Genetic relationships among Hylocereus and Selenicereus vine cacti (Cactaceae): evidence from hybridization and cytological studies

BACKGROUND AND AIMS: Hylocereus and Selenicereus are native to tropical and sub-tropical America. Based on its taxonomic status and crossability relations it was postulated that H. megalanthus (syn. S. megalanthus) is an allotetraploid (2n = 4x = 44) derived from natural hybridization between two closely related diploid taxa. The present work aimed at elucidating the genetic relationships between species of the two genera. METHODS: Crosses were performed and the putative hybrids were analysed by chromosome counts and morphological traits. The ploidy level of hybrids was confirmed by fluorescent in situ hybridization (FISH) of rDNA sites. Genomic in situ hybridization (GISH) was used in an attempt to identify the putative diploid genome donors of H. megalanthus and an artificial interploid hybrid. KEY RESULTS: Reciprocal crosses among four diploid Hylocereus species (H. costaricensis, H. monacanthus (syn. H. polyrhizus), H. undatus and Hylocereus sp.) yielded viable diploid hybrids, with regular chromosome pairing. Reciprocal crosses between these Hylocereus spp. and H. megalanthus yielded viable triploid, pentaploid, hexaploid and aneuploid hybrids. Morphological and phenological traits confirm the hybrid origin. In situ detection of rDNA sites was in accord with the ploidy status of the species and hybrid studied. GISH results indicated that overall sequence composition of H. megalanthus is similar to that of H. ocamponis and S. grandiflorus. High sequence similarity was also found between the parental genomes of H. monacanthus and H. megalanthus in one triploid hybrid. CONCLUSIONS: The ease of obtaining partially fertile F1 hybrids and the relative sequence similarity (in GISH study) suggest close genetic relationships among the taxa analysed.     

小麦背景下 BYDV抗性携带染色体的遗传行为

在鉴定遗4212中BYDV抗性携带染色体的染色体组起源以及被代换小麦染色体的基础上,研究了BYDV抗性携带染色体补偿小麦染色体的能力以及传递率等问题.结果表明,BYDV抗性携带染色体能较好补偿小麦第2、第5以及第7部分同源群的染色体;在二体代换系中,该染色体优先取代2D小麦染色体、而非2A、2B小麦染色体;(77-5433×遗4212)自交F2群体中共出现10种染色体组成类型,其中一种为非预期类型,染色体数目变异较大而结构变异较少;该染色体的传递率以及携带该染色体配子的传递率分别为56.3%和33%,低于理论值75%和50%;并结合遗4212染色体组成鉴定结果探讨了相关结果产生的原因.染色体原位杂交是研究小麦背景下外源染色体遗传行为快速而准确的方法.     

Cytogenetic characterization of six species of flatfishes with comments to karyotype differentiation patterns in Pleuronectiformes (Teleostei)

The karyotypes and cytogenetic characteristics of flatfishes species Paralichthys orbignyanus , Paralichthys patagonicus , Citarichthys spilopterus and Etropus crossotus (Paralichthyidae), Bothus ocellatus (Bothidae) and Symphurus tessellatus (Cynoglossidae) were investigated by conventional [Giemsa staining, C-banding, Ag- and chromomycin (CMA₃)-stainings] and molecular [ in situ hybridization (ISH)] cytogenetic techniques. The results showed 2n = 46 and FN = 48 (2msm + 46sta) in P. orbignyanus , 2n = 46 and FN = 46 (46sta) in P. patagonicus , 2n = 26 and FN = 44 (18msm + 8sta) in C. spilopterus , 2n = 38 and FN = 64 (26msm + 12sta) in E. crossotus , 2n = 32 and FN = 50 (18msm + 14sta) in B. ocellatus , and 2n = 46 and FN = 62 (46msm + 62sta) in S. tessellatus . All species exhibited weak C-band positive segments in terminal and centromeric positions of some chromosome pairs. Silver staining of the nucleolus organizer regions (Ag-NOR) technique showed a single Ag-NOR-bearing chromosome pair in all species except E. crossotus . All these sites were CMA₃ positive and showed clear ISH signals after probing with a 18S rRNA probe. Etropus crossotus presented until seven chromosomes with Ag-NORs and CMA₃ positively stained segments in five chromosome pairs. Conversely only one chromosome pair was identified with the ISH experiments in this species. The available results show that the fishes of the order Pleuronectiformes experienced a marked chromosome evolution that included reduction in diploid number, mainly due to Robertsonian rearrangements, and several chromosome inversions.     

中间偃麦草(Thinopyrum intermedium)18S-5.8S-26S rDNA位点在染色体上的分布及对其核ITS序列异质性的分析(英文)

中间偃麦草(Thinopyrum intermedium(Host)Barkworth et Dewey)是禾本科小麦族植物中的一个异源六倍体物种,是重要的牧草植物,在小麦的抗病育种中发挥了重要作用。利用荧光原位杂交(FISH)技术,在体细胞中期染色体上,对18S-5.8S-26S rDNA位点进行了物理定位,发现该物种有3～4对染色体携带18S-5.8S-26S rDNA主位点。结合基因组原位杂交(GISH)分析,证明中间偃麦草的St基因组中有一对同源染色体短臂末端携带一个主位点,其余2～3对主位点位于E基因组染色体上。对不同来源的材料研究表明:18S-5.8S-26S rDNA位点的数目(包括主位点和小位点)、位置、拷贝数在不同收集材料之间的差异较大,甚至在同一个体的不同细胞中也存在差异。讨论了rDNA物理作图数据在分析系统发育问题中的局限性。结合中间偃麦草的三个可能的二倍体基因组供体(Th.bessarabicum、Th. elongatum和Pseudoroegneria stipifolia)rDNA位点分析的结果,对中间偃麦草进化过程中rDNA位点的变化进行了分析,同时,对其中一份材料的核ITS序列进行了克隆、测序和系统发育分析,发现在中间偃麦草中,ITS序列具有很高的异质性。     

