ISSN:0192-253X    

DOI:10.1002/dvg.1020130102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractEuplotes raikovi, like other ciliates, passes through a postconjugal immaturity, operatively identified by an apparent cell inability to form mating pairs under experimental conditions that are the same as those used for inducing mating at maturity. In cells homozygous for the genemat‐2, which controls the pheromone Er‐2, Er‐2 mRNA synthesis and mature Er‐2 secretion were shown to start from the very beginning of the life cycle and continue throughout immaturity, although to extents estimated to be 5‐ to 10‐fold lower than at maturity. In addition, experiments of125I‐Er‐2 binding and crosslinking provided evidence that autocrine pheromone‐binding sites, showing values of the dissociation constant of the order of 10−9M, are on the surface of immature cells. The number of these sites per cell was estimated to increase from less than 106per cell of 5–7 fissions of age, to about 16 × 106at maturity. These results were taken to suggest that a pheromone‐receptor production is stimulated during immaturity by autocrine pheromone binding to cells and that this production might be essential for the development of a pheromone‐receptor density high enough to transform the cell from “immature” to “adult,” that is competent to respond as well to pheromones of conspecific, genetically diffe

ISSN:0192-253X    

DOI:10.1002/dvg.1020130103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractWe have cloned and sequenced a 1.7 kb macronuclear chromosome encoding the pheromone 4 gene ofEuplotes octocarinatus.The sequence of the secreted pheromone is preceded by a 42 amino acid leader peptide, which ends with a lysine residue. The sequence coding for the leader peptide contains information for a putative signal peptide and is interrupted by a 772 bp intron as shown by comparison with a cDNA clone. A 64 bp intron and a 145 bp intron interrupt the sequence coding for the secreted pheromone. The three introns contain typical 5′ and 3′ splice junctions and a putative branch point site. The small introns have a low GC content. The large intron has a GC content similar to that of the pheromone 4 gene exons. The amino acid sequence of pheromone 4, deduced from both the genomic DNA and the cDNA of pheromone 4, shows that the secreted pheromone consists of 85 amino acids. One of its amino acids is encoded by a UGA codon. Since it has been shown for pheromone 3 ofE. octocarinatusthat UGA is translated as cysteine, it is assumed that the UGA codon encodes cysteine in pheromone 4 as well. The 164 bp noncoding region upstream of the leader peptide is AT‐rich and contains an inverted repeat capable of forming a stem‐loop structure with a stem of 11 bp. The 151 bp noncoding region at the 3′ end of the chromosome contains a putative polyadenylation sequence and an inverted repeat. The macro‐nuclear molecule is flanked by telomeres and carries the pentanucleotide motif TTGAA, located at a distance of 17 nucleotides from the telomeres. This motif has been suggested to be involved in the formation of macronuclear chromosomes. © 1992 Wil

ISSN:0192-253X    

DOI:10.1002/dvg.1020130104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractTo investigate the role of cilia in mating interactions ofTetrahymena thermophila, ciliary membrane‐rich fractions were isolated from two wild‐type strains, a non‐discharge mucocyst mutant which possesses mating behavior similar to wild‐type, and a mating mutant which is able to costimulate cells of complementary mating type but cannot enter into pair formation. In each case, proteins from the ciliary membrane‐rich fractions of starved, mating‐competent (“initiated”) cells were compared with those from non‐starved, mating‐incompetent (“non‐initiated”) cells, by gel electro‐phoresis and lectin blotting. In stained gels, a 43 kDa polypeptide was reduced or absent in initiated cells but present in non‐initiated cells, in all strains. In silver‐stained gels, a 25 kDa polypeptide was present in all strains, both initiated and non‐initiated. In blots probed with Con A‐peroxidase, a 25 kDa glycoprotein was present in ciliary membrane fractions from non‐initiated cells and absent in membranes of initiated cells of the two wild‐type strains and the mucocyst mutant, but is present in initiated and non‐initiated cells of the mating mutant (several hypotheses are presented to explain these findings). In addition, ciliary proteins of the mating mutant included at least two unique Con A‐binding polypeptides. Our results support the idea that development of mating competence during starvation involves an extensive remodeling of ciliary membranes, and identify a 25 kDa glyco‐conjugate as having a potential role in control of pair fo

ISSN:0192-253X    

DOI:10.1002/dvg.1020130105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractTetrahymena thermophilahas a multiple mating type system. While a sexually mature cell usually expresses only one mating type, its germline (micronucleus) carries the genetic potential for 5 to 7 mating types. The set of allowed mating types is specified by thematlocus. The choice of which particular mating type is expressed by a cell reflects a somatically inherited, developmentally programmed differentiation of the somatic nucleus (macronucleus). In this work we report that thematlocus maps to the left arm of chromosome 2, as determined by nullisomic deletion mapping. We also report a distance of 29 cM between thematlocus and the ribosomal RNA gene, previously mapped to chromosome 2L. This represents another (rare) case of meiotic linkage inTetrahymena.© 1992 Wiley‐Liss, I

