Gamete duplication
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The genomes of many plants, animals, and fungi frequently comprise dispensable B chromosomes that rely upon various chromosomal drive mechanisms to counteract the tendency of non-essential genetic elements to be purged over time. The B chromosome of rye - a model system for nearly a century - undergoes targeted nondisjunction during first pollen mitosis, favouring segregation into the generative nucleus, thus increasing their numbers over generations. However, the genetic mechanisms underlying this process are poorly understood. Here, using a newly-assembled, ~430 Mb-long rye B chromosome pseudomolecule, we identify five candidate genes whose role as trans-acting moderators of the chromosomal drive is supported by karyotyping, chromosome drive analysis and comparative RNA-seq. Among them, we identify DCR28, coding a microtubule-associated protein related to cell division, and detect this gene also in the B chromosome of Aegilops speltoides. The DCR28 gene family is neo-functionalised and serially-duplicated with 15 B chromosome-located copies that are uniquely highly expressed in the first pollen mitosis of rye.
- MeSH
- Aegilops genetika metabolismus MeSH
- chromozomy rostlin * genetika MeSH
- karyotypizace MeSH
- mitóza * genetika MeSH
- nondisjunkce genetická MeSH
- pyl genetika MeSH
- regulace genové exprese u rostlin MeSH
- rostlinné geny MeSH
- rostlinné proteiny genetika metabolismus MeSH
- žito * genetika MeSH
- Publikační typ
- časopisecké články MeSH
Genome size and chromosome number of five Cimicidae species were compared with the similar data recently received from Cimex lectularius parasitizing human. The average nuclear DNA content (males) was 2C = 1.47 pg in C. hemipterus, 2C = 1.61 pg in C. hirundinis, 2C = 1.80 pg in C. lectularius from bats, 2C = 1.68 pg in C. pipistrelli, and 2C = 1.22 pg in Paracimex cf. chaeturus. In the genomes of all cimicid species analyzed, the average GC content ranged from 32.74% in C. pipistrelli to 35.87% in P. cf. chaeturus. Chromosome variability with two male cytotypes, 2n = 28 + X1 X2 Y and 28 + X1 X2 X3 Y, was confirmed in C. pipistrelli. In addition, intraspecific variability in chromosome number was revealed in C. lectularius from bats with 2n = 26 + X1 X2 Y and 26 + X1 X2 X3 Y. We suggest that the origin of intraspecific variability in chromosome number of C. lectularius from bats and C. pipistrelli is not only the result of simple fragmentation, but additive rearrangements like duplications are probably also involved. © 2019 International Society for Advancement of Cytometry.
- MeSH
- buněčné jádro genetika metabolismus MeSH
- Chiroptera MeSH
- chromozomy genetika MeSH
- cytogenetické vyšetření MeSH
- délka genomu MeSH
- fragmentace DNA MeSH
- gonády cytologie MeSH
- lidé MeSH
- ploidie MeSH
- pohlavní chromozomy genetika MeSH
- průtoková cytometrie MeSH
- štěnice genetika metabolismus MeSH
- zárodečné buňky chemie metabolismus MeSH
- zastoupení bazí genetika MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- srovnávací studie MeSH
BACKGROUND: A decade ago, the mixed reproductive strategy Asexual Queen Succession (AQS) was first described in termites. In AQS species, the workers, soldiers and dispersing reproductives are produced through sexual reproduction, while non-dispersing (neotenic) queens arise through automictic thelytokous parthenogenesis, replace the founding queen and mate with the founding king. As yet, AQS has been documented in six species from three lineages of lower (Rhinotermitidae) and higher (Termitinae: Termes group and Syntermitinae) termites. Independent evolution of the capacity of thelytoky as a preadaptation to AQS is supported by different mechanisms of automixis in each of the three clades. These pioneering discoveries prompt the question on the extent of thelytoky and AQS in the diversified family of higher termites. RESULTS: Here, we investigated the capacity of thelytoky and occurrence of AQS in three species from the phylogenetic proximity of the neotropical AQS species Cavitermes tuberosus (Termitinae: Termes group): Palmitermes impostor, Spinitermes trispinosus, and Inquilinitermes inquilinus. We show that queens of all three species are able to lay unfertilized eggs, which undergo thelytokous parthenogenesis (via gamete duplication as in C. tuberosus) and develop through the transitional stage of aspirants into replacement neotenic queens. CONCLUSIONS: The breeding system in P. impostor is very reminiscent of that described in C. tuberosus and can be characterized as AQS. In the remaining two species, our limited data do not allow classifying the breeding system as AQS; yet, also in these species the thelytokous production of neotenic females appears to be a systematic element of reproductive strategies. It appears likely that the capacity of thelytokous parthenogenesis evolved once in the Termes group, and may ultimately be found more widely, well beyond these Neotropical species.
