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Plant Physiology Mar 2017Meiosis is a specialized cell division, essential in most reproducing organisms to halve the number of chromosomes, thereby enabling the restoration of ploidy levels... (Review)
Review
Meiosis is a specialized cell division, essential in most reproducing organisms to halve the number of chromosomes, thereby enabling the restoration of ploidy levels during fertilization. A key step of meiosis is homologous recombination, which promotes homologous pairing and generates crossovers (COs) to connect homologous chromosomes until their separation at anaphase I. These CO sites, seen cytologically as chiasmata, represent a reciprocal exchange of genetic information between two homologous nonsister chromatids. This gene reshuffling during meiosis has a significant influence on evolution and also plays an essential role in plant breeding, because a successful breeding program depends on the ability to bring the desired combinations of alleles on chromosomes. However, the number and distribution of COs during meiosis is highly constrained. There is at least one CO per chromosome pair to ensure accurate segregation of homologs, but in most organisms, the CO number rarely exceeds three regardless of chromosome size. Moreover, their positions are not random on chromosomes but exhibit regional preference. Thus, genes in recombination-poor regions tend to be inherited together, hindering the generation of novel allelic combinations that could be exploited by breeding programs. Recently, much progress has been made in understanding meiotic recombination. In particular, many genes involved in the process in Arabidopsis () have been identified and analyzed. With the coming challenges of food security and climate change, and our enhanced knowledge of how COs are formed, the interest and needs in manipulating CO formation are greater than ever before. In this review, we focus on advances in understanding meiotic recombination and then summarize the attempts to manipulate CO formation. Last, we pay special attention to the meiotic recombination in polyploidy, which is a common genomic feature for many crop plants.
Topics: Crossing Over, Genetic; DNA Breaks, Double-Stranded; Evolution, Molecular; Gene Rearrangement; Homologous Recombination; Meiosis; Models, Genetic; Plant Breeding; Plants; Polyploidy
PubMed: 28108697
DOI: 10.1104/pp.16.01530 -
Plant Reproduction Mar 2023Chromatin state, and dynamic loading of pro-crossover protein HEI10 at recombination intermediates shape meiotic chromosome patterning in plants. Meiosis is the basis of... (Review)
Review
Chromatin state, and dynamic loading of pro-crossover protein HEI10 at recombination intermediates shape meiotic chromosome patterning in plants. Meiosis is the basis of sexual reproduction, and its basic progression is conserved across eukaryote kingdoms. A key feature of meiosis is the formation of crossovers which result in the reciprocal exchange of segments of maternal and paternal chromosomes. This exchange generates chromosomes with new combinations of alleles, increasing the efficiency of both natural and artificial selection. Crossovers also form a physical link between homologous chromosomes at metaphase I which is critical for accurate chromosome segregation and fertility. The patterning of crossovers along the length of chromosomes is a highly regulated process, and our current understanding of its regulation forms the focus of this review. At the global scale, crossover patterning in plants is largely governed by the classically observed phenomena of crossover interference, crossover homeostasis and the obligatory crossover which regulate the total number of crossovers and their relative spacing. The molecular actors behind these phenomena have long remained obscure, but recent studies in plants implicate HEI10 and ZYP1 as key players in their coordination. In addition to these broad forces, a wealth of recent studies has highlighted how genomic and epigenomic features shape crossover formation at both chromosomal and local scales, revealing that crossovers are primarily located in open chromatin associated with gene promoters and terminators with low nucleosome occupancy.
Topics: Crossing Over, Genetic; Chromatin; Meiosis
PubMed: 35834006
DOI: 10.1007/s00497-022-00445-4 -
Philosophical Transactions of the Royal... Mar 2018The terminal regions of eukaryotic chromosomes, composed of telomere repeat sequences and sub-telomeric sequences, represent some of the most variable and rapidly... (Review)
Review
The terminal regions of eukaryotic chromosomes, composed of telomere repeat sequences and sub-telomeric sequences, represent some of the most variable and rapidly evolving regions of the genome. The sub-telomeric regions are characterized by segmentally duplicated repetitive DNA elements, interstitial telomere repeat sequences and families of variable genes. Sub-telomeric repeat sequence families are shared among multiple chromosome ends, often rendering detailed sequence characterization difficult. These regions are composed of constitutive heterochromatin and are subjected to high levels of meiotic recombination. Dysfunction within telomere repeat arrays, either due to disruption in the chromatin structure or because of telomere shortening, can lead to chromosomal fusion and the generation of large-scale genomic rearrangements across the genome. The dynamic nature of telomeric regions, therefore, provides functionally useful variation to create genetic diversity, but also provides a mechanism for rapid genomic evolution that can lead to reproductive isolation and speciation. This article is part of the theme issue 'Understanding diversity in telomere dynamics'.This article is part of the theme issue 'Understanding diversity in telomere dynamics'.