ISSN:0192-253X    

DOI:10.1002/dvg.1020130106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe life styles of ciliated protists are particularly suitable for experimental analyses of certain aspects of developmental and genetic biology. The progression from sexual immaturity tomaturity to senescence represents one of the most intriguing aspects of developmental programs. The extent to which progeny clones, their subclones, and testers used in the assay result in different lengths of immaturity has been investigated inEuplotes crassus.Six subclones from each of 12 progeny clones from a cross between stocks EC1 and EC2 were tested for maturity with stocks EC3, EC4, and EC5 on every transfer. Analysis of variance was used to partition thetotal variation in fissions to maturity into parts due to clones, subclones, and testers and the interactions between these levels. The error, interaction of subclones and testers, corresponds to a standard deviation of only 4.1 fissions, while the within clone within tester means range from 15.2 to 46.7 fissions; all levels except testers contribute significantly to the total variation. Most of the variability is attributable to clones (66%), the next most to error (16%), the next most to interaction of clones by testers (13%), and the least to subclones (5%). An a posteriori analysis examined whether the differences among clones were due to the cytoplasm of the clone ancestor (exconjugant), itsmat(mating‐type) locus genotype, or the mated pair it came from. None of these characteristics was able to interpret simply the large variability among clones. These results provide evidence that the transition from immaturity to maturity is quantitative and complex rather than a jump from one well‐defined state to another. © 1992 Wiley‐Lis

ISSN:0192-253X    

DOI:10.1002/dvg.1020130107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractA significant fraction of theTetrahymenaclones isolated from natural habitats self (mating occurs within a clone). Early attempts to study such clones failed because stable subclones were rarely, if ever, observed, and isolated pairs all died. Isozyme analysis revealed that these wild selfers were a diverse group; some were very similar toT. australis, a species with synclonal mating type determination and toT. elliotti, shown recently to have a karyonidal mating type system. One originally stable clone ofT. australisincluded some selfing clones after a few years in our laboratory. Other clones manifested unique zymograms.Subclones isolated from 18 selfer strains were heterogeneous. All subclones of several selfers mated massively at each transfer through 100 fissions. Selfing among subclones of other selfers was highly variable or not observed. Although 77% of the pairs isolated died, and 9% of the pair cultures selfed, 15 selfers yielded some viable nonselfing “immature” progeny. Additionalimmatureprogeny were obtained by isolating pairs from macronuclear retentionsynclones.Although some “immature” progeny eventually selfed, most remained stable. Giemsa staining revealed macronuclear anlagen in nearly all mating pairs and some anomalies. Crosses among the F1 progeny clones of theT. elliottiselfers yield viability data comparable to those from crosses amongnormalstrains. Perhaps perpetual selfing is a mechanism of getting rid of deleterious combinations of genes and uncovering better combinations in homozygous state by playing genetic roulette. © 1992 Wiley

ISSN:0192-253X    

DOI:10.1002/dvg.1020130108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractWe obtained a monoclonal antibody (MA‐1) specific for macronuclei of the ciliateParamecium caudotumand P.dubosqui.Immunoblotting showed that the antigen was a poly‐peptide of 50 kilodalton (kDa). During the process of nuclear differentiation inP. caudatum, the MA‐1 antigens appeared in the macronuclear anlagen immediately after four out of eight post zygotic nuclei differentiated morphologically into the macro‐nuclear anlagen. Afterwards, the antigens could be detected in the macronucleus through the cell cycle, and disappeared when the macronucleus began to degenerate in exconjugant cells. These results suggest that the antigens may play a role in the differentiation and function of the macronucleus. © 1992 Wiley

ISSN:0192-253X    

DOI:10.1002/dvg.1020130109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractA new recessive conjugation lethal mutation was found inTetrahymena thermophilawhich was namedmrafor macronuclear resorption arrest. Other events affected by themramutations are separation of pairs, DNA replication in the macronuclear anlagen, and resorption of one of the two micronuclei. In wild‐type crosses 50% of the pairs had separated by 12 hr after mixing two mating types and had completed resorption of the old macronucleus 1–2 hr later. In contrast mostmraconjugants did not separate even by 24 hr after mixing and the old relic (condensed) macronucleus was seen in over 90% of them.After addition of 10mM calcium to the conjugation medium, themraconjugants did separate but they still failed to complete resorption of the old macronucleus and to replicate macronuclear anlagen DNA in the exconjugants. The calcium induced separation of themraconjugants occurred later than the separation of control pairs.During normal conjugation cell separation occurs before the first expression of known macronuclear genes and prior to processing of the macro‐nuclear DNA. Therefore, themraphenotype infers that separation of conjugants requires a signal which is produced by the macronuclear anlagen at an unusually early time. © 1992 Wiley‐L

ISSN:0192-253X    

DOI:10.1002/dvg.1020130110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractIn the hypotrichous ciliateOxytricha novathe cloned precursor gene from the micronuclear genome that encodes actin I is composed of highly disordered blocks of deoxynucle‐otide sequences. We present and illustrate in detail a recombination model that explains how the actin I gene may be unscrambled during macronuclear development after cell mating. The model was described in a previous publication (Greslinet al.: Proc Natl Acad Sci USA86:6264‐6268, 1989). Here we show the data, described in the earlier publication, that support the model. The data show that scrambling is not an artifact of cloning. They rule against the presence of an unscrambled copy of the actin I gene in the micronucleus, which means that unscrambling must be a part of macro‐nuclear development. Finally, the data prove that the actin I gene inO. trifallaxis scrambled in a pattern that resembles the pattern inO. nova.© 1992 Wiley‐L

ISSN:0192-253X    

DOI:10.1002/dvg.1020130111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY