Early Prophase Research Articles

Spectrum of chromosomal configurations in pollen mother cells ofRhoeo spathacea(Swartz) Stearn

Abstract Rhoeo spathacea is unusual in that its twelve chromosomes are involved in complex translocations that results in atypical meiosis with all chromosomes frequently joined end-to-end into a single ring. The detailed meiotic studies, for the first time, revealed that alignment of chromosomes into a ring and / or a chain begins at very early prophase I. However, the cells at diakinesis and metaphase I do not exclusively have a ring or a chain of 12 chromosomes. Instead, they carry a range of chain configurations formed due to slipping of the chiasmata off the pairing segments in complex structures. While in 57.61% cells, at diakinesis, a ring or a chain was observed, in the rest 2–7 chain configurations existed. Similarly, at metaphase I a ring of 12 chromosomes was observed in 33.87% cells whereas in 66.13 % cells 2–9 chain configurations existed. The various groups of chromosomes in cells at diakinesis generally did not show any specific orientation pattern. However, in 17.31% cells a disjunctional arrangement of chromosomes was observed. At metaphase I also while in 82.26% cells chromosomes showed more or less non disjunctional orientations, in 17.74% cells regular arrangement of chromosomes was observed. Owing to non-disjunctional arrangement of chromosomes at metaphase I, the anaphase I distribution of chromosomes was erratic in 44.18% cells. Three to nine chromosomes were seen at two poles in 33.06% cells whereas in 11.11% cells 1-8 lagging chromosomes existed. Regular distribution of 6:6 was seen in 55.82% cells. The Pollen sterility recorded was very high i.e. 81.24% using cotton blue staining procedure. It is suggested that a wide range of chromosome configurations, hitherto unidentified, might exist in Rhoeo spathacea which awaits to be discovered.

Structure and functions of lampbrush chromosomes

Lampbrush Chromosomes (LBCs) are present in the oocytes of birds, lower vertebrata and invertebrates during the prolonged prophase of the first meiotic division. Their name stems from their similarity to bottle brushes. Lampbrush chromosome of the early prophase is a bivalent, made up of two conjugating homologues. The axis of each homologous chromosome is formed by sister chromatids that are differentiated into regions of transcriptionally active and inactive chromatin. Transcription activity of LBCs is observed as a mantle of symmetrically distributed side loops along the chromosome axis. Changes in transcriptional activity are reflected in changes in their morphology. Transcriptional activity of LBCs is directly connected with physiological processes of the body and shows in the morphological structure of the chromosomes. The use of cytogenetic techniques and in situ hybridization have made it possible to identify unique and repeating sequences as well as DNA replication proteins in LBCs. Particularly, interesting prospects are offered by the possibility of using LBCs in studies of transcriptional activity, cytogenetic investigations of karyotype evolution and genome mapping.

Meiotic Checkpoints: Repair or Removal?

Defects in meiosis can produce different checkpoint responses in female and male animals, suggesting that meiotic checkpoints exhibit sexual dimorphism. A recent study in Caenorhabditis elegans indicates that meiotic checkpoint activation is similar between the sexes and the primary difference lies in the downstream consequences.

Structural Basis of Poly(ADP-ribose) Recognition by the Multizinc Binding Domain of Checkpoint with Forkhead-associated and RING Domains (CHFR)

Cellular stress in early mitosis activates the antephase checkpoint, resulting in the decondensation of chromosomes and delayed mitotic progression. Checkpoint with forkhead-associated and RING domains (CHFR) is central to this checkpoint, and its activity is ablated in many tumors and cancer cell lines through promoter hypermethylation or mutation. The interaction between the PAR-binding zinc finger (PBZ) of CHFR and poly(ADP-ribose) (PAR) is crucial for a functional antephase checkpoint. We determined the crystal structure of the cysteine-rich region of human CHFR (amino acids 425-664) to 1.9 Å resolution, which revealed a multizinc binding domain of elaborate topology within which the PBZ is embedded. The PBZ of CHFR closely resembles the analogous motifs from aprataxin-like factor and CG1218-PA, which lie within unstructured regions of their respective proteins. Based on co-crystal structures of CHFR bound to several different PAR-like ligands (adenosine 5'-diphosphoribose, adenosine monophosphate, and P(1)P(2)-diadenosine 5'-pyrophosphate), we made a model of the CHFR-PAR interaction, which we validated using site-specific mutagenesis and surface plasmon resonance. The PBZ motif of CHFR recognizes two adenine-containing subunits of PAR and the phosphate backbone that connects them. More generally, PBZ motifs may recognize different numbers of PAR subunits as required to carry out their functions.

