Longiflorum and Asiatic lilies of the genus Lilium of the family Liliaceae are two important groups of modem lily cultivars. One of the main trends of lily breeding is to realize introgression between these groups. Wi...Longiflorum and Asiatic lilies of the genus Lilium of the family Liliaceae are two important groups of modem lily cultivars. One of the main trends of lily breeding is to realize introgression between these groups. With cut style pollination and embryo rescue, distant hybrids between the two groups have been obtained. However, the FI hybrids are highly sterile or some of them could produce a small number of 2n gametes, and their BC1 progenies are usually triploids. Dutch lily breeders have selected many cultivars from these BC1 progenies based on their variation. It is presumably suggested that such variation could be caused by intergenomic recombination and abnormal meiosis during gamete formation in F1 hybrids of Longiflorum × Asiatic (LA) hybrids in Lilium. Therefore, the meiotic process of ten F1 LA hybrids was cytologically investigated using genomic in situ hybridization and traditional cytological methods in the present research. The results showed that: at metaphase I, the homoeologous chromosome pairing among different F1 hybrids ranged from 2.0 to 11.4 bivalents formed by homoeologous chromosomes per pollen mother cell (PMC), and very few multivalents, and even very few bivalents were formed by two chromosomes within one genome rather than homoeologous chromosomes in some PMCs; at anaphase I, all biva- lents were disjoined and most univalents were divided. Both the disjoined bivalents (half-bivalents) and the divided univalents (sister chromatids) moved to the opposite poles, and then formed two groups of chromosomes; because the two resulting half-bivalents retained their axes in the cell undisturbed, many crossover types, including single crossovers, three strand double crossovers, four strand double crossovers, four strand triple crossovers, and four strand multiple crossovers between the non-sister chromatids in the tetrads of bivalents, were clearly inferred by analyzing the breakpoints on the disjoined bivalents. The present investigation not only explained the reason for sterility of the Fl LA hybrids and the variation of their BCx progenies, but also provided a new method to analyze crossover types in other F1 interspecific hybrids as well.展开更多
Interspecific hybridization and allopolyploidization contribute to the improvement of many important crops. Recently, we successfully developed an amphidiploid from an interspecific cross between cucumber(Cucumis sati...Interspecific hybridization and allopolyploidization contribute to the improvement of many important crops. Recently, we successfully developed an amphidiploid from an interspecific cross between cucumber(Cucumis sativus, 2n = 2x = 14) and its relative C. hystrix(2n = 2x = 24) followed by chemical induction of chromosome doubling. The resulting allotetraploid plant was self-pollinated for three generations. The fertility and seed set of the amphidiploid plants were very low. In this study, we investigated the meiotic chromosome behavior in pollen mother cells with the aid of fluorescence in situ hybridization, aiming to identify the reasons for the low fertility and seed set in the amphidiploid plants. Homologous chromosome pairing appeared normal, but chromosome laggards were common, owing primarily to asynchronous meiosis of chromosomes from the two donor genomes. We suggest that asynchronous meiotic rhythm between the two parental genomes is the main reason for the low fertility and low seed set of the C. hystrix–cucumber amphidiploid plants.展开更多
Proper chromosome separation in both mitosis and meiosis depends on the correct connection between kinetochores of chromosomes and spindle microtubules. Kinetochore dysfunction can lead to unequal distribution of chro...Proper chromosome separation in both mitosis and meiosis depends on the correct connection between kinetochores of chromosomes and spindle microtubules. Kinetochore dysfunction can lead to unequal distribution of chromosomes during cell division and result in aneuploidy, thus kinetochores are critical for faithful segregation of chromosomes. Centromere protein A(CENP-A) is an important component of the inner kinetochore plate. Multiple studies in mitosis have found that deficiencies in CENP-A could result in structural and functional changes of kinetochores, leading to abnormal chromosome segregation, aneuploidy and apoptosis in cells. Here we report the expression and function of CENP-A during mouse oocyte meiosis. Our study found that microinjection of CENP-A blocking antibody resulted in errors of homologous chromosome segregation and caused aneuploidy in eggs. Thus, our findings provide evidence that CENP-A is critical for the faithful chromosome segregation during mammalian oocyte meiosis.展开更多
During meiosis in flowering plants,degradation of the callose wall in tetrads releases newly produced microspores,which develop into mature pollen grains.In this study,we identified zbs1,a male-sterile mutant of naked...During meiosis in flowering plants,degradation of the callose wall in tetrads releases newly produced microspores,which develop into mature pollen grains.In this study,we identified zbs1,a male-sterile mutant of naked oat(Avena nuda L.)that displayed complete spikelet sterility due to inviable mature pollen.The abnormal pollen grains originated from microspores with a defective callose wall and cell plate during meiosis.The defective callose wall and cell plate of the zbs1 mutant were detected by the labeling of cell wall epitopes(β-1,3-glucan) with immunogold during meiosis,and an abnormal chromosome configuration was observed by propidium iodide staining.The mature pollen grains of the zbs1 mutant were irregular in shape,and abnormal germination was observed by scanning electron microscopy.Together,our results indicate that the cause of male sterility in zbs1 is abnormal meiosis.展开更多
Alternative splicing can generate multiple mRNAs that differ in their untranslated regions or coding sequences,and these differences might affect mRNA stability or result in different protein isoforms with diverse fun...Alternative splicing can generate multiple mRNAs that differ in their untranslated regions or coding sequences,and these differences might affect mRNA stability or result in different protein isoforms with diverse functions and/or localizations.In this study,we isolated a sterile mutant in rice with abnormal meiosis of microspore mother cells and megaspore mother cells that carried a point mutation in OsRAD1 gene.Cloning of OsRAD1 cDNAs revealed three transcript variants,named as OsRAD1.1,OsRAD1.2 and OsRAD1.3,respectively,which were derived from alternative splicing of the last intron.Proteins derived from the three transcripts were mostly identical except the difference in the very C-terminal domain.The three transcripts exhibited similar expression patterns in various tissues,but the expression level of OsRAD1.1 was the highest.Specific knockout of OsRAD1.1 led to sterility,while knockout of OsRAD1.2 and OsRAD1.3 together did not change the plant fertility.Overexpression of OsRAD1.2 and OsRAD1.3 cDNAs in OsRAD1.1-specific mutant did not complement the plant fertility.Yeast two-hybrid assay showed that OsRAD1.1,but not OsRAD1.2 and OsRAD1.3,interacted with the three other meiosis proteins OsHUS1,OsRAD9 and OsRAD17,suggesting that the C-terminal domain of OsRAD1.1 is critical for the protein function.展开更多
