基于淫羊藿属(Epimedium L.)核型似近系数的聚类分析及其系统演化意义

为揭示淫羊藿属(Epimedium L.)植物染色体组遗传与进化,阐明该属植物系统亲缘关系和现代地理分布格局形成。该文对淫羊藿属植物51个分类群(43种、1亚种、6变种和1个栽培品种)和2种温哥华属(Vancouveria Morren et Decne.)植物的根尖进行了有丝分裂中期染色体核型分析,并运用核型似近系数聚类分析方法对这53个分类群植物的核型进行了聚类研究。结果表明:所有种类的染色体数均为12,二倍体(2n=2x=12),第1对同源染色体均为随体染色体,核型均为Stebbins的2A或1A型。可见,淫羊藿属植物染色体组在遗传进化中确实较为保守,种间核型非常相似。核型似近系数聚类分析为淫羊藿属植物系统进化研究提供了一些明显的线索。分析结果完全支持该属属下两个亚属(Subgen.Rhizophyllum和Subgen.Epimedium)的划分。亚属Epimedium的核型似近系数聚类结果显示,该类群物种间的系统亲缘关系与地理分布密切相关。核型似近系数分析结果还发现,来自东亚地区的淫羊藿属植物染色体组具有明显的变异,显示了更高的遗传多样性。基于上述研究结果,推断了淫羊藿属植物现代地理分布格局的形成过程。该研究结果可为淫羊藿属植物的资源利用、系统分类和遗传演化等领域的研究提供参考。     

Fissions,fusions, and translocations shaped the karyotype and multiple sex chromosome constitution of the northeast‐Asian wood white butterfly,Leptidea amurensis

Previous studies have shown a dynamic karyotype evolution and the presence of complex sex chromosome systems in three cryptic Leptidea species from the Western Palearctic. To further explore the chromosomal particularities of Leptidea butterflies, we examined the karyotype of an Eastern Palearctic species, Leptidea amurensis. We found a high number of chromosomes that differed between the sexes and slightly varied in females (i.e. 2n = 118–119 in females and 2n = 122 in males). The analysis of female meiotic chromosomes revealed multiple sex chromosomes with three W and six Z chromosomes. The curious sex chromosome constitution [i.e. W_1–3/Z_1–6 (females) and Z_1–6/Z_1–6 (males)] and the observed heterozygotes for a chromosomal fusion are together responsible for the sex‐specific and intraspecific variability in chromosome numbers. However, in contrast to the Western Palearctic Leptidea species, the single chromosomal fusion and static distribution of cytogenetic markers (18S rDNA and H3 histone genes) suggest that the karyotype of L. amurensis is stable. The data obtained for four Leptidea species suggest that the multiple sex chromosome system, although different among species, is a common feature of the genus Leptidea. Furthermore, inter‐ and intraspecific variations in chromosome numbers and the complex meiotic pairing of these multiple sex chromosomes indicate the role of chromosomal fissions, fusions, and translocations in the karyotype evolution of Leptidea butterflies.     

Comparative molecular cytogenetic analysis of three <Emphasis Type="Italic">Leuciscus</Emphasis> species (Pisces,Cyprinidae) using chromosome banding and FISH with rDNA

A comparative molecular cytogenetic analysis was performed on three species of the genus Leuciscus viz. ide L. idus, chub L. cephalus and dace L. leuciscus distributed in Poland, using C-, Ag- and chromomycin A₃ (CMA₃)-stainings and fluorescence in situ hybridization (FISH) with 5.8S + 28S rDNA as a probe. Although the three species examined shared 2n = 50 chromosomes and the largest acrocentric chromosome pair in the complement, they were characterized with karyotypic differences in terms of the number of uni- and biarmed chromosomes and the localization of nucleolar organizer regions (NORs) revealed by Ag-staining and FISH. L. idus and L. cephalus showed the rDNA sites on the long arms of one submetacentric (SM) chromosome pair and on the short arms of one subtelocentric (ST) chromosome pair, respectively. These NORs were CMA₃-positive, GC-rich and C-positive heterochromatic sites in both species. Such chromosome banding features were also true for four NORs localizing on one of each SM and ST pair in L. leuciscus, but considerable numerical NOR polymorphism became apparent with Ag-staining and FISH due to a different combination of these NOR-bearing SMs and STs in this dace. The present results indicate that the molecular cytogenetic analysis applied herein may become useful to elucidate the karyotype evolution and phylogenetic relationships among the species in the genus Leuciscus and other related groups.     

