共查询到20条相似文献,搜索用时 31 毫秒
1.
The intriguing diversity of highly abundant satellite repeats found even among closely related species can result from processes
leading to dramatic changes in copy number of a particular sequence in the genome and not from rapid accumulation of mutations.
To test this hypothesis, we investigated the distribution of the PRAT satellite DNA family, a highly abundant major satellite
in the coleopteran species Palorus ratzeburgii, in eight species belonging to the related genera (Tribolium, Tenebrio, Latheticus), the subfamily (Pimeliinae), and the family (Chrysomelidae). Dot blot analysis and PCR assay followed by Southern hybridization
revealed that the PRAT satellite, in the form of low-copy number repeats, was present in all tested species. The PRAT satellite
detected in the species Pimelia elevata has been sequenced, and compared with previously cloned PRAT monomers from Palorus ratzeburgii and Palorus subdepressus. Although the two Palorus species diverged at least 7 Myr ago, and the subfamily Pimeliinae separated from the genus Palorus 50–60 Myr ago, all PRAT clones exhibit high mutual homology, with average variability relative to the common consensus sequence
of 1.3%. The presence of ancestral mutations found in PRAT clones from all three species as well as the absence of species
diagnostic mutations illustrate extremely slow sequence evolution. This unexpectedly high conservation of PRAT satellite DNA
sequence might be induced by a small bias of turnover mechanisms favoring the ancestral sequence in the process of molecular
drive. 相似文献
2.
Miroslav Plohl Nevenka Mestrović Branka Bruvo Đurđica Ugarković 《Journal of molecular evolution》1998,46(2):234-239
A novel highly abundant satellite DNA comprising 20% of the genome has been characterized in Palorus subdepressus (Insecta, Coleoptera). The 72-bp-long monomer sequence is composed of two copies of T2A5T octanucleotide alternating with 22-nucleotide-long elements of an inverted repeat. Phylogenetic analysis revealed clustering
of monomer sequence variants into two clades. Two types of variants are prevalently organized in an alternating pattern, thus
showing a tendency to generate a new complex repeating unit 144 bp in length. Fluorescent in situ hybridization revealed even
distribution of the satellite in the region of pericentric heterochromatin of all 20 chromosomes. P. subdepressus satellite sequence is clearly species specific, lacking similarity even with the satellite from congeneric species P. ratzeburgii. However, on the basis of similarity in predicted tertiary structure induced by intrinsic DNA curvature and in repeat length,
P. subdepressus satellite can be classified into the same group with satellites from related tenebrionid species P. ratzeburgii, Tenebrio molitor, and T. obscurus. It can be reasonably inferred that repetitive sequences of different origin evolve under constraints to adopt and conserve
particular features. Obtained results suggest that the higher-order structure and repeat length, but not the nucleotide sequence
itself, are maintained through evolution of these species.
Received: 23 April 1997 / Accepted: 11 July 1997 相似文献
3.
L. Bachmann M. Raab D. Sperlich 《Journal of Zoological Systematics and Evolutionary Research》1989,27(2):84-93
The heterochromatin of the chromosomes of Drosophila gunche consists mainly of a satellite DNA composed of multiple, tandemly arranged copies of a 290 b p basic sequence. Five clones containing one or two copies of the basic unit were sequenced. As expected from CsCl density centrifugation and AT specific staining of mitotic chromosomes the sequence is AT rich. The average nucleotid variability between the cloned sequences is 11.6%. In situ hybridization on the mitotic chromosomes revealed, that this satellite DNA is present in the centromeric regions of all chromosomes but the Y. The nucleotide variability between copies of different tandem clusters seems to be higher than between members of the same cluster. The copy number of the sequence in the haploid genome was estimated to be approximately 80000. The sequence is species specific and is not present in the genome of sibling species D. subobscura and D. madeiren-sis. The evolutionary origin of the satellite DNA and its possible role in species formation is discussed. 相似文献
4.
5.
