Meiotic Chromosome Behavior Research Articles

Mouse TRIP13/PCH2 Is Required for Recombination and Normal Higher-Order Chromosome Structure during Meiosis

Accurate chromosome segregation during meiosis requires that homologous chromosomes pair and become physically connected so that they can orient properly on the meiosis I spindle. These connections are formed by homologous recombination closely integrated with the development of meiosis-specific, higher-order chromosome structures. The yeast Pch2 protein has emerged as an important factor with roles in both recombination and chromosome structure formation, but recent analysis suggested that TRIP13, the mouse Pch2 ortholog, is not required for the same processes. Using distinct Trip13 alleles with moderate and severe impairment of TRIP13 function, we report here that TRIP13 is required for proper synaptonemal complex formation, such that autosomal bivalents in Trip13-deficient meiocytes frequently displayed pericentric synaptic forks and other defects. In males, TRIP13 is required for efficient synapsis of the sex chromosomes and for sex body formation. Furthermore, the numbers of crossovers and chiasmata are reduced in the absence of TRIP13, and their distribution along the chromosomes is altered, suggesting a role for TRIP13 in aspects of crossover formation and/or control. Recombination defects are evident very early in meiotic prophase, soon after DSB formation. These findings provide evidence for evolutionarily conserved functions for TRIP13/Pch2 in both recombination and formation of higher order chromosome structures, and they support the hypothesis that TRIP13/Pch2 participates in coordinating these key aspects of meiotic chromosome behavior.

Meiotic analysis of XX/XY and neo-XX/XY sex chromosomes in Phyllostomidae by cross-species chromosome painting revealing a common chromosome 15-XY rearrangement in Stenodermatinae

We analyzed the meiotic behavior of the sex chromosomes of the bats Glossophaga soricina (XX/XY), Artibeus cinereus and Uroderma magnirostrum (neo-XX/XY) using multicolor FISH. The X chromosome and pair 15 autosome probes are from Phyllostomus hastatus and the Y from Carollia brevicauda. On both species with the neo-XX/XY system, the autosome translocated to the sex chromosomes is the pair 15 in P. hastatus, a synapomorphy. The analysis of meiosis confirms that the X and Y have a pseudo-autosomal region, with a typical end-to-end pairing. The autosomal regions of the neo-XX/XY shows different levels of condensation when compared to the original XX/XY. The compound system presented a characteristic shape, as if it was a closed ring with a tail. The ring represents the non-paired segments of the X and Y and the small pairing region of the original sex chromosomes. The tail corresponds to the pairing of the 15 P. hastatus autosomal bivalent, which are translocated to the sex chromosomes. Probably the non-pairing is responsible for the meiotic silencing of these segments.

THE BEHAVIOUR OF MEIOTIC CHROMOSOMES AFTER X-IRRADIATION

HereditasVolume 19, Issue 3 p. 303-322 Open Access THE BEHAVIOUR OF MEIOTIC CHROMOSOMES AFTER X-IRRADIATION K. MATHER, K. MATHER SVERIGES UTSÄDESFÖRENING, SVALÖF, SWEDENSearch for more papers by this author K. MATHER, K. MATHER SVERIGES UTSÄDESFÖRENING, SVALÖF, SWEDENSearch for more papers by this author First published: June 1934 https://doi.org/10.1111/j.1601-5223.1934.tb02628.xCitations: 5AboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume19, Issue3June 1934Pages 303-322 ReferencesRelatedInformation

Karyotype plasticity in crickets: numerical, morphological, and nucleolar organizer region distribution pattern of Anurogryllus sp.

Within the Orthopteran species, those of the suborder Ensifera have been rarely studied from the cytogenetic point of view, mainly due to the difficulties for taxonomic identification of its species. The Gryllidae is the second largest family of this suborder and possesses some genera, such as Anurogryllus, that occur only on the American continents. The aim of this work was to determine the karyotype characteristics, the meiotic chromosome behaviour, and the nucleolar organizer region (NOR) pattern of Anurogryllus sp (Orthoptera: Gryllidae). In the analyzed sample, high levels of numerical, morphological, and NORs polymorphisms were detected. Within five distinct karyotypes that were found, the basic karyotype of Anurogryllus sp. showed 2n(♂) = 22 + X0 with acrocentric autosomes and a metacentric X sex chromosome; furthermore, a conspicuous secondary constriction related to the NOR was present along the entire short arm on pair 5. The other four types of karyotypes arose from centric fusions between elements of pairs 1/3, 2/6, 4/7 and a NOR partial translocation from pair 5 onto the long arm terminal region of one element of the fused pair 2/6. Such intraspecific variability and the consequences of high levels of polymorphism are discussed, leading to conjectures about the mechanisms that led to these chromosome rearrangements.