Interploidy hybridization in sympatric zones: the formation of Epidendrum fulgens × E. puniceoluteum hybrids (Epidendroideae,Orchidaceae)

Interspecific hybridization is a primary cause of extensive morphological and chromosomal variation and plays an important role in plant species diversification. However, the role of interploidal hybridization in the formation of hybrid swarms is less clear. Epidendrum encompasses wide variation in chromosome number and lacks strong premating barriers, making the genus a good model for clarifying the role of chromosomes in postzygotic barriers in interploidal hybrids. In this sense, hybrids from the interploidal sympatric zone between E. fulgens (2n = 2x = 24) and E. puniceoluteum (2n = 4x = 56) were analyzed using cytogenetic techniques to elucidate the formation and establishment of interploidal hybrids. Hybrids were not a uniform group: two chromosome numbers were observed, with the variation being a consequence of severe hybrid meiotic abnormalities and backcrossing with E. puniceoluteum. The hybrids were triploids (2n = 3x = 38 and 40) and despite the occurrence of enormous meiotic problems associated with triploidy, the hybrids were able to backcross, producing successful hybrid individuals with broad ecological distributions. In spite of the nonpolyploidization of the hybrid, its formation is a long‐term evolutionary process rather than a product of a recent disturbance, and considering other sympatric zones in Epidendrum, these events could be recurrent.     

Cytology and systematics in JapaneseArisaema (Araceae)

Chromosome numbers are determined from 37 populations attributed to 22 taxa of JapaneseArisaema. Of them, chromosome numbers ofA. limbatum var.conspicuum (2n=26),A. minus (2n=26),A. nambae (2n=28) andA. seppikoense (2n=26) are determined for the first time. New chromosome numbers, 2n=26, are reported forA. aequinoctiale, A. limbatum, A. stenophyllum, A. undulatifolium andA. yoshinagae. Three modes of basic chromosome numbers,x=14,x=13 andx=12, occur in JapaneseArisaema. Precise karyotypic comparisons of 20 taxa reveal that taxa withx=14 andx=13 share 26 major chromosome arms and have an obvious chromosomal relationship. One of two submeta-centric chromosomes inx=13 corresponds to two telo-centric chromosomes inx=14. InA. ternatipartitum with 2n=6x=72, ten out of 12 basic chromosomes are the most similar in size and arm ratio with larger ten chromosomes ofA. ringens among JapaneseArisaema examined. A basic chromosome number ofx=14 is the commonest in the genusArisaema and the remaining basic chromosome numbers,x=13 andx=12, seem to be derived through dysploidal reduction by translocating large segments of major arm of telo-centric chromosome onto other minor arm of telo-centric followed by loss of the remainings including a centromere, and by loss of two telo-centrics fromx=14, respectively. Some systematic problems of JapaneseArisaema are discussed based on new cytological data.Arisaema hatizyoense, A. minus andA. nambae are accepted as independent species.     

Karyological analysis of the genus Canna (Cannaceae)

Somatic chromosome numbers and karyological features in 22 taxa of the genus Canna (Cannaceae) were investigated and are presented here for the first time. The chromosome numbers were primarily reported for C. bangii, C. indica var. sanctae-rosae and C. tulianensis. A triploid somatic chromosome number of 2n = 27 was found only in C. discolor, while the remaining taxa were diploids with 2n = 18. Chromosome numbers are considered to be remarkably stable within the Cannaceae. Canna shows a symmetric karyotype that consists mostly of median chromosomes, but with some subterminal or submedian chromosomes, and a karyotype homogenous in variation in chromosome length. The karyotype of some taxa of Canna, furthermore, is characterized by median chromosomes with a secondary constriction in the centromeric region. Cytotaxonomical characteristics of the family Cannaceae and the related groups in the Zingiberales are discussed.     

