1-4
EN
Sexual immaturity in the Paramecium aurelia species complex is genetically controlled, its duratin being expressed by the number of cell divisions between successive conjugations or autogamies.During post-conjugational immaturity mating eractivity is regulated by a cytoplasmic protein - immaturin.The present study revealed that cytoplasm containing immaturin of Paramecium primaurellia injected into preautogampus cells of Paramecium tetraurelia does not inhibit the latter in entering autogamy.This results suggests that immaturin is inefective in the inhibition of autogamy.
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