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Journal of Experimental Botany Nov 2017Meiosis is a specialized cell division that produces haploid gametes required for sexual reproduction. During the first meiotic division, homologous chromosomes pair and... (Review)
Review
Meiosis is a specialized cell division that produces haploid gametes required for sexual reproduction. During the first meiotic division, homologous chromosomes pair and undergo reciprocal crossing over, which recombines linked sequence variation. Meiotic recombination frequency varies extensively both within and between species. In this review, we will examine the molecular basis of meiotic recombination rate variation, with an emphasis on plant genomes. We first consider cis modification caused by polymorphisms at the site of recombination, or elsewhere on the same chromosome. We review cis effects caused by mismatches within recombining joint molecules, the effect of structural hemizygosity, and the role of specific DNA sequence motifs. In contrast, trans modification of recombination is exerted by polymorphic loci encoding diffusible molecules, which are able to modulate recombination on the same and/or other chromosomes. We consider trans modifiers that act to change total recombination levels, hotspot locations, or interactions between homologous and homeologous chromosomes in polyploid species. Finally, we consider the significance of genetic variation that modifies meiotic recombination for adaptation and evolution of plant species.
Topics: Adaptation, Biological; Biological Evolution; Genome, Plant; Homologous Recombination; Meiosis; Plants; Polymorphism, Genetic; Polyploidy
PubMed: 28992351
DOI: 10.1093/jxb/erx306 -
Molecules and Cells May 2022During meiosis, homologous chromosomes (homologs) pair and undergo genetic recombination via assembly and disassembly of the synaptonemal complex. Meiotic recombination... (Review)
Review
During meiosis, homologous chromosomes (homologs) pair and undergo genetic recombination via assembly and disassembly of the synaptonemal complex. Meiotic recombination is initiated by excess formation of DNA double-strand breaks (DSBs), among which a subset are repaired by reciprocal genetic exchange, called crossovers (COs). COs generate genetic variations across generations, profoundly affecting genetic diversity and breeding. At least one CO between homologs is essential for the first meiotic chromosome segregation, but generally only one and fewer than three inter-homolog COs occur in plants. CO frequency and distribution are biased along chromosomes, suppressed in centromeres, and controlled by pro-CO, anti-CO, and epigenetic factors. Accurate and high-throughput detection of COs is important for our understanding of CO formation and chromosome behavior. Here, we review advanced approaches that enable precise measurement of the location, frequency, and genomic landscapes of COs in plants, with a focus on .
Topics: Arabidopsis; Crossing Over, Genetic; DNA Breaks, Double-Stranded; Homologous Recombination; Meiosis; Plants
PubMed: 35444069
DOI: 10.14348/molcells.2022.2054 -
BioEssays : News and Reviews in... Sep 2017The functions of the Bloom syndrome helicase (BLM) and its orthologs are well characterized in mitotic DNA damage repair, but their roles within the context of meiotic... (Review)
Review
The functions of the Bloom syndrome helicase (BLM) and its orthologs are well characterized in mitotic DNA damage repair, but their roles within the context of meiotic recombination are less clear. In meiotic recombination, multiple repair pathways are used to repair meiotic DSBs, and current studies suggest that BLM may regulate the use of these pathways. Based on literature from Saccharomyces cerevisiae, Arabidopsis thaliana, Mus musculus, Drosophila melanogaster, and Caenorhabditis elegans, we present a unified model for a critical meiotic role of BLM and its orthologs. In this model, BLM and its orthologs utilize helicase activity to regulate the use of various pathways in meiotic recombination by continuously disassembling recombination intermediates. This unwinding activity provides the meiotic program with a steady pool of early recombination substrates, increasing the probability for a DSB to be processed by the appropriate pathway. As a result of BLM activity, crossovers are properly placed throughout the genome, promoting proper chromosomal disjunction at the end of meiosis. This unified model can be used to further refine the complex role of BLM and its orthologs in meiotic recombination.
Topics: Animals; Bloom Syndrome; Chromosomes; DNA Helicases; DNA Repair; Humans; Meiosis; RecQ Helicases; Recombination, Genetic
PubMed: 28792069
DOI: 10.1002/bies.201700073 -
Genetics Mar 2022The number and placement of meiotic crossover events during meiosis have important implications for the fidelity of chromosome segregation as well as patterns of...
