DOCSLIB.ORG

MATING TYPE MUTATIONS in VARIETY 1 of PARARIECIULI AURELIA, and THEIR BEARING UPON the PROBLEM of MATING TYPE Deterptiinationl HENRY M

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
MATING TYPE MUTATIONS in VARIETY 1 of PARARIECIULI AURELIA, and THEIR BEARING UPON the PROBLEM of MATING TYPE Deterptiinationl HENRY M MATING TYPE MUTATIONS IN VARIETY 1 OF PARARIECIULI AURELIA, AND THEIR BEARING UPON THE PROBLEM OF MATING TYPE DETERPtIINATIONl HENRY M. BUTZEL, JR.* Department oj Zoology, Indiana University, Bloonzinglon, Indiana Received August 16, 1954 HE discovery of complementary mating types in Paramecium aurelia (SONNE- T~~~~1937), together with the later finding that the complementary mating types are hereditarily diverse but genically identical (SONNEBORN1942), raised a fundamental problem in the genetics of this organism: how do genically identical cells become hereditarily diverse mating types? The general rule of genic identity is shown by all but two of the nearly 200 stocks in SONNEBORN'Scollection; an entirely homozygous clone can give rise to both mat- ing types following autogamy. Stocks of this sort are called two-type stocks. The two exceptions show that the genic constitution can play a role in control of mating type. Here we deal with one of these two exceptions, stock P of variety 1, which is pure for mating type I and never yields the complementary type 11. Stocks of this sort are called one-type stocks. By suitable crosses SONNEBORN(1939) has shown that the difference between the one-type condition and the more frequent two-type condition is due to genes at a single locus. A dominant allele, +mtr, determines the two-type condition, and its re- cessive allele, mtI, the one-type condition. Stocks homozygous for mtI are therefore genetically incapable of producing mating type 11. This paper deals with the analysis of two mutant stocks incapable of producing mating type 11, and with the analysis of a genetic character responsible for an al- tered frequency of the two alternative mating types in stocks genetically capable of producing either mating type I or 11. As will be made clear, the two mutant stocks pure for mating type I contain genes apparently similar to that in stock P, while the genetic character responsible for the altered frequency of mating type deter- mination is probably not allelic to the mtr locus. Following the presentation of the data, an hypothesis dealing with mating type determination and development will be presented. METHODS AND MATERIALS The methods used throughout this work, with one exception to be described, fol- low those set forth by SONNEBORN(1950). 1 Contribution No. 556 from the Department of Zoology, Indiana University. Submitted to the Faculty of the Graduate School in partial fulfillment of the requirements for the Degree Doctor of Philosophy in the Department of Zoology, Indiana University. This investigation was supported in part by grants to DR. T. M. SONNEBORNfrom the Rockefeller Foundation and from the American Cancer Society upon recommendation of the Committee on Growth of the National Research Coun- cil. * The author was a National Science Foundation Predoctoral Fellow during 1952-53, and a Cra- mer Fellow during 1948-49. Present address: Department of Biology, Union College, Schenectady 8, New York. 322 HENRY M. BUTZEL, JR. Stocks P and 90 of variety 1 served as the normal stocks in these experiments. Stock P, as has already been mentioned, is pure for mtr, while stock 90 of this variety is a normal two-type stock, giving rise to clones of mating type I and I1 following nuclear reorganization. Both mutant stocks arose from stock 90. One stock, now designated as stock d-11, was obtained by NANNEY(personal communication) by exposing a single line of descent to heat shock during three successive nuclear reorganizations. At each reor- ganization macronuclear regeneration (SONNEBORN1940) occurred. Following the third reorganization a single isolated individual, the first to be studied in this line of descent, gave rise to culture d-11 which has remained pure for mating type I for three years. The second mutant stock, designated as stock d-40, arose as follows: a single animal from a type I1 clone was irradiated under a General Electric Germicidal Lamp (dosage equalled 1100 in approximately 0.10 mm. depth of stand- ard bacterized culture fluid contained in a pyrex depression slide. Irradiation was carried out in a dark room with a yellow bulb furnishing the only source of extrane- ous light. Since the experiments were designed to obtain mutants no attempt was made to avoid the possible further actions of various components in the medium by reisolating the irradiated cell into fresh medium. Following irradiation the slide depression was merely