Adhesions between different cells and extracellular matrix have been studied extensively in vitro, but little is known about their functions in testicular tissue counterparts. Spermatogonia and their companion somatic...Adhesions between different cells and extracellular matrix have been studied extensively in vitro, but little is known about their functions in testicular tissue counterparts. Spermatogonia and their companion somatic cells maintain a close association throughout spermatogenesis and this association is necessary for normal spermatogenesis. In order to keep the relative integrity of the testicular tissues, and to detect the development in vitro, culture testicular tissues in a three- dimensional (3D) agarose matrix was examined. Testicular tissues isolated from 6.5 d postpartum (dpp) mouse were cultured on the top of the matrix for 26 d with a medium height up to 4/5 of the 3D agarose matrix. The results showed that in this 3D culture environment, each type of testicular cells kept the same structure, localization and function as in vivo and might be more biologically relevant to living organisms. After culture, germ cell marker VASA and meiosis markers DAZL and SCP3 showed typical positive analysed by immunofluorescence staining and RT-PCR. It demonstrated that this 3D culture system was able to maintain the number of germ cells and promote the meiosis initiation of male germ cells.展开更多
Meiosis is the process of producing haploid gametes through a series of complex chromosomal events and the coordinated action of various proteins.The mitochondrial protease complex(ClpXP),which consists of caseinolyti...Meiosis is the process of producing haploid gametes through a series of complex chromosomal events and the coordinated action of various proteins.The mitochondrial protease complex(ClpXP),which consists of caseinolytic mitochondrial matrix peptidase X(ClpX)and caseinolytic protease P(ClpP)and mediates the degradation of misfolded,damaged,and oxidized proteins,is essential for maintaining mitochondrial homeostasis.ClpXP has been implicated in meiosis regulation,but its precise role is currently unknown.In this study,we engineered an inducible male germ cell-specific knockout caseinolytic mitochondrial matrix peptidase X(Clpx^(cKO))mouse model to investigate the function of ClpX in meiosis.We found that disrupting Clpx in male mice induced germ cell apoptosis and led to an absence of sperm in the epididymis.Specifically,it caused asynapsis of homologous chromosomes and impaired meiotic recombination,resulting in meiotic arrest in the zygotene-to-pachytene transition phase.The loss of ClpX compromised the double-strand break(DSB)repair machinery by markedly reducing the recruitment of DNA repair protein RAD51 homolog 1(RAD51)to DSB sites.This dysfunction may be due to an insufficient supply of energy from the aberrant mitochondria in Clpx^(cKO) spermatocytes,as discerned by electron microscopy.Furthermore,ubiquitination signals on chromosomes and the expression of oxidative phosphorylation subunits were both significantly attenuated in Clpx^(cKO) spermatocytes.Taken together,we propose that ClpX is essential for maintaining mitochondrial protein homeostasis and ensuring homologous chromosome pairing,synapsis,and recombination in spermatocytes during meiotic prophase I.展开更多
Meiosis is a highly complex process significantly influenced by transcriptional regulation.However,studies on the mechanisms that govern transcriptomic changes during meiosis,especially in prophase I,are limited.Here,...Meiosis is a highly complex process significantly influenced by transcriptional regulation.However,studies on the mechanisms that govern transcriptomic changes during meiosis,especially in prophase I,are limited.Here,we performed single-cell ATAC-seq of human testis tissues and observed reprogramming during the transition from zygotene to pachytene spermatocytes.This event,conserved in mice,involved the deactivation of genes associated with meiosis after reprogramming and the activation of those related to spermatogenesis before their functional onset.Furthermore,we identified 282 transcriptional regulators(TRs)that underwent activation or deactivation subsequent to this process.Evidence suggested that physical contact signals from Sertoli cells may regulate these TRs in spermatocytes,while secreted ENHO signals may alter metabolic patterns in these cells.Our results further indicated that defective transcriptional reprogramming may be associated with non-obstructive azoospermia(NOA).This study revealed the importance of both physical contact and secreted signals between Sertoli cells and germ cells in meiotic progression.展开更多
Unreduced gametes through chromosome doubling play a major role in the process of plant polyploidization.Our previous work confirmed that Camellia oleifera can produce natural 2n pollen,and it is possible to induce th...Unreduced gametes through chromosome doubling play a major role in the process of plant polyploidization.Our previous work confirmed that Camellia oleifera can produce natural 2n pollen,and it is possible to induce the 2n pollen formation by high temperature treatment.This study focused on the optimization of the 2n pollen induction technique and the mechanisms of high temperature-induced2n pollen formation in C.oleifera.We found that the optimal protocol for inducing 2n pollen via high temperature was to perform 45℃with4 h at the prophaseⅠstage of the pollen mother cells(PMCs).Meanwhile,high temperature significantly decreased the yield and fertility of2n pollen.Through the observation of meiosis,abnormal chromosome and cytological behaviour was discovered under high-temperature treatment,and we confirmed that the formation of 2n pollen is caused by abnormal cell plate.Based on weighted gene co-expression network analysis,fifteen hub genes related to cell cycle control were identified.After male flower buds were exposed to heat shock,polygalacturonase gene(CoPGX3)was significantly upregulated.We inferred that high temperature causes the CoPGX3 gene to be overexpressed and that CoPGX3 is redistributed into the cytosol where it degrades cytoplasmic pectin,which leads to an abnormal cell plate.Furthermore,abnormal cytokinesis resulted in the formation of dyads and triads,and PMCs divided to produce 2n pollen.Our findings provide new insights into the mechanism of 2n pollen induced by high temperature in a woody plant and lay a foundation for further ploidy breeding of C.oleifera.展开更多
