Cross-species chromosome painting was used to investigate genome rearrangements between tammar wallaby Macropus eugenii (2n = 16) and the swamp wallaby Wallabia bicolor (2n = 10♀/11♂), which diverged about 6 million years ago. The swamp wallaby has an XX female:XY1Y2 male sex chromosome system thought to have resulted from a fusion between an autosome and the small original X, not involving
the Y. Thus, the small Y1 should represent the original Y and the large Y2 the original autosome. DNA paints were prepared from flow-sorted and microdissected chromosomes from the tammar wallaby.
Painting swamp wallaby spreads with each tammar chromosome-specific probe gave extremely strong and clear signals in single-,
two-, and three-color FISH. These showed that two tammar wallaby autosomes are represented unchanged in the swamp wallaby,
two are represented by different centric fusions, and one by a tandem fusion to make the very long arms of swamp wallaby Chromosome
(Chr) 1. The large swamp wallaby X comprises the tammar X as its short arm, and a tandemly fused 7 and 2 as the long arm.
The acrocentric swamp wallaby Y2 is a 2/7 fusion, homologous with the long arm of the X. The small swamp wallaby Y1 is confirmed as the original Y by its painting with the tammar Y. However, the presence of sequences shared between the microdissected
tammar Xp and Y on the swamp wallaby Y2 implies that the formation of the compound sex chromosomes involved addition of autosome(s) to both the original X and Y.
We propose that this involved fusion with an ancient pseudoautosomal region followed by fission proximal to this shared region.
Received: 16 October 1996/Accepted: 30 January 1997 相似文献
Harttia is a genus of the subfamily Loricariinae that posses a broad chromosomal variation. In addition to interspecific karyotype diversity within this group, a multiple sex chromosome system, XX/XY1Y2, has been described for Harttia carvalhoi. Thus, this study aimed to determine the role of chromosomal rearrangements in karyotype differentiation in Harttia by classical and molecular cytogenetic procedures. The results show that Robertsonian rearrangements have a prominent role in the chromosomal diversification of the species analysed, which initially leads to hypothesize a diploid number reduction in Harttia torrenticola and H. carvalhoi. The metacentric chromosome 1, shared between H. torrenticola and H. carvalhoi, could have originated from centric fusions from the ancestral karyotype. A centric fission event associated with the first metacentric pair allowed for the origination of a multiple sex chromosome system XX/XY1Y2, specific to H. carvalhoi. This study highlights the relevance of Robertsonian rearrangements in karyotypic differentiation of the species studied and demonstrates that the occurrence of a centric fission, as opposed to a previously hypothesised chromosome fusion, is directly implicated in the origin of the sex chromosome system of H. carvalhoi.相似文献
Rumex papillaris Boiss, & Reut., an Iberian endemic, belongs to the section Acetosa of the genus Rumex whose main representative is R. acetosa L., a species intensively studied in relation to sex-chromosome evolution. Here, we characterize cytogenetically the chromosomal
complement of R. papillaris in an effort to enhance future comparative genomic approaches and to better our understanding of sex chromosome structure
in plants. Rumex papillaris, as is common in this group, is a dioecious species characterized by the presence of a multiple sex chromosome system (with
females 2n = 12 + XX and males 2n = 12 + XY1Y2). Except for the X chromosome both Y chromosomes are the longest in the karyotype and appear heterochromatic due to the accumulation
of at least two satellite DNA families, RAE180 and RAYSI. Each chromosome of pair VI has an additional major heterochromatin
block at the distal region of the short arm. These supernumerary heterochromatic blocks are occupied by RAE730 satellite DNA
family. The Y-related RAE180 family is also present in an additional minor autosomal locus. Our comparative study of the chromosomal
organization of the different satellite-DNA sequences in XX/XY and XX/XY1Y2Rumex species demonstrates that of active mechanisms of heterochromatin amplification occurred and were accompanied by chromosomal
rearrangements giving rise to the multiple XX/XY1Y2 chromosome systems observed in Rumex. Additionally, Y1 and Y2 chromosomes have undergone further rearrangements leading to differential patterns of Y-heterochromatin distribution between
Rumex species with multiple sex chromosome systems. 相似文献
The dioecious plant Rumex acetosa has a multiple sex chromosome system: XX in female and XY1Y2 in male. Both types of Y chromosome were isolated from chromosome spreads of males by manual microdissection, and their chromosomal
DNA was amplified using degenerate oligonucleotide primed-polymerase chain reaction (DOP-PCR). When the biotin-labeled DOP-PCR
product was hybridized with competitor DNA in situ, the fluorescent signal painted the Y chromosomes. A library of Y chromosome
DNA was constructed from the DOP-PCR product and screened for DNA sequences specific to the Y chromosome. One Y chromosome-specific
DNA sequence was identified and designated RAYSI (R. acetosa Y chromosome-specific sequence I). RAYSI is a tandemly arranged repetitive DNA sequence that maps to the 4’,6-diamidino-2-phenylindole bands of both Y chromosomes.