Cytosystematics of threeOnobrychisspecies (Fabaceae) in Iran

Abstract In this study, we describe the morphological characters and meiotic chromosome number and behavior of different wild populations belonging to Onobrychis viciifolia Scop., O. transcaucasica Grossh. and O. altissima Grossh. belonging to Onobrychis sect. Onobrychis in Iran. All Iranian populations of O. viciifolia and O. altissima studied here were tetraploid and showed 2n = 4x = 28 chromosome number, but O. transcaucasica populations were diploid. The basic chromosome number (x = 7) is consistent with the proposed base number for O. viciifolia and O. altissima from IPCN. For O. altissima, two ploidy levels (2n = 2x = 14 and 2n = 4x = 28) have been previously reported from Caucasus. The fact that no diploid populations of O. altissima were found in Iran, would suggest a relatively recent origin of the species, most probably in Caucasus. Although O. transcaucasica is diploid, its remarkable similarities in morphology to O. viciifolia and O. altissima can be suggested its relatively recent origin for ...

Complete Switchgrass Genetic Maps Reveal Subgenome Collinearity, Preferential Pairing and Multilocus Interactions

Polyploidy is an important aspect of the evolution of flowering plants. The potential of gene copies to diverge and evolve new functions is influenced by meiotic behavior of chromosomes leading to segregation as a single locus or duplicated loci. Switchgrass (Panicum virgatum) linkage maps were constructed using a full-sib population of 238 plants and SSR and STS markers to access the degree of preferential pairing and the structure of the tetraploid genome and as a step toward identification of loci underlying biomass feedstock quality and yield. The male and female framework map lengths were 1645 and 1376 cM with 97% of the genome estimated to be within 10 cM of a mapped marker in both maps. Each map coalesced into 18 linkage groups arranged into nine homeologous pairs. Comparative analysis of each homology group to the diploid sorghum genome identified clear syntenic relationships and collinear tracts. The number of markers with PCR amplicons that mapped across subgenomes was significantly fewer than expected, suggesting substantial subgenome divergence, while both the ratio of coupling to repulsion phase linkages and pattern of marker segregation indicated complete or near complete disomic inheritance. The proportion of transmission ratio distorted markers was relatively low, but the male map was more extensively affected by distorted transmission ratios and multilocus interactions, associated with spurious linkages.

The paternal effect of chromosome translocation carriers observed from meiotic segregation in embryos

Human translocation carriers may present alterations in meiosis. Understanding the mechanism of meiotic segregation of reciprocal translocations is important for estimation of the risk of either pregnancy loss or birth defects. The objective of this work was to estimate meiotic segregation rates in preimplantation embryos from preimplantation genetic diagnosis (PGD) cycles of female and male reciprocal translocation carriers. In 20 cycles for 14 couples, PGD was performed on 118 day three embryos using fluorescence in situ hybridization (FISH) with specific probes for each translocation. The meiotic segregation modes and the effect of the paternal origin of translocated carrier were estimated. Overall, the proportions of alternate segregation for normal or balanced chromosome contents in preimplantation embryos from PGD cycles in reciprocal male and female carriers were not significantly different (35.5 versus 23.8%). However, the frequencies of adjacent-1 and adjacent-2 segregation were lower in embryos from female reciprocal translocation carriers than from male carriers. For male translocations, alternate segregation was the most frequent mode. The proportion of 3:1 segregation was the most frequent in female translocations carriers. We report differences in segregation modes in embryos obtained from PGD cycles according to the gender of reciprocal translocation carrier. However, these differences did not affect the proportion of balanced embryos and the take home baby rate. The analysis of the meiotic behaviour of chromosomes and the differences between the meiotic products of female and male for a chromosomal rearrangement could help predict the outcome of PGD for translocation carriers.