Abstract: Little systematic analysis has been undertaken in rice (Oryza sativa L.) on the stages of male meiosis from leptotene to telophase II or of pollen development from microspores to mature pollen grains. The pr...Abstract: Little systematic analysis has been undertaken in rice (Oryza sativa L.) on the stages of male meiosis from leptotene to telophase II or of pollen development from microspores to mature pollen grains. The present study describes multiple stages in detail from analysis of rice chromosome spreading with staining of 4′,6-diamidino-2-phenylindole. The description of normal wild-type male meiosis provides an important morphological reference for analyses of meiotic mutants. Meiosis in rice is largely similar to those of the well characterizing model plants Arabidopsis thaliana L. and Zea mays L. However, rice meiosis differs from that in Arabidopsis in that rice meiosis I is followed by the formation of a cell plate, instead of an organelle band that forms between the two nuclei and persist through meiosis II. This suggests a difference in the control of organelle biogenesis and distribution and cytokinesis. Our results should facilitate studies of rice meiosis and pollen development using molecular genetic and cell biological approaches.展开更多
Mitogen-activated protein kinase (MAPK) is a family of Ser/Thr protein kinases expressed widely in eu-karyotic cells. MAPK is activated by a cascade of protein kinase phosphorylation and plays pivotal roles in regulat...Mitogen-activated protein kinase (MAPK) is a family of Ser/Thr protein kinases expressed widely in eu-karyotic cells. MAPK is activated by a cascade of protein kinase phosphorylation and plays pivotal roles in regulating meiosis process in oocytes. As an important physical substrate of MAPK, p90rsk mediates numerous MAPK functions. MAPK was activated at G2/M transition during meiosis. Its activity reached the peak at M I stage and maintained at this level until the time before the pronuclear formation after fertilization. There is complex interplay between MAPK and MPF in the meiosis regulation. Furthermore, other intracel-lular signal transducers, such as cAMP, protein kinase C and protein phosphotase, ect., also regulated the activity of MAPK at different stages during meiosis in oocytes. In the present article, the roles of MAPK signaling pathway in oo-cyte meiosis are reviewed and discussed.展开更多
MSH5, a meiosis-specific member of the MutS-homolog family, is required for normal level of recombination in budding yeast, mice, Caenorhabditis elegans, and Arabidopsis. Here, we report the identification and charact...MSH5, a meiosis-specific member of the MutS-homolog family, is required for normal level of recombination in budding yeast, mice, Caenorhabditis elegans, and Arabidopsis. Here, we report the identification and characterization of its rice homolog, OsMSH5, and demonstrate its function in rice meiosis. Five independent Osmsh5 mutants exhibited normal vegetative growth and severe sterility. The synaptonemal complex is well installed in Osmsh5, while the chiasma frequency is greatly reduced to approximately 10% of that observed in the wild-type, leading to the homologous non- disjunction and complete sterile phenotype. OsMSH5 is predominantly expressed in panicles. Immunofluorescence studies indicate that OsMSH5 chromosomal localization is limited to the early meiotic prophase I. OsMSH5 can be loaded onto meiotic chromosomes in Oszip4, Osmer3, and hellO. However, those ZMM proteins cannot be localized normally in the absence of OsMSH5. Furthermore, the residual chiasmata were shown to be the least frequent among the zmm mutants, including Osmer3, Oszip4, hellO, and Osmsh5. Taken together, we propose that OsMSH5 functions upstream of OsZIP4, OsMER3, and HEIl0 in class I crossover formation.展开更多
Germ-line cells are responsible for transmitting genetic and epigenetic information across generations, and ensuring the creation of new individuals from one generation to the next. Gametogenesis process requires seve...Germ-line cells are responsible for transmitting genetic and epigenetic information across generations, and ensuring the creation of new individuals from one generation to the next. Gametogenesis process requires several rigorous steps, including primordial germ cell (PGC) specification, proliferation, migration to the gonadal ridges and differentiation into mature gametes such as sperms and oocytes. But this process is not clearly explored because a small number of PGCs are deeply embedded in the developing embryo. In the attempt to establish an in vitro model for understanding gametogenesis process well, several groups have made considerable progress in differen- tiating embryonic stem cells (ESCs) and adult stem cells (ASCs) into germ-like cells over the past ten years. These stem cell-derived germ cells appear to he capable of undergoing meiosis and generating both male and female gametes. But most of gametes turn out to be not fully functional due to their abnormal meiosis process compared to endogenous germ cells. Therefore, a robust system of differentiating stem cells into germ cells would enable us to investigate the genetic, epigenetic and environmental factors associated with germ cell development. Here, we review the stem cell-derived germ cell development, and discuss the potential and challenges in the differentiation of functional germ cells from stem cells.展开更多
Meiotic recombination is carried out through a special- ized pathway for the formation and repair of DNA dou- ble-strand breaks (DSBs) made by the Spo11 protein. The present study shed light on the functional role o...Meiotic recombination is carried out through a special- ized pathway for the formation and repair of DNA dou- ble-strand breaks (DSBs) made by the Spo11 protein. The present study shed light on the functional role of cyclin, CYC2, in Tetrahymena thermophila which has transcriptionally high expression level during meiosis process. Knocking out the CYC2 gene results in arrest of meiotic conjugation process at 2.5-3.5 h after conjugation initiation, before the meiosis division starts, and in company with the absence of DSBs. To investigate the underlying mechanism of this phenomenon, a complete transcriptome profile was performed between wild-type strain and CYC2 knock-out strain. Functional analysis of RNA-Seq results identifies related differentially expressed genes (DEGs) including SP011 and these DEGs are enriched in DNA repair/mismatch repair (MMR) terms in homologous recombination (HR), which indicates that CYC2 could play a crucial role in meiosis by regulating SP011 and participating in HR.展开更多
Polyploidization is a basic feature of plant evolution. Nearly all of the main food, cotton and oil crops are polyploid. When ploidy levels increase, yields double; this phenomenon suggested a new strategy of rice bre...Polyploidization is a basic feature of plant evolution. Nearly all of the main food, cotton and oil crops are polyploid. When ploidy levels increase, yields double; this phenomenon suggested a new strategy of rice breeding that utilizes wide crosses and polyploidization dual advantages to breed super rice. Because low seed set rates in polyploid rice usually makes it difficult to breed, the selection of Ph-liked gene lines was emphasized. After progenies of indica-japonica were identified and selected, two poly- ploid lines, PMeS-1 and PMeS-2 with Polyploid Meiosis Stability (PMeS) genes were bred. The proce- dure included seven steps: selecting parents, crossing or multiple crossing, back-crossing, doubling chromosomes, identifying the polyploid, and choosing plants with high seed set rates that can breed themselves into stable lines. The characteristics of PMeS were determined by observing meiotic be- haviors