The Role of Fusion in Ant Chromosome Evolution: Insights from Cytogenetic Analysis Using a Molecular Phylogenetic Approach in the Genus Mycetophylax

Among insect taxa, ants exhibit one of the most variable chromosome numbers ranging from n = 1 to n = 60. This high karyotype diversity is suggested to be correlated to ants diversification. The karyotype evolution of ants is usually understood in terms of Robertsonian rearrangements towards an increase in chromosome numbers. The ant genus Mycetophylax is a small monogynous basal Attini ant (Formicidae: Myrmicinae), endemic to sand dunes along the Brazilian coastlines. A recent taxonomic revision validates three species, Mycetophylax morschi, M. conformis and M. simplex. In this paper, we cytogenetically characterized all species that belongs to the genus and analyzed the karyotypic evolution of Mycetophylax in the context of a molecular phylogeny and ancestral character state reconstruction. M. morschi showed a polymorphic number of chromosomes, with colonies showing 2n = 26 and 2n = 30 chromosomes. M. conformis presented a diploid chromosome number of 30 chromosomes, while M. simplex showed 36 chromosomes. The probabilistic models suggest that the ancestral haploid chromosome number of Mycetophylax was 17 (Likelihood framework) or 18 (Bayesian framework). The analysis also suggested that fusions were responsible for the evolutionary reduction in chromosome numbers of M. conformis and M. morschi karyotypes whereas fission may determines the M. simplex karyotype. These results obtained show the importance of fusions in chromosome changes towards a chromosome number reduction in Formicidae and how a phylogenetic background can be used to reconstruct hypotheses about chromosomes evolution.     

Biosystematic study of the genus <Emphasis Type="Italic">Berberis</Emphasis> L. (Berberidaceae) in Khorassan,NE Iran

Four species of the genus Berberis L. have been reported from different regions, including Khorassan provinces. In this article, a revision of this genus in Khorassan provinces is presented. For better validation of the results, morphological, palynological, chromosomal and molecular studies were conducted on specimens collected from Khorassan provinces and preserved in FUMH and TARI herbaria. Morphological study resulted in recognition of three species of Berberis, from which two species are new records for Khorassan. Four unknown new taxa with new morphological characters were also identified, but left for further analysis because of the high percentage of polyploidy and hybridization in this genus. In order to analyze morphological data, 35 OTUs were provided and scored using the distance method and PCoA. The shape and size of pollen grains were nearly equal in the examined taxa, and there were no obvious differences between them. Chromosomal examination indicated tetraploidy (2n = 4x = 56) in all of the studied taxa. Molecular studies were accomplished by RAPD and sequencing of the ITS region to construct a framework of relationships between the taxa. Molecular studies emphasized the difference in the four unknown taxa from others. The total evidence indicates that Berberis L. shows a high percentage of polyploidy and hybridization.     

In vitro induction of a trisomic of Agave tequilana Weber var. Azul (Agavaceae) by para-fluorophenylalanine treatment

The effect of para-fluorophenylalanine (PFP) on the production of trisomic plants of Agave tequilana Weber var. Azul produced through somatic embryogenesis was investigated. Normal diploid plants with 2n = 2x = 60 were obtained in the control treatment and with 4 mg L⁻¹ PFP exposure, while use of 8 and 12 mg L⁻¹ PFP led to production of trisomics with 2n = 2x = 61. Normal diploid plants showed a bimodal karyotype with five pairs of large chromosomes and 25 pairs of small chromosomes. Trisomic plants also had a bimodal karyotype with a group of three chromosomes in position five of the chromosome set. More than 13 homologous chromosome pairs exhibited structural changes. Differences in chromosome arm ratio (long arm/short arm) were also found in eight chromosome pairs; all these aberrations in the chromosome complement of trisomic plants were probably caused by inversions, deletions, and/or duplications produced by high concentrations of PFP. The gross chromosome structural changes and the presence of a single extra chromosome could have been induced by the effect of PFP on the mitotic spindle by inducing nondisjunction of sister chromatids, resulting in hyperploids (2n + x) and hypoploids (2n − x). Flow cytometric analysis of nuclear DNA content was performed using nuclei isolated from young leaves of normal and trisomic plants. The 2C DNA content of 8.635 pg (1Cx = 4,223 Mbp of trisomic plants was different (p < 0.001) than that of normal plants (2C DNA = 8.389 pg (1Cx = 4,102 Mbp). The difference in genome size was correlated with the large structural changes in the trisomic plant genomes.     

