DOCSLIB.ORG

Inferences from Fungi on the Evolution of Anisogamy and Mating Types

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Inferences from Fungi on the Evolution of Anisogamy and Mating Types Biol. Rev. (2010), pp. 000–000. 1 doi: 10.1111/j.1469-185X.2010.00153.x Having sex, yes, but with whom? Inferences from fungi on the evolution of anisogamy and mating types Sylvain Billiard1,∗,ManuelaLopez-Villavicencio´ 2, Benjamin Devier3,Michael E. Hood4,Cecile´ Fairhead5 and Tatiana Giraud3 1 Universit´e Lille Nord de France, USTL, GEPV, CNRS, FRE 3268, F-59650 Villeneuve d’Ascq, France 2 Origine, Structure, Evolution de la Biodiversit´e, UMR 7205 CNRS-MNHN, Mus´eum National d’Histoire Naturelle, CP39, 57 rue Cuvier, 75231 Paris Cedex 05, France 3 Ecologie, Syst´ematique et Evolution, Universit´e Paris-Sud, F-91405 Orsay cedex, France; CNRS F-91405 Orsay cedex, France 4 Department of Biology, McGuire Life Sciences Building, Amherst College, Amherst, MA 01002-5000, USA 5 Institut de G´en´etique et Microbiologie, Universit´e Paris-Sud, UMR CNRS 8621, F-91405 Orsay cedex, France (Received 3 November 2009; revised 15 July 2010; accepted 16 July 2010) ABSTRACT The advantage of sex has been among the most debated issues in biology. Surprisingly, the question of why sexual repro- duction generally requires the combination of distinct gamete classes, such as small and large gametes, or gametes with different mating types, has been much less investigated. Why do systems with alternative gamete classes (i.e. systems with either anisogamy or mating types or both) appear even though they restrict the probability of finding a compatible mating partner? Why does the number of gamete classes vary from zerotothousands,withmostoftenonlytwoclasses?Wereview here the hypotheses proposed to explain the origin, maintenance, number, and loss of gamete classes. We argue that fungi represent highly suitable models to help resolve issues related to the evolution of distinct gamete classes, because the num- ber of mating types vary from zero to thousands across taxa, anisogamy is present or not, and because there are frequent transitions between these conditions. We review the nature and number of gamete classes in fungi, and we attempt to draw inferences from these data on the evolutionary forces responsible for their appearance, loss or maintenance, and number. Key words: sexual reproduction, gametes, syngamy, mitochondrial inheritance, cytoplasmic genetic elements, gamete classes, mating types. CONTENTS I. Introduction ................................................................................................ 2 II. Models explaining the origin, number and loss of gamete classes ........................................... 3 (1) Origin of gamete classes ................................................................................ 3 (a) The ‘‘by-product’’ model ........................................................................... 3 (b) The ‘‘selfish element’’ model ........................................................................ 4 (c) The ‘‘inbreeding depression avoidance’’ model ..................................................... 4 (d) The ‘‘sex advantage enhancer’’ model .............................................................. 4 (e) The ‘‘ploidy’’ model ................................................................................ 4 (f ) The ‘‘organelle inheritance’’ model ................................................................. 4 (g) The ‘‘gamete size’’ model ........................................................................... 5 (h) The ‘‘anisogamy consequence’’ model .............................................................. 6 (2) The optimal number of gamete classes ................................................................. 6 * Address for correspondence: (E-mail: [email protected]). Biological Reviews (2010) 000–000 © 2010 The Authors. Biological Reviews © 2010 Cambridge Philosophical Society 2 Sylvain Billiard and others (a) The number of gamete classes depends on negative frequency-dependent selection and the effective size of the population ............................................................................... 6 (b) The number of gamete classes depends on their mechanism of origin .............................. 6 (c) The mating type number depends on the mating system ........................................... 6 (d) The mating type number depends on mating dynamics ............................................ 7 (e) The mating type number depends on genomic constraints ......................................... 7 (3) The loss or maintenance of gamete classes ............................................................. 7 (a) Gamete classes can be lost when population or ecological factors render universal compatibility advantageous ....................................................................................... 