Heat stress is a major threat to global crop production, and understanding its impact on plant fertility is crucial for developing climate-resilient crops. Despite the known negative effects of heat stress on plant reproduction, the underlying molecular mechanisms remain poorly understood. Here, we investigated the impact of elevated temperature on centromere structure and chromosome segregation during meiosis in Arabidopsis thaliana. Consistent with previous studies, heat stress leads to a decline in fertility and micronuclei formation in pollen mother cells. Our results reveal that elevated temperature causes a decrease in the amount of centromeric histone and the kinetochore protein BMF1 at meiotic centromeres with increasing temperature. Furthermore, we show that heat stress increases the duration of meiotic divisions and prolongs the activity of the spindle assembly checkpoint during meiosis I, indicating an impaired efficiency of the kinetochore attachments to spindle microtubules. Our analysis of mutants with reduced levels of centromeric histone suggests that weakened centromeres sensitize plants to elevated temperature, resulting in meiotic defects and reduced fertility even at moderate temperatures. These results indicate that the structure and functionality of meiotic centromeres in Arabidopsis are highly sensitive to heat stress, and suggest that centromeres and kinetochores may represent a critical bottleneck in plant adaptation to increasing temperatures.
- Klíčová slova
- A. thaliana, cell biology, centremeres, centromeric histone, chromosomes, gene expression, meiosis, micronuclei, spindle assembly checkpoint,
- MeSH
- Arabidopsis * genetika metabolismus MeSH
- centromera metabolismus MeSH
- histony metabolismus MeSH
- kinetochory metabolismus MeSH
- meióza MeSH
- reakce na tepelný šok MeSH
- rostliny genetika MeSH
- segregace chromozomů MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- histony MeSH
Centromere is the chromosomal site of kinetochore assembly and microtubule attachment for chromosome segregation. Given its importance, markers that allow specific labeling of centromeric chromatin throughout the cell cycle and across all chromosome types are sought for facilitating various centromere studies. Antibodies against the N-terminal region of CENH3 are commonly used for this purpose, since CENH3 is the near-universal marker of functional centromeres. However, because the N-terminal region of CENH3 is highly variable among plant species, antibodies directed against this region usually function only in a small group of closely related species. As a more versatile alternative, we present here antibodies targeted to the conserved domains of two outer kinetochore proteins, KNL1 and NDC80. Sequence comparison of these domains across more than 350 plant species revealed a high degree of conservation, particularly within a six amino acid motif, FFGPVS in KNL1, suggesting that both antibodies would function in a wide range of plant species. This assumption was confirmed by immunolabeling experiments in angiosperm (monocot and dicot) and gymnosperm species, including those with mono-, holo-, and meta-polycentric chromosomes. In addition to centromere labeling on condensed chromosomes during cell division, both antibodies detected the corresponding regions in the interphase nuclei of most species tested. These results demonstrated that KNL1 and NDC80 are better suited for immunolabeling centromeres than CENH3, because antibodies against these proteins offer incomparably greater versatility across different plant species which is particularly convenient for studying the organization and function of the centromere in non-model species.
- Klíčová slova
- CENH3, Centromere, KNL1, NDC80, immunolabeling, kinetochore,
- MeSH
- centromera * MeSH
- chromatin MeSH
- kinetochory * MeSH
- rostlinné proteiny * genetika MeSH
- segregace chromozomů MeSH
- sekvence aminokyselin MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- chromatin MeSH
- rostlinné proteiny * MeSH
Chromosome segregation in female germ cells and early embryonic blastomeres is known to be highly prone to errors. The resulting aneuploidy is therefore the most frequent cause of termination of early development and embryo loss in mammals. And in specific cases, when the aneuploidy is actually compatible with embryonic and fetal development, it leads to severe developmental disorders. The main surveillance mechanism, which is essential for the fidelity of chromosome segregation, is the Spindle Assembly Checkpoint (SAC). And although all eukaryotic cells carry genes required for SAC, it is not clear whether this pathway is active in all cell types, including blastomeres of early embryos. In this review, we will summarize and discuss the recent progress in our understanding of the mechanisms controlling chromosome segregation and how they might work in embryos and mammalian embryos in particular. Our conclusion from the current literature is that the early mammalian embryos show limited capabilities to react to chromosome segregation defects, which might, at least partially, explain the widespread problem of aneuploidy during the early development in mammals.