Characterization of Apomictic BC7 and BC8 Pearl Millet: Meiotic Chromosome Behavior and Construction of an ASGR‐carrier Chromosome‐specific Library

Apospory in Pennisetum squamulatum Fresen is inherited as a single‐locus dominant trait. Molecular analysis has identified the apospory‐specific genomic region (ASGR), a large segment of one chromosome that is necessary and sufficient to confer apomixis. To transfer apospory from P. squamulatum to pearl millet [P. glaucum (L.) R. Br.], advanced backcrosses were generated. Here we report the characterization of apomictic BC7 and BC8 generations. A BC7–derived genotype has two P. squamulatum chromosomes, while BC8–derived apomictic lines inherited only the ASGR chromosome that confers apospory to pearl millet. Morphologically, no significant differences were observed between backcross generations for plant height, leaf length, leaf width, and first internode and inflorescence lengths. However, the BC7 and BC8 lines differed significantly with regard to pollen viability, flowering time, and seed set. Pollen viability increased to 81% in the BC8 lines compared with 37% in BC7. The frequency of aposporous embryo sacs was lower in BC8 (79%) lines compared to BC7 (93%). Meiotic behavior of chromosomes during metaphase I and anaphase I showed that BC8 typically had a single univalent, identified as the ASGR chromosome by FISH (fluorescence in situ hybridization) and GISH (genomic in situ hybridization). Utilizing its unique behavior during meiosis the ASGR chromosome was microdissected and a chromosome‐specific library was constructed and sequenced. Analysis of sequences identified both novel and previously known ASGR‐linked sequences.

Meiosis in Three Species of Heteroptera from Ethiopia (East Africa)

Regardless of rich biodiversity, cytogenetic work on African Heteroptera is meagre. This paper reports meiotic behaviour of chromosomes in 3 species of Heteroptera from Ethiopia for the first time. Paracritheus trimaculatus and Eurydema pulchrum, both belonging to Pentatomidae, possess 2n=14=12A+XY while Cletus punctulatus belonging to Coreidae possesses 2n=18=14A+2m+X1X20. Certain characteristics are common in the 2 species of Pentatomidae such as fusion of the X and Y to form a heteropycnotic body at diffuse stage, and their behaviour at diakinesis and metaphase II. The 2 species, however, differ in chiasma frequency, the pattern of chromosomes at metaphase I and the degree of association between X and Y in the pseudobivalent at metaphase II. In Cletus punctulatus, the 2 sex chromosomes, X1 and X2, remain fused throughout meiosis except for a brief period during metaphase I. The fused X chromosomes precedes the autosomes during anaphase II. The Chiasma frequency is seen to be higher.

Meiotically asynapsis-induced aneuploidy in autopolyploid Arabidopsis thaliana

The patterns of homologue segregation are the basis for euploidy or aneuploidy formation in diploids and allo-/auto-polyploids. Homologue segregation in diploids resembles that in allopolyploids during meiosis; however, meiotic chromosome behavior in autopolyploids is complicated by multiplication of homologous chromosome components. Obviously, loss of single chromosomes (or segmented chromosomes) frequently leads to abortion of reproductive gametes in diploids and allopolyploids. In contrast, the consequence of chromosome loss in autopolyploids is effortlessly compensated for by the presence of multiplied chromosome complements. Here, we use the meiotically asynaptic gene asy1, in combination with polyploidization, to elucidate aneuploidy formation in autotetraploid Arabidopsis. The results indicate that, due to homologous asynapsis in meiotic prophase I, retarded chromosome losses could induce aneuploidy during gametogenesis in autotetraploid asy1. The severe loss of individual chromosomes probably reaches the haploid genome among selfed or backcrossed progeny, leading to stochastic chromosome loss in Arabidopsis. Reciprocal crosses of autotetraploid asy1 with wild-type prove a pathway of duoparental transmission of aneuploidy (hypoploidy and hyperploidy). Viable hypoploids over-transmit via male gametes; conversely, viable hyperploids transmit mainly in female gametogenesis. This result suggests a more stringent maternal restriction of ploidy transmission in autopolyploid Arabidopsis.