8 (b) Gamete classes can be maintained for the same reasons they appeared ............................. 8 III. Mating types, anisogamy and sex in fungi .................................................................. 8 (1) Anisogamy and mitochondrial inheritance in fungi .................................................... 8 (2) Mating types in fungi, homothallism and heterothallism ............................................... 9 IV. Origin, number and loss of gamete classes in fungi ......................................................... 10 (1) The origin and maintenance of gamete classes in fungi ................................................. 10 (a) The ‘‘organelle inheritance’’ model ................................................................. 14 (b) The ‘‘inbreeding depression avoidance’’ model ..................................................... 14 (c) The ‘‘sex advantage enhancer’’ model .............................................................. 14 (d)Othermodels ....................................................................................... 15 (e) An evolutionary scenario for the origin of gamete classes in fungi and in other taxa ................ 15 (2) The optimal number of gamete classes in fungi ........................................................ 16 (3) The loss and maintenance of gamete classes in fungi ................................................... 17 V. Conclusions ................................................................................................ 17 VI. Acknowledgements ......................................................................................... 18 VII. References .................................................................................................. 18 VIII. Supporting Information .................................................................................... 22 I. INTRODUCTION population evolve by natural selection? In the extreme, when there are two gamete classes, each gamete can only fuse with Sexual reproduction involves a variety of costs relative to one half of the potential gamete partners. How, then, can a asexual or clonal reproduction (e.g. energy, time, infection system with two gamete classes arise from a system with no risk, and the ‘‘cost of males’’ in anisogamous species), and restrictions? And why are there thousands of gamete classes many investigations have attempted to find evolutionary in some species while others have reverted to no size or benefits to sex that balance these costs (Otto, 2009). These mating type restrictions on syngamy? The most problematic investigations have mainly focused on the consequences of case, with the existence of two gamete classes, appears para- sex in terms of the genetic variation generated by recombi- doxically the most frequent among eukaryotes (male and female, or two mating types). Any new rare gamete class, natorial meiosis during the transition from the diploid to the being compatible with all other existing classes, should be haploid phase of the sexual life cycle. Syngamy, the counter- selected for, leading to an increase in the number of gamete part of meiosis that restores the diploid phase, has received classes. Both why gamete classes exist at all and what the much less attention, although the regulation of syngamy is forces are that act upon the number of classes need to be central to the evolution of sexual eukaryotes. Indeed, syn- understood from an evolutionary point of view. gamy is generally not random, occurring almost exclusively Broadly satisfying answers to the questions raised above through the combination of distinct and alternative gamete are still lacking, and groups such as fungi represent highly classes, such as small and large gametes (anisogamy, i.e. a suitable organisms to test various hypotheses that have been system regulating syngamy between different gamete classes put forward based upon theoretical grounds. Indeed, fungi that is dependent upon size) or gametes with different mating constitute a unique kingdom where all combinations of types (hereafter referring to a molecular mechanism of the gamete classes are represented, and with frequent transitions gamete allowing discrimination for syngamy, independent of between different numbers of mating types and/or gamete size dimorphism). We use the generic term ‘‘gamete classes’’ size dimorphism. Importantly, anisogamy is decoupled from to refer to forms of gametes that are intercompatible but that mating types in fungi, allowing separate consideration of cannot undergo syngamy within the same class, including the evolutionary forces acting on the two determinants of both anisogamy and mating types as properties that may gamete classes. Finally, data on the number of mating types, distinguish gamete classes (Fig. 1).