- Klíčová slova
- CDK1, aneuploidy, cell size, chromosome division, embryo, segregation errors, spindle, spindle assembly checkpoint,
- MeSH
- aneuploidie MeSH
- chromozomy MeSH
- embryonální vývoj * genetika MeSH
- lidé MeSH
- savci genetika MeSH
- segregace chromozomů * MeSH
- velikost buňky MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
The segregation of chromosomes depends on the centromere. Most species are monocentric, with the centromere restricted to a single region per chromosome. In some organisms, the monocentric organization changed to holocentric, in which the centromere activity is distributed over the entire chromosome length. However, the causes and consequences of this transition are poorly understood. Here, we show that the transition in the genus Cuscuta was associated with dramatic changes in the kinetochore, a protein complex that mediates the attachment of chromosomes to microtubules. We found that in holocentric Cuscuta species, the KNL2 genes were lost; the CENP-C, KNL1, and ZWINT1 genes were truncated; the centromeric localization of CENH3, CENP-C, KNL1, MIS12, and NDC80 proteins was disrupted; and the spindle assembly checkpoint (SAC) degenerated. Our results demonstrate that holocentric Cuscuta species lost the ability to form a standard kinetochore and do not employ SAC to control the attachment of microtubules to chromosomes.
- Klíčová slova
- Cuscuta, centromere, holocentric, kinetochore, monocentric,
- MeSH
- centromera genetika MeSH
- Cuscuta * MeSH
- kinetochory * MeSH
- mikrotubuly metabolismus MeSH
- segregace chromozomů MeSH
- struktury chromozomu MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Receiving complete and undamaged genetic information is vital for the survival of daughter cells after chromosome segregation. The most critical steps in this process are accurate DNA replication during S phase and a faithful chromosome segregation during anaphase. Any errors in DNA replication or chromosome segregation have dire consequences, since cells arising after division might have either changed or incomplete genetic information. Accurate chromosome segregation during anaphase requires a protein complex called cohesin, which holds together sister chromatids. This complex unifies sister chromatids from their synthesis during S phase, until separation in anaphase. Upon entry into mitosis, the spindle apparatus is assembled, which eventually engages kinetochores of all chromosomes. Additionally, when kinetochores of sister chromatids assume amphitelic attachment to the spindle microtubules, cells are finally ready for the separation of sister chromatids. This is achieved by the enzymatic cleavage of cohesin subunits Scc1 or Rec8 by an enzyme called Separase. After cohesin cleavage, sister chromatids remain attached to the spindle apparatus and their poleward movement on the spindle is initiated. The removal of cohesion between sister chromatids is an irreversible step and therefore it must be synchronized with assembly of the spindle apparatus, since precocious separation of sister chromatids might lead into aneuploidy and tumorigenesis. In this review, we focus on recent discoveries concerning the regulation of Separase activity during the cell cycle.
- Klíčová slova
- CDK1, Cyclin B1, Mad2, Sgo2, aneuploidy, chromosome division, cohesin, securin, segregation errors, separase,
- MeSH
- anafáze * MeSH
- aparát dělícího vřeténka metabolismus MeSH
- chromatidy * metabolismus MeSH
- mitóza MeSH
- proteiny buněčného cyklu metabolismus MeSH
- segregace chromozomů MeSH
- separáza genetika metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
- Názvy látek
- proteiny buněčného cyklu MeSH
- separáza MeSH
Generation of functional gametes is accomplished through a multilayered and finely orchestrated succession of events during meiotic progression. In the Caenorhabditis elegans germline, the HORMA-domain-containing protein HTP-3 plays pivotal roles for the establishment of chromosome axes and the efficient induction of programmed DNA double-strand breaks, both of which are crucial for crossover formation. Double-strand breaks allow for accurate chromosome segregation during the first meiotic division and therefore are an essential requirement for the production of healthy gametes. Phosphorylation-dependent regulation of HORMAD protein plays important roles in controlling meiotic chromosome behavior. Here, we document a phospho-site in HTP-3 at Serine 285 that is constitutively phosphorylated during meiotic prophase I. pHTP-3S285 localization overlaps with panHTP-3 except in nuclei undergoing physiological apoptosis, in which pHTP-3 is absent. Surprisingly, we observed that phosphorylation of HTP-3 at S285 is independent of the canonical kinases that control meiotic progression in nematodes. During meiosis, the htp-3(S285A) mutant displays accelerated RAD-51 turnover, but no other meiotic abnormalities. Altogether, these data indicate that the Ser285 phosphorylation is independent of canonical meiotic protein kinases and does not regulate HTP-3-dependent meiotic processes. We propose a model wherein phosphorylation of HTP-3 occurs through noncanonical or redundant meiotic kinases and/or is likely redundant with additional phospho-sites for function in vivo.