filled with 1 cc of standard bacterized culture fluid and then placed in a metal moist chamber and kept in the dark for 24 hours at 27°C. The single irradiated animal was allowed to give rise by fission to a small culture. A single animal isolated from this culture gave rise to another small culture in which conjugating pairs were observed and isolated. (This suggests that autogamy occurred during the development of this subculture and so yielded both mating types.) One product of the first fission of one exconjugant gave rise to stock d-40 which has remained pure for mating type I for over two years. RESULTS Evidence for the dependence of the one-type condition of stocks d-11 and d-40 upon a single recessive gene If the one-type condition in the two mutant stocks depends upon a single reces- sive gene in each, crosses of each stock to a two-type stock should yield the follow- ing: 1) the F1 should be capable of producing both mating types I and 11; 2) the backcross to the mutants should result in a 1:l ratio of one-type to two-type ex- conjugant pairs; 3) the backcross to the two-type parent should give no segregation; 4) the Fz by autogamy should segregate in a 1: 1 ratio of one-type to two-type clones; and 5) the FZ obtained by selfing the FI should result in a 3:l ratio of two-type to one-type exconjugant pairs. The data confirm the hypothesis that both the mutant stocks contain a single recessive gene restricting them to mating type I. Crosses of both mutant stocks to stock 90 resulted in an F1 showing the two-type condition. The backcross of Fl clones from the cross of stock d-11 X stock 90 to the mutant parent yielded 97 one- type and 85 two-type exconjugant pairs. Backcrossing the same F1 to stock 90 re- MATING TYPES IN PARAMECIUM 323 sulted in no segregation in the 30 pairs observed. Similarly, a backcross of stock d-40 X stock 90 F1 clones to stock d-40 yielded 60 one-type and 65 two-type ex- conjugant pairs, and no segregation was obtained in 30 backcross pairs with stock 90 used as one parent. In addition, Fz clones obtained by autogamy in the FI of the d-40 X 90 cross yielded a total of 132 one-type clones, and 140 two-type clones (183 clones failed to survive autogamy). Selfing in one F1 clone resulted in 92 two-type and 29 one-type exconjugant pairs. All these data are reasonably close to the expected ratios, and indicate that stocks d-11 and d-40 contain a single recessive gene restricting each of them to the one-type condition. Evidence for the allelism of the genes controlling the one-type trait in stocks P, d-11, and d-40 In order to determine whether the genetic basis of the one-type condition in the two mutant stocks was dependent upon the presence in each stock of an allele of mfz, stocks d-11 and d-40 were each crossed to stock 90 and an Fl obtained. The Fl from each was then crossed to stock P. If the mutant stocks contain an allele of the mtz gene a 1: 1 segregation of one-type to two-type progeny should be found, since this would be similar to a backcross. Such was the case for both stocks; the F1 of the d-11 X 90 cross when crossed to stock P yielded an FZof 35 one-type and 47 two- type exconjugant pairs, and the F1 of the d-40 X 90 cross yielded an FZconsisting of 74 one-type and 82 two-type exconjugant pairs after being crossed to stock P. At the same time the crosses to stock P were carried out, control backcrosses were made to prove the Fl was heterozygous at the mt locus (data given above). Again the segregation data indicate a 1:l ratio is found, and give evidence that both stocks d-11 and d-40 contain an allele of the mtz gene previously known in stock P. Evidence for the presence of a dominant modifying factor, InI, in stock d-40 Before discussing the further results of crosses of stock d-40 to stock 90, the usual method of scoring for mating type ratios must be described. First, however, the meaning of the term caryonide needs to be recalled. A caryonide is a group of cells containing macronuclei descended from the same ancestral macronucleus. Normally this means descent from one product of the first fission after autogamy or conjuga- tion, for products of the fertilization nucleus give rise independently to two new macronuclei that separate into different cells at the first fission. SONNEBORN(1937) and KIMBALL(1937) have shown that the members of a caryonide are nearly always identical in mating type, but that the two caryonides from a single fertilized cell are often different in mating type. Hence the usual method of scoring is to grow and test all caryonides separately. The modiiication of this procedure used in the present study, in order to examine larger numbers, was to forego isolation of caryonides, growing the two caryonides from each fertilized cell in one culture, a clone.