The number and placement of meiotic crossover events during meiosis have important implications for the fidelity of chromosome segregation as well as patterns of inheritance. Despite the functional importance of recombination, recombination landscapes vary widely among and within species, and this can have a strong impact on evolutionary processes. A good knowledge of recombination landscapes is important for model systems in evolutionary and ecological genetics, since it can improve interpretation of genomic patterns of differentiation and genome evolution, and provides an important starting point for understanding the causes and consequences of recombination rate variation. Arabidopsis arenosa is a powerful evolutionary genetic model for studying the molecular basis of adaptation and recombination rate evolution. Here, we generate genetic maps for 2 diploid A. arenosa individuals from distinct genetic lineages where we have prior knowledge that meiotic genes show evidence of selection. We complement the genetic maps with cytological approaches to map and quantify recombination rates, and test the idea that these populations might have distinct patterns of recombination. We explore how recombination differs at the level of populations, individuals, sexes and genomic regions. We show that the positioning of crossovers along a chromosome correlates with their number, presumably a consequence of crossover interference, and discuss how this effect can cause differences in recombination landscape among sexes or species. We identify several instances of female segregation distortion. We found that averaged genome-wide recombination rate is lower and sex differences subtler in A. arenosa than in Arabidopsis thaliana.
Topics: Arabidopsis; Chromosome Segregation; Crossing Over, Genetic; Diploidy; Female; Humans; Male; Meiosis; Recombination, Genetic
PubMed: 35100396
DOI: 10.1093/genetics/iyab236 -
Methods in Molecular Biology (Clifton,... 2022Meiotic recombination initiates from ~100-200 s of programmed DNA double stranded breaks (DSBs) in plants. Meiotic DSBs can be repaired using homologous chromosomes to...
Meiotic recombination initiates from ~100-200 s of programmed DNA double stranded breaks (DSBs) in plants. Meiotic DSBs can be repaired using homologous chromosomes to generate a crossover . Meiotic crossover is critical for chromosomal segregation and increasing genetic variation. The number of crossovers is limited to one and three per chromosome pair in most plant species. Genetic, epigenetic, and environmental factors control crossover frequency and distribution. Due to the limited number of crossovers it is challenging to measure crossover frequency along chromosomes. We adapted fluorescence-tagged lines (FTLs ) that contain quartet1 mutations and linked transgenes expressing dsRed, eYFP, and eCFP in pollen tetrads into the deep learning-based image analysis tool, DeepTetrad. DeepTetrad enables the measurement of crossover frequency and interference by classifying 12 types of tetrads from three-color FTLs in a high-throughput manner, using conventional microscope instruments and a Linux machine. Here, we provide detailed procedures for preparing tetrad samples, tetrad imaging, running DeepTetrad, and analysis of DeepTetrad outputs. DeepTetrad-based measurements of crossover frequency and interference ratio will accelerate the genetic dissection of meiotic crossover control.
Topics: Chromosome Segregation; Crossing Over, Genetic; Homologous Recombination; Meiosis; Pollen
PubMed: 35461458
DOI: 10.1007/978-1-0716-2253-7_19 -
Philosophical Transactions of the Royal... Dec 2017Meiotic recombination is necessary for successful gametogenesis in most sexually reproducing organisms and is a fundamental genomic parameter, influencing the efficacy... (Review)
Review
Meiotic recombination is necessary for successful gametogenesis in most sexually reproducing organisms and is a fundamental genomic parameter, influencing the efficacy of selection and the fate of new mutations. The molecular and evolutionary functions of recombination should impose strong selective constraints on the range of recombination rates. Yet, variation in recombination rate is observed on a variety of genomic and evolutionary scales. In the past decade, empirical studies have described variation in recombination rate within genomes, between individuals, between sexes, between populations and between species. At the same time, theoretical work has provided an increasingly detailed picture of the evolutionary advantages to recombination. Perhaps surprisingly, the causes of natural variation in recombination rate remain poorly understood. We argue that empirical and theoretical approaches to understand the evolution of recombination have proceeded largely independently of each other. Most models that address the evolution of recombination rate were created to explain the evolutionary advantage of recombination rather than quantitative differences in rate among individuals. Conversely, most empirical studies aim to describe variation in recombination rate, rather than to test evolutionary hypotheses. In this Perspective, we argue that efforts to integrate the rich bodies of empirical and theoretical work on recombination rate are crucial to moving this field forward. We provide new directions for the development of theory and the production of data that will jointly close this gap.This article is part of the themed issue 'Evolutionary causes and consequences of recombination rate variation in sexual organisms'.