- Klíčová slova
- Caenorhabditis elegans meiosis, HORMA-domain proteins, HTP-3,
- MeSH
- Caenorhabditis elegans genetika metabolismus MeSH
- fosforylace MeSH
- meióza * MeSH
- proteiny buněčného cyklu genetika MeSH
- proteiny Caenorhabditis elegans * metabolismus MeSH
- segregace chromozomů MeSH
- serin metabolismus MeSH
- synaptonemální komplex metabolismus MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
- Názvy látek
- proteiny buněčného cyklu MeSH
- proteiny Caenorhabditis elegans * MeSH
- serin MeSH
OBJECTIVE: Miscarriages affect 10% of women aged 25-29, and 53% of women over 45. The primary cause of miscarriage is aneuploidy that originated in eggs. The Aurora kinase family has three members that regulate chromosome segregation. Therefore, distinguishing the roles of these isoforms is important to understand aneuploidy etiology. In meiosis, Aurora kinase A (AURKA) localizes to spindle poles, where it binds TPX2. Aurora kinase C (AURKC) localizes on chromosomes, where it replaces AURKB as the primary AURK in the chromosomal passenger complex (CPC) via INCENP binding. Although AURKA compensates for CPC function in oocytes lacking AURKB/C, it is unknown whether AURKA binds INCENP in wild type mouse oocytes. ZINC08918027 (ZC) is an inhibitor that prevents the interaction between AURKB and INCENP in mitotic cells. We hypothesized that ZC would block CPC function of any AURK isoform. RESULTS: ZC treatment caused defects in meiotic progression and spindle building. By Western blotting and immunofluorescence, we observed that activated AURKA and AURKC levels in ZC-treated oocytes decreased compared to controls. These results suggest there is a population of AURKA-CPC in mouse oocytes. These data together suggest that INCENP-dependent AURKA and AURKC activities are needed for spindle bipolarity and meiotic progression.
- Klíčová slova
- Aurora kinase, Chromosomal passenger complex, Meiosis, Oocyte,
- MeSH
- aparát dělícího vřeténka metabolismus MeSH
- aurora kinasa B genetika metabolismus MeSH
- meióza * MeSH
- myši MeSH
- oocyty * metabolismus MeSH
- protein - isoformy genetika MeSH
- segregace chromozomů MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- aurora kinasa B MeSH
- protein - isoformy MeSH
Structural maintenance of chromosome 5/6 (SMC5/6) complex is a crucial factor for preserving genome stability. Here, we show that mutants for several Arabidopsis (Arabidopsis thaliana) SMC5/6 complex subunits produce triploid offspring. This phenotype is caused by a meiotic defect leading to the production of unreduced male gametes. The SMC5/6 complex mutants show an absence of chromosome segregation during the first and/or the second meiotic division, as well as a partially disorganized microtubule network. Importantly, although the SMC5/6 complex is partly required for the repair of SPO11-induced DNA double-strand breaks, the nonreduction described here is SPO11-independent. The measured high rate of ovule abortion suggests that, if produced, such defects are maternally lethal. Upon fertilization with an unreduced pollen, the unbalanced maternal and paternal genome dosage in the endosperm most likely causes seed abortion observed in several SMC5/6 complex mutants. In conclusion, we describe the function of the SMC5/6 complex in the maintenance of gametophytic ploidy in Arabidopsis.