Received: 22 December 1998; in revised form: 22 March 1999 / Accepted: 23 March 1999 相似文献
The Neotropical fish, Hoplias malabaricus, is one of the most cytogenetically studied fish taxon with seven distinct karyomorphs (A–G) comprising varying degrees of sex chromosome differentiation, ranging from homomorphic to highly differentiated simple and multiple sex chromosomes. Therefore, this fish offers a unique opportunity to track evolutionary mechanisms standing behind the sex chromosome evolution and differentiation. Here, we focused on a high-resolution cytogenetic characterization of the unique XX/XY1Y2 multiple sex chromosome system found in one of its karyomorphs (G). For this, we applied a suite of conventional (Giemsa-staining, C-banding) and molecular cytogenetic approaches, including fluorescence in situ hybridization FISH (with 5S and 18S rDNAs, 10 microsatellite motifs and telomeric (TTAGGG)n sequences as probes), comparative genomic hybridization (CGH), and whole chromosome painting (WCP). In addition, we performed comparative analyses with other Erythrinidae species to discover the evolutionary origin of this unique karyomorph G-specific XY1Y2 multiple sex chromosome system. WCP experiments confirmed the homology between these multiple sex chromosomes and the nascent XX/XY sex system found in the karyomorph F, but disproved a homology with those of karyomorphs A–D and other closely related species. Besides, the putative origin of such XY1Y2 system by rearrangements of several chromosome pairs from an ancestral karyotype was also highlighted. In addition, clear identification of a male-specific region on the Y1 chromosome suggested a differential pattern of repetitive sequences accumulation. The present data suggested the origin of this unique XY1Y2 sex system, revealing evidences for the high level of plasticity of sex chromosome differentiation within the Erythrinidae. 相似文献
Common shrews have an XX/XY1Y2 sex chromosome system, with the X chromosome being a translocation (tandem fusion) between the original X and an autosome; in males this autosome is represented by the Y2 chromosome. From G-banded chromosomes, the Y2 is homologous to the long arm and centromeric part of the short arm of the X. The region of the X that is homologous to the Y2 and also the telomeric region of the short arm of the X were found to be early replicating in somatic cells from a female shrew after 5-bromo-2-deoxyuridine (BrdU) treatment in vitro. The remainder of the short arm of the X was shown to be late replicating. Electron microscopic examination of synaptonemal complexes in males at pachytene revealed pairing of the Y2 axis with the long arm of the X, and Y1 with the short arm. At early stages of pachytene, there is apparently extensive nonhomologous pairing between the X and Y1. In essence, the short arm of the shrew X chromosome behaves like a typical eutherian X chromosome (it is inactivated in female somatic cells and is paried with the Y1 during male meiosis) while the long arm behaves like an autosome (escapes the inactivation and pairs with the Y2). 相似文献
Karyotype and genetic variation of the common shrew (Sorex araneus) from Mt. Pelister in southern Macedonia has been studied. Whereas all autosomes in the chromosomal set (2 na, = 28, the only present metacentrics being af, bc, jl, and tu) were of the standard type as well as the sex chromosomes X and Y2 in males, the Y1 chromosome was a small metacentric. This chromosomal feature is unique among the common shrew populations studied cytogenetically so far. Three out of 33 loci analysed (Sdh, 6Pgd, Mdh-1) were discriminant between the Mt. Pelister population and Sorex araneus from Slovenia and two loci (Est-3, Ada) were partially discriminant. A relatively high value of Nei's genetic distance (D = 0.137) confirms unique character of the Pelister population. 相似文献