Karyotype evolution in apomictic Boechera and the origin of the aberrant chromosomes

Chromosome rearrangements may result in both decrease and increase of chromosome numbers. Here we have used comparative chromosome painting (CCP) to reconstruct the pathways of descending and ascending dysploidy in the genus Boechera (tribe Boechereae, Brassicaceae). We describe the origin and structure of three Boechera genomes and establish the origin of the previously described aberrant Het and Del chromosomes found in Boechera apomicts with euploid (2n = 14) and aneuploid (2n = 15) chromosome number. CCP analysis allowed us to reconstruct the origin of seven chromosomes in sexual B. stricta and apomictic B. divaricarpa from the ancestral karyotype (n = 8) of Brassicaceae lineage I. Whereas three chromosomes (BS4, BS6, and BS7) retained their ancestral structure, five chromosomes were reshuffled by reciprocal translocations to form chromosomes BS1‐BS3 and BS5. The reduction of the chromosome number (from x = 8 to x = 7) was accomplished through the inactivation of a paleocentromere on chromosome BS5. In apomictic 2n = 14 plants, CCP identifies the largely heterochromatic chromosome (Het) being one of the BS1 homologues with the expansion of pericentromeric heterochromatin. In apomictic B. polyantha (2n = 15), the Het has undergone a centric fission resulting in two smaller chromosomes – the submetacentric Het′ and telocentric Del. Here we show that new chromosomes can be formed by a centric fission and can be fixed in populations due to the apomictic mode of reproduction.     

Molecular cytogenetics of <Emphasis Type="Italic">Bellevalia</Emphasis> (Hyacinthaceae) species occurring in Greece

Eight taxa of the genus Bellevalia (Hyacinthaceae) occurring in Greece, all with basic chromosome number x = 4, were cytologically studied using classical and molecular-cytogenetic techniques [fluorochrome banding with chromomycin A₃, fluorescence in situ hybridization (FISH) using probes of 18S–5.8S–26S and 5S ribosomal RNA genes]. Two of the examined taxa are endemic, i.e., B. brevipedicellata and B. sitiaca, both restricted to the Island of Kriti. B. hyacinthoides and B. edirnensis are Balkan endemics, and the four remaining taxa, i.e., B. dubia subsp. boissieri, B. trifoliata, B. romana, and B. ciliata, are more widely distributed Mediterranean elements. Genome size, estimated by flow cytometry, ranged from 18.59 to 53.38 pg. The results of fluorochrome banding and FISH are reported for the first time for the genus Bellevalia. Despite the morphological similarity of the chromosome complement, which is in accordance with the general “basic” Bellevalia karyotype formula, the karyotypes of the studied species are clearly distinguished by the number and position of GC-rich bands and ribosomal DNA (rDNA) loci, revealing clear interspecific differentiation among the taxa. Additionally, examination of the polyploid species B. sitiaca and B. edirnensis and populations of B. hyacinthoides and B. ciliata with different ploidy levels permits discussion about the origin of polyploids and the taxonomic relationships among the taxa.     

Cytogenetic characterization of the ant Trachymyrmex fuscus Emery, 1934 (Formicidae: Myrmicinae: Attini) with the description of a chromosomal polymorphism