MOV10L1 is necessary for protection of spermatocytes against retrotransposons by Piwi-interacting RNAs

Piwi-interacting RNAs (piRNAs) comprise a broad class of small noncoding RNAs that function as an endogenous defense system against transposable elements. Here we show that the putative DExD-box helicase MOV10-like-1 (MOV10L1) is essential for silencing retrotransposons in the mouse male germline. Mov10l1 is specifically expressed in germ cells with increasing expression from gonocytes/type A spermatogonia to pachytene spermatocytes. Primary spermatocytes of Mov10l1(-/-) mice show activation of LTR and LINE-1 retrotransposons, followed by cell death, causing male infertility and a complete block of spermatogenesis at early prophase of meiosis I. Despite the early expression of Mov10l1, germline stem cell maintenance appears unaffected in Mov10l1(-/-) mice. MOV10L1 interacts with the Piwi proteins MILI and MIWI. MOV10L1 also interacts with heat shock 70-kDa protein 2 (HSPA2), a testis-enriched chaperone expressed in pachytene spermatocytes and also essential for male fertility. These studies reveal a crucial role of MOV10L1 in male fertility and piRNA-directed retrotransposon silencing in male germ cells and suggest that MOV10L1 functions as a key component of a safeguard mechanism for the genetic information in male germ cells of mammals.

Meiotic Cohesin Promotes Pairing of Nonhomologous Centromeres in Early Meiotic Prophase

A period of pairing between nonhomologous centromeres occurs early in meiosis in a diverse collection of organisms. This early, homology-independent, centromere pairing, referred to as centromere coupling in budding yeast, gives way to an alignment of homologous centromeres as homologues synapse later in meiotic prophase. The regulation of centromere coupling and its underlying mechanism have not been elucidated. In budding yeast, the protein Zip1p is a major component of the central element of the synaptonemal complex in pachytene of meiosis, and earlier, is essential for centromere coupling. The experiments reported here demonstrate that centromere coupling is mechanistically distinct from synaptonemal complex assembly. Zip2p, Zip3p, and Red1p are all required for the assembly of Zip1 into the synaptonemal complex but are dispensable for centromere coupling. However, the meiotic cohesin Rec8p is required for centromere coupling. Loading of meiotic cohesins to centromeres and cohesin-associated regions is required for the association of Zip1 with these sites, and the association of Zip1 with the centromeres then promotes coupling. These findings reveal a mechanism that promotes associations between centromeres before the assembly of the synaptonemal complex, and they demonstrate that chromosomes are preloaded with Zip1p in a manner that may promote synapsis.

Mating system, auxosporulation, species taxonomy and evidence for homoploid evolution in Amphora (Bacillariophyta)

Mann D.G. and Poulíčková A. 2010. Mating system, auxosporulation, species taxonomy and evidence for homoploid evolution in Amphora (Bacillariophyta). Phycologia 49: 183–201. DOI: 10.2216/09-08.1Cytological characteristics of the mitotic cycle, sexual reproduction and auxospore formation are described for three members of the type group of Amphora: A. ovalis, A. copulata and A. minutissima. All have a single lobed ventral chloroplast, nuclei with granular heterochromatin and a single nucleolus (unusually large in A. ovalis). Amphora copulata is heterothallic, with two mating types that do not differ in gamete behaviour. All three species reproduce allogamously via fusion of two rearranged gametes per gametangium to produce elongate zygotes enclosed within the volume delimited by the gametangial thecae. Pairing is strictly via the ventral sides of the cells, with tight apposition of the cells, and expansion of the auxospores is strictly perpendicular to the gametangium long axes. Comparisons are made with other Amphora species, particularly A. proteus (also belonging to the subgenus Amphora) and A. arcus. Meiosis is described in detail in A. copulata, revealing no movement of the nucleus away from the dorsal position it occupies during the mitotic cycle, a synizetic knot in early prophase, no cytokinesis accompanying meiosis II, and rapid degeneration of the supernumerary nuclei in the gametic cells; the usual two acytokinetic mitoses accompany formation of the initial epivalve (which lacks a functional raphe) and hypovalve. The potential for formation of autopolyploids is demonstrated in A. copulata. Nevertheless, chromosome counts of 2n = 34 in A. copulata, 2n = 28 or 30 in A. ovalis and an undetermined but not significantly lower number in A. minutissima, suggest that homoploid evolution is more likely than polyploid. In mixed sexualized populations of the species, no interbreeding occurs, supporting separation of minutissima from copulata. Measurements of initial cell sizes, coupled with slight differences in valve width and pattern, suggest that A. copulata may be a species complex.

