scholarly journals A Willow Sex Chromosome Reveals Convergent Evolution of Complex Palindromic Repeats

2019 ◽  
Author(s):  
Ran Zhou ◽  
David Macaya-Sanz ◽  
Craig H. Carlson ◽  
Jeremy Schmutz ◽  
Jerry W. Jenkins ◽  
...  
Keyword(s):  
Gene Conversion ◽  
Sex Chromosomes ◽  
Convergent Evolution ◽  
Sex Chromosome ◽  
Expression Patterns ◽  
Sequence Conservation ◽  
Closely Related Species ◽  
Salix Purpurea ◽  
Plant Sex Chromosomes ◽  
Plant Sex

AbstractBackgroundSex chromosomes in a wide variety of species share common characteristics, including the presence of suppressed recombination surrounding sex determination loci. They have arisen independently in numerous lineages, providing a conclusive example of convergent evolution. Mammalian sex chromosomes contain multiple palindromic repeats across the non-recombining region that facilitate sequence conservation through gene conversion, and contain genes that are crucial for sexual reproduction. Plant sex chromosomes are less well understood, and in particular it is not clear how coding sequence conservation is maintained in the absence of homologous recombination.ResultsHere we present the first evidence of large palindromic structures in a plant sex chromosome, based on a highly contiguous assembly of the W chromosome of the dioecious shrub Salix purpurea. Two consecutive palindromes span over a region of 200 kb, with conspicuous 20 kb stretches of highly conserved sequences among the four arms. The closely-related species S. suchowensis also has two copies of a portion of the palindrome arm and provides strong evidence for gene conversion. Four genes in the palindrome are homologous to genes in the SDR of the closely-related genus Populus, which is located on a different chromosome. These genes show distinct, floral-biased expression patterns compared to paralogous copies on autosomes.ConclusionThe presence of palindromic structures in sex chromosomes of mammals and plants highlights the intrinsic importance of these features in adaptive evolution in the absence of recombination. Convergent evolution is driving both the independent establishment of sex chromosomes as well as their fine-scale sequence structure.

High intrachromosomal similarity of retrotransposon long terminal repeats: Evidence for homogenization by gene conversion on plant sex chromosomes?

Gene ◽  
2007 ◽  
Vol 390 (1-2) ◽  
pp. 92-97 ◽  
Author(s):  
Eduard Kejnovsky ◽  
Roman Hobza ◽  
Zdenek Kubat ◽  
Alex Widmer ◽  
Gabriel A.B. Marais ◽  
...  
Keyword(s):  
Gene Conversion ◽  
Sex Chromosomes ◽  
Long Terminal Repeats ◽  
Terminal Repeats ◽  
Plant Sex Chromosomes ◽  
Plant Sex

scholarly journals A high-throughput segregation analysis identifies the sex chromosomes of Cannabis sativa

2019 ◽  
Author(s):  
Djivan Prentout ◽  
Olga Razumova ◽  
Bénédicte Rhoné ◽  
Hélène Badouin ◽  
Hélène Henri ◽  
...  
Keyword(s):  
Sex Chromosomes ◽  
Segregation Analysis ◽  
Cannabis Sativa ◽  
Sex Chromosome ◽  
Probabilistic Method ◽  
Female Offspring ◽  
Single Chromosome ◽  
Sex Chromosome System ◽  
Plant Sex Chromosomes ◽  
Plant Sex

AbstractCannabis sativa-derived tetrahydrocannabinol (THC) production is increasing very fast worldwide. C. sativa is a dioecious plant with XY chromosomes, and only females (XX) are useful for THC production. The C. sativa sex chromosomes sequence would improve early sexing and better management of this crop; however, the C. sativa genome projects failed to identify the sex chromosomes so far. Moreover, dioecy in the Cannabaceae family is ancestral, C. sativa sex chromosomes are potentially old and thus very interesting to study as little is known about the last steps of sex chromosome evolution in plants. Here we RNA-sequenced a C. sativa family (2 parents and 10 male and female offspring) and performed a segregation analysis for all C. sativa genes using the probabilistic method SEX-DETector. We identified >500 sex-linked genes. Mapping of these sex-linked genes to a C. sativa genome assembly identified a single chromosome pair with a large non-recombining region. Further analysis of the >500 sex-linked genes revealed that C. sativa has a strongly degenerated Y chromosome and represents the oldest plant sex chromosome system documented so far. Our study revealed that old plant sex chromosomes can have large non-recombining regions and be very differentiated and still be of similar size (homomorphic).