Load more

Recommended publications
  • Sexual Selection in Fungi
    Sexual selection in Fungi Bart P. S. Nieuwenhuis Thesis committee Thesis supervisor Prof. dr. R.F. Hoekstra Emeritus professor of Genetics (Population and Quantitative Genetics) Wageningen University Thesis co-supervisor Dr. D.K. Aanen Assistant professor at the Laboratory of Genetics Wageningen University Other members Prof. dr. J. B. Anderson, University of Toronto, Toronto, Canada Prof. dr. W. de Boer, NIOO, Wageningen and Wageningen University Prof. dr. P.G.L. Klinkhamer, Leiden University, Leiden Prof. dr. H.A.B. Wösten, Utrecht Univesity, Utrecht This research was conducted under the auspices of the C.T. de Wit Graduate School for Production Ecology and Resource Conservation (PE&RC) Sexual selection in Fungi Bart P. S. Nieuwenhuis Thesis submittted in fulfilment of the requirements for the degree of doctor at Wageningen University by the authority of the Rector Magnificus Prof. dr. M.J. Kropff, in the presence of the Thesis Committee appointed by the Academic Board to be defended in public on Friday 21 September 2012 at 4 p.m. in the Aula. Bart P. S. Nieuwenhuis Sexual selection in Fungi Thesis, Wageningen University, Wageningen, NL (2012) With references, with summaries in Dutch and English ISBN 978-94-6173-358-0 Contents Chapter 1 7 General introduction Chapter 2 17 Why mating types are not sexes Chapter 3 31 On the asymmetry of mating in the mushroom fungus Schizophyllum commune Chapter 4 49 Sexual selection in mushroom-forming basidiomycetes Chapter 5 59 Fungal fidelity: Nuclear divorce from a dikaryon by mating or monokaryon regeneration Chapter 6 69 Fungal nuclear arms race: experimental evolution for increased masculinity in a mushroom Chapter 7 89 Sexual selection in the fungal kingdom Chapter 8 109 Discussion: male and female fitness Bibliography 121 Summary 133 Dutch summary 137 Dankwoord 147 Curriculum vitea 153 Education statement 155 6 Chapter 1 General introduction Bart P.
    [Show full text]
  • Self-Fertility and Uni-Directional Mating-Type Switching in Ceratocystis Coerulescens, a Filamentous Ascomycete
    Curr Genet (1997) 32: 52–59 © Springer-Verlag 1997 ORIGINAL PAPER T. C. Harrington · D. L. McNew Self-fertility and uni-directional mating-type switching in Ceratocystis coerulescens, a filamentous ascomycete Received: 6 July 1996 / 25 March 1997 Abstract Individual perithecia from selfings of most some filamentous ascomycetes. Although a switch in the Ceratocystis species produce both self-fertile and self- expression of mating-type is seen in these fungi, it is not sterile progeny, apparently due to uni-directional mating- clear if a physical movement of mating-type genes is in- type switching. In C. coerulescens, male-only mutants of volved. It is also not clear if the expressed mating-types otherwise hermaphroditic and self-fertile strains were self- of the respective self-fertile and self-sterile progeny are sterile and were used in crossings to demonstrate that this homologs of the mating-type genes in other strictly heter- species has two mating-types. Only MAT-2 strains are othallic species of ascomycetes. capable of selfing, and half of the progeny from a MAT-2 Sclerotinia trifoliorum and Chromocrea spinulosa show selfing are MAT-1. Male-only, MAT-2 mutants are self- a 1:1 segregation of self-fertile and self-sterile progeny in sterile and cross only with MAT-1 strains. Similarly, self- perithecia from selfings or crosses (Mathieson 1952; Uhm fertile strains generally cross with only MAT-1 strains. and Fujii 1983a, b). In tetrad analyses of selfings or crosses, MAT-1 strains only cross with MAT-2 strains and never self. half of the ascospores in an ascus are large and give rise to It is hypothesized that the switch in mating-type during self-fertile colonies, and the other ascospores are small and selfing is associated with a deletion of the MAT-2 gene.