Meiotic silencing and fragmentation of the male germline restricted chromosome in zebra finch

During male meiotic prophase in mammals, X and Y are in a largely unsynapsed configuration, which is thought to trigger meiotic sex chromosome inactivation (MSCI). In avian species, females are ZW, and males ZZ. Although Z and W in chicken oocytes show complete, largely heterologous synapsis, they too undergo MSCI, albeit only transiently. The W chromosome is already inactive in early meiotic prophase, and inactive chromatin marks may spread on to the Z upon synapsis. Mammalian MSCI is considered as a specialised form of the general meiotic silencing mechanism, named meiotic silencing of unsynapsed chromatin (MSUC). Herein, we studied the avian form of MSUC, by analysing the behaviour of the peculiar germline restricted chromosome (GRC) that is present as a single copy in zebra finch spermatocytes. In the female germline, this chromosome is present in two copies, which normally synapse and recombine. In contrast, during male meiosis, the single GRC is always eliminated. We found that the GRC in the male germline is silenced from early leptotene onwards, similar to the W chromosome in avian oocytes. The GRC remains largely unsynapsed throughout meiotic prophase I, although patches of SYCP1 staining indicate that part of the GRC may self-synapse. In addition, the GRC is largely devoid of meiotic double strand breaks. We observed a lack of the inner centromere protein INCENP on the GRC and elimination of the GRC following metaphase I. Subsequently, the GRC forms a micronucleus in which the DNA is fragmented. We conclude that in contrast to MSUC in mammals, meiotic silencing of this single chromosome in the avian germline occurs prior to, and independent of DNA double strand breaks and chromosome pairing, hence we have named this phenomenon meiotic silencing prior to synapsis (MSPS).Electronic supplementary materialThe online version of this article (doi:10.1007/s00412-010-0258-9) contains supplementary material, which is available to authorized users.

Cytomixis and associated meiotic abnormalities affecting pollen fertility in Clematis orientalis

Present cytological investigations from the cold desert regions of Lahaul-Spiti and Kinnaur (India) record the first ever tetraploid (2n=32) chromosome count and cytomixis in Clematis orientalis L. var. acutifolia Hook. f. et Thoms. The phenomenon of cytomixis (9.33-29.80 %) involving chromatin transfer among 2-3 proximate pollen mother cells (PMCs) during male meiosis occurs through narrow and broad cytoplasmic channels from early prophase to tetrad stage. However, frequency of its occurrence during the later meiotic stages is rather low. Chromatin transfer results into the formation of hypo-, hyperploid and enucleated PMCs. Various meiotic abnormalities associated with cytomixis such as chromatin stickiness, pycnotic chromatin, interbivalent connections, out of plate bivalents, late disjunction of bivalents, and laggards and bridges resulted into some pollen sterility (16.33-49.30 %) and heterogeneous pollen grains size.

The Central Element Protein ZEP1 of the Synaptonemal Complex Regulates the Number of Crossovers during Meiosis in Rice

ZEP1, a transverse filament (TF) protein, is the rice (Oryza sativa) homolog of Arabidopsis thaliana ZYP1. In the Tos17-insertional zep1 mutants, homologous chromosomes align along the entire length of the chromosome, but the synaptonemal complex is not assembled in early prophase I. Crossovers are well formed, and 12 bivalents could be detected from diakinesis to metaphase I, which leads to equal chromosomal segregation in anaphase I. Moreover, the number of crossovers has a tendency to be increased compared with that in the wild type. These phenomena are different from the TF mutants identified so far in other organisms. Chiasma terminalization of the bivalent, which occurs frequently in the wild type, seldom occurred in zep1. Transmission electron micrographs and immunodetection using an antibody against ZEP1 showed that ZEP1 is the central element of the synaptonemal complex. Although PAIR2 and MER3 were loaded normally in zep1, their dissociation was delayed severely compared with the wild type. In addition, ZEP1 is reloaded onto chromosomes in early microspores as the chromosome decondense, suggesting that ZEP1 might have other biological functions during this process.