A comparative cytogenetic study of the rice (Oryza sativa L.) autotetraploid restorers and hybrids

We studied pollen fertility, seed set and cytogenetic characteristics of restorer lines and F1 hybrids of autotetraploid rice. T4002, T4063, T461A x T4002 and T461A x T4063 showed significantly higher pollen fertility and seed set than T4132 and T461A x T4132. Meiotic pairing configurations of T4002, T4063, T4132, T461A x T4002, T461A x T4063 and T461A x T4132 were 0.051 + 19.96II (9.89 rod + 10.07 ring) + 0.01III + + 2.00IV, 0.11I + 19.17II (8.90 rod + 10.37 ring) + 0.09III + 2.26IV + 0.01VI, 1.34I + 9.46II (4.50 rod + 4.96 ring) + 0.80III + 6.02IV + 0.09VI + 0.09VIII, 0.02I + 14.36II (6.44 rod + 7.91 ring) + 0.01III + 4.80IV + 0.01VIII, 0.06I + 17.67II (11.01 rod + 6.67 ring) + 0.06III + 3.10IV + 0.01VI and 1.11I + 11.31II (5.80 rod + 5.51 ring) + 0.41III + 5.63IV + 0.03VI + 0.03VIII, respectively. Configuration 16II + 4IV and 12II + 6IV occurred in the highest frequency among the autotetraploid restorers and hybrids. Meiotic chromosome behaviors were less abnormal in the tetraploids with high seed set than those with low seed set. The hybrids had fewer frequencies of bivalents, univalents, trivalents and multivalents than the restorers, but higher frequency of quatrivalents than the restorers at MI. The frequency of univalents at MI had the most impact on pollen fertility and seed set, i.e., pollen fertility decreased with the increase of univalents. The secondary impact factors were trivalents and multivalents, and bivalents and quatrivalents had no effect on pollen fertility and seed set. The correlative relationship between pollen fertility and cytogenetic behaviors could be utilized to improve seed set in autotetraploidy breeding.

Rapid genomic changes in polyploid wheat and related species: implications for genome evolution and genetic improvement

A polyploid organism by possessing more than two sets of chromosomes from one species (autopolyploidy) or two or more species (allopolyploidy) is known to have evolutionary advantages. However, by what means a polyploid accommodates increased genetic dosage or divergent genomes (allopolyploidy) in one cell nucleus and cytoplasm constitutes an enormous challenge. Recent years have witnessed efforts and progress in exploring the possible mechanisms by which these seemingly intangible hurdles of polyploidy may be ameliorated or eventually overcome. In particular, the documentation of rapid and extensive non-Mendelian genetic and epigenetic changes that often accompany nascent polyploidy is revealing: the resulting non-additive and novel gene expression at global, regional and local levels, and timely restoration of meiotic chromosomal behavior towards bivalent pairing and disomic inheritance may ensure rapid establishment and stabilization as well as its long-term evolutionary success. Further elucidation on these novel mechanisms underpinning polyploidy will promote our understanding on fundamental issues in evolutionary biology and in our manipulation capacities in future genetic improvement of important crops that are currently polyploids in genomic constitution. This review is intended to provide an updated discussion on these interesting and important issues within the scope of a specific yet one of the most important plant groups-polyploid wheat and its related species.

Pairing and recombination features during meiosis in Cebus paraguayanus (Primates: Platyrrhini).

BackgroundAmong neotropical Primates, the Cai monkey Cebus paraguayanus (CPA) presents long, conserved chromosome syntenies with the human karyotype (HSA) as well as numerous C+ blocks in different chromosome pairs.In this study, immunofluorescence (IF) against two proteins of the Synaptonemal Complex (SC), namely REC8 and SYCP1, two recombination protein markers (RPA and MLH1), and one protein involved in the pachytene checkpoint machinery (BRCA1) was performed in CPA spermatocytes in order to analyze chromosome meiotic behavior in detail.ResultsAlthough in the vast majority of pachytene cells all autosomes were paired and synapsed, in a small number of nuclei the heterochromatic C-positive terminal region of bivalent 11 remained unpaired. The analysis of 75 CPA cells at pachytene revealed a mean of 43.22 MLH1 foci per nucleus and 1.07 MLH1 foci in each CPA bivalent 11, always positioned in the region homologous to HSA chromosome 21.ConclusionOur results suggest that C blocks undergo delayed pairing and synapsis, although they do not interfere with the general progress of pairing and synapsis.