    [Show full text]
  • The Diversity of Plant Sex Chromosomes Highlighted Through Advances in Genome Sequencing
    G C A T T A C G G C A T genes Review The Diversity of Plant Sex Chromosomes Highlighted through Advances in Genome Sequencing Sarah Carey 1,2 , Qingyi Yu 3,* and Alex Harkess 1,2,* 1 Department of Crop, Soil, and Environmental Sciences, Auburn University, Auburn, AL 36849, USA; [email protected] 2 HudsonAlpha Institute for Biotechnology, Huntsville, AL 35806, USA 3 Texas A&M AgriLife Research, Texas A&M University System, Dallas, TX 75252, USA * Correspondence: [email protected] (Q.Y.); [email protected] (A.H.) Abstract: For centuries, scientists have been intrigued by the origin of dioecy in plants, characterizing sex-specific development, uncovering cytological differences between the sexes, and developing theoretical models. Through the invention and continued improvements in genomic technologies, we have truly begun to unlock the genetic basis of dioecy in many species. Here we broadly review the advances in research on dioecy and sex chromosomes. We start by first discussing the early works that built the foundation for current studies and the advances in genome sequencing that have facilitated more-recent findings. We next discuss the analyses of sex chromosomes and sex-determination genes uncovered by genome sequencing. We synthesize these results to find some patterns are emerging, such as the role of duplications, the involvement of hormones in sex-determination, and support for the two-locus model for the origin of dioecy. Though across systems, there are also many novel insights into how sex chromosomes evolve, including different sex-determining genes and routes to suppressed recombination. We propose the future of research in plant sex chromosomes should involve interdisciplinary approaches, combining cutting-edge technologies with the classics Citation: Carey, S.; Yu, Q.; to unravel the patterns that can be found across the hundreds of independent origins.
    [Show full text]
  • The Genetics of Sex: Exploring Differences
    COMMENTARY: GENETICS OF SEX The Genetics of Sex: Exploring Differences Michelle N. Arbeitman,*,1 Artyom Kopp,† Mark L. Siegal,‡ and Mark Van Doren§ *Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida 32306, †Department of Evolution and Ecology, University of California, Davis, California 95616, ‡Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York 10003, and §Biology Department, Johns Hopkins University, Baltimore, Maryland 21218 In this commentary, Michelle Arbeitman et al., examine the previously existed. The fundamental genetic differences be- topic of the Genetics of Sex as explored in this month’s tween the sexes and how they arise continue to fascinate issues of GENETICS and G3: Genes|Genomes|Genetics.These biologists, and the results from genetic explorations of these inaugural articles are part of a joint Genetics of Sex col- topics are featured in an ongoing collection of articles published lection (ongoing) in the GSA journals. in GENETICS and G3: Genes|Genomes|Genetics. The inaugural articles address some of these topics. Two EX differences affect nearly every biological process. studies focus on the biology of reproduction: the transition These differences may be seen in obvious morpholog- S from predominantly sexual reproduction to asexuality in ical traits, such as deer antlers, beetle horns, and the sex- fungi (Solieri et al. 2014) and self-incompatibility in plants specific color patterns of birds and butterflies. Reproductive (Leducq et al. 2014). Two other articles examine differences behaviors may also be quite different between the sexes and in the evolution of sex chromosomes: Blackmon and Demuth include elaborate courtship displays, parental care of progeny, (2014) look at the evolutionary turnover of sex chromosomes and aggressive or territorial behaviors.