SOLO: a meiotic protein required for centromere cohesion, coorientation, and SMC1 localization in Drosophila melanogaster

Sister chromatid cohesion is essential to maintain stable connections between homologues and sister chromatids during meiosis and to establish correct centromere orientation patterns on the meiosis I and II spindles. However, the meiotic cohesion apparatus in Drosophila melanogaster remains largely uncharacterized. We describe a novel protein, sisters on the loose (SOLO), which is essential for meiotic cohesion in Drosophila. In solo mutants, sister centromeres separate before prometaphase I, disrupting meiosis I centromere orientation and causing nondisjunction of both homologous and sister chromatids. Centromeric foci of the cohesin protein SMC1 are absent in solo mutants at all meiotic stages. SOLO and SMC1 colocalize to meiotic centromeres from early prophase I until anaphase II in wild-type males, but both proteins disappear prematurely at anaphase I in mutants for mei-S332, which encodes the Drosophila homologue of the cohesin protector protein shugoshin. The solo mutant phenotypes and the localization patterns of SOLO and SMC1 indicate that they function together to maintain sister chromatid cohesion in Drosophila meiosis.

Sgo1 establishes the centromeric cohesion protection mechanism in G2 before subsequent Bub1-dependent recruitment in mitosis

Bub1 was one of the first protein kinases identified as a component of the spindle-assembly checkpoint, a surveillance mechanism that delays anaphase onset until all chromosomes are stably attached to spindle microtubules. Whereas the kinase activity of Bub1 is not required for checkpoint function in yeast, its requirement in mammalian cells is still unclear. Using a complementation assay with bona fide BUB1-null mouse embryonic fibroblasts, we show that the kinase activity of Bub1 is not required for checkpoint function or chromosome alignment. Its activity is, however, required for centromeric localisation of Sgo1, a known protector of centromeric cohesion. Despite the absence of Sgo1 from mitotic centromeres in cells devoid of Bub1 activity, centromeric cohesion is still maintained until anaphase. An explanation for this comes from observations showing that Sgo1 is first recruited to centromeric heterochromatin in G2, but then becomes diffusely localised throughout the nucleus in early prophase, before returning to centromeres later in prophase. Importantly, whereas centromeric localisation of Sgo1 in prophase is dependent on the kinase activity of Bub1, its recruitment to centromeric heterochromatin in G2 is not. Rather, the localisation of Sgo1 in G2 is abolished when heterochromatin protein 1 is not bound to centromeric heterochromatin. Thus, it seems that Sgo1 sets up the centromeric protection mechanism in G2, but that its Bub1-dependent localisation to centromeres during mitosis is not required to maintain cohesion.

10.1007/s11174-008-1005-5

The cytoplasmic dynein is a multisubunit complex driving organelles along microtubules to their minus-end. We used antibodies against two functional domains (motor and microtubule-binding) of one of principal components of the complex—dynein heavy chain of slime mould Dictyostelium discoideum—to test root meristem cells of wheat Triticum aestivum. The antibodies reacted with a high molecular weight protein (>500 kDa) in the total cell extract and the band recognized by the antibodies in plant extracts had a lower electrophoretic mobility than the high molecular weight band of mammalian dynein. Antibodies coupled to protein A-Sepharose precipitated the high molecular weight protein from the purified cell extracts. Immunocytochemical analysis demonstrated that the antigen recognized by antibodies against dynein heavy chains is associated with the vesicles whose localization depends on the cell cycle stage. The antigen-positive vesicles were localized to the perinuclear region in interphase and early prophase, to the spindle periphery and to spindle pole region during mitosis, and to the interzonal region in the period of fragmoplast and cell plate formation. Some antigen-positive vesicles also reacted with antibodies against Golgi protein markers. The obtained data indicate that higher plant cells contain a high molecular weight protein interacting with antibodies against the motor and microtubules-binding domains of Dictyostelium dynein heavy chain. The revealed antigen was associated with the vesicular structures in the cytoplasm including the Golgi apparatus.

Impact of Chromatin Transfer and Spindle Abnormalities on Pollen Fertility and Pollen Size in Plantago lanceolata L.