Topics: Chromosomal Instability; Chromosomes; Evolution, Molecular; Genetic Variation; Humans; Neoplasms; Recombinational DNA Repair; Telomere; Telomere Homeostasis
PubMed: 29335376
DOI: 10.1098/rstb.2016.0437 -
Molecular Biology and Evolution Jan 2022Meiotic recombination is a biological process of key importance in breeding, to generate genetic diversity and develop novel or agronomically relevant haplotypes. In...
Meiotic recombination is a biological process of key importance in breeding, to generate genetic diversity and develop novel or agronomically relevant haplotypes. In crop tomato, recombination is curtailed as manifested by linkage disequilibrium decay over a longer distance and reduced diversity compared with wild relatives. Here, we compared domesticated and wild populations of tomato and found an overall conserved recombination landscape, with local changes in effective recombination rate in specific genomic regions. We also studied the dynamics of recombination hotspots resulting from domestication and found that loss of such hotspots is associated with selective sweeps, most notably in the pericentromeric heterochromatin. We detected footprints of genetic changes and structural variants, among them associated with transposable elements, linked with hotspot divergence during domestication, likely causing fine-scale alterations to recombination patterns and resulting in linkage drag.
Topics: DNA Transposable Elements; Domestication; Solanum lycopersicum; Plant Breeding; Recombination, Genetic
PubMed: 34597400
DOI: 10.1093/molbev/msab287 -
PLoS Genetics Aug 2018During meiosis, maternal and paternal chromosomes undergo exchanges by homologous recombination. This is essential for fertility and contributes to genome evolution. In... (Review)
Review
During meiosis, maternal and paternal chromosomes undergo exchanges by homologous recombination. This is essential for fertility and contributes to genome evolution. In many eukaryotes, sites of meiotic recombination, also called hotspots, are regions of accessible chromatin, but in many vertebrates, their location follows a distinct pattern and is specified by PR domain-containing protein 9 (PRDM9). The specification of meiotic recombination hotspots is achieved by the different activities of PRDM9: DNA binding, histone methyltransferase, and interaction with other proteins. Remarkably, PRDM9 activity leads to the erosion of its own binding sites and the rapid evolution of its DNA-binding domain. PRDM9 may also contribute to reproductive isolation, as it is involved in hybrid sterility potentially due to a reduction of its activity in specific heterozygous contexts.
Topics: Amino Acid Sequence; Animals; Binding Sites; Chromosome Mapping; DNA-Binding Proteins; Evolution, Molecular; Fertility; Heterozygote; Histone-Lysine N-Methyltransferase; Homologous Recombination; Humans; Infertility; Male; Meiosis; Mice; Protein Conformation; Reproductive Isolation; Spermatocytes
PubMed: 30161134
DOI: 10.1371/journal.pgen.1007479 -
Cold Spring Harbor Perspectives in... Oct 2015The study of homologous recombination has its historical roots in meiosis. In this context, recombination occurs as a programmed event that culminates in the formation... (Review)
Review
The study of homologous recombination has its historical roots in meiosis. In this context, recombination occurs as a programmed event that culminates in the formation of crossovers, which are essential for accurate chromosome segregation and create new combinations of parental alleles. Thus, meiotic recombination underlies both the independent assortment of parental chromosomes and genetic linkage. This review highlights the features of meiotic recombination that distinguish it from recombinational repair in somatic cells, and how the molecular processes of meiotic recombination are embedded and interdependent with the chromosome structures that characterize meiotic prophase. A more in-depth review presents our understanding of how crossover and noncrossover pathways of meiotic recombination are differentiated and regulated. The final section of this review summarizes the studies that have defined defective recombination as a leading cause of pregnancy loss and congenital disease in humans.
Topics: Chromosomes; Crossing Over, Genetic; DNA; DNA Breaks, Double-Stranded; Endonucleases; Female; Humans; Maternal Age; Meiosis; Models, Genetic; Recombination, Genetic; Reproduction
PubMed: 26511629
DOI: 10.1101/cshperspect.a016618 -
Biochemical Society Transactions Feb 2024Meiotic recombination, a cornerstone of eukaryotic diversity and individual genetic identity, is essential for the creation of physical linkages between homologous... (Review)
Review
Meiotic recombination, a cornerstone of eukaryotic diversity and individual genetic identity, is essential for the creation of physical linkages between homologous chromosomes, facilitating their faithful segregation during meiosis I. This process requires that germ cells generate controlled DNA lesions within their own genome that are subsequently repaired in a specialised manner. Repair of these DNA breaks involves the modulation of existing homologous recombination repair pathways to generate crossovers between homologous chromosomes. Decades of genetic and cytological studies have identified a multitude of factors that are involved in meiotic recombination. Recent work has started to provide additional mechanistic insights into how these factors interact with one another, with DNA, and provide the molecular outcomes required for a successful meiosis. Here, we provide a review of the recent developments with a focus on protein structures and protein-protein interactions.