    [Show full text]
  • Using Caenorhabditis to Explore the Evolution of the Germ Line
    Chapter 14 Using Caenorhabditis to Explore the Evolution of the Germ Line Eric S. Haag and Qinwen Liu Abstract Germ cells share core attributes and homologous molecular components across animal phyla. Nevertheless, abrupt shifts in reproductive mode often occur that are mediated by the rapid evolution of germ cell properties. Studies of Caenorhabditis nematodes show how the otherwise conserved RNA-binding pro- teins (RBPs) that regulate germline development and differentiation can undergo surprisingly rapid functional evolution. This occurs even as the narrow biochemical tasks performed by the RBPs remain constant. The biological roles of germline RBPs are thus highly context-dependent, and the inference of archetypal roles from isolated models in different phyla may therefore be premature. Keywords RNA-binding protein • Translation • PUF proteins • GLD-1 14.1 Comparative Biology of Germline Development 14.1.1 Evolutionary Overview In this chapter, we seek to put attributes of the C. elegans germ line covered by other authors in this volume in an evolutionary context. Two major themes run through it. First, C. elegans germ cells share many features with those of other animals and are thus a useful model system for inferring general principles. Second, we discuss how comparisons with other closely related nematodes offer an important window onto the role germ cells play in the evolution of important new reproductive adaptations. E. S. Haag (*) • Q. Liu Department of Biology , University of Maryland , Building 144 , College Park , MD 20742 , USA e-mail: [email protected] T. Schedl (ed.), Germ Cell Development in C. elegans, Advances in Experimental 405 Medicine and Biology 757, DOI 10.1007/978-1-4614-4015-4_14, © Springer Science+Business Media New York 2013 406 E.S.
    [Show full text]
  • On Sexual Selection
    On Sexual Selection Larry Bull Department of Computer Science & Creative Technologies University of the West of England, Bristol BS16 1QY, UK [email protected] Abstract Sexual selection is a fundamental aspect of evolution for all eukaryotic organisms with mating types. This paper suggests intersexual selection is best viewed as a mechanism to compensate for the unavoidable dynamics of coevolution between sexes that emerge with isogamy. Using the NK model of fitness landscapes, the conditions under which allosomes emerge are first explored. This extends previous work on the evolution of sex where the fitness landscape smoothing of a rudimentary form of the Baldwin effect is suggested as the underlying cause. The NKCS model of coevolution is then used to show how varying fitness landscape size, ruggedness, and connectedness can vary the conditions under which a very simple sexual selection mechanism proves beneficial. This is found to be the case whether one or both sexes exploit sexual selection. Keywords: Baldwin effect, diploid, eukaryote, isogamy, NK model, NKCS model Introduction Sexual selection is the component of natural selection usually referring to both opposite-sex mate choice and same-sex competition for mating opportunities. In the former case, males and females can be seen to be coevolving within their species. At an abstract level coevolution is typically considered as the coupling together of the fitness landscapes of the interacting species. Hence the adaptive moves made by one species in its fitness landscape causes deformations in the fitness landscapes of its coupled partner(s). That sexes coevolve and that this need not be to their mutual benefit has been used to explain phenomena such as female-damaging genitalia and sperm selection (eg, [18]).
    [Show full text]
  • Evidence for Equal Size Cell Divisions During Gametogenesis in a Marine Green Alga Monostroma Angicava
    www.nature.com/scientificreports OPEN Evidence for equal size cell divisions during gametogenesis in a marine green alga Monostroma Received: 18 March 2015 Accepted: 03 August 2015 angicava Published: 03 September 2015 Tatsuya Togashi1, Yusuke Horinouchi1, Hironobu Sasaki2 & Jin Yoshimura1,3,4 In cell divisions, relative size of daughter cells should play fundamental roles in gametogenesis and embryogenesis. Differences in gamete size between the two mating types underlie sexual selection. Size of daughter cells is a key factor to regulate cell divisions during cleavage. In cleavage, the form of cell divisions (equal/unequal in size) determines the developmental fate of each blastomere. However, strict validation of the form of cell divisions is rarely demonstrated. We cannot distinguish between equal and unequal cell divisions by analysing only the mean size of daughter cells, because their means can be the same. In contrast, the dispersion of daughter cell size depends on the forms of cell divisions. Based on this, we show that gametogenesis in the marine green alga, Monostroma angicava, exhibits equal size cell divisions. The variance and the mean of gamete size (volume) of each mating type measured agree closely with the prediction from synchronized equal size cell divisions. Gamete size actually takes only discrete values here. This is a key theoretical assumption made to explain the diversified evolution of isogamy and anisogamy in marine green algae. Our results suggest that germ cells adopt equal size cell divisions during gametogenesis. Differences in sperm and egg size are evident in many animals and land plants1. However, variable mat- ing systems are also found in green algal taxa: 1) isogamy, where gamete sizes are identical between the two mating types, 2) slight anisogamy, where the sizes of male and female gametes are slightly different, and 3) marked anisogamy, where their sizes are markedly different2,3.