The phenomenon of cytomixis involving chromatin transfer and spindle abnormalities were recorded for the first time in the diploid (n=6) accession of Plantago lanceolata scored from Parvati Valley, Kullu District, Himachal Pradesh (India). Cytomixis with chromatin transfer involved 2–3 PMCs (pollen mother cells) at different stages of meiosis from early prophase-I to T-II, but the maximum frequency of PMCs involved in cytomixis was recorded during the early prophase stages of meiosis-I (11.03%). The transfer of chromatin material among meiocytes was observed to be both partial and complete resulting into PMCs with hypo- and hyperploid chromosome numbers (2n=14, 15). During cytomixis, nucleolus also transmigrated to neighbouring PMCs and the PMCs with supernumerary nucleoli also resulted. Other meiotic abnormalities associated with cytomixis included chromatin stickiness, out of plate bivalents, laggards, bridges, unoriented chromosomes during A-I/T-I and A-II/T-II, and micronuclei. The effect of chromatin transfer, spindle abnormalities and associated meiotic anomalies on meiotic behaviour, pollen fertility and pollen size has been discussed. The cytomixis in P. lanceolata seems to be a natural phenomenon under genetic control and certainly have played a role in the origin of aneuploids and polyploids.

Meiotic chromosomes and nucleolar behavior in testicular cells of the grassland spittlebugs Deois flavopicta, Mahanarva fimbriolata and Notozulia entreriana (Hemiptera, Auchenorrhyncha)

Spittlebugs annually infest pastures and cause severe damage, representing a serious problem for the tropical American beef cattle industry. Spittlebugs are an important biotic constraint to forage production and there is a lack of cytogenetic data for this group of insects. For these reasons, we conducted this work, in which the spermatogenesis and nucleolar behavior of Deois flavopicta, Mahanarva fimbriolata and Notozulia entreriana were studied. The males possessed testes in the shape of a “bunch of grapes”; a variable number of testicular lobes per individual and polyploid nuclei composed of several heteropycnotic bodies. A heteropycnotic area was located in the periphery of the nucleus (prophase I); the chiasmata were terminal or interstitial; metaphases I were circular or linear and anaphase showed late migration of the sex chromosome. The chromosome complement had 2n = 19, except for N. entreriana (2n = 15); the spermatids were round with heteropycnotic material in the center and elongated with conspicuos chromatin. The analysis of testes after silver nitrate staining showed polyploid nuclei with three large and three smaller nucleolar bodies. Early prophase cells had an intensely stained nucleolar body located close to the chromatin and another less evident body located away from the chromatin. The nucleolar bodies disintegrated during diplotene. Silver staining occurred in two autosomes, in terminal and subterminal locations, the latter probably corresponding to the nucleolus organizer regions (NORs). The spermatids were round with a round nucleolar body and silver staining was observed in the medial and posterior region of the elongated part of the spermatid head.

Live imaging of rapid chromosome movements in meiotic prophase I in maize

The ability of chromosomes to move across the nuclear space is essential for the reorganization of the nucleus that takes place in early meiotic prophase. Chromosome dynamics of prophase I have been studied in budding and fission yeasts, but little is known about this process in higher eukaryotes, where genomes and chromosomes are much larger and meiosis takes a longer time to complete. This knowledge gap has been mainly caused by difficulties in culturing isolated live meiocytes of multicellular eukaryotes. To study the nuclear dynamics during meiotic prophase in maize, we established a system to observe live meiocytes inside intact anthers. We found that maize chromosomes exhibited extremely dynamic and complex motility in zygonema and pachynema. The movement patterns differed dramatically between the two stages. Chromosome movements included rotations of the entire chromatin and movements of individual chromosome segments, which were mostly telomere-led. Chromosome motility was coincident with dynamic deformations of the nuclear envelope. Both, chromosome and nuclear envelope motility depended on actin microfilaments as well as tubulin. The complexity of the nuclear movements implies that several different mechanisms affect chromosome motility in early meiotic prophase in maize. We propose that the vigorous nuclear motility provides a mechanism for homologous loci to find each other during zygonema.

Cytomixis inThinopyrum intermedium, Thinopyrum ponticumand its hybrids with wheat

Cytomixis has been described in many plant species, but not in Thinopyrum . The present study reports spontaneous cytomixis during microsporogenesis in Thinopyrum intermedium (2n = 42), Thinopyrum ponticum (2n = 70), and their F 1 hybrids with wheat. Cytomixis frequently occurred in early prophase I but very rarely in meiosis II. The type of cytomixis that occurred most often was where chromatins migrate from one nucleus into an adjacent cel1. Migration from one nucleus into two or more cells or from two or more nuclei into one cel1 was also observed. After a donor cell transferred chromatin to a recipient cell, the recipient cell would sometimes pass the chromatin on to another cell. Migration did not necessarily occur between cells in the same stage. Cytomixis in Th. ponticum and its hybrids with wheat was more complex than that in Th. intermedium . The possible causes, cytological consequences and genetic significance of cytomixis are discussed.

