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Homologous chromosome pairing

Philippe Lefrançois, Beth Rockmill, Pingxing Xie, G Shirleen Roeder, Michael Snyder
During meiosis, chromosomes undergo a homology search in order to locate their homolog to form stable pairs and exchange genetic material. Early in prophase, chromosomes associate in mostly non-homologous pairs, tethered only at their centromeres. This phenomenon, conserved through higher eukaryotes, is termed centromere coupling in budding yeast. Both initiation of recombination and the presence of homologs are dispensable for centromere coupling (occurring in spo11 mutants and haploids induced to undergo meiosis) but the presence of the synaptonemal complex (SC) protein Zip1 is required...
October 2016: PLoS Genetics
Traci Kantarski, Steve Larson, Xiaofei Zhang, Lee DeHaan, Justin Borevitz, James Anderson, Jesse Poland
Development of the first consensus genetic map of intermediate wheatgrass gives insight into the genome and tools for molecular breeding. Intermediate wheatgrass (Thinopyrum intermedium) has been identified as a candidate for domestication and improvement as a perennial grain, forage, and biofuel crop and is actively being improved by several breeding programs. To accelerate this process using genomics-assisted breeding, efficient genotyping methods and genetic marker reference maps are needed. We present here the first consensus genetic map for intermediate wheatgrass (IWG), which confirms the species' allohexaploid nature (2n = 6x = 42) and homology to Triticeae genomes...
October 13, 2016: TAG. Theoretical and Applied Genetics. Theoretische und Angewandte Genetik
Timothy L Haskett, Jason J Terpolilli, Amanuel Bekuma, Graham W O'Hara, John T Sullivan, Penghao Wang, Clive W Ronson, Joshua P Ramsay
Integrative and conjugative elements (ICEs) are ubiquitous mobile genetic elements present as "genomic islands" within bacterial chromosomes. Symbiosis islands are ICEs that convert nonsymbiotic mesorhizobia into symbionts of legumes. Here we report the discovery of symbiosis ICEs that exist as three separate chromosomal regions when integrated in their hosts, but through recombination assemble as a single circular ICE for conjugative transfer. Whole-genome comparisons revealed exconjugants derived from nonsymbiotic mesorhizobia received three separate chromosomal regions from the donor Mesorhizobium ciceri WSM1271...
October 12, 2016: Proceedings of the National Academy of Sciences of the United States of America
Mitzi I Kuroda, Andres Hilfiker, John C Lucchesi
The sex chromosomes have special significance in the history of genetics. The chromosomal basis of inheritance was firmly established when Calvin Bridges demonstrated that exceptions to Mendel's laws of segregation were accompanied at the cytological level by exceptional sex chromosome segregation. The morphological differences between X and Y exploited in Bridges' experiments arose as a consequence of the evolution of the sex chromosomes. Originally a homologous chromosome pair, the degeneration of the Y chromosome has been accompanied by a requirement for increased expression of the single X chromosome in males...
October 2016: Genetics
Marcello Stanzione, Marek Baumann, Frantzeskos Papanikos, Ihsan Dereli, Julian Lange, Angelique Ramlal, Daniel Tränkner, Hiroki Shibuya, Bernard de Massy, Yoshinori Watanabe, Maria Jasin, Scott Keeney, Attila Tóth
DNA double-strand breaks (DSBs) are induced by SPO11 during meiosis to initiate recombination-mediated pairing and synapsis of homologous chromosomes. Germline genome integrity requires spatiotemporal control of DSB formation, which involves the proteinaceous chromosome axis along the core of each meiotic chromosome. In particular, a component of unsynapsed axes, HORMAD1, promotes DSB formation in unsynapsed regions where DSB formation must occur to ensure completion of synapsis. Despite its importance, the underlying mechanism has remained elusive...
October 10, 2016: Nature Cell Biology
Tyler S Machovina, Rana Mainpal, Anahita Daryabeigi, Olivia McGovern, Dimitra Paouneskou, Sara Labella, Monique Zetka, Verena Jantsch, Judith L Yanowitz
Crossover (CO) recombination creates a physical connection between homologs that promotes their proper segregation at meiosis I (MI). Failure to realize an obligate CO causes homologs to attach independently to the MI spindle and separate randomly, leading to nondisjunction. However, mechanisms that determine whether homolog pairs have received crossovers remain mysterious. Here we describe a surveillance system in C. elegans that monitors recombination intermediates and couples their formation to meiotic progression...
October 1, 2016: Current Biology: CB
R C R Noronha, L M R Barros, R E F Araújo, D F Marques, C Y Nagamachi, C Martins, J C Pieczarka
BACKGROUND: Cytogenetic studies were conducted in the Brazilian Amazon turtles, Podocnemis expansa Schweigger, 1912 (PEX) and Podocnemis unifilis Troschel, 1848 (PUN) to understand their karyoevolution. Their chromosomal complements were compared using banding techniques (C, G-, Ag-NOR and Chromomycin A3) and fluorescence in situ hybridization (FISH), and efforts were made to establish evolutionary chromosomal relationships within the Podocnemidae family. RESULTS: Our results revealed that both species have a chromosome complement of 2n = 28...