The maintenance of genome integrity over cell divisions is critical for plant development and the correct transmission of genetic information to the progeny. A key factor involved in this process is the STRUCTURAL MAINTENANCE OF CHROMOSOME5 (SMC5) and SMC6 (SMC5/6) complex, related to the cohesin and condensin complexes that control sister chromatid alignment and chromosome condensation, respectively. Here, we characterize NON-SMC ELEMENT4 (NSE4) paralogs of the SMC5/6 complex in Arabidopsis (Arabidopsis thaliana). NSE4A is expressed in meristems and accumulates during DNA damage repair. Partial loss-of-function nse4a mutants are viable but hypersensitive to DNA damage induced by zebularine. In addition, nse4a mutants produce abnormal seeds, with noncellularized endosperm and embryos that maximally develop to the heart or torpedo stage. This phenotype resembles the defects in cohesin and condensin mutants and suggests a role for all three SMC complexes in differentiation during seed development. By contrast, NSE4B is expressed in only a few cell types, and loss-of-function mutants do not have any obvious abnormal phenotype. In summary, our study shows that the NSE4A subunit of the SMC5-SMC6 complex is essential for DNA damage repair in somatic tissues and plays a role in plant reproduction.
- MeSH
- Arabidopsis embryologie genetika imunologie MeSH
- duplikace genu MeSH
- genom rostlinný MeSH
- oprava DNA * genetika MeSH
- podjednotky proteinů metabolismus MeSH
- poškození DNA * genetika MeSH
- proteiny buněčného cyklu genetika metabolismus MeSH
- proteiny huseníčku genetika metabolismus MeSH
- pyl genetika MeSH
- regulace genové exprese u rostlin MeSH
- semena rostlinná genetika metabolismus MeSH
- transkriptom genetika MeSH
- upregulace genetika MeSH
- vajíčko rostlin genetika MeSH
- vazba proteinů MeSH
- vývojová regulace genové exprese MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Callose is a plant-specific polysaccharide (β-1,3-glucan) playing an important role in angiosperms in many developmental processes and responses to biotic and abiotic stresses. Callose is synthesised at the plasma membrane of plant cells by callose synthase (CalS) and, among others, represents the main polysaccharide in the callose wall surrounding the tetrads of developing microspores and in the growing pollen tube wall. CalS proteins involvement in spore development is a plesiomorphic feature of terrestrial plants, but very little is known about their evolutionary origin and relationships amongst the members of this protein family. We performed thorough comparative analyses of callose synthase family proteins from major plant lineages to determine their evolutionary history across the plant kingdom. A total of 1211 candidate CalS sequences were identified and compared amongst diverse taxonomic groups of plants, from bryophytes to angiosperms. Phylogenetic analyses identified six main clades of CalS proteins and suggested duplications during the evolution of specialised functions. Twelve family members had previously been identified in Arabidopsis thaliana. We focused on five CalS subfamilies directly linked to pollen function and found that proteins expressed in pollen evolved twice. CalS9/10 and CalS11/12 formed well-defined clades, whereas pollen-specific CalS5 was found within subfamilies that mostly did not express in mature pollen vegetative cell, although were found in sperm cells. Expression of five out of seven mature pollen-expressed CalS genes was affected by mutations in bzip transcription factors. Only three subfamilies, CalS5, CalS10, and CalS11, however, formed monophyletic, mostly conserved clades. The pairs CalS9/CalS10, CalS11/CalS12 and CalS3 may have diverged after angiosperms diversified from lycophytes and bryophytes. Our analysis of fully sequenced plant proteins identified new evolutionary lineages of callose synthase subfamilies and has established a basis for understanding their functional evolution in terrestrial plants.
Termite colonies are typically founded by a pair of sexually reproducing dispersers, which can sometimes be replaced by some of their offspring. Some Reticulitermes and Embiratermes species routinely practice asexual queen succession (AQS): the queen is replaced by neotenic daughters produced by parthenogenesis, which mate with the primary king. Here, to cast light on the evolution of AQS, we investigated another candidate species, Cavitermes tuberosus (Termitinae). Of 95 nests, 39 contained a primary queen and 28 contained neotenic females (2-667 individuals), usually with the primary king. Microsatellite analyses confirmed that colonies were initiated by single pairs after large dispersal flights. More than 80% of the neotenic females were of exclusively maternal origin and completely homozygous, suggesting automictic parthenogenesis with gamete duplication. Conversely, workers, soldiers, and most alates and primary reproductives were produced sexually. AQS often occurs late, after colonies have reached maturity, whereas early AQS in other species may boost the young colony's growth rate. We suggest additional benefits of AQS in C. tuberosus, related with a smaller size, lesser stability and higher mobility of colonies. Our data add to the phylogenetical dispersion and diversity of modalities of AQS in termites, supporting a multiple evolutionary origin of this process.
