Strange Genetics

2021 ◽  
pp. 52-59
Author(s):  
Thomas E. Schindler
Keyword(s):  
Sexual Reproduction ◽  
Genetic Recombination ◽  
Bacterial Host ◽  
Genetic Transfer ◽  
Genetic Traits ◽  
F Factor ◽  
Transfer Genes ◽  
Dissertation Research ◽  
At Will ◽  
Joshua Lederberg

This chapter relates how, in the 1950s, Esther and Joshua Lederberg and their colleagues uncovered a whole new kind of genetic transfer involving plasmids and viruses. In plants and animals, genetic recombination is integrated within the processes of sexual reproduction. Imagine if you could trade genes with strangers at will! That’s what bacteria can do. Esther Lederberg’s discoveries of the F-plasmid and the λ‎ bacteriophage were happy accidents that occurred while she working to complete her dissertation research. Serendipity happens to those who are very attentive, broadly experienced, and open to surprises. Esther Lederberg discovered a transferable factor, the F-factor, that could transform recipients into donors. Then she discovered a lysogenic virus, hiding harmlessly inside the chromosome of its bacterial host. These two surprising discoveries showed that bacteria could transfer genes and pieces of chromosomes horizontally, as opposed to the classical inheritance of plants and animals which pass on genetic traits vertically, down through generations.

Clarifying the Unique Features of Bacterial Sex

2021 ◽  
pp. 60-71
Author(s):  
Thomas E. Schindler
Keyword(s):  
Sexual Reproduction ◽  
Genetic Recombination ◽  
Entire Genome ◽  
Genetic Transfer ◽  
Time Points

This chapter considers bacterial sex, the details of which turned out to be counter-intuitive, quite different from Joshua Lederberg’s conceptions that were influenced by the ways that higher organisms recombined genes. The contributions of Luca Cavalli, William Hayes, and later, Elie Wollman and Francoise Jacob served to clarify the apparent anomalies, finally to reveal that bacterial sex was very, very different from the modes of genetic recombination of other organisms. The French team clarified the stages of conjugation by interrupting the mating of Hfr x F- at different time points. HGT, can occur by three different processes: transformation, conjugation, and transduction. In every case, HGT is fragmentary and unidirectional, much different than genetic transfer in sexual reproduction in higher organisms, which involves the entire genome in a mutual, two-way recombination of genes.

scholarly journals Microsatellite and Chromosome Evolution of Parthenogenetic Sitobion Aphids in Australia

Genetics ◽  
1996 ◽  
Vol 144 (2) ◽  
pp. 747-756 ◽  
Author(s):  
Paul Sunnucks ◽  
Phillip R England ◽  
Andrea C Taylor ◽  
Dinah F Hales
Keyword(s):  
Sexual Reproduction ◽  
Chromosome Evolution ◽  
Genetic Recombination ◽  
Allelic Variation ◽  
Repeat Unit ◽  
Chromosomal Evolution ◽  
Microsatellite Variation ◽  
Wide Range ◽  
Sexual Recombination ◽  
Minimum Numbers

Abstract Single-locus microsatellite variation correlated perfectly with chromosome number in Sitobion miscanthi aphids. The microsatellites were highly heterozygous, with up to 10 alleles per locus in this species. Despite this considerable allelic variation, only seven different S. miscanthi genotypes were discovered in 555 individuals collected from a wide range of locations, hosts and sampling periods. Relatedness between genotypes suggests only two successful colonizations of Australia. There was no evidence for genetic recombination in 555 S. miscanthi so the occurrence of recent sexual reproduction must be near zero. Thus diversification is by mutation and chromosomal rearrangement alone. Since the aphids showed no sexual recombination, microsatellites can mutate without meiosis. Five of seven microsatellite differences were a single repeat unit, and one larger jump is likely. The minimum numbers of changes between karyotypes corresponded roughly one-to-one with microsatellite allele changes, which suggests very rapid chromosomal evolution. A chromosomal fission occurred in a cultured line, and a previously unknown chromosomal race was detected. All 121 diverse S. near fragariae were heterozygous but revealed only one genotype. This species too must have a low rate of sexual reproduction and few colonizations of Australia.

scholarly journals Fungal clones win the battle, but recombination wins the war

IMA Fungus ◽  
2019 ◽  
Vol 10 (1) ◽  
Author(s):  
André Drenth ◽  
Alistair R. McTaggart ◽  
Brenda D. Wingfield
Keyword(s):  
Sexual Reproduction ◽  
Fungal Pathogen ◽  
Genetic Recombination ◽  
Genetic Material ◽  
Clonal Reproduction ◽  
Changing Environment ◽  
Space And Time ◽  
Pathogen Populations