2016: Molecular Cytogenetics
Andrew N Keller, Yue Xin, Stephanie Boer, Jonathan Reinhardt, Rachel Baker, Lidia K Arciszewska, Peter J Lewis, David J Sherratt, Jan Löwe, Ian Grainge
Bacterial chromosomes are most often circular DNA molecules. This can produce a topological problem; a genetic crossover from homologous recombination results in dimerization of the chromosome. A chromosome dimer is lethal unless resolved. A site-specific recombination system catalyses this dimer-resolution reaction at the chromosomal site dif. In Escherichia coli, two tyrosine-family recombinases, XerC and XerD, bind to dif and carry out two pairs of sequential strand exchange reactions. However, what makes the reaction unique among site-specific recombination reactions is that the first step, XerD-mediated strand exchange, relies on interaction with the very C-terminus of the FtsK DNA translocase...
October 6, 2016: Scientific Reports
Aimee Jaramillo-Lambert, Amy S Fabritius, Tyler J Hansen, Harold E Smith, Andy Golden
Topoisomerase II alleviates DNA entanglements that are generated during mitotic DNA replication, transcription, and sister chromatid separation. In contrast to mitosis, meiosis has two rounds of chromosome segregation following one round of DNA replication. In meiosis II, sister chromatids segregate from each other similar to mitosis. Meiosis I, on the other hand, segregates homologs, which requires pairing, synapsis, and recombination. The exact role that topoisomerase II plays during meiosis is unknown. In a screen re-examining Caenorhabditis elegant legacy mutants isolated thirty years ago, we identified a novel allele of the gene encoding topoisomerase II, top-2(it7) In this study, we demonstrate that top-2(it7) males produce dead embryos, even when fertilizing wild-type oocytes...
October 5, 2016: Genetics
Jamille A Bitencourt, Iracilda Sampaio, Robson T C Ramos, Marcelo Ricardo Vicari, Paulo Roberto A de M Affonso
American soles (family Achiridae) have been characterized by remarkable chromosomal variation even though several species lack basic cytogenetic information. This trend indicates that chromosomal traits can be useful to taxonomy once the morphological identification of some taxa in this family (e.g., Achirus species) is controversial. In this work, we expand the cytogenetic data in Achiridae by providing the first karyotypic analysis of Achirus achirus. An unusual multiple sex chromosome system (X1X1X2X2/X1X2Y) was detected, once males presented 2n = 33 with three unpaired chromosomes (X1X2Y) while females presented 2n = 34 with two acrocentric pairs (X1X1 and X2X2) found in hemizygosis in males...
September 27, 2016: Zebrafish
Jinsil Kim, Dong-Uk Kim, Kwang-Lae Hoe
Targeted gene deletion is a useful tool for understanding the function of a gene and its protein product. We have developed an efficient and robust gene deletion approach in yeast that employs oligonucleotide-based gene synthesis. This approach requires a deletion cassette composed of three modules: a central 1397-bp KanMX4 selection marker module and two 366-bp gene-specific flanking modules. The invariable KanMX4 module can be used in combination with different pairs of flanking modules targeting different genes...
2017: Methods in Molecular Biology
Xiaohong Yan, Xinhua Zeng, Shasha Wang, Keqi Li, Rong Yuan, Hongfei Gao, Junling Luo, Fang Liu, Yuhua Wu, Yunjing Li, Li Zhu, Gang Wu
Genic male sterility (GMS) has already been extensively utilized for hybrid rapeseed production. TE5A is a novel thermo-sensitive dominant GMS line in Brassica napus, however, its mechanisms of GMS remain largely unclear. Histological and Transmission electron microscopy (TEM) analyses of anthers showed that the male gamete development of TE5A was arrested at meiosis prophase I. EdU uptake of S-phase meiocytes revealed that the TE5A mutant could accomplish DNA replication, however, chromosomal and fluorescence in situ hybridization (FISH) analyses of TE5A showed that homologous chromosomes could not pair, synapse, condense and form bivalents...
September 27, 2016: Scientific Reports
Xuli Zhu, Huan Li, Meixia Ye, Libo Jiang, Mengmeng Sang, Rongling Wu
Allopolyploids are a group of polyploids with more than two sets of chromosomes derived from different species. Previous linkage analysis of allopolyploids is based on the assumption that different chromosomes pair randomly during meiosis. A more sophisticated model to relax this assumption has been developed for allotetraploids by incorporating the preferential pairing behavior of homologous over homoeologous chromosomes. Here, we show that the basic principle of this model can be extended to perform linkage analysis of higher-ploidy allohexaploids, where multiple preferential pairing factors are used to characterize chromosomal-pairing meiotic features between different constituent species...