- MeSH
- genetická variace * MeSH
- Isoptera genetika fyziologie MeSH
- partenogeneze * MeSH
- zvířata MeSH
- Check Tag
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
In vitro maturation (IVM) and in vitro fertilization (IVF) technologies are facing with growing demands of older women to conceive. Although ovarian stem cells (OSCs) of older women are capable of producing in vitro fresh oocyte-like cells (OLCs), such cells cannot respond to IVM and IVF due to the lack of granulosa cells required for their maturation. Follicular renewal is also dependent on support of circulating blood mononuclear cells. They induce intermediary stages of meiosis (metaphase I chromosomal duplication and crossover, anaphase, telophase, and cytokinesis) in newly emerging ovarian germ cells, as for the first time demonstrated here, induce formation of granulosa cells, and stimulate follicular growth and development. A pretreatment of OSC culture with mononuclear cells collected from blood of a young healthy fertile woman may cause differentiation of bipotential OSCs into both developing germ and granulosa cells. A small blood volume replacement may enable treatment of ovarian infertility in vivo. The transferred mononuclear cells may temporarily rejuvenate virtually all tissues, including improvement of the function of endocrine tissues. Formation of new follicles and their development may be sufficient for IVM and IVF. The novel proposed in vitro approaches may be used as a second possibility. Infertility of human males affects almost a half of the infertility cases worldwide. Small blood volume replacement from young healthy fertile men may also be easy approach for the improvement of sperm quality in older or other affected men. In addition, body rejuvenation by small blood volume replacement from young healthy individuals of the same sex could represent a decline of in vitro methodology in favor of in vivo treatment for human functional diseases. Here we propose for the first time that blood mononuclear cells are essential for rejuvenation of those tissues, where immune system components participate in an appropriate division and differentiation of tissue stem cells. If needed, small blood volume replacement from distinct young healthy individuals could be utilized in six month intervals for repair of young altered or aged reproductive and other tissue functions. Systemic and local use of honey bee propolis tincture is an alternative option for functional rejuvenation of some tissues.
- MeSH
- fertilizace in vitro metody trendy MeSH
- kmenové buňky cytologie MeSH
- lidé MeSH
- mužská infertilita terapie MeSH
- ovarium cytologie MeSH
- primární ovariální insuficience komplikace MeSH
- testis cytologie MeSH
- zárodečné buňky cytologie MeSH
- ženská infertilita terapie MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- úvodní články MeSH
- úvodníky MeSH
Genome duplication (polyploidy) is a recurrent evolutionary process in plants, often conferring instant reproductive isolation and thus potentially leading to speciation. Outcome of the process is often seen in the field as different cytotypes co-occur in many plant populations. Failure of meiotic reduction during gametogenesis is widely acknowledged to be the main mode of polyploid formation. To get insight into its role in the dynamics of polyploidy generation under natural conditions, and coexistence of several ploidy levels, we developed a general gametic model for diploid-polyploid systems. This model predicts equilibrium ploidy frequencies as functions of several parameters, namely the unreduced gamete proportions and fertilities of higher ploidy plants. We used data on field ploidy frequencies for 39 presumably autopolyploid plant species/populations to infer numerical values of the model parameters (either analytically or using an optimization procedure). With the exception of a few species, the model fit was very high. The estimated proportions of unreduced gametes (median of 0.0089) matched published estimates well. Our results imply that conditions for cytotype coexistence in natural populations are likely to be less restrictive than previously assumed. In addition, rather simple models show sufficiently rich behaviour to explain the prevalence of polyploids among flowering plants.