and by cross-identification of seed sets. PMeS-1 and PMeS-2, (japonica rice), have several characteristics different from other polyploid rice lines, including a higher rate of seed set (more than 65%, increasing to more than 70% in their F1 offspring); and stable meiotic behaviors (pairing with bi- valents and quarivalents nearly without over-quarivalent in prophase, nearly without lagging chromo- somes in metaphase and without micronuclei in anaphase and telophase). The latter was obviously different from control polyploid line Dure-4X, which displayed abnormal meiotic behaviors including a higher rate of multivalents, univalents and trivalents in prophase, lagging chromosomes in metaphase and micronuclei in anaphase and telophase. There were also three differences of the breeding method between PMeS lines and normal diploid lines: chromosomes doubling, polyploidism identifying and higher seed set testing. The selection of PMeS lines is the first step in polyploid rice breeding; their use will advance the progress of polyploid rice breeding, which will in turn offer a new way to breed super rice.展开更多
Programmed DNA double-strand breaks(DSBs)are necessary for meiosis in mammals.A sufficient number of DSBs ensure the normal pairing/synapsis of homologous chromosomes.Abnormal DSB repair undermines meiosis,leading to ...Programmed DNA double-strand breaks(DSBs)are necessary for meiosis in mammals.A sufficient number of DSBs ensure the normal pairing/synapsis of homologous chromosomes.Abnormal DSB repair undermines meiosis,leading to sterility in mammals.The DSBs that initiate recombination are repaired as crossovers and noncrossovers,and crossovers are required for correct chromosome separation.Thus,the placement,timing,and frequency of crossover formation must be tightly controlled.Importantly,mutations in many genes related to the formation and repair of DSB result in infertility in humans.These mutations cause nonobstructive azoospermia in men,premature ovarian insufficiency and ovarian dysgenesis in women.Here,we have illustrated the formation and repair of DSB in mammals,summarized major factors influencing the formation of DSB and the theories of crossover regulation.展开更多
Meiosis is the specialized eukaryotic cell division that permits the halving of ploidy necessary for game- togenesis in sexually reproducing organisms, This involves a single round of DNA replication followed by two s...Meiosis is the specialized eukaryotic cell division that permits the halving of ploidy necessary for game- togenesis in sexually reproducing organisms, This involves a single round of DNA replication followed by two successive divisions. To ensure balanced segregation, homologous chromosome pairs must migrate to opposite poles at the first meiotic division and this means that they must recognize and pair with each other beforehand. Although understanding of the mechanisms by which meiotic chromosomes find and pair with their homologs has greatly advanced, it remains far from being fully understood. With some notable exceptions such as male Drosophila, the recognition and physical link- age of homologs at the first meiotic division involves homologous recombination. However, in addition to this, it is clear that many organisms, including plants, have also evolved a series of recombination-independent mechanisms to facili- tate homolog recognition and pairing. These implicate chromosome structure and dynamics, telomeres, centromeres, and, most recently, small RNAs. With a particular focus on plants, we present here an overview of understanding of these early, recombination-independent events that act in the pairing of homologous chromosomes during the first meiotic division,展开更多
Meiosis is a critical cell division program that produces haploid gametes for sexual reproduction.Abnormalities in meiosis are often causes of infertility and birth defects(e.g.,Down syndrome).Most organisms use a hig...Meiosis is a critical cell division program that produces haploid gametes for sexual reproduction.Abnormalities in meiosis are often causes of infertility and birth defects(e.g.,Down syndrome).Most organisms use a highly specialized zipper-like protein complex,the synaptonemal complex(SC),to guide and stabilize pairing of homologous chromosomes in meiosis.Although the SC is critical for meiosis in many eukaryotes,there are organisms that perform meiosis without a functional SC.However,such SC-less meiosis is poorly characterized.To understand the features of SC-less meiosis and its adaptive significance,the ciliated protozoan Tetrahymena was selected as a model.Meiosis research in Tetrahymena has revealed intriguing aspects of the regulatory programs utilized in its SC-less meiosis,yet additional efforts are needed for obtaining an in-depth comprehension of mechanisms that are associated with the absence of SC.Here,aiming at promoting a wider application of Tetrahymena for meiosis research,we introduce basic concepts and core techniques for studying meiosis in Tetrahymena and then suggest future directions for expanding the current Tetrahymena meiosis research toolbox.These methodologies could be adopted for dissecting meiosis in poorly characterized ciliates that might reveal novel features.Such data will hopefully provide insights into the function of the SC and the evolution of meiosis from a unique perspective.展开更多
Argonaute(AGO) proteins play a key role in regulation of gene expression through small RNA‐directed RNA cleavage and translational repression, and are essential for multiple developmental processes. In the present ...Argonaute(AGO) proteins play a key role in regulation of gene expression through small RNA‐directed RNA cleavage and translational repression, and are essential for multiple developmental processes. In the present study, 17 AGO genes of maize(Zea mays L., ZmAGOs) were identified using a Hidden Markov Model and validated by rapid amplification of cDNA ends assay. Subsequently, quantitative PCR revealed that expressions of these genes were higher in reproductive than in vegetative tissues. AGOs presented five temporal and spatial expression patterns, which were likely modulated by DNA methylation, 50‐untranslated exons and microRNA‐mediated feedback loops. Intriguingly, ZmAGO18 b was highly expressed in tassels during meiosis. Furthermore, in situ hybridization and immunofluorescence showed that ZmAResearchGO18b was enriched in the tapetum and germ cells in meiotic anthers. We hypothesized that ZmAGOs are highly expressed in reproductive tissues, and that ZmAGO18 b is a tapetum and germ cell‐specific member of the AGO family in maize.展开更多
THERE are 42 chromosomes in common wheat (Triticum aestivum L). The extra microchro-mosomes were discovered in alloplasmic lines of common wheat with cytoplasms of Ae. muti-ca, Secale cereale, Elytrigia elongatum and ...THERE are 42 chromosomes in common wheat (Triticum aestivum L). The extra microchro-mosomes were discovered in alloplasmic lines of common wheat with cytoplasms of Ae. muti-ca, Secale cereale, Elytrigia elongatum and Agropyron glaucum. The microchromo-somes were discovered in amphiploid of Triticum aestivum-Secale cereale (DDRR) too.展开更多
基金the National Natural Science Foundation of China(No.30471222)