Evolution of Tribolium madens (Insecta,Coleoptera) Satellite DNA Through DNA Inversion and Insertion
Two different satellite DNAs from tenebrionid speciesTribolium madens (Insecta, Coleoptera) have been detected, cloned, and sequenced. Satellite I comprises 30% of the genome; it has a monomer
size of 225 by and a high A + T content of 74%. Satellite 11, with a monomer size of 711 by and A + T content of 70%, is less
abundant, making 4% of the total DNA. Sequence variability of the monomers relative to consensus sequence is 4.1% and 1.2%
for satellite I and II, respectively. Both satellites are localized in the heterochromatic regions of all chromosomes. A search
for internal motifs showed that both satellites contain a related subsequences, about 100 by long. The creation of satellite
I monomer is explained by duplication of the basic subunit, followed by subsequent divergence by single point mutations, deletions,
and gene conversion. Inversion of the subsequence in addition to its duplication has occurred in satellite II. The result
of this inversion is possible formation of a long, stable dyad structure. The 408-bp sequence, inserted within satellite II
monomer, shares no similarity with a basic subunit. Frequent direct repeats found within the inserted sequence point to its
evolution by duplication of shorter motifs. It is proposed that both satellites have been derived from a common ancestral
sequence whose duplication played a major role in the formation of satellite I monomer, while insertion of a new sequence
together with inversion of an ancestral one induced the occurrence of satellite II.
Correspondence to: D. Ugarković 相似文献
6.
Plants possess photoreceptors to perceive light which controls most aspects of their lives. Three photoreceptor families are
well characterized: cryptochromes (crys), phototropins (phots), and phytochromes (phys). Two putative families have been identified
more recently: Zeitlupes (ZTLs) and UV-B photoreceptors (ULI). Using Arabidopsis thaliana and Oryza sativa photoreceptor sequences as references, we have searched for photoreceptor encoding genes in the major phyla of plant kingdom.
For each photoreceptor family, using a phylogenetic tree based on the alignment of conserved amino acid sequences, we have
tried to trace back the evolution and the emergence of the diverse photoreceptor ancestral sequences.
The green alga Chlamydomonas contains one cry and one phot sequence, probably close to the corresponding ancestral sequences, and no phy-related sequence.
The putative UV-B photoreceptors seem to be restricted to the Brassicacae. Except for mosses and ferns, which contain divergent
photoreceptor numbers, the composition of the diverse photoreceptor families is conserved between species. A high conservation
of the residues within domains is observed in each photoreceptor family. The complete phylogenic analysis of the photoreceptor
families in plants has confirmed the existence of crucial evolutionary nodes between the major phyla. For each photoreceptor
class, a major duplication occurred before the separation between Mono- and Eudicotyledons. This allowed postulating on the
putative ancestral function of the photoreceptors.
[Reviewing Editor: Dr. Rudiger Cerff] 相似文献
7.
Major satellites of species in the genus Pimelia comprise large portions of their genomes and belong to seven major satellite families which all originate from a common ancestral
sequence. Here we present the results of comprehensive screening of 26 Pimelia species belonging to three distinct geographic groups (Ibero-Balearic, African and Canary Islands) for the presence of different
Pimelia satellite families in their genomes. Dot-blot hybridization experiments suggest that together with one dominant, highly abundant
satellite family, other families are also present in genomes of the majority of examined Pimelia species, but as low-copy number repeats. The estimated abundance of these underrepresented repeats is about 4,000 copies
per haploid genome. Signals of highly abundant satellite family from P. scabrosa (PSCA) in examined congeneric species, obtained after PCR amplification and Southern hybridization under high stringency
conditions, corroborate sequence preservation of low-copy representatives of satellite families. PRINS localized low-copy
repeats within the pericentromeric regions of all chromosomes. These results point to the existence of an extensive library
of repetitive DNAs that was already present in the genome of the common ancestor of extant Pimelia taxa, and shifts the period of diversification of Pimelia satellites far in the history of this genus. 相似文献
8.