Abstract Clonal reproduction is common in fungi and fungal-like organisms during epidemics and invasion events. The success of clonal fungi shaped systems for their classification and some pathogens are tacitly treated as asexual. We argue that genetic recombination driven by sexual reproduction must be a starting hypothesis when dealing with fungi for two reasons: (1) Clones eventually crash because they lack adaptability; and (2) fungi find a way to exchange genetic material through recombination, whether sexual, parasexual, or hybridisation. Successful clones may prevail over space and time, but they are the product of recombination and the next successful clone will inevitably appear. Fungal pathogen populations are dynamic rather than static, and they need genetic recombination to adapt to a changing environment.

scholarly journals Identification of Eighteen Berberis Species as Alternate Hosts of Puccinia striiformis f. sp. tritici and Virulence Variation in the Pathogen Isolates from Natural Infection of Barberry Plants in China

2013 ◽  
Vol 103 (9) ◽  
pp. 927-934 ◽  
Author(s):  
Jie Zhao ◽  
Long Wang ◽  
Zhiyan Wang ◽  
Xianming Chen ◽  
Hongchang Zhang ◽  
...  
Keyword(s):  
Sexual Reproduction ◽  
Stripe Rust ◽  
Puccinia Striiformis ◽  
Genetic Recombination ◽  
Natural Infection ◽  
Rust Fungi ◽  
Sexual Cycle ◽  
Natural Conditions ◽  
Rust Pathogen ◽  
Its Regions

The wheat stripe rust pathogen (Puccinia striiformis f. sp. tritici) population in China has been reported to be a distinct genetic group with higher diversity than those in many other countries. Genetic recombination in the P. striiformis f. sp. tritici population has been identified with molecular markers but whether sexual reproduction occurs in China is unknown. In this study, we surveyed barberry plants for infection by rust fungi in the stripe rust “hotspot” regions in Gansu, Sichuan, and Shaanxi provinces; collected barberry plants and inoculated plants of 20 Berberis spp. with germinated teliospores under controlled greenhouse conditions for susceptibility to P. striiformis f. sp. tritici; and tested P. striiformis f. sp. tritici isolates obtained from aecia on naturally infected barberry plants on the wheat genotypes used to differentiate Chinese P. striiformis f. sp. tritici races to determine virulence variations. Different Berberis spp. were widely distributed and most surveyed plants had pycnia and aecia of rust fungi throughout the surveyed regions. In total, 28 Berberis spp. were identified during our study. From 20 Berberis spp. tested with teliospores of P. striiformis f. sp. tritici from wheat plants, 18 species were susceptible under greenhouse conditions. Among 3,703 aecia sampled from barberry plants of three species (Berberis shensiana, B. brachypoda, and B. soulieana) under natural infections in Gansu and Shaanxi provinces, four produced P. striiformis f. sp. tritici uredinia on susceptible wheat ‘Mingxian 169’. Sequence of the internal transcribed spacer (ITS) regions of the four isolates from barberry shared 99% identity with the P. striiformis f. sp. tritici sequences in the National Center for Biotechnology Information database. The four isolates had virulence patterns different from all previously reported races collected from wheat plants. Furthermore, 82 single-uredinium isolates obtained from the four barberry isolates had high virulence diversity rates of 9.0 to 28.1%, indicating that the diverse isolates were produced through sexual reproduction on barberry plants under natural conditions. In addition to P. striiformis f. sp. tritici, sequence analysis of polymerase chain reaction products of the ITS regions and inoculation tests on wheat identified P. graminis (the stem rust pathogen). Our results indicated that P. striiformis f. sp. tritici can infect some Berberis spp. under natural conditions, and the sexual cycle of the fungus may contribute to the diversity of P. striiformis f. sp. tritici in China.

scholarly journals Identification of the Mating-Type (MAT) Locus That Controls Sexual Reproduction of Blastomyces dermatitidis

2012 ◽  
Vol 12 (1) ◽  
pp. 109-117 ◽  
Author(s):  
Wenjun Li ◽  
Thomas D. Sullivan ◽  
Eric Walton ◽  
Anna Floyd Averette ◽  
Sharadha Sakthikumar ◽  
...  
Keyword(s):  
Sexual Reproduction ◽  
Mating Type ◽  
Genetic Recombination ◽  
Sexual Cycle ◽  
Blastomyces Dermatitidis ◽  
Comparative Genomic ◽  
Dimorphic Fungi ◽  
Content Type ◽  
Long Time ◽  
Northern United States