文摘Longiflorum and Asiatic lilies of the genus Lilium of the family Liliaceae are two important groups of modem lily cultivars. One of the main trends of lily breeding is to realize introgression between these groups. With cut style pollination and embryo rescue, distant hybrids between the two groups have been obtained. However, the FI hybrids are highly sterile or some of them could produce a small number of 2n gametes, and their BC1 progenies are usually triploids. Dutch lily breeders have selected many cultivars from these BC1 progenies based on their variation. It is presumably suggested that such variation could be caused by intergenomic recombination and abnormal meiosis during gamete formation in F1 hybrids of Longiflorum × Asiatic (LA) hybrids in Lilium. Therefore, the meiotic process of ten F1 LA hybrids was cytologically investigated using genomic in situ hybridization and traditional cytological methods in the present research. The results showed that: at metaphase I, the homoeologous chromosome pairing among different F1 hybrids ranged from 2.0 to 11.4 bivalents formed by homoeologous chromosomes per pollen mother cell (PMC), and very few multivalents, and even very few bivalents were formed by two chromosomes within one genome rather than homoeologous chromosomes in some PMCs; at anaphase I, all biva- lents were disjoined and most univalents were divided. Both the disjoined bivalents (half-bivalents) and the divided univalents (sister chromatids) moved to the opposite poles, and then formed two groups of chromosomes; because the two resulting half-bivalents retained their axes in the cell undisturbed, many crossover types, including single crossovers, three strand double crossovers, four strand double crossovers, four strand triple crossovers, and four strand multiple crossovers between the non-sister chromatids in the tetrads of bivalents, were clearly inferred by analyzing the breakpoints on the disjoined bivalents. The present investigation not only explained the reason for sterility of the Fl LA hybrids and the variation of their BCx progenies, but also provided a new method to analyze crossover types in other F1 interspecific hybrids as well.
基金supported by Agriculture and Food Research Initiative Competitive Grant 2013-67013-21105 from the U.S. Department of Agriculture National Institute of Food to YWthe National Natural Science Foundation of China to YH (No. 31271350)
文摘Interspecific hybridization and allopolyploidization contribute to the improvement of many important crops. Recently, we successfully developed an amphidiploid from an interspecific cross between cucumber(Cucumis sativus, 2n = 2x = 14) and its relative C. hystrix(2n = 2x = 24) followed by chemical induction of chromosome doubling. The resulting allotetraploid plant was self-pollinated for three generations. The fertility and seed set of the amphidiploid plants were very low. In this study, we investigated the meiotic chromosome behavior in pollen mother cells with the aid of fluorescence in situ hybridization, aiming to identify the reasons for the low fertility and seed set in the amphidiploid plants. Homologous chromosome pairing appeared normal, but chromosome laggards were common, owing primarily to asynchronous meiosis of chromosomes from the two donor genomes. We suggest that asynchronous meiotic rhythm between the two parental genomes is the main reason for the low fertility and low seed set of the C. hystrix–cucumber amphidiploid plants.
基金supported by the National Natural Science Foundation of China(No.30930065 and No.31271605)
文摘Proper chromosome separation in both mitosis and meiosis depends on the correct connection between kinetochores of chromosomes and spindle microtubules. Kinetochore dysfunction can lead to unequal distribution of chromosomes during cell division and result in aneuploidy, thus kinetochores are critical for faithful segregation of chromosomes. Centromere protein A(CENP-A) is an important component of the inner kinetochore plate. Multiple studies in mitosis have found that deficiencies in CENP-A could result in structural and functional changes of kinetochores, leading to abnormal chromosome segregation, aneuploidy and apoptosis in cells. Here we report the expression and function of CENP-A during mouse oocyte meiosis. Our study found that microinjection of CENP-A blocking antibody resulted in errors of homologous chromosome segregation and caused aneuploidy in eggs. Thus, our findings provide evidence that CENP-A is critical for the faithful chromosome segregation during mammalian oocyte meiosis.
基金supported by the Natural Science Foundation of Hebei Province,China(C2004000747)
文摘During meiosis in flowering plants,degradation of the callose wall in tetrads releases newly produced microspores,which develop into mature pollen grains.In this study,we identified zbs1,a male-sterile mutant of naked oat(Avena nuda L.)that displayed complete spikelet sterility due to inviable mature pollen.The abnormal pollen grains originated from microspores with a defective callose wall and cell plate during meiosis.The defective callose wall and cell plate of the zbs1 mutant were detected by the labeling of cell wall epitopes(β-1,3-glucan) with immunogold during meiosis,and an abnormal chromosome configuration was observed by propidium iodide staining.The mature pollen grains of the zbs1 mutant were irregular in shape,and abnormal germination was observed by scanning electron microscopy.Together,our results indicate that the cause of male sterility in zbs1 is abnormal meiosis.
基金supported by grants from Natural Science Foundation of Guangdong Province(Grant Nos.B030308008,2017A030310500 and A03013104)National Key Research and Development Plan Program(Grant Nos.2016YFD0101801 and 2016YFD0100406)+2 种基金Shenzhen Commission on Innovation and Technology Programs(Grant No.JCYJ20160229204920363)Guangzhou Science and Technology Innovation Commission(Grant No.201804010034)National Natural Science Foundation of China(Grant No.31500254).
文摘Alternative splicing can generate multiple mRNAs that differ in their untranslated regions or coding sequences,and these differences might affect mRNA stability or result in different protein isoforms with diverse functions and/or localizations.In this study,we isolated a sterile mutant in rice with abnormal meiosis of microspore mother cells and megaspore mother cells that carried a point mutation in OsRAD1 gene.Cloning of OsRAD1 cDNAs revealed three transcript variants,named as OsRAD1.1,OsRAD1.2 and OsRAD1.3,respectively,which were derived from alternative splicing of the last intron.Proteins derived from the three transcripts were mostly identical except the difference in the very C-terminal domain.The three transcripts exhibited similar expression patterns in various tissues,but the expression level of OsRAD1.1 was the highest.Specific knockout of OsRAD1.1 led to sterility,while knockout of OsRAD1.2 and OsRAD1.3 together did not change the plant fertility.Overexpression of OsRAD1.2 and OsRAD1.3 cDNAs in OsRAD1.1-specific mutant did not complement the plant fertility.Yeast two-hybrid assay showed that OsRAD1.1,but not OsRAD1.2 and OsRAD1.3,interacted with the three other meiosis proteins OsHUS1,OsRAD9 and OsRAD17,suggesting that the C-terminal domain of OsRAD1.1 is critical for the protein function.