The endocannabinoid system and pivotal role of the CB 2 receptor in mouse spermatogenesis

The exact role of the endocannabinoid system (ECS) during spermatogenesis has not been clarified. We used purified germ cell fractions representative of all phases of spermatogenesis and primary cultures of spermatogonia. This approach allowed the precise quantification of the cannabinoid receptor ligands, anandamide and 2-arachidonoylglycerol, and of the expression at transcriptional and transductional levels of their metabolic enzymes and receptors. Our data indicate that male mouse germ cells possess an active and complete ECS, which is modulated during meiosis, and suggest the presence of an autocrine endocannabinoid signal during spermatogenesis. Mitotic cells possess higher levels of 2-arachidonoylglycerol, which decrease in spermatocytes and spermatids. Accordingly, spermatogonia express higher and lower levels of 2-arachidonoylglycerol biosynthetic and degrading enzymes, respectively, as compared to meiotic and postmeiotic cells. This endocannabinoid likely plays a pivotal role in promoting the meiotic progression of germ cells by activating CB(2) receptors. In fact, we found that the selective CB(2) receptor agonist, JWH133, induced the Erk 1/2 MAPK phosphorylation cascade in spermatogonia and their progression toward meiosis, because it increased the number of cells positive for SCP3, a marker of meiotic prophase, and the expression of early meiotic prophase genes.

Disintegration of microsporocytes in a male sterile mutant of Brassica napus L. is possibly associated with endoplasmic reticulum-dependent autophagic programmed cell death

The mechanism of anther abortion in a male sterile (ms) line (Longyou 9S) of Brassica napus L. was evaluated by a combination of light and electron microscopies. Light microscopy showed that the tapetal cells of the ms line appeared smaller than those of its fertile line, sporogenous cells were rich in vacuoles, and pollen mother cells dismantled before the tetrad stage. Electron microscopy demonstrated that sporogenous cells were also rich in very long, plate-shaped endoplasmic reticulum cisternae that actively encircled portions of cytoplasm with organelles. In later stages, many large membrane-bound inclusions were observed in the sporogenous cells. These membrane-bound inclusions were lined by single or multiple layer(s) of the endoplasmic reticulum membranes and contained vacuoles, ribosome, plastid, mitochondria, small membrane-bound inclusion, and/or intact nuclei. In meiotic interphase and early meiosis prophase I, many vesicle aggregations and multivesicular bodies containing numerous vesicles appeared in pollen mother cells. More interestingly, some of the multivesicular bodies lay in deep cytoplasm or near cell wall, and some appeared fused with plasmalemma and released the inner vesicles out of plasmalemma. Such released vesicles gradually dispersed and later disappeared. The observations suggest that active endoplasmic reticulum-dependent autophagic programmed cell death and multivesicular body-dependent polar vesicle trafficking are probably present in the studied male sterile line.

Telomere Distribution and Dynamics in Somatic and Meiotic Nuclei of Arabidopsis thaliana

The ends of linear eukaryotic chromosomes are protected by the telomere, a specialised nucleoprotein complex. The primary role of the telomere is to protect the chromosome ends from being degraded or recognised and processed as double strand breaks. Additionally, the telomeres are involved in interphase chromosome organisation and also in chromosome pairing, synapsis and movement during meiotic prophase. The main emphasis of this review is concerned with the distribution and dynamics of the telomeres in the somatic cell and meiocytes of plants, focusing on the model plant Arabidopsis thaliana. In Arabidopsis the telomeres are organised around the nucleolus in both the somatic and meiotic interphase. One of the outstanding questions in meiosis is how homologous chromosomes pair (align) and synapse during meiotic prophase. Recent attention has been paid to the bouquet formation, a nearly universal event, during which the telomeres cluster on the nuclear membrane in early prophase. It has been suggested that because the telomeres are in close proximity this would enhance their pairing and subsequent synapsis of the homologues. In Arabidopsis we observe that the telomeres are paired homologously in early meiosis whilst still arranged around the nucleolus. They are moved to the nuclear membrane preceding synapsis and reveal only a loose clustering, which may represent a transient bouquet. On completion of synapsis the paired telomeres are dispersed and remain attached to the nuclear membrane until diplotene when they dissociate from the nuclear membrane. We also discuss the prospects for live imaging of the telomeres in Arabidopsis.