According to the library model, related species can have in common satellite DNA (satDNA) families amplified in differing abundances, but reasons for persistence of particular sequences in the library during long periods of time are poorly understood. In this paper, we characterize 3 related satDNAs coexisting in the form of a library in mitotic parthenogenetic root-knot nematodes of the genus Meloidogyne. Due to sequence similarity and conserved monomer length of 172 bp, this group of satDNAs is named MEL172. Analysis of sequence variability patterns among monomers of the 3 MEL172 satellites revealed 2 low-variable (LV) domains highly reluctant to sequence changes, 2 moderately variable (MV) domains characterized by limited number of mutations, and 1 highly variable (HV) domain. The latter domain is prone to rapid spread and homogenization of changes. Comparison of the 3 MEL172 consensus sequences shows that the LV domains have 6% changed nucleotide positions, the MV domains have 48%, whereas 78% divergence is concentrated in the HV domain. Conserved distribution of intersatellite variability might indicate a complex pattern of interactions in heterochromatin, which limits the range and phasing of allowed changes, implying a possible selection imposed on monomer sequences. The lack of fixed species-diagnostic mutations in each of the examined MEL172 satellites suggests that they existed in unaltered form in a common ancestor of extant species. Consequently, the evolution of these satellites seems to be driven by interplay of selective constraints and stochastic events. We propose that new satellites were derived from an ancestral progenitor sequence by nonrandom accumulation of mutations due to selective pressure on particular sequence segments. In the library of particular taxa, established satellites might be subject to differential amplification at chance due to stochastic mechanisms of concerted evolution. 相似文献
9.
Jeffrey E. Motychak Edmund D. Brodie Edmund D. Brodie III 《Evolution; international journal of organic evolution》1999,53(5):1528-1535
Coevolutionary interactions typically involve only a few specialized taxa. The factors that cause some taxa and not others to respond evolutionarily to selection by another species are poorly understood. Preadaptation may render some species predisposed for evolutionary response to new pressures, whereas a lack of genetic variation may limit the evolutionary potential of other taxa. We evaluate these factors in the predator-prey interaction between toxic newts (Taricha granulosa) and their resistant garter snake predators (Thamnophis sirtalis). Using a bioassay of resistance to tetrodotoxin (TTX), the primary toxin in the prey, we examined phenotypic evolution in the genus Thamnophis. Reconstruction of ancestral character states suggests that the entire genus Thamnophis, and possibly natricine snakes in general, has slightly elevated TTX resistance compared to other lineages of snakes. While this suggests that T. sirtalis is indeed predisposed to evolving TTX resistance, it also indicates that the potential exists in sympatric congeners not expressing elevated levels of TTX resistance. We also detected significant family level variation for TTX resistance in a species of Thamnophis that does not exhibit elaborated levels of the trait. This finding suggests that evolutionary response in other taxa is not limited by genetic variability. In this predator-prey system, species and population differences in resistance appear to be largely determined by variation in the selective environment rather than preadaptation or constraint. 相似文献
10.
Philippe Castagnone-Sereno Hélène Leroy Jean-Philippe Semblat Frédéric Leroy Pierre Abad Carolien Zijlstra 《Journal of molecular evolution》1998,46(2):225-233
An AluI satellite DNA family has been isolated in the genome of the root-knot nematode Meloidogyne chitwoodi. This repeated sequence was shown to be present at approximately 11,400 copies per haploid genome, and represents about 3.5%
of the total genomic DNA. Nineteen monomers were cloned and sequenced. Their length ranged from 142 to 180 bp, and their A
+ T content was high (from 65.7 to 79.1%), with frequent runs of As and Ts. An unexpected heterogeneity in primary structure
was observed between monomers, and multiple alignment analysis showed that the 19 repeats could be unambiguously clustered
in six subfamilies. A consensus sequence has been deduced for each subfamily, within which the number of positions conserved
is very high, ranging from 86.7% to 98.6%. Even though blocks of conserved regions could be observed, multiple alignment of
the six consensus sequences did not enable the establishment of a general unambiguous consensus sequence. Screening of the
six consensus sequences for evidence of internal repeated subunits revealed a 6-bp motif (AAATTT), present in both direct
and inverted orientation. This motif was found up to nine times in the consensus sequences, also with the occurrence of degenerated
subrepeats. Along with the meiotic parthenogenetic mode of reproduction of this nematode, such structural features may argue
for the evolution of this satellite DNA family either (1) from a common ancestral sequence by amplification followed by mechanisms
of sequence divergence, or (2) through independent mutations of the ancestral sequence in isolated amphimictic nematode populations
and subsequent hybridization events. Overall, our results suggest the ancient origin of this satellite DNA family, and may
reflect for M. chitwoodi a phylogenetic position close to the ancestral amphimictic forms of root-knot nematodes.