Harttia is a genus in the subfamily Loricariinae that accommodates fishes popularly known as armored catfishes. They show extensive karyotypic diversity regarding interspecific numerical/structural variation of the karyotypes, with the presence of the XX/XY1Y2 multiple sex chromosome system, as found in H. carvalhoi. In this context, this study aimed to characterize Harttia punctata chromosomally, for the first time, and to infer the rearrangements that originated the X1X1X2X2/X1X2Y multiple sex chromosome system present in this species. The data obtained in this study, with classical (Giemsa, C-banding and AgNORs) and molecular methodologies (fluorescence in situ hybridization) and chromosome microdissection, indicated that a translocation between distinct acrocentric chromosomes bearing rRNA genes, accompanied by deletions in both chromosomes, might have originated the neo-Y chromosome in this species. The data also suggest that the multiple sex chromosome systems present in H. carvalhoi and H. punctata had an independent origin, evidencing the recurrence of chromosome alterations in species from this genus. 相似文献
The study of the molecular structure of young heteromorphic sex chromosomes of plants has shed light on the evolutionary forces
that control the differentiation of the X and Y during the earlier stages of their evolution. We have used the model plant
Rumex acetosa, a dioecious species with multiple sex chromosomes, 2n = 12 + XX female and 2n = 12 + XY1Y2 male, to analyse the significance of repetitive DNA accumulation during the differentiation of the Y. A bulk segregant analysis
(BSA) approach allowed us to identify and isolate random amplified polymorphic DNA (RAPD) markers linked to the sex chromosomes.
From a total of 86 RAPD markers in the parents, 6 markers were found to be linked to the Ys and 1 to the X. Two of the Y-linked
markers represent two AT-rich satellite DNAs (satDNAs), named RAYSII and RAYSIII, that share about 80% homology, as well as
with RAYSI, another satDNA of R. acetosa. Fluorescent in situ hybridisation demonstrated that RAYSII is specific for Y1, whilst RAYSIII is located in different clusters along Y1 and Y2. The two satDNAs were only detected in the genome of the dioecious species with XX/XY1Y2 multiple sex chromosome systems in the subgenus Acetosa, but were absent from other dioecious species with an XX/XY system
of the subgenera Acetosa or Acetosella, as well as in gynodioecious or hermaphrodite species of the subgenera Acetosa, Rumex
and Platypodium. Phylogenetic analysis with different cloned monomers of RAYSII and RAYSIII from both R. acetosa and R. papillaris indicate that these two satDNAs are completely separated from each other, and from RAYSI, in both species. The three Y-specific
satDNAs, however, evolved from an ancestral satDNA with repeating units of 120 bp, through intermediate satDNAs of 360 bp.
The data therefore support the idea that Y-chromosome differentiation and heterochromatinisation in the Rumex species having a multiple sex chromosome system have occurred by different amplification events from a common ancestral satDNA.