Load more

Recommended publications
  • Evolutionary Trajectories Explain the Diversified Evolution of Isogamy And
    Evolutionary trajectories explain the diversified evolution of isogamy and anisogamy in marine green algae Tatsuya Togashia,b,c,1, John L. Barteltc,d, Jin Yoshimuraa,e,f, Kei-ichi Tainakae, and Paul Alan Coxc aMarine Biosystems Research Center, Chiba University, Kamogawa 299-5502, Japan; bPrecursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan; cInstitute for Ethnomedicine, Jackson Hole, WY 83001; dEvolutionary Programming, San Clemente, CA 92673; eDepartment of Systems Engineering, Shizuoka University, Hamamatsu 432-8561, Japan; and fDepartment of Environmental and Forest Biology, State University of New York College of Environmental Science and Forestry, Syracuse, NY 13210 Edited by Geoff A. Parker, University of Liverpool, Liverpool, United Kingdom, and accepted by the Editorial Board July 12, 2012 (received for review March 1, 2012) The evolution of anisogamy (the production of gametes of dif- (11) suggested that the “gamete size model” (Parker, Baker, and ferent size) is the first step in the establishment of sexual dimorphism, Smith’s model) is the most applicable to fungi (11). However, and it is a fundamental phenomenon underlying sexual selection. none of these models successfully account for the evolution of It is believed that anisogamy originated from isogamy (production all known forms of isogamy and anisogamy in extant marine of gametes of equal size), which is considered by most theorists to green algae (12). be the ancestral condition. Although nearly all plant and animal Marine green algae are characterized by a variety of mating species are anisogamous, extant species of marine green algae systems linked to their habitats (Fig.
    [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]
  • Heterothallism and Potential Hybridization Events Inferred For
    Du et al. IMA Fungus (2020) 11:4 https://doi.org/10.1186/s43008-020-0027-1 IMA Fungus RESEARCH Open Access Heterothallism and potential hybridization events inferred for twenty-two yellow morel species Xi-Hui Du1* , Dongmei Wu2, Heng Kang3*, Hanchen Wang1, Nan Xu1, Tingting Li1 and Keliang Chen1 Abstract Mating-type genes are central to sexual reproduction in ascomycete fungi and result in the establishment of reproductive barriers. Together with hybridization, they both play important roles in the evolution of fungi. Recently, potential hybridization events and MAT genes were separately found in the Elata Clade of Morchella. Herein, we characterized the MAT1–1-1 and MAT1–2-1 genes of twenty-two species in the Esculenta Clade, another main group in the genus Morchella, and proved heterothallism to be the predominant mating strategy among the twenty-two species tested. Ascospores of these species were multi-nuclear and had many mitochondrial nucleoids. The number of ascospore nuclei might be positively related with the species distribution range. Phylogenetic analyses of MAT1–1-1, MAT1–2-1, intergenic spacer (IGS), and partial histone acetyltransferase ELP3 (F1) were performed and compared with the species phylogeny framework derived from the ribosomal internal transcribed spacer region (ITS) and translation elongation factor 1-alpha (EF1-a) to evaluate their species delimitation ability and investigate potential hybridization events. Conflicting topologies among these genes genealogies and the species phylogeny were revealed and hybridization events were detected between several species. Different evolutionary patterns were suggested for MAT genes between the Esculenta and the Elata Clades. Complex evolutionary trajectories of MAT1–1-1, MAT1–2-1, F1 andIGSintheEsculentaCladewerehighlighted.Thesefindings contribute to a better understanding of the importance of hybridization and gene transfer in Morchella andespeciallyfortheappearanceofreproductivemodesduring its evolutionary process.
    [Show full text]
  • Plant Kingdom Dpp. No.-03
    BIOLOGY Daily Practice Problems MEDICAL ENTRANCE - 2020 CLASS : XI TOPIC : PLANT KINGDOM DPP. NO.-03 SECTION - A Q.1 Identify A, B, C, D & E in given diagram. Answer : A. ________ A B. ________ C. ________ D. ________ B E. ________ C D E Q.2 Identify A, B & C in given diagram. Answer : A A. ________ B. ________ C. ________ B C Q.3 Identify A, B & C in given diagram. Answer : A. ________ B. ________ C. ________ A B C Q.4 (i) Identify A & B. (ii) Which stage show by part (1) & (2) Answer : A A. ________ B B. ________ (1) (2) Q.5 (i) Identify A & B in given diagram. (ii) What is syngamy. A Answer : A. ________ B. ________ (1) B (2) Q.6 Identify A, B & C in given diagram. Answer : B A. ________ B. ________ A C. ________ SECTION - B Q.7 The sporophytes bear sporangia that are subtended by leaf-like appendages called ________. Q.8 In majority of the pteridophytes all the spores are of similar kinds; such plants are called ________. Q.9 The cones bearing megasporophylls with ovules or ________ are called macrosporangiate or ________. Q.10 The nucellus is protected by envelopes and the composite structure is called an ________. Q.11 Unlike the gymnosperms where the ovules are naked, in the angiosperms or flowering plants, the pollen grains and ovules are developed in specialised structures called ________. Q.12 Within ovules are present highly reduced female gametophytes termed ________. Q.13 The dominant, photosynthetic phase in such plants is the free-living gametophyte.