The genus Trachymyrmex is a key group in the tribe Attini because of its close phylogenetic relationship to leaf-cutter ants, Acromyrmex and Atta. Cytogenetic data are only available for five taxa of Trachymyrmex, with chromosome numbers of 2n = 12, 18, 20 and 22, and morphology with predominantly metacentric chromosomes. The aim of the present study was to characterize the karyotype of the ant Trachymyrmex fuscus Emery, 1934, by means of the number and morphology of its chromosomes, heterochromatin pattern, CMA₃ and DAPI fluorochromes in the population of two nests collected at Paraopeba, state of Minas Gerais, Brazil. Nineteen females presented 2n = 18 chromosomes (16m + 2sm) and a single male presented n = 9 (8m + 1sm). A size chromosomal polymorphism involving the short arm of the submetacentric pair was confirmed by statistical analysis, with three character conditions: heterozygous SB (with a difference in size between the short arms), standard SS (smaller short arms) and homozygote BB (bigger short arms). In the first nest, both SB and SS workers were observed. The other nest contained heterozygous (SB), homozygous (BB), and a male carrying the B chromosome (larger size). The presence of heterochromatin on all centromeric and pericentromeric chromosomes of T. fuscus suggests that the size difference observed in the submetacentric pair in the SB and BB workers is not related to the heterochromatin but to a duplication of euchromatic regions through intra- or inter- chromosomal rearrangements. The fluorochrome CMA₃ matched the C-banding markings, indicating that the heterochromatin is rich in GC base pairs. As far as we know, this is the first chromosomal polymorphism reported in the tribe Attini.     

Sugarcane genome architecture decrypted with chromosome‐specific oligo probes

Sugarcane (Saccharum spp.) is probably the crop with the most complex genome. Modern cultivars (2n = 100–120) are highly polyploids and aneuploids derived from interspecific hybridization between Saccharum officinarum (2n = 80) and Saccharum spontaneum (2n = 40–128). Chromosome‐specific oligonucleotide probes were used in combination with genomic in situ hybridization to analyze the genome architecture of modern cultivars and representatives of their parental species. The results validated a basic chromosome number of x = 10 for S. officinarum. In S. spontaneum, rearrangements occurred from a basic chromosome of x = 10, probably in the Northern part of India, in two steps leading to x = 9 and then x = 8. Each step involved three chromosomes that were rearranged into two. Further polyploidization led to the wide geographical extension of clones with x = 8. We showed that the S. spontaneum contribution to modern cultivars originated from cytotypes with x = 8 and varied in proportion between cultivars (13–20%). Modern cultivars had mainly 12 copies for each of the first four basic chromosomes, and a more variable number for those basic chromosomes whose structure differs between the two parental species. One?four of these copies corresponded to entire S. spontaneum chromosomes or interspecific recombinant chromosomes. In addition, a few inter‐chromosome translocations were revealed. The new information and cytogenetic tools described in this study substantially improve our understanding of the extreme level of complexity of modern sugarcane cultivar genomes.     

华南地区3种兔儿风属植物(菊科-帚菊木族)的细胞学研究

首次报道了华南地区兔儿风属(Ainsliaea DC.)(菊科-帚菊木族Asteraceae-Pertyeae)3种植物共4个居群的染色体数目和核型。其中长穗兔儿风(A.henryi Diels)的染色体数目为2n=24,核型公式为2n=16m+8sm;三脉兔儿风(A.trinervis Y.C.Tseng)的染色体数目为2n=26,核型公式为2n=16m+10sm;莲沱兔儿风(A.ramosa Hemsl.)2个居群的染色体数目均为2n=26,核型公式为2n=26=22m+4sm。所有居群的染色体由大到小逐渐变化,核型没有明显的二型性。这些结果表明兔儿风属植物确有x=12和x=13两个基数,其中x=13可能是该属的原始基数。     

Karyological studies in <Emphasis Type="Italic">Deschampsia antarctica</Emphasis> Desv. (Poaceae)

Deschampsia antarctica Desv. (Poaceae), known as Antarctic hairgrass, is the only grass species and one of the two vascular plant species native to Antarctica and it is a valuable source for gene discovery associated with freezing-tolerance. In this work the karyotype of D. antarctica collected near Jubany Antarctic Base was reported for the first time. This species presents a chromosome number of 2n = 2x = 26, with karyotypic formula 10m + 6sm + 8st + 2t. The nucleolar organizer region is located in the short arm in one of the submetacentric pairs forming a terminal satellite. Aneusomaty, a phenomenon already reported in the genus, was detected during this study. The cytogenetic information, together with the recent phylogenetic data will be useful for breeding strategies in agronomically valuable crops.     