ABSTRACTBlastomyces dermatitidisis a dimorphic fungal pathogen that primarily causes blastomycosis in the midwestern and northern United States and Canada. While the genes controlling sexual development have been known for a long time, the genes controlling sexual reproduction ofB. dermatitidis(teleomorph,Ajellomyces dermatitidis) are unknown. We identified the mating-type (MAT) locus in theB. dermatitidisgenome by comparative genomic approaches. TheB. dermatitidis MATlocus resembles those of other dimorphic fungi, containing either an alpha-box (MAT1-1) or an HMG domain (MAT1-2) gene linked to theAPN2,SLA2, andCOX13genes. However, in some strains ofB. dermatitidis, theMATlocus harbors transposable elements (TEs) that make it unusually large compared to theMATlocus of other dimorphic fungi. Based on theMATlocus sequences ofB. dermatitidis, we designed specific primers for PCR determination of the mating type. TwoB. dermatitidisisolates of opposite mating types were cocultured on mating medium. Immature sexual structures were observed starting at 3 weeks of coculture, with coiled-hyphae-containing cleistothecia developing over the next 3 to 6 weeks. Genetic recombination was detected in potential progeny by mating-type determination, PCR-restriction fragment length polymorphism (PCR-RFLP), and random amplification of polymorphic DNA (RAPD) analyses, suggesting that a meiotic sexual cycle might have been completed. The F1 progeny were sexually fertile when tested with strains of the opposite mating type. Our studies provide a model for the evolution of theMATlocus in the dimorphic and closely related fungi and open the door to classic genetic analysis and studies on the possible roles of mating and mating type in infection and virulence.

scholarly journals A phage mechanism for selective nicking of dUMP-containing DNA

2021 ◽  
Vol 118 (23) ◽  
pp. e2026354118
Author(s):  
Tridib Mahata ◽  
Shahar Molshanski-Mor ◽  
Moran G. Goren ◽  
Biswanath Jana ◽  
Miriam Kohen-Manor ◽  
...  
Keyword(s):  
Cell Division ◽  
Growth Inhibition ◽  
High Throughput Sequencing ◽  
Growth Inhibitor ◽  
Bacterial Host ◽  
Abasic Sites ◽  
Biochemical Assays ◽  
Bacterial Mutants ◽  
Base Excision ◽  
At Will

Bacteriophages (phages) have evolved efficient means to take over the machinery of the bacterial host. The molecular tools at their disposal may be applied to manipulate bacteria and to divert molecular pathways at will. Here, we describe a bacterial growth inhibitor, gene product T5.015, encoded by the T5 phage. High-throughput sequencing of genomic DNA of bacterial mutants, resistant to this inhibitor, revealed disruptive mutations in the Escherichia coli ung gene, suggesting that growth inhibition mediated by T5.015 depends on the uracil-excision activity of Ung. We validated that growth inhibition is abrogated in the absence of ung and confirmed physical binding of Ung by T5.015. In addition, biochemical assays with T5.015 and Ung indicated that T5.015 mediates endonucleolytic activity at abasic sites generated by the base-excision activity of Ung. Importantly, the growth inhibition resulting from the endonucleolytic activity is manifested by DNA replication and cell division arrest. We speculate that the phage uses this protein to selectively cause cleavage of the host DNA, which possesses more misincorporated uracils than that of the phage. This protein may also enhance phage utilization of the available resources in the infected cell, since halting replication saves nucleotides, and stopping cell division maintains both daughters of a dividing cell.

scholarly journals On the enigmatic origin of the Mediterranean invasive Caulerpa racemosa (Caulerpales, Chlorophyta)

2006 ◽  
Vol 7 (1) ◽  
pp. 119 ◽  
Author(s):  
P. PANAYOTIDIS
Keyword(s):  
Invasive Species ◽  
Sexual Reproduction ◽  
20Th Century ◽  
Genetic Recombination ◽  
Rapid Expansion ◽  
Caulerpa Racemosa ◽  
The Mediterranean

The successful sexual reproduction of the Mediterranean invasive species Caulerpa racemosa could explain not only its rapid expansion during the last decade of the 20th century, but also its origin, through hybridation and genetic recombination of preexisting varieties. This paper argues on the cryptogenic origin of the Mediterranean invasive Caulerpa racemosa.