    [Show full text]
  • Discovery of a Sexual Cycle in Aspergillus Lentulus, a Close Relative of A
    Discovery of a Sexual Cycle in Aspergillus lentulus, a Close Relative of A. fumigatus Sameira S. Swilaiman,a Céline M. O’Gorman,a S. Arunmozhi Balajee,b Paul S. Dyera School of Biology, University of Nottingham, University Park, Nottingham, United Kingdoma; Center for Global Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USAb Aspergillus lentulus was described in 2005 as a new species within the A. fumigatus sensu lato complex. It is an opportunistic human pathogen causing invasive aspergillosis with high mortality rates, and it has been isolated from clinical and environmen- tal sources. The species is morphologically nearly identical to A. fumigatus sensu stricto, and this similarity has resulted in their frequent misidentification. Comparative studies show that A. lentulus has some distinguishing growth features and decreased in vitro susceptibility to several antifungal agents, including amphotericin B and caspofungin. Similar to the once-presumed-asex- ual A. fumigatus, it has only been known to reproduce mitotically. However, we now show that A. lentulus has a heterothallic sexual breeding system. A PCR-based mating-type diagnostic detected isolates of either the MAT1-1 or MAT1-2 genotype, and examination of 26 worldwide clinical and environmental isolates revealed similar ratios of the two mating types (38% versus 62%, respectively). MAT1-1 and MAT1-2 idiomorph regions were analyzed, revealing the presence of characteristic alpha and high-mobility-group (HMG) domain genes, together with other more unusual features such as a MAT1-2-4 gene. We then dem- onstrated that A. lentulus possesses a functional sexual cycle with mature cleistothecia, containing heat-resistant ascospores, being produced after 3 weeks of incubation.
    [Show full text]
  • The Rate of Facultative Sex Governs the Number of Expected Mating Types in Isogamous Species
    ARTICLES https://doi.org/10.1038/s41559-018-0580-9 The rate of facultative sex governs the number of expected mating types in isogamous species George W. A. Constable 1* and Hanna Kokko2 It is unclear why sexually reproducing isogamous species frequently contain just two self-incompatible mating types. Deterministic theory suggests that since rare novel mating types experience a selective advantage (by virtue of their many potential partners), the number of mating types should consistently grow. However, in nature, species with thousands of mat- ing types are exceedingly rare. Several competing theories for the predominance of species with two mating types exist, yet they lack an explanation for how many are possible and in which species to expect high numbers. Here, we present a theoretical null model that explains the distribution of mating type numbers using just three biological parameters: mutation rate, popu- lation size and the rate of sex. If the number of mating types results from a mutation–extinction balance, the rate of sexual reproduction plays a crucial role. If sex is facultative and rare (a very common combination in isogamous species), mating type diversity will remain low. In this rare sex regime, small fitness differences between the mating types lead to more frequent extinctions, further lowering mating type diversity. We also show that the empirical literature supports the role of drift and facultativeness of sex as a determinant of mating type dynamics. n most sexually reproducing species, gametes do not fuse indis- Our aim is to explain the preponderance of species with very criminately: syngamy only occurs between gametes of complemen- few mating types, as well as the existence of species with many tary mating types.