Meiotic defects derived from incorrect DNA repair during gametogenesis can lead to mutations, aneuploidies and infertility. The coordinated resolution of meiotic recombination intermediates is required for crossover formation, ultimately necessary for the accurate completion of both rounds of chromosome segregation. Numerous master kinases orchestrate the correct assembly and activity of the repair machinery. Although much less is known, the reversal of phosphorylation events in meiosis must also be key to coordinate the timing and functionality of repair enzymes. Cdc14 is a crucial phosphatase required for the dephosphorylation of multiple CDK1 targets in many eukaryotes. Mutations that inactivate this phosphatase lead to meiotic failure, but until now it was unknown if Cdc14 plays a direct role in meiotic recombination. Here, we show that the elimination of Cdc14 leads to severe defects in the processing and resolution of recombination intermediates, causing a drastic depletion in crossovers when other repair pathways are compromised. We also show that Cdc14 is required for the correct activity and localization of the Holliday Junction resolvase Yen1/GEN1. We reveal that Cdc14 regulates Yen1 activity from meiosis I onwards, and this function is essential for crossover resolution in the absence of other repair pathways. We also demonstrate that Cdc14 and Yen1 are required to safeguard sister chromatid segregation during the second meiotic division, a late action that is independent of the earlier role in crossover formation. Thus, this work uncovers previously undescribed functions of the evolutionary conserved Cdc14 phosphatase in the regulation of meiotic recombination.
- Klíčová slova
- CDK1, Cdc14, Cdc20, Cdc5, Holliday junction, Mus81, Ndt80, Sgs1, Yen1, aneuploidy, meiotic recombination,
- MeSH
- crossing over (genetika) genetika MeSH
- fosforylace genetika MeSH
- gametogeneze genetika MeSH
- homologní rekombinace genetika MeSH
- křížová struktura DNA genetika MeSH
- meióza genetika MeSH
- mutace genetika MeSH
- oprava DNA genetika MeSH
- proteinkinasa CDC2 genetika MeSH
- proteiny buněčného cyklu genetika MeSH
- resolvasy Hollidayova spojení genetika MeSH
- Saccharomyces cerevisiae - proteiny genetika MeSH
- Saccharomyces cerevisiae genetika MeSH
- segregace chromozomů genetika MeSH
- tyrosinfosfatasy genetika MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- CDC14 protein, S cerevisiae MeSH Prohlížeč
- křížová struktura DNA MeSH
- proteinkinasa CDC2 MeSH
- proteiny buněčného cyklu MeSH
- resolvasy Hollidayova spojení MeSH
- Saccharomyces cerevisiae - proteiny MeSH
- tyrosinfosfatasy MeSH
- Yen1 protein, S cerevisiae MeSH Prohlížeč
Whole genome duplication (WGD) can promote adaptation but is disruptive to conserved processes, especially meiosis. Studies in Arabidopsis arenosa revealed a coordinated evolutionary response to WGD involving interacting proteins controlling meiotic crossovers, which are minimized in an autotetraploid (within-species polyploid) to avoid missegregation. Here, we test whether this surprising flexibility of a conserved essential process, meiosis, is recapitulated in an independent WGD system, Cardamine amara, 17 My diverged from A. arenosa. We assess meiotic stability and perform population-based scans for positive selection, contrasting the genomic response to WGD in C. amara with that of A. arenosa. We found in C. amara the strongest selection signals at genes with predicted functions thought important to adaptation to WGD: meiosis, chromosome remodeling, cell cycle, and ion transport. However, genomic responses to WGD in the two species differ: minimal ortholog-level convergence emerged, with none of the meiosis genes found in A. arenosa exhibiting strong signal in C. amara. This is consistent with our observations of lower meiotic stability and occasional clonal spreading in diploid C. amara, suggesting that nascent C. amara autotetraploid lineages were preadapted by their diploid lifestyle to survive while enduring reduced meiotic fidelity. However, in contrast to a lack of ortholog convergence, we see process-level and network convergence in DNA management, chromosome organization, stress signaling, and ion homeostasis processes. This gives the first insight into the salient adaptations required to meet the challenges of a WGD state and shows that autopolyploids can utilize multiple evolutionary trajectories to adapt to WGD.
- Klíčová slova
- adaptation, convergence, genome duplication, polyploidy,
- MeSH
- Arabidopsis * genetika MeSH
- duplikace genu * MeSH
- genom rostlinný MeSH
- meióza genetika MeSH
- polyploidie MeSH
- segregace chromozomů MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