Výskyt paracentrických inverzí v běžné populaci není přesně stanoven, kolísá od 0,09 do 0,49 případů na 1000 jedinců. Párování homologních chromozómů při meióze bývá u těchto inverzímaximalizováno zformováníminverzní smyčky. Pokud v této smyčce dojde ke crossing-overu, může vzniknout acentrický a dicentrický chromozóm. Ve výsledných gametách tak dochází k různým duplikacím a deficiencím, které vedou k neživotaschopnosti plodu. Z tohoto pravidla existují výjimky, jednou z nich může být tzv. rekombinace U smyčkou. Jde o abnormální proces na základě chromatidových zlomů a znovuspojení, výsledkem jsou monocentrické rekombinované chromozómy. Většina paracentrických inverzí u člověka nepředstavuje větší riziko a pravděpodobnost narození dítěte s nevyváženým karyotypem je u heterozygotů – nosičů této inverze – relativně nízká. Proto je při těhotenství náhodně zachycených nosičů nabídka prenatálního vyšetření chromozómů víceméně nezávazná. Je však třeba mít na paměti, že u některých případů je velmi obtížné rozlišit paracentrickou inverzi od paracentrické inzerce – riziko inzerce je okolo 15 %. Dojde-li v plodové vodě k zachycení paracentrické inverze vzniklé de novo, to znamená, že rodiče mají karyotyp normální, je vhodné partnerům sdělit riziko postižení plodu ve výši 6,7 %, které je v podstatě platné pro všechny nově vzniklé dvouzlomové přestavby.
The incidence of paracentric inversions in the general population has not been clearly established, it ranges from 0.09 to 0.49/1,000. Homologue pairing during meiosis in a paracentric-inversion heterozygote is maximized by the formation of an inversion loop. If a crossing-over occurs within this loop, dicentric and acentric chromosomes are formed. Resulting gametes can have variety of duplications and deficiencies and give a non-viable progeny. One of the exceptions to the rule is a mutation event „U loop recombination“. FromU-loop event a monocentric recombinant chromosome can arise by an abnormal process, which involves chromatid breakage and reunion. Most of the paracentric inversions inman are harmless and the risk of heterozygotes having a child with an unbalanced karyotype is relatively low. In carriers of an accidentally discovered paracentric inversion, amniocentesis is optional. However, in some cases, it is difficult to distinguish between a paracentric inversion and paracentric insertion - the risk of the insertion is about 15 %. When a de novo inversion is detected in amniotic fluid, the overall risk for two-break rearrangements is 6.7 %.
Pericentrické inverze lidských chromozómů jsou přestavby, které vznikají dvěma zlomy na krátkém a na dlouhém rameni chromozómu a následným otočením a znovu připojením odděleného segmentu v opačné poloze. Tato abnormalita nevede u převážné většiny nosičů k žádnému klinickému projevu. Avšak základním rizikem nosičství inverzí je možnost vzniku rekombinační aneusomie - další přestavby invertovaného chromozómu, ke které může dojít v průběhu gametogeneze. Koncepce z rekombinované gamety většinou vede ke spontánnímu potratu, nebo k narození těžce postiženého jedince. Riziko rekombinace u každé nově zachycené inverze je třeba individuálně posoudit. Čím větší část chromozómu je zahrnuta v pericentrické inverzi, tím menší je rozsah vzniklé duplikace a deficience chromozomových částí v důsledku rekombinace, a tím je také větší životaschopnost postiženého plodu. V rodinách, ve kterých již byl výskyt rekombinace zjištěn, je plně indikováno chromozomální vyšetření plodu. Dále je nutné prenatální vyšetření nabídnout přinejmenším tehdy, je-li přestavba evidována v seznamu rizikových inverzí anebo je-li rozsahem větší, než uvedené inverze. Vedle rizikových existují také inverze „bezpečné“ bez prokázané rekombinace, mezi které patří především drobná, často se vyskytující přestavba chromozómu 2 - inv(2)(p11q13) a inverze na chromozómu 10 - inv(10)(p11q21).
Pericentric inversions of human chromosomes represent rearrangements are formed between two breaks on the short and on long arms of the chromosome with following rotation and new connection of the separated segment in the reversed position. The abnormality does not result in most of the carriers to any clinical manifestations. However, the basic risk the carriers of such inversion are exposed is the possibility of formation of a recombinant aneusomy - later transformation of the inverted chromosome during gametogenesis. Conception by the recombinant gamete usually results in spontaneous abortion or to a birth of seriously affected individual. The risk of recombination has to be in every newly registered inversion individually considered. The larger part of chromosome is taken into the pericentic inversion, the smaller is the extent of resulting duplication and smaller is the deficiency of chromosomal parts, which results from the recombination. The higher is then the viability of the affected foetus. In families with detected recombination, chromosomal examination is fully recommended. Prenatal examination is also indicated when the transformation is listed among the risk inversions or it has larger extent then recorded inversions. Beside the risk inversions, also the „safe“ inversions exist, which include minor and frequently occurring transformation of chromosome No 2 - inv(2)(p11q13) and inversion of chromosome 10 - inv(10)(p11q21).