A Natural Hybrid Between Ligularia paradoxa and L. duciformis (Asteraceae, Senecioneae) From Yunnan, China1

A putative natural hybrid in Ligularia Cass., which is morphologically intermediate between L. paradoxa Hand.-Mazz. and L. duciformis (C. Winkl.) Hand.-Mazz., was found on Mt. Maoniu in northwestern Yunnan, China. We employed analyses of morphology, seed vigor, somatic chromosome numbers, meiotic behavior of chromosomes, inter-simple sequence repeat (ISSR) markers, and trnL-F sequencing to test the hypothesis that the unidentified taxon is a natural interspecific hybrid between L. paradoxa and L. duciformis. Examination of morphological characters demonstrated the intermediacy of the putative natural hybrid between L. paradoxa and L. duciformis. Seed germination of the putative natural hybrid was absent, and no embryo was found in seeds of the putative natural hybrid. The meiotic behavior of the putative natural hybrid was abnormal. Among 10 ISSR primers that we tested in all three taxa, four primers produced different ISSR markers between the putative parents. The putative natural hybrid shared all ISSR markers of the putative parents. However, no taxon-specific band existed in the samples of the putative natural hybrid. The data from ISSR markers are concordant with morphology in implicating L. paradoxa and L. duciformis as parents of the putative natural hybrid. Ligularia paradoxa was determined as the female parent of this natural hybrid by nucleotide sequence from the chloroplast trnL-F region. Therefore, this taxon is confirmed to be a natural hybrid between L. paradoxa and L. duciformis and is described herein.

Cytological studies of a dihaploid and hybrid from intergeneric cross Elymus shandongensis × Triticum aestivum

One dihaploid (n=2x=14) and one true hybrid (2n=5x=35) were produced from the intergeneric cross Elymus shandongensis X Triticum aestivum. The dihaploid was a result of selective elimination of T. aestivum chromosomes early in embryo development. Meiotic chromosome behaviour was studied in the parents, dihaploid, and hybrid. E. shandongensis (2n=4x=28) and the hexaploid wheat formed only bivalents at metaphase I. Some homoeologous chromosome pairing with an average of 0.68 bivalents, ranging from zero to four, and a very low frequency of trivalents was observed in the dihaploid. This reveals a low affinity between S and Y genomes of E. shandongensis. A haplo-insufficient (hemizygous ineffective) genetic control of homoeologous chromosome pairing may also exist in the species. Homologous chromosome association in the hybrid (0.25 chiasmata/cell) was distinctly lower than in the dihaploid (0.73 chiasmata/cell). This indicates that chromosome pairing suppressors, e.g., the Ph gene system, in T. aestivum could affect homoeologous chromosome pairing between the genomes of wild species.

Achiasmatic male meiosis in two species of Saldula (Saldidae, Hemiptera).

Male meiosis in two species of Saldula, S. orthothila and S. saltatoria was studied. The diploid chromosome numbers were found to be 2n=32+m+XY and 2n=32+2m+XO respectively. The existence of a Y-chromosome was recorded for the first time in this primitive heteropteran genus. The meiotic behaviour of the sex chromosomes was found to be similar to that of sex chromosomes in more advanced Heteroptera. Autosomal bivalents during late meiotic prophase and metaphase I consisted of two parallelly aligned chromosomes. No traces of chiasmata could be found. The role of Y-chromosome in the evolution of sex chromosome systems in Heteroptera, the mechanisms behind the regular segregation of achiasmatic chromosomes, the adaptive significance of achiasmatic meiosis and the restriction of achiasmatic meiosis to the heterogametic sex are discussed.

DNA double-strand breaks, but not crossovers, are required for the reorganization of meiotic nuclei in Tetrahymena.