    [Show full text]
  • The Evolution of Mating Type Switching
    ORIGINAL ARTICLE doi:10.1111/evo.12959 The evolution of mating type switching Zena Hadjivasiliou,1,2,3 Andrew Pomiankowski,1,2 and Bram Kuijper1,2 1CoMPLEX, Centre for Mathematics and Physics in the Life sciences and Experimental biology, University College London, Gower Street, London, United Kingdom 2Department of Genetics, Evolution and Environment, University College London, Gower Street, London, United Kingdom 3E-mail: [email protected] Received January 27, 2016 Accepted May 9, 2016 Predictions about the evolution of sex determination mechanisms have mainly focused on animals and plants, whereas unicellular eukaryotes such as fungi and ciliates have received little attention. Many taxa within the latter groups can stochastically switch their mating type identity during vegetative growth. Here, we investigate the hypothesis that mating type switching overcomes distortions in the distribution of mating types due to drift during asexual growth. Using a computational model, we show that smaller population size, longer vegetative periods and more mating types lead to greater distortions in the distribution of mating types. However, the impact of these parameters on optimal switching rates is not straightforward. We find that longer vegetative periods cause reductions and considerable fluctuations in the switching rate over time. Smaller population size increases the strength of selection for switching but has little impact on the switching rate itself. The number of mating types decreases switching rates when gametes can freely sample each other, but increases switching rates when there is selection for speedy mating. We discuss our results in light of empirical work and propose new experiments that could further our understanding of sexuality in isogamous eukaryotes.
    [Show full text]
  • Sexual Development in the Industrial Workhorse Trichoderma Reesei
    Sexual development in the industrial workhorse Trichoderma reesei Verena Seidl, Christian Seibel, Christian P. Kubicek, and Monika Schmoll1 Research Area Gene Technology and Applied Biochemistry, Institute of Chemical Engineering, Vienna University of Technology, Getreidemarkt 9/166–5, 1060 Vienna, Austria Edited by Arnold L. Demain, Drew University, Madison, NJ, and approved June 30, 2009 (received for review May 5, 2009) Filamentous fungi are indispensable biotechnological tools for the ings, as have been established for the model fungi Aspergillus production of organic chemicals, enzymes, and antibiotics. Most of nidulans or Neurospora crassa, are unavailable. the strains used for industrial applications have been—and still The genus Trichoderma/Hypocrea contains several hundred are—screened and improved by classical mutagenesis. Sexual species, some of which only occur as teleomorphs, i.e., in their crossing approaches would yield considerable advantages for sexual form, whereas others have so far only been observed as research and industrial strain improvement, but interestingly, asexually propagating anamorphs (5). In the last decade, the use industrially applied filamentous fungal species have so far been of DNA-based molecular phylogenetic approaches has suc- considered to be largely asexual. This is also true for the ascomy- ceeded in the identification of anamorph-teleomorph relation- cete Trichoderma reesei (anamorph of Hypocrea jecorina), which is ships for several fungi (including Trichoderma spp.) that were so used for production of cellulolytic and hemicellulolytic enzymes. In far believed to occur only in an asexual form. However, only few this study, we report that T. reesei QM6a has a MAT1-2 mating type of these could be mated under laboratory conditions (6).
    [Show full text]
  • Are All Sex Chromosomes Created Equal?