Revision of ploidy status of Dioscorea alata L. (Dioscoreaceae) by cytogenetic and microsatellite segregation analysis

Dioscorea alata is a polyploid species with several ploidy levels and its basic chromosome number has been considered by most authors to be x = 10. Standard chromosome counting and flow cytometry analysis were used to determine the chromosome number of 110 D. alata accessions of the CIRAD germplasm collection. The results revealed that 76% of accessions have 2n = 40 chromosomes, 7% have 2n = 60 chromosomes and 17% have 2n = 80 chromosomes. Progenies were produced from 2n = 40 types of D. alata and the segregation patterns of six microsatellite markers in four different progenies were analysed. The Bayesian method was used to test for diploid versus tetraploid (allo- and autotetraploid) modes of inheritance. The results provided the genetic evidence to establish the diploidy of plants with 2n = 40 chromosomes and to support the hypothesis that plants with 2n = 40, 60 and 80 chromosomes are diploids, triploids and tetraploids, respectively, and that the basic chromosome number of D. alata is x = 20. The findings obtained in the present study are significant for effective breeding programs, genetic diversity analysis and elucidation of the phylogeny and the species origin of D. alata.     

Karyotype analysis of the Russian wheat aphid, <Emphasis Type="Italic">Diuraphis noxia</Emphasis> (Kurdjumov) (Hemiptera: Aphididae) reveals a large X chromosome with rRNA and histone gene families

The Russsian wheat aphid (RWA), Diuraphis noxia (Kurdjumov), is a worldwide pest of cereals. Despite its economic importance, little is known about its genome. Here we investigated physical genomic features in RWA by karyotype analysis using differential staining with AgNO₃, CMA₃, and DAPI, by chromosomal localization of ribosomal DNA (rDNA), H3 and H4 histone genes, and the “arthropod” telomeric sequence (TTAGG) _n using fluorescence in situ hybridization (FISH), and by measuring the RWA genome size using flow cytometry. The female karyotype, 2n = 10, is composed of four autosome pairs and a pair of X chromosomes, whereas the male karyotype, 2n = 9, has a single X. The X chromosome is the largest element in the karyotype. All three molecular markers used, i.e., 18S rRNA and both H3 and H4 probes are co-localized at one end of the X chromosome. The FISH probes revealed that the AgNO₃-positive bridge between two prometaphase X chromosomes of females, which is believed to be responsible for the elimination of one X chromosome in aphid oocytes determined to undergo male development, contains clusters of both histone genes, in addition to an rDNA cluster. Interestingly, RWA lacks the (TTAGG) _n telomeric sequence in its genome, in contrast to several previously investigated aphid species. Additionally, we compared female and male genome sizes. The female genome size is 2C = 0.86 pg, whereas the male genome size is 2C = 0.70 pg. The difference between the DNA content in the two genders suggests that the RWA X chromosome occupies about 35% of the female haploid genome (1C = 0.43 pg), which makes it one of the largest sex chromosomes in the animal kingdom.     

The chromosome number, karyotype and genome size of the desert plant diploid Reaumuria soongorica (Pall.) Maxim

Extreme drought and salt resistant plant Reaumuria soongorica is of great potential for revealing genetic bases unique to naturally stress-tolerant plants. A preliminary genome survey, including chromosome number, karyotype, chromosomal localization of 45S rDNA loci and genome size was conducted with R. soongorica collected from Lanzhou, China. Chromosome counting showed that R. soongorica is diploid with chromosome number of 22. Karyotypical analysis illustrated that the chromosomes size ranges from 3.38 to 5.51 μm, and the chromosomal formula is 2n = 2x = 22 = 4 m + 14sm + 4st. Fluorescence in situ hybridization revealed that four pairs of 45SrDNA signals were detected at the end of R. soongorica chromosomes. The flow cytometry analysis indicated that the mean C value of R. soongorica is 0.806 pg with predicted genome size of about 778 Mb. The results indicate that the extreme drought and salt resistance of R. soongorica was not attributed to a big and complicate genome and also offer some clues in resolving the problems of taxonomy and evolution in Tamaricaceae.