    [Show full text]
  • Topic: Heterothallism in Fungi
    M.SC SEMESTER I : E CONTENT FOR MBOTCC-I: Phycology, Mycology and Bryology ,Unit 3 continued Faculty : Dr Tanuja, University Department of Botany, Patliputra University Topic: Heterothallism in fungi Ehrenbergh (1829), for the first time studied zygospores in the order Mucorales. The American mycologist Blakeslee (1904), reported that in the several genera of the order Mucorales, the zygospores are not formed at all. The term Heterothallism was first by A.F. Blakeslee in 1904 when he observed that zygospores could develop in some spp. only when two mycelia of different strains were allowed to come in contact with each other. According to Blakeslee (1904) Heterothallic condition is “essentially similar to that in dioecious plants and animals and although in this case the two complimentary individuals which are needed for sexual reproduction are in general not so conspicuously differentiated morphologically as in higher forms, such a morphological difference is often distinctly visible.” He also supported his view with facts and reasons, and also investigated that in the same order two types of species are found which may be named as homothallic and heterothallic species. When the two hyphae of the same mycelium produced by a single spore fuse with each other and a zygospore is developed, the species is said to be homothallic, e.g., Mucor hiemalis. Mucor mucedo and Mucor stolonifer are the typical heterothallic species. In heterothallic species the fusion can take place only among the different strained hyphae, which develop on different mycelia of different (+ and -) strains. In these species the zygospores cannot be produced by the fusion of two hyphae of the same strain.
    [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]
  • New Species and Changes in Fungal Taxonomy and Nomenclature
    Journal of Fungi Review From the Clinical Mycology Laboratory: New Species and Changes in Fungal Taxonomy and Nomenclature Nathan P. Wiederhold * and Connie F. C. Gibas Fungus Testing Laboratory, Department of Pathology and Laboratory Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA; [email protected] * Correspondence: [email protected] Received: 29 October 2018; Accepted: 13 December 2018; Published: 16 December 2018 Abstract: Fungal taxonomy is the branch of mycology by which we classify and group fungi based on similarities or differences. Historically, this was done by morphologic characteristics and other phenotypic traits. However, with the advent of the molecular age in mycology, phylogenetic analysis based on DNA sequences has replaced these classic means for grouping related species. This, along with the abandonment of the dual nomenclature system, has led to a marked increase in the number of new species and reclassification of known species. Although these evaluations and changes are necessary to move the field forward, there is concern among medical mycologists that the rapidity by which fungal nomenclature is changing could cause confusion in the clinical literature. Thus, there is a proposal to allow medical mycologists to adopt changes in taxonomy and nomenclature at a slower pace. In this review, changes in the taxonomy and nomenclature of medically relevant fungi will be discussed along with the impact this may have on clinicians and patient care. Specific examples of changes and current controversies will also be given. Keywords: taxonomy; fungal nomenclature; phylogenetics; species complex 1. Introduction Kingdom Fungi is a large and diverse group of organisms for which our knowledge is rapidly expanding.
    [Show full text]
  • Evolution of the Two Sexes Under Internal Fertilization and Alternative Evolutionary Pathways
    vol. 193, no. 5 the american naturalist may 2019 Evolution of the Two Sexes under Internal Fertilization and Alternative Evolutionary Pathways Jussi Lehtonen1,* and Geoff A. Parker2 1. School of Life and Environmental Sciences, Faculty of Science, University of Sydney, Sydney, 2006 New South Wales, Australia; and Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, 2052 New South Wales, Australia; 2. Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, United Kingdom Submitted September 8, 2018; Accepted November 30, 2018; Electronically published March 18, 2019 Online enhancements: supplemental material. abstract: ogy. It generates the two sexes, males and females, and sexual Transition from isogamy to anisogamy, hence males and fl females, leads to sexual selection, sexual conflict, sexual dimorphism, selection and sexual con ict develop from it (Darwin 1871; and sex roles. Gamete dynamics theory links biophysics of gamete Bateman 1948; Parker et al. 1972; Togashi and Cox 2011; limitation, gamete competition, and resource requirements for zygote Parker 2014; Lehtonen et al. 2016; Hanschen et al. 2018). survival and assumes broadcast spawning. It makes testable predic- The volvocine green algae are classically the group used to tions, but most comparative tests use volvocine algae, which feature study both the evolution of multicellularity (e.g., Kirk 2005; internal fertilization. We broaden this theory by comparing broadcast- Herron and Michod 2008) and transitions from isogamy to spawning predictions with two plausible internal-fertilization scenarios: gamete casting/brooding (one mating type retains gametes internally, anisogamy and oogamy (e.g., Knowlton 1974; Bell 1982; No- the other broadcasts them) and packet casting/brooding (one type re- zaki 1996; da Silva 2018; da Silva and Drysdale 2018; Han- tains gametes internally, the other broadcasts packets containing gametes, schen et al.