Received: 23 April 1997 / Accepted: 9 July 1997 相似文献
11.
D. Ahmad A. Kikuchi S.A. Jatoi M. Mimura & K.N. Watanabe 《The Annals of applied biology》2009,155(1):91-101
We examined genetic variation in 22 accessions belonging to 11 species in four genera of the Zingiberaceae, mainly from Myanmar, by PCR–restriction fragment length polymorphism analysis to investigate their relationships within this family. Two of 10 chloroplast gene regions ( trnS-trnfM and trnK2 – trnQr ) showed differential PCR amplification across the taxa. Restriction enzyme digestion of the PCR products revealed interspecific variability. The restriction patterns were used to classify the regions as either highly conserved or variable across the taxa. None of the regions was highly conserved across the four genera, and the level of conservation varied. The gene region trnS-trnfM appeared to display interspecific variability among most of the species. However, the relative efficiency of different restriction enzymes depended on the gene regions and genera investigated. Cluster analysis revealed interspecific discrimination among the taxa. The two Curcuma species ( Curcuma zedoaria and Curcuma xanthorrhiza ) appeared to be identical, thus supporting their recent classification as synonyms. The results provide the basis for selecting specific combinations of restriction enzymes and gene regions of chloroplast DNA (cpDNA) to identify interspecific variation in the Zingiberaceae and to identify both highly conserved and variable regions. Overall, cpDNA depicted comparatively diverse genetic profile of the studied germplasm. The genetic information revealed here can be applied to the conservation and future breeding of Zingiber and Curcuma species. 相似文献
12.
M. A. Fregene J. Vargas J. Ikea F. Angel J. Tohme R. A. Asiedu M. O. Akoroda W. M. Roca 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1994,89(6):719-727
Chloroplast DNA (cp) and nuclear ribosomal DNA (rDNA) variation was investigated in 45 accessions of cultivated and wild Manihot species. Ten independent mutations, 8 point mutations and 2 length mutations were identified, using eight restriction enzymes and 12 heterologous cpDNA probes from mungbean. Restriction fragment length polymorphism analysis defined nine distinct chloroplast types, three of which were found among the cultivated accessions and six among the wild species. Cladistic analysis of the cpDNA data using parsimony yielded a hypothetical phylogeny of lineages among the cpDNAs of cassava and its wild relatives that is congruent with morphological evolutionary differentiation in the genus. The results of our survey of cpDNA, together with rDNA restriction site change at the intergenic spacer region and rDNA repeat unit length variation (using rDNA cloned fragments from taro as probe), suggest that cassava might have arisen from the domestication of wild tuberous accessions of some Manihot species, followed by intensive selection. M. esculenta subspp flabellifolia is probably a wild progenitor. Introgressive hybridization with wild forms and pressures to adapt to the widely varying climates and topography in which cassava is found might have enhanced the crop's present day variability. 相似文献
13.