    Review Are all sex chromosomes created equal? Doris Bachtrog1, Mark Kirkpatrick2, Judith E. Mank3, Stuart F. McDaniel4, J. Chris Pires5, William R. Rice6 and Nicole Valenzuela7* 1 Department of Integrative Biology, University of California, Berkeley, Berkeley, CA94720, USA 2 Section of Integrative Biology, University of Texas, Austin TX 78712, USA 3 Department of Zoology, Edward Grey Institute, University of Oxford, Oxford OX1 3PS, England 4 Department of Biology, University of Florida, Gainesville, FL 32611 USA 5 Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA 6 Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106, USA 7 Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames IA 50011, USA Three principal types of chromosomal sex determination Glossary are found in nature: male heterogamety (XY systems, as in mammals), female heterogamety (ZW systems, as in Androdioecy: a breeding system with both males and hermaphrodites. Dioecy: a breeding system with separate sexes (males and females). birds), and haploid phase determination (UV systems, as Dosage compensation: hyper-transcription of the single Z or X chromosome in in some algae and bryophytes). Although these systems the heterogametic sex to balance the ratio of sex-linked to autosomal gene share many common features, there are important bio- products. Environmental sex determination (ESD): sex determination caused by an logical differences between them that have broad evo- environmental cue such as temperature. This contrasts with genetic sex lutionary and genomic implications. Here we combine determination (GSD) where sex determination is caused by the genotype of the theoretical predictions with empirical observations to individual.
    [Show full text]
  • How to Determine Mating Type
    DDP FINAL 25 Oct 2005 How to determine mating type. David Perkins Background Determining the mating type of segregants or newly acquired strains is a prerequisite for proceeding with genetic analysis. In heterothallic Neurospora species, crossing takes place only between strains of opposite mating type, while heterokaryons are normally formed only between strains of the same mating type. Crosses are required for building stocks, determining linkage, studying recombination, detecting and diagnosing chromosome rearrangements, and identifying the species of newly acquired isolates. Crosses are also required for detecting and studying meiotic mutants, Spore killer elements, and other variants that are expressed during the sexual phase. Crosses have been essential for discovering and analyzing repeat induced point mutation (RIP) and meiotic silencing of unpaired DNA (MSUD). The mating type of an unknown isolate can be determined by crossing it to a fertile strain of known mating type. The highly fertile aconidiate mutant fluffy (fl) is superior to wild type for determining mating type. When used as protoperithecial (female) parents, fluffy strains form perithecia quickly and abundantly, and the perithecia are more readily observed than in crosses by wild type, where they may be obscured by the abundant overlying macroconidia. See How to use fluffy testers for determining mating type and for other applications. If mat A and mat a are both available when cultures of a new mutation are sent to the Fungal Genetics Stock Center, they should both be deposited. Having them both available may expedite setting up crosses. The redundancy also provides insurance against loss of the mutation. Procedure Tests are conveniently made using the tester as female parent and spotting conidia or mycelial fragmetns from unknowns onto lawns of the appropriate testers.
    [Show full text]
  • Hedgehog Shows The
    HIGHLIGHTS GENE REGULATION Although it is known that fertilization protein synthesis, indicating that pre- triggers events that ultimately lead to exisiting factors in one or both the transcriptional activation of the gametes regulate the expression of Probing zygotic gene control zygotic genome, we know surprisingly these genes. As zygote maturation little about these events — a factor continues, zygotes clump together to that probably contributes to the low form large aggregates and mt−-derived success rates of current mammalian- choloroplasts are selectively degraded cloning efforts. So, to investigate the — zygotes germinate on return to a mechanisms that control zygotic gene nutrient-rich medium. transcription, Zhao et al. turned to The previous finding that GSP1 Chlamydomonas reinhardtii — a uni- is present only in mt+ gametes led cellular alga — in which early zygotic the authors to consider it as a candi- development is easier to study. Here date regulator of zygotic gene tran- they report that the gamete-specific, scription in Chlamydomonas. To test homeodomain protein GSP1 can acti- this, they expressed gsp1 in mt− cells, vate the transcription of some zygotic and found that although the vegeta- genes in the absence of gamete fusion. tive mt− transformants appeared Their findings show that both gametes normal, they formed zygote-like contribute proteins that are required aggregates on undergoing gameto- for zygote development. genesis — a behaviour not seen in Chlamydomonas’s quirky life cycle transformed mt+ cells. The trans- makes it amenable to studies of fertil- formed mt− gametes expressed six ization. Upon nutrient starvation, its out of seven zygote-specific genes — haploid vegetative cells of two mating the unexpressed gene, ezy1,is types — mt− and mt+ — undergo thought to be required for mt− gametogenesis.
    [Show full text]