    [Show full text]
  • Mating Type Specific Roles During the Sexual Cycle of Phycomyces
    MATING TYPE SPECIFIC ROLES DURING THE SEXUAL CYCLE OF PHYCOMYCES BLAKESLEEANUS A DISSERTATION IN Cell Biology and Biophysics And Molecular Biology and Biochemistry Presented to the Faculty of the University of Missouri-Kansas City in partial fulfillment of the requirements for the degree DOCTOR OF PHILOSOPHY by Viplendra Pratap Singh Shakya Kansas City, Missouri 2014 © 2014 VIPLENDRA PRATAP SINGH SHAKYA ALL RIGHTS RESERVED MATING TYPE SPECIFIC ROLES DURING THE SEXUAL CYCLE OF PHYCOMYCES BLAKESLEEANUS Viplendra Pratap Singh Shakya, Candidate for the Doctor of Philosophy Degree University of Missouri - Kansas City, 2014 ABSTRACT Phycomyces blakesleeanus is a filamentous fungus that belongs in the order Mucorales. It can propagate through both sexual and asexual reproduction. The asexual structures of Phycomyces called sporangiophores have served as a model for phototropism and many other sensory aspects. The MadA-MadB protein complex (homologs of WC proteins) is essential for phototropism. Light also inhibits sexual reproduction in P. blakesleeanus but the mechanism by which inhibition occurs has remained uncharacterized. In this study the role of the MadA-MadB complex was tested. Three genes that are required for pheromone biosynthesis or cell type determination in the sex locus are regulated by light, and require MadA and MadB. However, this regulation acts through only one of the two mating types, plus (+), by inhibiting the expression of the sexP gene that encodes an HMG-domain transcription factor that confers the (+) mating type properties. This suggests that the inhibitory effect of light on mating can be executed through the plus partner. These results provide an example of convergence in the mechanisms underlying signal transduction for mating in fungi.
    [Show full text]
  • Introduction to Algae
    Algae are autotrophic, diverse group of eukaryotic organisms, ranging from unicellular to multicellular forms. Marine Algae Aquatic (fresh water and marine) and terrestrial environment. They also occur in moist stones, soils, wood, on snow and on ice. Algae on wood Microscopic Colonial forms unicellular eg. Chlamydomonas eg. Volvox Filamentous forms Marine forms eg.Ulothrix, Spirogyra eg. Kelps Reproduction in Algae Vegetative Asexual Sexual 1. Vegetative reproduction is by fragmentation. 2. Asexual reproduction is by the production of different types of spores, the most common being the zoospores. 3. Sexual reproduction takes place through fusion of two gametes. Gametes may be isogamy or anisogamy or oogamy. I. Isogamy - Fusion of two morphologically identical gametes. e.g. Spirogyra II. Anisogamy - Fusion of two dissimilar gametes, i.e., one gamete is smaller than the other. e.g. some species of Chlamydomonas III. Oogamy - Fusion between one large, non-motile female gamete and a smaller, motile male gamete. e.g. Volvox, Fucus Source of food Used as biofertilizer Sewage treatment Alternative to chemical dyes and colouring agents Commercial uses Agar 1. At least a half of the total carbon dioxide fixation on earth is carried out by algae through photosynthesis. 2. Major component in aquatic food chain as primary producers. 3. Porphyra, Laminaria and Sargassum are used as food. 4. Algin (brown algae) and carrageen (red algae) are used as hydrocolloids, which is a fibrous structure holds water and used to transport seedling. 5. Agar is used as commercial products. 6. Gelidium, Graularia are used to grow microbes, make ice creams and jellies. 7.
    [Show full text]