The genomics of plant sex chromosomes

Plant Science ◽  
2015 ◽  
Vol 236 ◽  
pp. 126-135 ◽  
Author(s):  
Boris Vyskot ◽  
Roman Hobza
Keyword(s):  
Sex Chromosomes ◽  
Plant Sex Chromosomes ◽  
Plant Sex

Speciation in black flies

Genome ◽  
1989 ◽  
Vol 32 (4) ◽  
pp. 500-509 ◽  
Author(s):  
Klaus Rothfels
Keyword(s):  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Sympatric Speciation ◽  
Chromosome Polymorphism ◽  
Black Flies ◽  
Closely Related Species ◽  
Black Fly ◽  
Progressive Development ◽  
Temporal Relationships ◽  
Species Pairs

In many Simuliidae, patterns of spatial and temporal relationships among the most closely related species are more readily interpreted in terms of sympatric speciation than of allopatric speciation. Specific examples are (i) the allotriploid taxa in Gymnopais and other genera, (ii) the black fly faunas of geologically recent islands (Tahiti), and (iii) species in Prosimulium onychodactylum, a prototype of a continental multisibling species complex. A model of sympatric speciation is presented based on coadaptation of polymorphic sex chromosomes in pairs reinforced by progressive development of assortative mating. This model predicts that (i) populations should frequently exhibit sex-chromosome polymorphism, (ii) these sex-chromosome polymorphisms, and autosomal ones, should in some cases display linkage or association disequilibria, (iii) species pairs or complexes should be incurred that differ only in sex chromosomes and that share extensive ancestral autosomal polymorphisms, and (iv) such species should differ in their biology and perhaps their present-day distribution. Recent publications and observations are in accordance, in general, with predictions from the model. Genetic control, e.g., of diapause, larval developmental timing, and niche preference or ethology, could substitute as a basis of incipient cleavage. The evidence for sympatric speciation is purely inferential, but this is equally true for the allopatric interpretation, and in black flies the circumstantial evidence for prevalence of sympatric speciation appears more compelling. This is not to deny the efficacy of allopatry and founder effect in the origin of some species complexes.Key words: sympatric speciation, black fly, evolution.

scholarly journals High-quality chromosome-level genomes of two tilapia species reveal their evolution of repeat sequences and sex chromosomes

2020 ◽  
Author(s):  
Wenjing Tao ◽  
Luohao Xu ◽  
Lin Zhao ◽  
Zexian Zhu ◽  
Xin Wu ◽  
...  
Keyword(s):  
Sex Chromosomes ◽  
Nile Tilapia ◽  
Sex Chromosome ◽  
Expression Patterns ◽  
Heterochromatic Region ◽  
Single Nucleotide Variants ◽  
Evolutionary Mechanisms ◽  
Unequal Distribution ◽  
Functional Studies ◽  
Blue Tilapia

AbstractBackgroundTilapias are one of the most farmed fishes that are coined as ‘aquatic chicken’ by the food industry. Like many other teleosts, Nile tilapia and blue tilapia exhibit very recent transition of sex chromosome systems since their divergence about 5 million years ago, making them a great model for elucidating the molecular and evolutionary mechanisms of sex chromosome turnovers. Studies into their sex-determining pathways are also critical for developing genetic sex control in aquaculture.ResultsWe report here the newly produced genomes of Nile tilapia and blue tilapia that integrate long-read sequencing and chromatin conformation data. The two nearly complete genomes have anchored over 97% of the sequences into linkage groups (LGs), and assembled majorities of complex repetitive regions including telomeres, centromeres and rDNA clusters. In particular, we inferred two episodes of repeat expansion at LG3 respectively in the ancestor of cichlids and that of tilapias. The consequential large heterochromatic region concentrated at one end of LG3 comprises tandem arrays of mRNA and small RNA genes, among which we have identified a candidate female determining gene Paics in blue tilapia. Paics show female-specific patterns of single-nucleotide variants, copy numbers and expression patterns in gonads during early gonadogenesis.ConclusionsOur work provide a very important genomic resource for functional studies of cichlids, and suggested that unequal distribution of repeat content that impacts the local recombination rate might make some chromosomes more likely to become sex chromosomes.

scholarly journals The diversity of plant sex chromosomes highlighted through advances in genome sequencing

