The World Created by the Sex of Microbes: Exploring the Essence of Species Diversity

A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Molecular Microbiology and Immunology".

Deadline for manuscript submissions: closed (30 March 2024) | Viewed by 1248

Special Issue Editor


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Guest Editor
Department of Biological Sciences, Faculty of Science and Technology, Senshu University of Ishinomaki, Miyagi 986-8580, Japan
Interests: cell biology; mating type inheritance in paramecium; mating reaction; clonal development and aging

Special Issue Information

Dear Colleagues,

We will consider the entire topic of microbial sex in this Issue. The function of sex is to introduce genetic diversity in offspring genomes. The diversity that arises in offspring genomes can be thought of as an organism's multiple proposals to natural selection. Sex includes the mechanism of sex type determination, inheritance patterns from parents to offspring, the ability of gametes to discriminate between sexes, and the creation of genetic diversity in offspring populations. Protists are a group of single-celled organisms that are members of all seven major eukaryotic supergroups. The seven major supergroups have classification criteria based on cellular ultrastructural and genomic structural features, and protists share these criteria with multicellular organisms. On the other hand, protist diversity is evident in its morphology, genome organization, and biological function.

Species-specific phenomena such as gamete sex recognition and interspecific mating inhibition have been reported. It turns out that the sex-determining mechanisms established for each protist species represent a diverse world. We aim to deepen our understanding of the diversity of sexual functions in the evolutionary process of individual species and the conservation of sexual functions common to protists by adopting a bird's-eye view of these characteristics of protists.

Prof. Dr. Nobuyuki Haga
Guest Editor

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Keywords

  • mating type determination
  • mating-type inheritance
  • mating type substances and genes
  • mating pheromones
  • genomic DNA rearrangement
  • meiosis and gamete genesis

Published Papers (2 papers)

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Research

26 pages, 4848 KiB  
Article
Identification and Characterization of the Gene Responsible for the O3 Mating Type Substance in Paramecium caudatum
by Yuta Chiba, Yasuhiro Takenaka and Nobuyuki Haga
Microorganisms 2024, 12(3), 588; https://doi.org/10.3390/microorganisms12030588 - 15 Mar 2024
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Abstract
The process of sexual reproduction in eukaryotes starts when gametes from two different sexes encounter each other. Paramecium, a unicellular eukaryote, undergoes conjugation and uses a gametic nucleus to enter the sexual reproductive process. The molecules responsible for recognizing mating partners, hypothetically [...] Read more.
The process of sexual reproduction in eukaryotes starts when gametes from two different sexes encounter each other. Paramecium, a unicellular eukaryote, undergoes conjugation and uses a gametic nucleus to enter the sexual reproductive process. The molecules responsible for recognizing mating partners, hypothetically called mating-type substances, are still unclear. We have identified an O3-type mating substance polypeptide and its gene sequence using protein chemistry, molecular genetics, immunofluorescence, RNA interference, and microinjection. The O3-type substance is a polypeptide found in the ciliary membranes, located from the head to the ventral side of cells. The O3-type substance has a kinase-like domain in its N-terminal part located outside the cell and four EF-hand motifs that bind calcium ions in its C-terminal part located inside the cell. RNA interference and immunofluorescence revealed that this polypeptide positively correlated with the expression of mating reactivity. Microinjection of an expression vector incorporating the O3Pc-MSP gene (Oms3) induced additional O3 mating type in the recipient clones of different mating types or syngen. Phylogenetic analysis indicates that this gene is widely present in eukaryotes and exhibits high homology among closely related species. The O3Pc-MSP (Oms3) gene had nine silent mutations compared to the complementary mating type of the E3 homologue gene. Full article
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16 pages, 3324 KiB  
Article
Mating Pheromone (Gamone 1) in Blepharisma: A Glycoprotein Responsible for Species Diversity in Unicellular Organisms (Alveolata, Ciliophora)
by Mayumi Kobayashi, Mayumi Sugiura, Shoko Iwasaki, Naoyuki Iwabe and Terue Harumoto
Microorganisms 2024, 12(2), 299; https://doi.org/10.3390/microorganisms12020299 - 30 Jan 2024
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Abstract
The genus Blepharisma (Alveolata, Ciliophora) is a unicellular organism distributed worldwide, even in extreme environments, and comprises numerous species. While usually proliferating through cell division, Blepharisma undergoes sexual reproduction (conjugation) when cells are moderately starved. Conjugation is initiated by mating pheromones (gamone 1 [...] Read more.
The genus Blepharisma (Alveolata, Ciliophora) is a unicellular organism distributed worldwide, even in extreme environments, and comprises numerous species. While usually proliferating through cell division, Blepharisma undergoes sexual reproduction (conjugation) when cells are moderately starved. Conjugation is initiated by mating pheromones (gamone 1 and gamone 2) secreted by complementary mating-type cells. Gamone 1, a glycoprotein, functions in a species-specific manner, while gamone 2, an amino acid derivative, is a common molecule across species. The specific function of gamone 1 suggests the possibility that mutations in gamone 1 might have led to reproductive isolation during the evolutionary process, triggering species diversification. In this study, by comparing the amino acid sequences of gamone 1 homologs from 15 strains (representing five species), we found that mutations resulting in distinct amino acid properties occur across species boundaries and are mainly concentrated at two specific regions within gamone 1. These mutations potentially alter the binding affinity of gamone 1 to its receptors, suggesting their effect in causing reproductive isolation. The interspecies artificial conjugation conducted previously and the molecular phylogenetic tree constructed using the gamone 1 homolog sequences in this study provide insights into the speciation process within the genus Blepharisma. Full article
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