基金supported by the National Natural Science Foundation of China(31272518)the program for the New Century Excellent Talents of Ministry of Education of China(NCET-09-0654)+1 种基金the Doctoral Fund of Ministry of Education of P.R.China(RFDP,20120204110030)the Fundamental Research Funds for the Central Universities,China(QN2011012)
文摘Adhesions between different cells and extracellular matrix have been studied extensively in vitro, but little is known about their functions in testicular tissue counterparts. Spermatogonia and their companion somatic cells maintain a close association throughout spermatogenesis and this association is necessary for normal spermatogenesis. In order to keep the relative integrity of the testicular tissues, and to detect the development in vitro, culture testicular tissues in a three- dimensional (3D) agarose matrix was examined. Testicular tissues isolated from 6.5 d postpartum (dpp) mouse were cultured on the top of the matrix for 26 d with a medium height up to 4/5 of the 3D agarose matrix. The results showed that in this 3D culture environment, each type of testicular cells kept the same structure, localization and function as in vivo and might be more biologically relevant to living organisms. After culture, germ cell marker VASA and meiosis markers DAZL and SCP3 showed typical positive analysed by immunofluorescence staining and RT-PCR. It demonstrated that this 3D culture system was able to maintain the number of germ cells and promote the meiosis initiation of male germ cells.
基金supported by the Shenzhen Science and Technology Program,China(No.KQTD20190929172749226).
文摘Meiosis is the process of producing haploid gametes through a series of complex chromosomal events and the coordinated action of various proteins.The mitochondrial protease complex(ClpXP),which consists of caseinolytic mitochondrial matrix peptidase X(ClpX)and caseinolytic protease P(ClpP)and mediates the degradation of misfolded,damaged,and oxidized proteins,is essential for maintaining mitochondrial homeostasis.ClpXP has been implicated in meiosis regulation,but its precise role is currently unknown.In this study,we engineered an inducible male germ cell-specific knockout caseinolytic mitochondrial matrix peptidase X(Clpx^(cKO))mouse model to investigate the function of ClpX in meiosis.We found that disrupting Clpx in male mice induced germ cell apoptosis and led to an absence of sperm in the epididymis.Specifically,it caused asynapsis of homologous chromosomes and impaired meiotic recombination,resulting in meiotic arrest in the zygotene-to-pachytene transition phase.The loss of ClpX compromised the double-strand break(DSB)repair machinery by markedly reducing the recruitment of DNA repair protein RAD51 homolog 1(RAD51)to DSB sites.This dysfunction may be due to an insufficient supply of energy from the aberrant mitochondria in Clpx^(cKO) spermatocytes,as discerned by electron microscopy.Furthermore,ubiquitination signals on chromosomes and the expression of oxidative phosphorylation subunits were both significantly attenuated in Clpx^(cKO) spermatocytes.Taken together,we propose that ClpX is essential for maintaining mitochondrial protein homeostasis and ensuring homologous chromosome pairing,synapsis,and recombination in spermatocytes during meiotic prophase I.
基金supported by the National Natural Science Foundation of China(82271645)National Key Research and Development Program of China(2021YFC2700200 to F.S.)。
文摘Meiosis is a highly complex process significantly influenced by transcriptional regulation.However,studies on the mechanisms that govern transcriptomic changes during meiosis,especially in prophase I,are limited.Here,we performed single-cell ATAC-seq of human testis tissues and observed reprogramming during the transition from zygotene to pachytene spermatocytes.This event,conserved in mice,involved the deactivation of genes associated with meiosis after reprogramming and the activation of those related to spermatogenesis before their functional onset.Furthermore,we identified 282 transcriptional regulators(TRs)that underwent activation or deactivation subsequent to this process.Evidence suggested that physical contact signals from Sertoli cells may regulate these TRs in spermatocytes,while secreted ENHO signals may alter metabolic patterns in these cells.Our results further indicated that defective transcriptional reprogramming may be associated with non-obstructive azoospermia(NOA).This study revealed the importance of both physical contact and secreted signals between Sertoli cells and germ cells in meiotic progression.
基金supported by the National Natural Science Foundation of China(Grant No.32101489)Forestry Science and Technology Innovation Program of Hunan Province(Grant No.XLK202101-2)Science and Technology Innovation Platform and Talent Program of Hunan Province(Grant Nos.2023RC3164,2021NK1007)。
文摘Unreduced gametes through chromosome doubling play a major role in the process of plant polyploidization.Our previous work confirmed that Camellia oleifera can produce natural 2n pollen,and it is possible to induce the 2n pollen formation by high temperature treatment.This study focused on the optimization of the 2n pollen induction technique and the mechanisms of high temperature-induced2n pollen formation in C.oleifera.We found that the optimal protocol for inducing 2n pollen via high temperature was to perform 45℃with4 h at the prophaseⅠstage of the pollen mother cells(PMCs).Meanwhile,high temperature significantly decreased the yield and fertility of2n pollen.Through the observation of meiosis,abnormal chromosome and cytological behaviour was discovered under high-temperature treatment,and we confirmed that the formation of 2n pollen is caused by abnormal cell plate.Based on weighted gene co-expression network analysis,fifteen hub genes related to cell cycle control were identified.After male flower buds were exposed to heat shock,polygalacturonase gene(CoPGX3)was significantly upregulated.We inferred that high temperature causes the CoPGX3 gene to be overexpressed and that CoPGX3 is redistributed into the cytosol where it degrades cytoplasmic pectin,which leads to an abnormal cell plate.Furthermore,abnormal cytokinesis resulted in the formation of dyads and triads,and PMCs divided to produce 2n pollen.Our findings provide new insights into the mechanism of 2n pollen induced by high temperature in a woody plant and lay a foundation for further ploidy breeding of C.oleifera.