Topics: DNA Breaks, Double-Stranded; Homologous Recombination; DNA Repair; Meiosis; Chromosomes
PubMed: 38348856
DOI: 10.1042/BST20230712 -
Chromosoma Jun 2016Meiotic homologous recombination is a specialized process that involves homologous chromosome pairing and strand exchange to guarantee proper chromosome segregation and... (Review)
Review
Meiotic homologous recombination is a specialized process that involves homologous chromosome pairing and strand exchange to guarantee proper chromosome segregation and genetic diversity. The formation and repair of DNA double-strand breaks (DSBs) during meiotic recombination differs from those during mitotic recombination in that the homologous chromosome rather than the sister chromatid is the preferred repair template. The processing of single-stranded DNA (ssDNA) formed on intermediate recombination structures is central to driving the specific outcomes of DSB repair during meiosis. Replication protein A (RPA) is the main ssDNA-binding protein complex involved in DNA metabolism. However, the existence of RPA orthologs in plants and the recent discovery of meiosis specific with OB domains (MEIOB), a widely conserved meiosis-specific RPA1 paralog, strongly suggest that multiple RPA complexes evolved and specialized to subdivide their roles during DNA metabolism. Here we review ssDNA formation and maturation during mitotic and meiotic recombination underlying the meiotic specific features. We describe and discuss the existence and properties of MEIOB and multiple RPA subunits in plants and highlight how they can provide meiosis-specific fates to ssDNA processing during homologous recombination. Understanding the functions of these RPA homologs and how they interact with the canonical RPA subunits is of major interest in the fields of meiosis and DNA repair.
Topics: Animals; DNA, Single-Stranded; Homologous Recombination; Humans; Meiosis; Plants; Replication Protein A
PubMed: 26520106
DOI: 10.1007/s00412-015-0552-7 -
Philosophical Transactions of the Royal... Dec 2017One of the most striking patterns of genome structure is the tight, typically negative, association between transposable elements (TEs) and meiotic recombination rates.... (Review)
Review
One of the most striking patterns of genome structure is the tight, typically negative, association between transposable elements (TEs) and meiotic recombination rates. While this is a highly recurring feature of eukaryotic genomes, the mechanisms driving correlations between TEs and recombination remain poorly understood, and distinguishing cause versus effect is challenging. Here, we review the evidence for a relation between TEs and recombination, and discuss the underlying evolutionary forces. Evidence to date suggests that overall TE densities correlate negatively with recombination, but the strength of this correlation varies across element types, and the pattern can be reversed. Results suggest that heterogeneity in the strength of selection against ectopic recombination and gene disruption can drive TE accumulation in regions of low recombination, but there is also strong evidence that the regulation of TEs can influence local recombination rates. We hypothesize that TE insertion polymorphism may be important in driving within-species variation in recombination rates in surrounding genomic regions. Furthermore, the interaction between TEs and recombination may create positive feedback, whereby TE accumulation in non-recombining regions contributes to the spread of recombination suppression. Further investigation of the coevolution between recombination and TEs has important implications for our understanding of the evolution of recombination rates and genome structure.This article is part of the themed issue 'Evolutionary causes and consequences of recombination rate variation in sexual organisms'.
Topics: DNA Transposable Elements; Eukaryota; Evolution, Molecular; Recombination, Genetic
PubMed: 29109221
DOI: 10.1098/rstb.2016.0458 -
Cell Cycle (Georgetown, Tex.) 2018Meiosis is the basis for sexual reproduction and is marked by the sequential reduction of chromosome number during successive cell cycles, resulting in four haploid... (Review)
Review
Meiosis is the basis for sexual reproduction and is marked by the sequential reduction of chromosome number during successive cell cycles, resulting in four haploid gametes. A central component of the meiotic program is the formation and repair of programmed double strand breaks. Recombination-driven repair of these meiotic breaks differs from recombination during mitosis in that meiotic breaks are preferentially repaired using the homologous chromosomes in a process known as homolog bias. Homolog bias allows for physical interactions between homologous chromosomes that are required for proper chromosome segregation, and the formation of crossover products ensuring genetic diversity in progeny. An important aspect of meiosis in the differential regulation of the two eukaryotic RecA homologs, Rad51 and Dmc1. In this review we will discuss the relationship between biological programs designed to regulate recombinase function.
Topics: Cell Cycle Proteins; Chromosome Segregation; DNA-Binding Proteins; Homologous Recombination; Meiosis; Rad51 Recombinase; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins
PubMed: 30482074
DOI: 10.1080/15384101.2018.1553355