September 19, 2016: Briefings in Bioinformatics
Stephen Gray, Paula E Cohen
Meiosis, the mechanism of creating haploid gametes, is a complex cellular process observed across sexually reproducing organisms. Fundamental to meiosis is the process of homologous recombination, whereby DNA double-strand breaks are introduced into the genome and are subsequently repaired to generate either noncrossovers or crossovers. Although homologous recombination is essential for chromosome pairing during prophase I, the resulting crossovers are critical for maintaining homolog interactions and enabling accurate segregation at the first meiotic division...
September 14, 2016: Annual Review of Genetics
Pingbo Zhang, Min Zhu, Minghui Geng-Spyropoulos, Michelle Shardell, Marta Gonzalez-Freire, Vilmundur Gudnason, Gudny Eiriksdottir, Debra Schaumberg, Jennifer E Van Eyk, Luigi Ferrucci, Richard D Semba
Age-related macular degeneration (AMD) is a leading cause of visual loss among older adults. Two variants in the complement factor H (CFH) gene, Y402H and I62V, are strongly associated with risk of AMD. CFH is encoded in Regulator of Complement Activation gene cluster in chromosome 1q32, which includes complement factor-related (CFHR) proteins, CFHR1 to CFHR5, with high amino acid sequence homology to CFH. Our goal was to build a selected reaction monitoring (SRM) assay to measure plasma concentrations of CFH variants Y402, H402, I62, and V62, and CFHR1-5...
September 20, 2016: Proteomics
Tiago Ribeiro, André Marques, Petr Novák, Veit Schubert, André L L Vanzela, Jiri Macas, Andreas Houben, Andrea Pedrosa-Harand
Satellite DNA repeats (or satDNA) are fast-evolving sequences usually associated with condensed heterochromatin. To test whether the chromosomal organisation of centromeric and non-centromeric satDNA differs in species with holocentric chromosomes, we identified and characterised the major satDNA families in the holocentric Cyperaceae species Rhynchospora ciliata (2n = 10), R. globosa (2n = 50) and R. tenuis (2n = 2x = 4 and 2n = 4x = 8). While conserved centromeric repeats (present in R. ciliata and R...
September 19, 2016: Chromosoma
Eugene Gladyshev, Nancy Kleckner
Numerous cytogenetic observations have shown that homologous chromosomes (or individual chromosomal loci) can engage in specific pairing interactions in the apparent absence of DNA breakage and recombination, suggesting that canonical recombination-mediated mechanisms may not be the only option for sensing DNA/DNA homology. One proposed mechanism for such recombination-independent homology recognition involves direct contacts between intact double-stranded DNA molecules. The strongest in vivo evidence for the existence of such a mechanism is provided by the phenomena of homology-directed DNA modifications in fungi, known as repeat-induced point mutation (RIP, discovered in Neurospora crassa) and methylation-induced premeiotically (MIP, discovered in Ascobolus immersus)...
September 14, 2016: Current Genetics
Adel Sepsi, James D Higgins, J S Pat Heslop-Harrison, Trude Schwarzacher
During meiosis, centromeres in some species undergo a series of associations, but the processes and progression to homologous pairing is still a matter of debate. Here, we aimed to correlate meiotic centromere dynamics and early telomere behaviour to the progression of synapotonemal complex (SC) construction in hexaploid wheat (2n=42) by triple immunolabelling of CENH3 protein marking functional centromeres, and SC proteins ASY1 (unpaired lateral elements) and ZYP1 (central elements in synapsed chromosomes)...
September 14, 2016: Plant Journal: for Cell and Molecular Biology
Kazuhiro Katsumata, Ami Hirayasu, Junpei Miyoshi, Eriko Nishi, Kento Ichikawa, Kazuki Tateho, Airi Wakuda, Hirotada Matsuhara, Ayumu Yamamoto
During meiotic prophase, telomeres cluster, forming the bouquet chromosome arrangement, and facilitate homologous chromosome pairing. In fission yeast, bouquet formation requires switching of telomere and centromere positions. Centromeres are located at the spindle pole body (SPB) during mitotic interphase, and upon entering meiosis, telomeres cluster at the SPB, followed by centromere detachment from the SPB. Telomere clustering depends on the formation of the microtubule-organizing center at telomeres by the linker of nucleoskeleton and cytoskeleton complex (LINC), while centromere detachment depends on disassembly of kinetochores, which induces meiotic centromere formation...
September 2016: PLoS Genetics
Mike V Van, Braden J Larson, JoAnne Engebrecht
Meiotic recombination establishes connections between homologous chromosomes to promote segregation. Hemizygous regions of sex chromosomes have no homologous chromosome to recombine with yet must be transmitted through meiosis. An extreme case of hemizygosity exists in the genus Caenorhabditis, where males have a single X chromosome that completely lacks a homologous partner. To determine whether similar strategies have evolved to accommodate hemizygosity of the X during male meiosis in Caenorhabditis with distinct modes of sexual reproduction, we examined induction and processing of meiotic double strand breaks (DSBs) in androdioecious (hermaphrodite/male) C...
September 7, 2016: Genetics
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