A highly abundant satellite DNA comprising 17% of the Tribolium castaneum
(Insecta, Coleoptera) genome was cloned and sequenced. The satellite
monomer is 360 bp long, has a high A+T content of 73%, and lacks
significant internal substructures. The sequence variability is 3.6%,
essentially due to random distribution of single-point mutations. The
satellite is evenly distributed in the regions of centromeric
heterochromatin of all 20 chromosomes, as shown by fluorescent in situ
hybridization. Comparison of T. castaneum satellite with those from three
different but congeneric species reveals the highest sequence similarity of
47.1% with the satellite from the sibling species Tribolium freemani. The
phylogenetic relationships among Tribolium species deduced from satellite
sequence agree with those based on karyological, chemotaxonomic, and
hybridization data. This indicates a parallel in the divergence of
satellites and some genetic and cytogenetic characters. Despite low mutual
sequence similarity, which makes them species-specific, Tribolium
satellites have a common structural characteristic: a block of about 95%
A+T content, 20 to 42 bp long, flanked at one side by an inverted repeat
which can potentially form a thermodynamically stable dyad structure. Since
similar structural features are found in centromeric DNA of Saccharomyces
cerevisiae and Chironomus pallidivittatus, their possible importance in
centromere function may be inferred.
相似文献
14.
The viviparous freshwater gastropod Tylomelania (Caenogastropoda: Cerithioidea: Pachychilidae) endemic to the Indonesian island Sulawesi has radiated extensively in two
ancient lake systems. We here present the first systematic species-level review of taxa in the five lakes of the Malili lake
system, which contains the most diverse and best studied freshwater fauna on Sulawesi. Our results indicate a significantly
higher diversity of Tylomelania in these lakes than previously perceived based on morphological evidence for delimiting the taxa. We describe nine new species,
thus increasing the number of taxa known from the Malili lakes to 25. Tylomelania species are inhabiting all available substrates in the lakes, and the diversity of habitats is reflected in an unparalleled
range of radula types in this closely related group. Several species show a high intraspecific variability in some characters,
and their closer investigation will probably lead to the discovery of more cryptic species. As it is, this species flock on
Sulawesi is among the largest freshwater mollusc radiations known. Since the Malili lake system also contains other large
endemic species flocks of e.g. crustaceans and fishes, it is a major hotspot of freshwater biodiversity in Asia to become
a conservation priority.
Handling editor: K. Martens 相似文献
15.
Coregonine fishes are notorious taxonomicproblems due to their extreme morphological andecological variation. In North America, diversity is particularly baffling among ciscoes, and both morphological and phylogenetic analyses have resulted in major polytomy among the 8 taxa of the ``Coregonus artedi' species complex. Ciscoes arealso a devastated group, accounting for 10% ofthe fish species listed by the Committee on theStatus of Endangered Wildlife in Canada. Here,we complete the genetic characterization ofNorth American ciscoes with mitochondrial andmicrosatellites markers previously used toanalyse populations of C. artedi in orderto elucidate the evolutionary history andidentify appropriate conservation units. Ourresults revealed a complex evolutionary historymarked by postglacial reticulation eventscoupled with recent and independent evolutionof similar phenotypes (taxa). Genetic variationreflects geography rather than taxonomy, andconsequently, we recommend that a single taxon,C. artedi (sensu lato) be recognized.Local genetic differentiation is often coupledwith ecophenotypic diversification, and gillraker polymorphisms, depth-related habitatpreference and reproductive behaviour areconsidered as phenotypic traits with probableadaptive value contributing to the nicheexpansion of ciscoes. Ecomorphotypes of eachparticular locale thus represent a uniqueexpression of a diverse genetic pool stillundergoing divergence and sorting.Consequently, ciscoes from lakes with distinctecomorphotypes are recognized as ESUs, as wellas each of sympatric forms when they aregenetically differentiated. We recommend thatan ESU strategy focusing at a very local levelbe adopted for continental ciscoes as a validalternative to protect significant evolutionaryprocesses of divergence encountered inpolytypic species of newly colonized habitats. 相似文献
16.