Since dioecious species with multiple XX/XY1Y2 sex chromosome systems of the section Acetosa appear to have evolved from dioecious species with an XX/XY system, the amplification
of tandemly repetitive elements in the Ys of the section Acetosa is a recent evolutionary process that has contributed to
an increase in the size and differentiation of the already non-recombining Y chromosomes. 相似文献
Sex chromosomes in vertebrates range from highly heteromorphic (as in most birds and mammals) to strictly homomorphic (as in many fishes, amphibians, and nonavian reptiles). Reasons for these contrasted evolutionary trajectories remain unclear, but species such as common frogs with polymorphism in the extent of sex chromosome differentiation may potentially deliver important clues. By investigating 92 common frog populations from a wide range of elevations throughout Switzerland, we show that sex chromosome differentiation strongly correlates with alleles at the candidate sex-determining gene Dmrt1. Y-specific Dmrt1 haplotypes cluster into two main haplogroups, YA and YB, with a phylogeographic signal that parallels mtDNA haplotypes: YA populations, with mostly well-differentiated sex chromosomes, occur primarily south of the main alpine ridge that bisects Switzerland, whereas YB populations, with mostly undifferentiated (proto-)sex chromosomes, occur north of this ridge. Elevation has only a marginal effect, opposing previous suggestions of a major role for climate on sex chromosome differentiation. The Y-haplotype effect might result from differences in the penetrance of alleles at the sex-determining locus (such that sex reversal and ensuing X-Y recombination are more frequent in YB populations), and/or fixation of an inversion on YA (as supported by the empirical observation that YA haplotypes might not recombine in XYA females). 相似文献
X and Y chromosomes of Hylemya antiqua occur in two forms each. XL and XS, and Y1 and Y2. The larger XL has an intercalary proximal segment which is absent in the more common smaller XS. The acrocentric Y chromosome (Y1), does not differ morphologically from XS. A smaller metacentric Y2 is apparently not homologous with Y1. Two types of males, XY1 and XXY2, coexist in at least one Dutch population. XY2 has been observed in one individual only. In larval ganglion cells an association has been observed between chromosome Y2 and a probably non-homologous, intercalary segment of autosome 4. A numerical somatic variation of Y2 can lead to gynandromorphs and sex ratios significantly different from 1∶1. XX cells can differentiate into functional spermatozoa
in XX/XXY2 mosaic testes. This indicates the presence of a diffusable male determining substance, which can reverse the “genotypic”
sex of a cell. The occurrence of some spermatozoa-containing “cysts” in ovaries of two gynanders suggests a more or less autonomous
(independent of the gonadal environment) differentiation of XXY2 germ cells. XXXY2 males and XXX females do not show a serious reduction in fertility. Even XXXXY2 males do not exhibit any sign of intersexuality and spermatogenesis seems unaffected. All 62 scored M II cells of X-tetrasomic
males contained 2 Xs. 相似文献
Here, we analyze the evolutionary dynamics of a satellite-DNA family in an attempt to understand the effect of factors such
as location, organization, and repeat-copy number in the molecular drive process leading to the concerted-evolution pattern
found in this type of repetitive sequences. The presence of RAE180 satellite-DNA in the dioecious species of the plant genus
Rumex is a noteworthy feature at this respect, as RAE180 satellite repeats have accumulated differentially, showing a distinct
distribution pattern in different species. The evolution of dioecious Rumex gave rise to two phylogenetic clades: one clade composed of species with an ancestral XX/XY sex chromosome system and a second,
derived clade of species with a multiple sex–chromosome system XX/XY1Y2. While in the XX/XY dioecious species, the RAE180 satellite-DNA is located only in a small autosomal locus, the RAE180 repeats
are present also in a small autosomal locus and additionally have been massively amplified in the Y chromosomes of XX/XY1Y2 species. Here, we have found that the RAE180 repeats of the autosomal locus of XX/XY species are characterized by intra-specific
sequence homogeneity and inter-specific divergence and that the comparison of individual nucleotide positions between related
species shows a general pattern of concerted evolution. On the contrary, both in the autosomal and the Y-linked loci of XX/XY1Y2 species, ancestral variability has remained with reduced rates of sequence homogenization and of evolution. Thus, this study
demonstrates that molecular mechanisms of non-reciprocal exchange are key factors in the molecular drive process; the satellite
DNAs in the non-recombining Y chromosomes show low rates of concerted evolution and intra-specific variability increase with
no inter-specific divergence. By contrast, freely recombining loci undergo concerted evolution with genetic differentiation