During meiosis, the micronuclei of the ciliated protist Tetrahymena thermophila elongate dramatically. Within these elongated nuclei, chromosomes are arranged in a bouquet-like fashion and homologous pairing and recombination takes place. We studied meiotic chromosome behavior in Tetrahymena in the absence of two genes, SPO11 and a homolog of HOP2 (HOP2A), which have conserved roles in the formation of meiotic DNA double-strand breaks (DSBs) and their repair, respectively. Single-knockout mutants for each gene display only a moderate reduction in chromosome pairing, but show a complete failure to form chiasmata and exhibit chromosome missegregation. The lack of SPO11 prevents the elongation of meiotic nuclei, but it is restored by the artificial induction of DSBs. In the hop2ADelta mutant, the transient appearance of gamma-H2A.X and Rad51p signals indicates the formation and efficient repair of DSBs; but this repair does not occur by interhomolog crossing over. In the absence of HOP2A, the nuclei are elongated, meaning that DSBs but not their conversion to crossovers are required for the development of this meiosis-specific morphology. In addition, by in silico homology searches, we compiled a list of likely Tetrahymena meiotic proteins as the basis for further studies of the unusual synaptonemal complex-less meiosis in this phylogenetically remote model organism.

Strait of Gibraltar: an effective gene‐flow barrier for wind‐pollinated Carex helodes (Cyperaceae) as revealed by DNA sequences, AFLP, and cytogenetic variation

The Strait of Gibraltar is the most important barrier disconnecting the landmasses of Europe and Africa on the western Mediterranean extreme. Carex helodes is a wind-pollinated species endemic to the western Mediterranean. Because molecular and cytogenetic data allow the inference of its evolutionary history, we analyzed variations in chromosome number, including meiotic chromosome behavior, amplified fragment length polymorphism (AFLP) fingerprints, and nucleotide substitutions in plastid and nuclear DNA sequences. Cytogeographic results showed that the African populations have stabilized at a single chromosome number of 2n = 74, whereas the most frequent cytotype in Iberia is 2n = 72. Phylogenetic reconstructions of 17 sequences from nine closely related species revealed that C. helodes is monophyletic and that the Moroccan populations are embedded in the Iberian lineages. The haplotype network is also consistent with a European origin of the northern African haplotype. AFLP analysis also revealed hierarchical levels of genetic variation compatible with a founder effect process responsible for the African populations. All sources of evidence support the hypothesis that the Strait of Gibraltar has been an effective gene-flow barrier, generating two isolated evolutionary lineages after their dispersal. Recent connections between the two lineages appear unlikely, whereas active gene flow occurs among populations within the two lineages.

Sexuality, apomixis, ploidy levels, and genomic relationships among four Paspalum species of the subgenus Anachyris (Poaceae)

The subgenus Anachyris of the genus Paspalum comprises six species, all native to the New World. Cytology, embryology, fertility, and hybridization experiments were examined in four of the six species and different chromosome races. Meiotic chromosome behavior supported autoploid origin for tetraploid P. procurrens and tetraploid P. usterii, and also corroborates autoploidy for P. malacophyllum. Meiosis of the three species was compared with the meiotic chromosome behavior of a tetraploid P. simplex strain acquired by artificial autopolyploidization. Moreover, chromosome associations observed in tetraploid interspecific hybrids of P. simplex× procurrens and P. simplex× usterii, in triploid hybrids of P. simplex× malacophyllum, and in diploid hybrids of P. simplex× malacophyllum, indicate that the four species share the same basic genome, and that the polyploid races are autoploids. Facultative apomixis of the aposporous type is reported for the first time in tetraploid strains of P. procurrens and P. usterii. It is also confirmed for tetraploid P. malacophyllum, a species whose diploid representative is here reported to reproduce sexually, though embryological analyses demonstrated some potential for apospory. Our results suggest that the whole subgenus Anachyris of Paspalum is basically an agamic complex. At least three species: P. simplex, P. procurrens, and P. malacophyllum involve sexual self-incompatible diploid races as well as apomictic polyploid (mainly tetraploid) representatives.

Meiotic chromosome behaviour in the male damselfly, Calopteryx virgo (LINNAEUS), with a discussion on the value of chromosome numbers and karyotype morphology in odonate systematics

Meiotic chromosome behaviour in the male damselfly, Calopteryx virgo (LINNAEUS), with a discussion on the value of chromosome numbers and karyotype morphology in odonate systematics