Topics: Evolution, Molecular; Genome; Models, Genetic; Recombination, Genetic
PubMed: 29109228
DOI: 10.1098/rstb.2016.0469 -
Chromosoma Jun 2016Genome architecture is shaped by gene-rich and repeat-rich regions also known as euchromatin and heterochromatin, respectively. Under normal conditions, the... (Review)
Review
Genome architecture is shaped by gene-rich and repeat-rich regions also known as euchromatin and heterochromatin, respectively. Under normal conditions, the repeat-containing regions undergo little or no meiotic crossover (CO) recombination. COs within repeats are risky for the genome integrity. Indeed, they can promote non-allelic homologous recombination (NAHR) resulting in deleterious genomic rearrangements associated with diseases in humans. The assembly of heterochromatin is driven by the combinatorial action of many factors including histones, their modifications, and DNA methylation. In this review, we discuss current knowledge dealing with the epigenetic signatures of the major repeat regions where COs are suppressed. Then we describe mutants for epiregulators of heterochromatin in different organisms to find out how chromatin structure influences the CO rate and distribution.
Topics: Animals; Crossing Over, Genetic; DNA Methylation; Epigenomics; Heterochromatin; Humans; Meiosis; Recombination, Genetic
PubMed: 26801812
DOI: 10.1007/s00412-016-0574-9 -
Experimental Cell Research Nov 2014Meiotic recombination has two key functions: the faithful assortment of chromosomes into gametes and the creation of genetic diversity. Both processes require that... (Review)
Review
Meiotic recombination has two key functions: the faithful assortment of chromosomes into gametes and the creation of genetic diversity. Both processes require that meiotic recombination occurs between homologous chromosomes, rather than sister chromatids. Accordingly, a host of regulatory factors are activated during meiosis to distinguish sisters from homologs, suppress recombination between sister chromatids and promote the chromatids of the homologous chromosome as the preferred recombination partners. Here, we discuss the recent advances in our understanding of the mechanistic basis of meiotic recombination template choice, focusing primarily on developments in the budding yeast, Saccharomyces cerevisiae, where the regulation is currently best understood.
Topics: DNA Repair; Meiosis; Recombination, Genetic; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Sister Chromatid Exchange
PubMed: 25158281
DOI: 10.1016/j.yexcr.2014.08.024 -
Biochemical Society Transactions Aug 2022Wheat is a major cereal crop that possesses a large allopolyploid genome formed through hybridisation of tetraploid and diploid progenitors. During meiosis, crossovers... (Review)
Review
Wheat is a major cereal crop that possesses a large allopolyploid genome formed through hybridisation of tetraploid and diploid progenitors. During meiosis, crossovers (COs) are constrained in number to 1-3 per chromosome pair that are predominantly located towards the chromosome ends. This reduces the probability of advantageous traits recombining onto the same chromosome, thus limiting breeding. Therefore, understanding the underlying factors controlling meiotic recombination may provide strategies to unlock the genetic potential in wheat. In this mini-review, we will discuss the factors associated with restricted CO formation in wheat, such as timing of meiotic events, chromatin organisation, pre-meiotic DNA replication and dosage of CO genes, as a means to modulate recombination.
Topics: Chromosomes; Crossing Over, Genetic; Homologous Recombination; Meiosis; Triticum
PubMed: 35901450
DOI: 10.1042/BST20220405 -
Methods in Molecular Biology (Clifton,... 2020Recombination and pairing are prominent features of meiosis where they play an important role in increasing genetic diversity. In most organisms recombination also plays...
Recombination and pairing are prominent features of meiosis where they play an important role in increasing genetic diversity. In most organisms recombination also plays mechanical roles in mediating pairing of homologous chromosomes during prophase and in ensuring regular segregation of homologous pairs at the first meiotic division. The laboratory directed by D. von Wettstein identified six key steps in the meiotic process: (1) Recombination mediated processes occur in physical and functional linkage with the synaptonemal complex (SC), a highly conserved, meiosis-specific structure that links homologous axes along their lengths. (2) The pairing process involves formation and resolution of chromosomal entanglements/interlockings. (3) The SC normally forms specifically between homologous chromosomes, but in unusual situations can form between nonhomologous chromosomes or regions resulting in two-phase SC formation. (4) In hexaploid common wheat, extensive multivalents form with multiple, pairing partner shifts, indicating homology recognition and SC formation among homoeologs as well as homologs. (5) Linkage between recombination and the SC is revealed by crossover-correlated nodules localized in the SC central region. (6) Modified SCs sometimes play a direct role in homolog segregation, providing the required connection between homologs in absence of crossovers/chiasmata.
Topics: Chromosome Pairing; Meiosis; Polyploidy; Recombination, Genetic; Triticum
PubMed: 32277447
DOI: 10.1007/978-1-0716-0356-7_2