between species as occurred in the autosomal locus of XX/XY species. However, evolutionary periods of rapid sequence change
might alternate with evolutionary periods of stasis with variability remaining by the reduced action of molecular mechanisms
of non-reciprocal exchange as occurred in XX/XY1Y2 species, which could depend on repeat-copy number and the processes involved in their amplification. 相似文献
Female-biased sex ratio is an interesting phenomenon observed in Rumex acetosa, a dioecious plant with an XX/XY1Y2 sex chromosome system. Previous authors have suggested that the biased sex ratio in this species is conditioned not only
postzygotically (sex-differential sporophytic mortality) but also prezygotically, because the sex ratio of seeds is also female-biased,
although to a lesser extent than the sex ratio of flowering plants. The mechanisms underlying female bias in Rumex seeds are only poorly understood. To gain more knowledge of them, we analysed male gametophyte development and used flow
cytometry to determine the frequency of female-determining (n = 7, A + X) and male-determining (n = 8, A + Y1Y2) pollen grains in anthers. Embryological studies showed a regular course of male gametophyte development in R. acetosa. There were no signs of degeneration of microspores or disturbances in pollen divisions (irregular nuclei, micronuclei, delayed
chromosomes and anaphase bridges). The Alexander test revealed only 1.6% nonviable pollen grains within anthers. All mature
pollen grains were uniformly equipped with starch granules. The two sexes were shown to substantially differ in nuclear 2C
DNA amount in somatic tissues (7.00 pg in 2A + XX females and 7.50 pg in 2A + XY1Y2 males), and two clearly different DNA classes of mature pollen grains, with lower and with higher DNA amounts (16.8% difference)
were found. Most probably the grains with the lower DNA amount possess seven chromosomes, and grains with the higher DNA amount
eight of them. The quantitative ratio of these grains in anthers at anthesis was 1:1.2, very close to the sex ratio of seeds
observed by the majority of previous authors. All these observations support the opinion that the sex-ratio bias in Rumex is determined prezygotically to some extent. 相似文献
Salinomys delicatus is considered a rare species due to its restricted and patchy distribution, poor records and low abundances. It is also the
phyllotine with the lowest known diploid chromosome number (2n = 18), however its sex chromosome system has never been described.
Here, we studied the chromosomes of six females and three males with bands G, C, DAPI/CMA3 and meiosis. In males, the chromosome number was 2n = 19, with one large metacentric X-chromosome and two medium-sized acrocentrics
absent in females. The karyotype of females was the same as previously described (2n = 18, FN = 32), with X-chromosomes being
metacentric and the largest elements of the complement. In males, the two acrocentrics and the large metacentric form a trivalent
in meiotic prophase. This indicates that S. delicatus has XY1Y2 sex chromosomes, which is confirmed by G and DAPI bands. Constitutive heterochromatin (CH) is restricted to small pericentromeric
blocks in all chromosomes. The X-chromosome shows the largest block of centromeric CH, which could favor the establishment
of this X-autosome translocation. This sex chromosome system is rare in mammals and, compared with other phyllotine rodents,
S. delicatus seems to have undergone a major chromosome restructuring during its karyotypic evolution. 相似文献
Prosimulium multidentatum (Twinn) has three metacentric pairs in its chromosome complement. All six arms are individually identifiably in polytene nuclei. XY1 males are heterozygous for a small basal non-conformity in section 59 of the non-pairing sex differential segments which extends from sextion 58 to section 62 of the IIL arm. XY2 males carry an additional large heterozygous inversion in the center of this same arm. Meiosis is chiasmate in both kinds of male. In XY2 individuals 14.2% of the pachytene nuclei show reverse loop pairing and 12.5% of the anaphase I cells form bridge-fragment configurations. A majority of these bridges persist into second division and 7.1% double sized spermatids are formed. No pachytene loops or anaphase bridges were found in XY1 males. It is concluded therefore that the bridges and fragments of XY2 males result from chiasma formation within the Y2 inversion. 相似文献