文摘Abstract: Little systematic analysis has been undertaken in rice (Oryza sativa L.) on the stages of male meiosis from leptotene to telophase II or of pollen development from microspores to mature pollen grains. The present study describes multiple stages in detail from analysis of rice chromosome spreading with staining of 4′,6-diamidino-2-phenylindole. The description of normal wild-type male meiosis provides an important morphological reference for analyses of meiotic mutants. Meiosis in rice is largely similar to those of the well characterizing model plants Arabidopsis thaliana L. and Zea mays L. However, rice meiosis differs from that in Arabidopsis in that rice meiosis I is followed by the formation of a cell plate, instead of an organelle band that forms between the two nuclei and persist through meiosis II. This suggests a difference in the control of organelle biogenesis and distribution and cytokinesis. Our results should facilitate studies of rice meiosis and pollen development using molecular genetic and cell biological approaches.
基金This work was supported by the Special Funds for Major State Basic Research ("973") Project of China (Grang No. Gl 999055902) the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KSCX2-SW-303).
文摘Mitogen-activated protein kinase (MAPK) is a family of Ser/Thr protein kinases expressed widely in eu-karyotic cells. MAPK is activated by a cascade of protein kinase phosphorylation and plays pivotal roles in regulating meiosis process in oocytes. As an important physical substrate of MAPK, p90rsk mediates numerous MAPK functions. MAPK was activated at G2/M transition during meiosis. Its activity reached the peak at M I stage and maintained at this level until the time before the pronuclear formation after fertilization. There is complex interplay between MAPK and MPF in the meiosis regulation. Furthermore, other intracel-lular signal transducers, such as cAMP, protein kinase C and protein phosphotase, ect., also regulated the activity of MAPK at different stages during meiosis in oocytes. In the present article, the roles of MAPK signaling pathway in oo-cyte meiosis are reviewed and discussed.
基金This work was supported by grants from the Ministry of Sciences and Technology of China (2011CB944602 and 2012AA10A301)the State Key Laboratory of Plant Genomics of China (2012A0527)and the National Natural Science Foundation of China (31160223 and 31230038). No conflict of interest declared.
文摘MSH5, a meiosis-specific member of the MutS-homolog family, is required for normal level of recombination in budding yeast, mice, Caenorhabditis elegans, and Arabidopsis. Here, we report the identification and characterization of its rice homolog, OsMSH5, and demonstrate its function in rice meiosis. Five independent Osmsh5 mutants exhibited normal vegetative growth and severe sterility. The synaptonemal complex is well installed in Osmsh5, while the chiasma frequency is greatly reduced to approximately 10% of that observed in the wild-type, leading to the homologous non- disjunction and complete sterile phenotype. OsMSH5 is predominantly expressed in panicles. Immunofluorescence studies indicate that OsMSH5 chromosomal localization is limited to the early meiotic prophase I. OsMSH5 can be loaded onto meiotic chromosomes in Oszip4, Osmer3, and hellO. However, those ZMM proteins cannot be localized normally in the absence of OsMSH5. Furthermore, the residual chiasmata were shown to be the least frequent among the zmm mutants, including Osmer3, Oszip4, hellO, and Osmsh5. Taken together, we propose that OsMSH5 functions upstream of OsZIP4, OsMER3, and HEIl0 in class I crossover formation.
基金supported by the National Basic Research Program of China(973 Program)(Grant Nos.2013CB947903 and 2012CB944401)Program for New Century Excellent Talents in University of China(Grant No.NCET-12-1026)Foundation of Distinguished Young Scholars of Shandong Province in China(Grant No.JQ201109)
文摘Germ-line cells are responsible for transmitting genetic and epigenetic information across generations, and ensuring the creation of new individuals from one generation to the next. Gametogenesis process requires several rigorous steps, including primordial germ cell (PGC) specification, proliferation, migration to the gonadal ridges and differentiation into mature gametes such as sperms and oocytes. But this process is not clearly explored because a small number of PGCs are deeply embedded in the developing embryo. In the attempt to establish an in vitro model for understanding gametogenesis process well, several groups have made considerable progress in differen- tiating embryonic stem cells (ESCs) and adult stem cells (ASCs) into germ-like cells over the past ten years. These stem cell-derived germ cells appear to he capable of undergoing meiosis and generating both male and female gametes. But most of gametes turn out to be not fully functional due to their abnormal meiosis process compared to endogenous germ cells. Therefore, a robust system of differentiating stem cells into germ cells would enable us to investigate the genetic, epigenetic and environmental factors associated with germ cell development. Here, we review the stem cell-derived germ cell development, and discuss the potential and challenges in the differentiation of functional germ cells from stem cells.
文摘Meiotic recombination is carried out through a special- ized pathway for the formation and repair of DNA dou- ble-strand breaks (DSBs) made by the Spo11 protein. The present study shed light on the functional role of cyclin, CYC2, in Tetrahymena thermophila which has transcriptionally high expression level during meiosis process. Knocking out the CYC2 gene results in arrest of meiotic conjugation process at 2.5-3.5 h after conjugation initiation, before the meiosis division starts, and in company with the absence of DSBs. To investigate the underlying mechanism of this phenomenon, a complete transcriptome profile was performed between wild-type strain and CYC2 knock-out strain. Functional analysis of RNA-Seq results identifies related differentially expressed genes (DEGs) including SP011 and these DEGs are enriched in DNA repair/mismatch repair (MMR) terms in homologous recombination (HR), which indicates that CYC2 could play a crucial role in meiosis by regulating SP011 and participating in HR.