Forensic science uses scientific methods to help the scientists who study evidence to assist in the solving of crimes. Coleoptera is the most diverse and speciose group of insects that have an important role in many scientific fields especially forensic entomology. In addition, it is difficult to morphologically identify and discriminate between them. In the present study, the molecular analysis using mitochondrial DNA information was conducted to swiftly and accurately identify the recovered Coleoptera species. A molecular identification method involving a 221‐bp segment of the 16 s ribosomal RNA (16 s rRNA) gene from three beetle species, collected from a rabbit carcass, was evaluated. The analysis with maximum likelihood method recovered a generally well supported phylogeny, with most currently accepted taxa and species groups as monophyletic. These results will be instrumental for the implementation of the Saudian database of forensically relevant beetles. 相似文献
17.
Sequence variability and distribution of a newly characterized MPA2 satellite DNA family are described in five root-knot nematode species of the genus Meloidogyne, the mitotic parthenogens M. paranaensis, M. incognita, M. arenaria and M. javanica, and the meiotic/mitotic M. hapla (isolates A and B, respectively). The lack of distinctive mutations and the considerable contribution (40.8%) of ancestral changes disclose an ancient satellite DNA which existed in the common ancestor of extant parthenogenetic species in the same or similar form and remained preserved for a period of at least 43 My. Nonuniformly distributed polymorphic sites along the satellite monomer suggest differences in constraints acting on particular sequence segments. Sequence diversity is clearly unaffected by significant differences in genomic abundance of the MPA2 satellite DNA in the examined species. Observed results suggest that the dynamics of this satellite DNA family might be in the first instance a consequence of characteristics of its nucleotide sequence and possible constraints imposed on it. Under conditions of mitotic and meiotic parthenogenesis, slow accumulation of mutations and slow replacement of old MPA2 sequence variants with new ones may be equivalent to the dynamics of some satellite DNA sequences conserved for extremely long evolutionary periods in sexual species. 相似文献
18.
R. Navajas-Pérez M. E. Quesada del Bosque M. A. Garrido-Ramos 《Molecular genetics and genomics : MGG》2009,282(4):395-406
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
19.
Beatrice Mariotti Susana Manzano Eduard Kejnovský Boris Vyskot Manuel Jamilena 《Molecular genetics and genomics : MGG》2009,281(3):249-259
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
20.
Melting pot of biodiversity: first insights into the evolutionary patterns of the Colchic bramble flora (Rubus subgenus Rubus,Rosaceae)
下载免费PDF全文
![点击此处可从《Botanical journal of the Linnean Society. Linnean Society of London》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Michal Sochor Bohumil Trávníček 《Botanical journal of the Linnean Society. Linnean Society of London》2016,181(4):610-620
The Caucasus is a biodiversity hotspot of global significance, containing a number of highly diverse and species‐rich plant taxa. The region is also thought to be an important evolutionary hotspot for Rubus subgenus Rubus (brambles). However, Caucasian brambles have only been poorly studied to date and our knowledge of their evolutionary mechanisms, systematics and taxonomic variability remains rudimentary. Therefore, the objectives of this study were to shed light on the evolution, diversity and reproduction modes of Rubus in one of the two Caucasian glacial refugia, Colchis. Flow cytometry measurements were used to estimate DNA ploidy, a flow cytometric seed screen was conducted to determine reproduction mode and Sanger sequencing of two non‐coding plastid regions was used to reveal phylogenetic patterns. The most common ploidy level was tetraploid, followed by diploid and (rarely) triploid. Intra‐individual variation in reproduction mode was low, as the morphoseries Glandulosi and Radula exhibited strict sexuality and other taxa were mostly apomictic. A few exceptions were observed that deserve further attention, e.g. sexuality induced hypothetically by haploid pollen or by environmental conditions, a high proportion of triploid embryos or polyspermy. Plastid haplotype variability revealed specific, ancient evolutionary patterns with limited involvement of extant diploid taxa and recent isolation from European brambles. We provide the first insight into the variability and evolution of Colchic brambles, which serves as a starting point for further systematic and evolutionary studies. 相似文献