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.

scholarly journals Mating types of Phytophthora colocasiae on the island of Upolu, Samoa

2018 ◽  
Vol 71 ◽  
pp. 289-292 ◽  
Author(s):  
Kieran D. Mellow ◽  
Joy L. Tyson ◽  
Robert A. Fullerton ◽  
Angelika Tugaga ◽  
Fa'alelei Tunupopo ◽  
...  
Keyword(s):  
Sexual Reproduction ◽  
Mating Type ◽  
Genetic Recombination ◽  
Leaf Blight ◽  
Phytophthora Nicotianae ◽  
Mating Types ◽  
Comprehensive Understanding ◽  
Phytophthora Colocasiae ◽  
Oospore Formation ◽  
Taro Leaf Blight

Taro leaf blight (TLB) caused by Phytophthora colocasiae is a damaging disease that destroyed Samoa’s taro industry following its introduction in 1993. The aim of this study was to determine the occurrence of the A1 and A2 mating types of P. colocasiae for a more comprehensive understanding of the risk the pathogen poses for the future of the taro industry in Samoa. In September 2015, 54 isolates of P. colocasiae were collected from taro leaf blight lesions from 13 farms around the island of Upolu, Samoa. The mating types of each isolate was determined by observation of oospore formation when paired with tester isolates of Phytophthora nicotianae of known mating types (A1 or A2). Fifty isolates were found to be A2 mating type and four did not form oospores with either mating type. No A1 or self-fertile isolates were found. These results suggest that the A1 mating type has not been introduced to the island of Upolu, preventing the formation of oospores between compatible mating types of P. colocasiae and lessening the risk of new and potentially more threatening genotypes of the pathogen from emerging through genetic recombination. Keywords taro leaf blight, Colocasia esculenta, taro, sexual reproduction

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.

Identification of biosynthetic intermediates for the mating hormone α2 of the plant pathogen Phytophthora

2021 ◽  
Author(s):  
Suguru Ariyoshi ◽  
Yusuke Imazu ◽  
Ryuji Ohguri ◽  
Ryo Katsuta ◽  
Arata Yajima ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Sexual Reproduction ◽  
Mating Type ◽  
Plant Pathogen ◽  
Type Strain ◽  
Mating Types ◽  
Synthetic Intermediates ◽  
The Cross

Abstract The heterothallic group of the plant pathogen Phytophthora can sexually reproduce between the cross-compatible mating types A1 and A2. The mating hormone α2, produced by A2 mating type and utilized to promote the sexual reproduction of the partner A1 type, is known to be biosynthesized from phytol. In this study, we identified two biosynthetic intermediates, 11- and 16-hydroxyphytols (1 and 2), for α2 by administering the synthetic intermediates to an A2 type strain to produce α2 and by administering phytol to A2 strains to detect the intermediates in the mycelia. The results suggest that α2 is biosynthesized by possibly two cytochrome P450 oxygenases via two hydroxyphytol intermediates (1 and 2) in A2 hyphae and secreted outside.

scholarly journals Gamete signalling underlies the evolution of mating types and their number

2016 ◽  
Vol 371 (1706) ◽  
pp. 20150531 ◽  
Author(s):  
Zena Hadjivasiliou ◽  
Andrew Pomiankowski
Keyword(s):  
Mathematical Model ◽  
Sexual Reproduction ◽  
Mating Types ◽  
Simple Mathematical Model ◽  
Unicellular Eukaryotes ◽  
Evolutionarily Stable

The gametes of unicellular eukaryotes are morphologically identical, but are nonetheless divided into distinct mating types. The number of mating types varies enormously and can reach several thousand, yet most species have only two. Why do morphologically identical gametes need to be differentiated into self-incompatible mating types, and why is two the most common number of mating types? In this work, we explore a neglected hypothesis that there is a need for asymmetric signalling interactions between mating partners. Our review shows that isogamous gametes always interact asymmetrically throughout sex and argue that this asymmetry is favoured because it enhances the efficiency of the mating process. We further develop a simple mathematical model that allows us to study the evolution of the number of mating types based on the strength of signalling interactions between gametes. Novel mating types have an advantage as they are compatible with all others and rarely meet their own type. But if existing mating types coevolve to have strong mutual interactions, this restricts the spread of novel types. Similarly, coevolution is likely to drive out less attractive mating types. These countervailing forces specify the number of mating types that are evolutionarily stable. This article is part of the themed issue ‘Weird sex: the underappreciated diversity of sexual reproduction’.

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 Genomic and Population Analyses of the Mating Type Loci in Coccidioides Species Reveal Evidence for Sexual Reproduction and Gene Acquisition

2007 ◽  
Vol 6 (7) ◽  
pp. 1189-1199 ◽  
Author(s):  
M. Alejandra Mandel ◽  
Bridget M. Barker ◽  
Scott Kroken ◽  
Steven D. Rounsley ◽  
Marc J. Orbach
Keyword(s):  
Sexual Reproduction ◽  
Mating Type ◽  
Mating Types ◽  
Coccidioides Immitis ◽  
Genome Sequences ◽  
Valley Fever ◽  
Population Analyses ◽  
Gene Acquisition ◽  
Close Proximity

ABSTRACT Coccidioides species, the fungi responsible for the valley fever disease, are known to reproduce asexually through the production of arthroconidia that are the infectious propagules. The possible role of sexual reproduction in the survival and dispersal of these pathogens is unexplored. To determine the potential for mating of Coccidioides, we analyzed genome sequences and identified mating type loci characteristic of heterothallic ascomycetes. Coccidioides strains contain either a MAT1-1 or a MAT1-2 idiomorph, which is 8.1 or 9 kb in length, respectively, the longest reported for any ascomycete species. These idiomorphs contain four or five genes, respectively, more than are present in the MAT loci of most ascomycetes. Along with their cDNA structures, we determined that all genes in the MAT loci are transcribed. Two genes frequently found in common sequences flanking MAT idiomorphs, APN2 and COX13, are within the MAT loci in Coccidioides, but the MAT1-1 and MAT1-2 copies have diverged dramatically from each other. Data indicate that the acquisition of these genes in the MAT loci occurred prior to the separation of Coccidioides from Uncinocarpus reesii. An analysis of 436 Coccidioides isolates from patients and the environment indicates that in both Coccidioides immitis and C. posadasii, there is a 1:1 distribution of MAT loci, as would be expected for sexually reproducing species. In addition, an analysis of isolates obtained from 11 soil samples demonstrated that at three sampling sites, strains of both mating types were present, indicating that compatible strains were in close proximity in the 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.

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