2021 ◽  
Author(s):  
Sarah Carey ◽  
Qingyi Yu ◽  
Alex Harkess
Keyword(s):  
Sex Determination ◽  
Genome Sequencing ◽  
Sex Chromosomes ◽  
Theoretical Models ◽  
Genomic Technologies ◽  
Interdisciplinary Approaches ◽  
Suppressed Recombination ◽  
Plant Sex Chromosomes ◽  
Plant Sex

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. However, 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 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 to unravel the patterns that can be found across the hundreds of independent origins.

scholarly journals Birth of a W sex chromosome by horizontal transfer of Wolbachia bacterial symbiont genome

2016 ◽  
Vol 113 (52) ◽  
pp. 15036-15041 ◽  
Author(s):  
Sébastien Leclercq ◽  
Julien Thézé ◽  
Mohamed Amine Chebbi ◽  
Isabelle Giraud ◽  
Bouziane Moumen ◽  
...  
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Nuclear Genome ◽  
Closely Related Species ◽  
Evolutionary Transitions ◽  
Female Sex ◽  
Bacterial Endosymbionts ◽  
The Common ◽  
And Behavior

Sex determination is a fundamental developmental pathway governing male and female differentiation, with profound implications for morphology, reproductive strategies, and behavior. In animals, sex differences between males and females are generally determined by genetic factors carried by sex chromosomes. Sex chromosomes are remarkably variable in origin and can differ even between closely related species, indicating that transitions occur frequently and independently in different groups of organisms. The evolutionary causes underlying sex chromosome turnover are poorly understood, however. Here we provide evidence indicating that Wolbachia bacterial endosymbionts triggered the evolution of new sex chromosomes in the common pillbug Armadillidium vulgare. We identified a 3-Mb insert of a feminizing Wolbachia genome that was recently transferred into the pillbug nuclear genome. The Wolbachia insert shows perfect linkage to the female sex, occurs in a male genetic background (i.e., lacking the ancestral W female sex chromosome), and is hemizygous. Our results support the conclusion that the Wolbachia insert is now acting as a female sex-determining region in pillbugs, and that the chromosome carrying the insert is a new W sex chromosome. Thus, bacteria-to-animal horizontal genome transfer represents a remarkable mechanism underpinning the birth of sex chromosomes. We conclude that sex ratio distorters, such as Wolbachia endosymbionts, can be powerful agents of evolutionary transitions in sex determination systems in animals.

scholarly journals Homomorphic ZW chromosomes 1 in a wild strawberry show distinctive recombination heterogeneity but a small sex-determining region

2015 ◽  
Author(s):  
Jacob A Tennessen ◽  
Rajanikanth Govindarajulu ◽  
Aaron Liston ◽  
Tia-Lynn Ashman
Keyword(s):  
Sex Chromosomes ◽  
Recombination Rate ◽  
Sex Chromosome ◽  
Pseudoautosomal Region ◽  
List Type ◽  
Recombination Suppression ◽  
Female Function ◽  
Wild Strawberry ◽  
Plant Sex Chromosomes ◽  
Recombination Dynamics

SummaryRecombination in ancient, heteromorphic sex chromosomes is typically suppressed at the sex-determining region (SDR) and proportionally elevated in the pseudoautosomal region (PAR). However, little is known about recombination dynamics of young, homomorphic plant sex chromosomes.We examine male and female function in crosses and unrelated samples of the dioecious octoploid strawberry Fragaria chiloensis in order to map the small and recently evolved SDR controlling both traits and to examine recombination patterns on the incipient ZW chromosome.The SDR of this ZW system is located within a 280kb window, in which the maternal recombination rate is lower than the paternal. In contrast to the SDR, the maternal PAR recombination rate is much higher than the rates of the paternal PAR or autosomes, culminating in an elevated chromosome-wide rate. W-specific divergence is elevated within the SDR and a single polymorphism is observed in high species-wide linkage disequilibrium with sex.Selection for recombination suppression within the small SDR may be weak, but fluctuating sex ratios could favor elevated recombination in the PAR to remove deleterious mutations on the W. The recombination dynamics of this nascent sex chromosome with a modestly diverged SDR may be typical of other dioecious plants.

Role of repetitive sequence and heterochromatize in recombination suppression of plant sex chromosomes

2010 ◽  
Vol 32 (1) ◽  
pp. 25-30
Author(s):  
Wu-Jun GAO ◽  
Lu XIE ◽  
Jing-Wen LU ◽  
Chuan-Liang DENG ◽  
Long-Dou LU
Keyword(s):  
Sex Chromosomes ◽  
Repetitive Sequence ◽  
Recombination Suppression ◽  
Plant Sex Chromosomes ◽  
Plant Sex
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