基金the National Natural Science Foundation of China (Grant Nos. 39970447, 30240090, 30471063 and 30650002)the High Technology Research and Development Program of China (Grant No. SZ-01-02-02)+1 种基金the Chenguang Youth Science and Technology Project of Wuhan City (Grant No. 20045006071-31)the Educational Commission of Hubei Province of China (Grant No. 2004D004)
文摘Polyploidization is a basic feature of plant evolution. Nearly all of the main food, cotton and oil crops are polyploid. When ploidy levels increase, yields double; this phenomenon suggested a new strategy of rice breeding that utilizes wide crosses and polyploidization dual advantages to breed super rice. Because low seed set rates in polyploid rice usually makes it difficult to breed, the selection of Ph-liked gene lines was emphasized. After progenies of indica-japonica were identified and selected, two poly- ploid lines, PMeS-1 and PMeS-2 with Polyploid Meiosis Stability (PMeS) genes were bred. The proce- dure included seven steps: selecting parents, crossing or multiple crossing, back-crossing, doubling chromosomes, identifying the polyploid, and choosing plants with high seed set rates that can breed themselves into stable lines. The characteristics of PMeS were determined by observing meiotic be- haviors and by cross-identification of seed sets. PMeS-1 and PMeS-2, (japonica rice), have several characteristics different from other polyploid rice lines, including a higher rate of seed set (more than 65%, increasing to more than 70% in their F1 offspring); and stable meiotic behaviors (pairing with bi- valents and quarivalents nearly without over-quarivalent in prophase, nearly without lagging chromo- somes in metaphase and without micronuclei in anaphase and telophase). The latter was obviously different from control polyploid line Dure-4X, which displayed abnormal meiotic behaviors including a higher rate of multivalents, univalents and trivalents in prophase, lagging chromosomes in metaphase and micronuclei in anaphase and telophase. There were also three differences of the breeding method between PMeS lines and normal diploid lines: chromosomes doubling, polyploidism identifying and higher seed set testing. The selection of PMeS lines is the first step in polyploid rice breeding; their use will advance the progress of polyploid rice breeding, which will in turn offer a new way to breed super rice.
基金This work is supported by National Key Research&Development Program of China(No.2018YFC1003400)National Natural Science Foundation of China(No.31771588)the Strategic Collaborative Research Program of the Ferring Institute of Reproductive Medicine(No.FIRMC200509)to MCL.
文摘Programmed DNA double-strand breaks(DSBs)are necessary for meiosis in mammals.A sufficient number of DSBs ensure the normal pairing/synapsis of homologous chromosomes.Abnormal DSB repair undermines meiosis,leading to sterility in mammals.The DSBs that initiate recombination are repaired as crossovers and noncrossovers,and crossovers are required for correct chromosome separation.Thus,the placement,timing,and frequency of crossover formation must be tightly controlled.Importantly,mutations in many genes related to the formation and repair of DSB result in infertility in humans.These mutations cause nonobstructive azoospermia in men,premature ovarian insufficiency and ovarian dysgenesis in women.Here,we have illustrated the formation and repair of DSB in mammals,summarized major factors influencing the formation of DSB and the theories of crossover regulation.
文摘Meiosis is the specialized eukaryotic cell division that permits the halving of ploidy necessary for game- togenesis in sexually reproducing organisms, This involves a single round of DNA replication followed by two successive divisions. To ensure balanced segregation, homologous chromosome pairs must migrate to opposite poles at the first meiotic division and this means that they must recognize and pair with each other beforehand. Although understanding of the mechanisms by which meiotic chromosomes find and pair with their homologs has greatly advanced, it remains far from being fully understood. With some notable exceptions such as male Drosophila, the recognition and physical link- age of homologs at the first meiotic division involves homologous recombination. However, in addition to this, it is clear that many organisms, including plants, have also evolved a series of recombination-independent mechanisms to facili- tate homolog recognition and pairing. These implicate chromosome structure and dynamics, telomeres, centromeres, and, most recently, small RNAs. With a particular focus on plants, we present here an overview of understanding of these early, recombination-independent events that act in the pairing of homologous chromosomes during the first meiotic division,
基金Funds for the Central Universities(No.202241003,to Dr.Miao Tian)the Natural Science Foundation of Shandong Province(ZR2022JQ13,to Dr.Miao Tian)+1 种基金by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement(No.101024333)Dr.Rachel Howard-Till is supported by NIH RO1GM127571.
文摘Meiosis is a critical cell division program that produces haploid gametes for sexual reproduction.Abnormalities in meiosis are often causes of infertility and birth defects(e.g.,Down syndrome).Most organisms use a highly specialized zipper-like protein complex,the synaptonemal complex(SC),to guide and stabilize pairing of homologous chromosomes in meiosis.Although the SC is critical for meiosis in many eukaryotes,there are organisms that perform meiosis without a functional SC.However,such SC-less meiosis is poorly characterized.To understand the features of SC-less meiosis and its adaptive significance,the ciliated protozoan Tetrahymena was selected as a model.Meiosis research in Tetrahymena has revealed intriguing aspects of the regulatory programs utilized in its SC-less meiosis,yet additional efforts are needed for obtaining an in-depth comprehension of mechanisms that are associated with the absence of SC.Here,aiming at promoting a wider application of Tetrahymena for meiosis research,we introduce basic concepts and core techniques for studying meiosis in Tetrahymena and then suggest future directions for expanding the current Tetrahymena meiosis research toolbox.These methodologies could be adopted for dissecting meiosis in poorly characterized ciliates that might reveal novel features.Such data will hopefully provide insights into the function of the SC and the evolution of meiosis from a unique perspective.
基金supported by the National Hi-Tech Program of China (2012AA10A307)the National Natural Science Foundation of China (31071429)the National Science and Technology Major Project (2011ZX08009‐001)
文摘Argonaute(AGO) proteins play a key role in regulation of gene expression through small RNA‐directed RNA cleavage and translational repression, and are essential for multiple developmental processes. In the present study, 17 AGO genes of maize(Zea mays L., ZmAGOs) were identified using a Hidden Markov Model and validated by rapid amplification of cDNA ends assay. Subsequently, quantitative PCR revealed that expressions of these genes were higher in reproductive than in vegetative tissues. AGOs presented five temporal and spatial expression patterns, which were likely modulated by DNA methylation, 50‐untranslated exons and microRNA‐mediated feedback loops. Intriguingly, ZmAGO18 b was highly expressed in tassels during meiosis. Furthermore, in situ hybridization and immunofluorescence showed that ZmAResearchGO18b was enriched in the tapetum and germ cells in meiotic anthers. We hypothesized that ZmAGOs are highly expressed in reproductive tissues, and that ZmAGO18 b is a tapetum and germ cell‐specific member of the AGO family in maize.
文摘THERE are 42 chromosomes in common wheat (Triticum aestivum L). The extra microchro-mosomes were discovered in alloplasmic lines of common wheat with cytoplasms of Ae. muti-ca, Secale cereale, Elytrigia elongatum and Agropyron glaucum. The microchromo-somes were discovered in amphiploid of Triticum aestivum-Secale cereale (DDRR) too.