The Society's notes

1980 ◽  
Vol 34 (2) ◽  
pp. 265-265
Keyword(s):  
New York ◽  
Particle Physics ◽  
Genetic Recombination ◽  
Genetic Material ◽  
University Of California ◽  
Chemical Physics ◽  
Elementary Particle Physics ◽  
The University ◽  
Academy Of Sciences ◽  
Joshua Lederberg

Election of Foreign Members 1979 Dr Julius Axelrod, Chief of the Section of Pharmacology at the National Institutes of Mental Health, Bethesda, U.S.A. Distinguished for his fundamental discoveries on the pharmacology, biosynthesis and metabolism of biogenic amines. Professor Joshua Lederberg, President of the Rockefeller University, New York, U.S.A. Distinguished for his discoveries concerning genetic recombination and the organization of the genetic material of bacteria, which laid the foundations of many aspects of molecular biology and his important contributions to immunology exobiology, and the application of computers to chemical analysis. Professor Jerzy Neyman, Professor and Director of the Statistical Laboratory at the University of California, Berkeley, U.S.A. Distinguished for his fundamental contributions to statistical theory and inference, with applications in astronomy, ecology, medicine and other fields. Professor Yakov Borisovich Zeldovich, Professor at the Institute of Chemical Physics in the Academy of Sciences, Moscow, U.S.S.R. Distinguished for his outstanding contributions to chemical physics, detonation, elementary particle physics and astrophysics

scholarly journals Sex and the Evolution of Intrahost Competition in RNA Virus φ6

Genetics ◽  
1998 ◽  
Vol 150 (2) ◽  
pp. 523-532 ◽  
Author(s):  
Paul E Turner ◽  
Lin Chao
Keyword(s):  
Sexual Reproduction ◽  
Rna Viruses ◽  
Rna Virus ◽  
Rapid Adaptation ◽  
Bacterial Host ◽  
Asexual Population ◽  
Sexual Population ◽  
Pseudomonas Phaseolicola ◽  
The Cost ◽  
Genetic Conflicts

Abstract Sex allows beneficial mutations that occur in separate lineages to be fixed in the same genome. For this reason, the Fisher-Muller model predicts that adaptation to the environment is more rapid in a large sexual population than in an equally large asexual population. Sexual reproduction occurs in populations of the RNA virus φ6 when multiple bacteriophages coinfect the same host cell. Here, we tested the model's predictions by determining whether sex favors more rapid adaptation of φ6 to a bacterial host, Pseudomonas phaseolicola. Replicate populations of φ6 were allowed to evolve in either the presence or absence of sex for 250 generations. All experimental populations showed a significant increase in fitness relative to the ancestor, but sex did not increase the rate of adaptation. Rather, we found that the sexual and asexual treatments also differ because intense intrahost competition between viruses occurs during coinfection. Results showed that the derived sexual viruses were selectively favored only when coinfection is common, indicating that within-host competition detracts from the ability of viruses to exploit the host. Thus, sex was not advantageous because the cost created by intrahost competition was too strong. Our findings indicate that high levels of coinfection exceed an optimum where sex may be beneficial to populations of φ6, and suggest that genetic conflicts can evolve in RNA viruses.

scholarly journals Genetic diversity in facultatively sexual populations and its implications for the origins of self-incompatibility in algae and fungi

2021 ◽  
Author(s):  
Aaron S.A. Smith ◽  
Sarah Penington ◽  
Ian Letter ◽  
Daniel B Wilson ◽  
George W. A. Constable
Keyword(s):  
Sexual Reproduction ◽  
Genetic Recombination ◽  
Competitive Dynamics ◽  
Small Populations ◽  
Mating Types ◽  
Self Incompatibility ◽  
Type Classes ◽  
Distinct Individual ◽  
Competing Hypotheses ◽  
Reproductive Events

The evolutionary mechanism that drove the establishment of self-incompatibility in early sexual eukaryotes is still a debated topic. While a number of competing hypotheses have been proposed, many have not received detailed theoretical attention. In particular, the hypothesis that self-incompatibility increases the benefits of genetic recombination in sexual haploids has been comparatively understudied. In this paper we address this topic by mathematically deriving how the probability of mating with a genetically distinct individual changes as a function of the presence or absence of self-incompatible mating type classes. We find that although populations with mating types successfully engage in sexual reproduction less frequently than their self-compatible competitors, they can nevertheless engage in useful sex with genetically distinct partners \emph{more} frequently. This conclusion holds when the number of sexual reproductive events per generation is low (i.e. in small populations with low rates of facultative sexual reproduction). Finally we demonstrate the potential for frequency-dependent selection in competitive dynamics between self-compatible and self-incompatible types. These analytic results provide a baseline for studying the sex advantage enhancer model for the evolutionary origin of mating types within each specific hypothesis for the evolution of recombination.

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