GPCR internalization, which is induced by arrestin recruitment, is an important mechanism for the regulation of signaling and receptor quantity at the cell surface.In this study, differences in the mechanism of arrestin-3 (arr-3) recruitment to the neuropeptide Y1 and Y2 receptor were identified. These receptors play an essential role in the regulation of feeding, energy homeostasis and cancer. The Y1R displays high affinity to arr-3, which induces rapid internalization of the arrestin/receptor complex. In contrast, the Y2R has a lower affinity for arr-3. Internalization is induced by arrestin binding, but arr-3 is released from the receptor and remains at the membrane while the receptor internalizes. Moreover, the deletion of the finger loop region of arr-3 reduces its agonist-dependent recruitment to the Y2R significantly, but not to the Y1R suggesting different binding conformations.For the first time, the formation of a supercomplex consisting of Y receptor, Gα0 protein and arrestin was studied by BRET-assay. We demonstrated that the Y1R is able to bind Gα0 protein as well as arr-3 simultaneously and internalizes as a supercomplex. For the Y2R no supercomplex formation was observed.By substituting the C-terminus or specific residues within the intracellular loop 1 and 2 of the receptors, the arr-3 recruitment of the Y1R and Y2R can be switched. Thus, we shed light on the specific spatio-temporal distribution of Gα0 protein and arrestin in response to Y1 versus Y2 receptor activation and identified the molecular determinants. 相似文献
Sex chromosomes undergo rapid turnover in certain taxonomic groups. One of the mechanisms of sex chromosome turnover involves fusions between sex chromosomes and autosomes. Sexual antagonism, heterozygote advantage, and genetic drift have been proposed as the drivers for the fixation of this evolutionary event. However, all empirical patterns of the prevalence of multiple sex chromosome systems across different taxa cannot be simply explained by these three mechanisms. In this study, we propose that female meiotic drive may contribute to the evolution of neo‐sex chromosomes. The results of this study showed that in mammals, the XY1Y2 sex chromosome system is more prevalent in species with karyotypes of more biarmed chromosomes, whereas the X1X2Y sex chromosome system is more prevalent in species with predominantly acrocentric chromosomes. In species where biarmed chromosomes are favored by female meiotic drive, X‐autosome fusions (XY1Y2 sex chromosome system) will be also favored by female meiotic drive. In contrast, in species with more acrocentric chromosomes, Y‐autosome fusions (X1X2Y sex chromosome system) will be favored just because of the biased mutation rate toward chromosomal fusions. Further consideration should be given to female meiotic drive as a mechanism in the fixation of neo‐sex chromosomes. 相似文献
The P2Y11 nucleotide receptor detects high extracellular ATP concentrations. Mutations of the human P2RY11 gene can play a role in brain autoimmune responses, and the P2Y11 receptor alanine‐87‐threonine (A87T) polymorphism has been suggested to affect immune‐system functions. We investigated receptor functionality of the P2Y11A87T mutant using HEK293 and 1321N1 astrocytoma cells. In HEK293 cells, the P2Y11 receptor agonist 3′‐O‐(4‐benzoylbenzoyl)adenosine 5′‐triphosphate (BzATP) was completely inactive in evoking intracellular calcium release while the potency of ATP was reduced. ATP was also less potent in triggering cAMP generation. However, 1321N1 astrocytoma cells, which lack any endogenous P2Y1 receptors, did not display a reduction. Only when 1321N1 cells were co‐transfected with P2Y11A87T and P2Y1 receptors, the calcium responses to the P2Y11 receptor‐specific agonist BzATP were reduced. It is already known that P2Y1 and P2Y11 receptors interact. We thus conclude that the physiological impact of A87T mutation of the P2Y11 receptor derives from detrimental effects on P2Y1–P2Y11 receptor interaction. We additionally investigated alanine‐87‐serine and alanine‐87‐tyrosine P2Y11 receptor mutants. Both mutations rescue the response to BzATP in HEK293 cells, thus ruling out polarity of amino acid‐87 to be the molecular basis for altered receptor characteristics. We further found that the P2Y11A87T receptor shows complete loss of nucleotide‐induced internalization in HEK293 cells. Thus, we demonstrate impaired signaling of the P2Y11 A87T‐mutated receptors when co‐operating with P2Y1 receptors.
Interspecific crosses between D. melanogaster and D. simulans or its sibling species result in unisexual inviability of the hybrids. Mostly, crosses of D. melanogaster females X D. simulans males produce hybrid females. On the other hand, only hybrid males are viable in the reciprocal crosses. A classical question is the cause of the unisexual hybrid inviability on the chromosomal level. Is it due to the absence of a D. simulans X chromosome or is it due to the presence of a D. simulans Y chromosome? A lack of adequate chromosomal rearrangements available in D. simulans has made it difficult to answer this question. However, it has been assumed that the lethality results from the absence of the D. simulans X rather than the presence of the D. simulans Y. Recently I synthesized the first D. simulans compound-XY chromosome that consists of almost the entire X and Y chromosomes. Males carrying the compound-XY and no free Y chromosome are fertile. By utilizing the compound-XY chromosome, the viability of hybrids with various constitutions of cytoplasm and sex chromosomes has been examined. The results consistently demonstrate that the absence of a D. simulans X chromosome in hybrid genome, and not the presence of the Y chromosome, is a determinant of the hybrid inviability. 相似文献