一种新的六倍体细胞类型水生薏苡的细胞遗传学鉴定

通过醋酸洋红压片和荧光原位杂交技术(包括基因组原位杂交技术),确定在我国广西西南部地区广泛分布着的水生薏苡(Coix aquatica Roxb.)属于一种新的六倍体细胞类型.这种水生薏苡与已报道的几种水生薏苡细胞类型的染色体数目均不相同,它的染色体数目是2n=30,在减数分裂前期Ⅰ和中期Ⅰ的细胞中形成10个二价体和10个单价体.基因组原位杂交结果表明,这种水生薏苡的20条染色体与四倍体的薏苡(C.lacryma-jobi,2n＝20)的基因组DNA是高度同源的.45S和5S rDNA分别杂交到这种水生薏苡的两条染色体上,其中各有一条染色体与薏苡中携带45S和5S rDNA杂交信号的染色体具有相同的形状和信号的分布状态.据此推测:四倍体的薏苡可能是这种新的水生薏苡细胞类型的一个亲本,它的另一个亲本可能是八倍体的水生薏苡(C.aquatica,2n＝40),因为这种八倍体的水生薏苡在核型、植株形态及生长环境等方面与新的六倍体细胞类型的水生薏苡相似.     

一种新的六倍体细胞类型水生薏苡的细胞遗传学鉴定

通过醋酸洋红压片和荧光原位杂交技术(包括基因组原位杂交技术), 确定在我国广西西南部地区广泛分布着的水生薏苡(Coix aquatica Roxb.)属于一种新的六倍体细胞类型。这种水生薏苡与已报道的几种水生薏苡细胞类型的染色体数目均不相同,它的染色体数目是2n = 30,在减数分裂前期Ⅰ和中期Ⅰ的细胞中形成10个二价体和10个单价体。基因组原位杂交结果表明,这种水生薏苡的20条染色体与四倍体的薏苡(C. lacryma-jobi, 2n = 20)的基因组DNA是高度同源的。45S 和5S rDNA分别杂交到这种水生薏苡的两条染色体上,其中各有一条染色体与薏苡中携带45S和5S rDNA杂交信号的染色体具有相同的形状和信号的分布状态。据此推测: 四倍体的薏苡可能是这种新的水生薏苡细胞类型的一个亲本,它的另一个亲本可能是八倍体的水生薏苡(C. aquatica, 2n = 40), 因为这种八倍体的水生薏苡在核型、植株形态及生长环境等方面与新的六倍体细胞类型的水生薏苡相似。     

Genome organization in diploid hybrid species of Argyranthemum (Asteraceae) in the Canary Islands

Two diploid species of hybrid origin, Argyranthemum lemsii and A. sundingii , have been described from different valleys in the Anaga peninsula, north-east Tenerife. They have previously been shown to originate from hybridization between the same parental species, the montane A. broussonetii and the coastal A. frutescens , A. broussonetii being the chloroplast donor in one valley and A. frutescens in the other. The specific status of the two hybrid species has been questioned. In this study we used karyotype analysis, FISH, and GISH to address the question of multiple diploid hybrid speciation. GISH did not discriminate clearly between the parental genomes, but differential labelling was observed in separate hybrid populations, indicating different chromosomal rearrangements in different valleys. Small karyotype differences and local loss of rDNA were also observed. Thus separate origins of the same hybrid combination in different valleys in Tenerife have been verified. Our results add some support to the recognition of two species of hybrid origin, but the case serves to illustrate some of the many problems connected with the species concept in plants.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 141 , 491–501.     

Long-term genome diploidization in allopolyploid Nicotiana section Repandae (Solanaceae)

Here, we analyze long-term evolution in Nicotiana allopolyploid section Repandae (the closest living diploids are N. sylvestris, the maternal parent, and N. obtusifolia, the paternal parent). We compare data with other more recently formed Nicotiana allopolyploids. We investigated 35S and 5S nuclear ribosomal DNA (rDNA) chromosomal location and unit divergence. A molecular clock was applied to the Nicotiana phylogenetic tree to determine allopolyploid ages. N. tabacum and species of Repandae were c. 0.2 and 4.5 Myr old, respectively. In all Repandae species, the numbers of both 35S and 5S rDNA loci were less than the sum of those of the diploid progenitors. Trees based on 5S rDNA spacer sequences indicated units of only the paternal parent. In recent Nicotiana allopolyploids, the numbers of rDNA loci equal the sum of those of their progenitors. In the Repandae genomes, diploidization is associated with locus loss. Sequence analysis indicates that 35S and 5S units most closely resemble maternal and paternal progenitors, respectively. In Nicotiana, 4.5 Myr of allopolyploid evolution renders genomic in situ hybridization (GISH) unsuitable for the complete resolution of parental genomes.     

Distribution of the Tnt1 retrotransposon family in the amphidiploid tobacco (Nicotiana tabacum) and its wild Nicotiana relatives

Transposable elements can generate considerable genetic diversity. Here we examine the distribution of the Tnt1 retrotransposon family in representative species of the genus Nicotiana . We show that multiple Tnt1 insertions are found in all Nicotiana species. However, Tnt1 insertions are too polymorphic to reveal species relationships. This indicates that Tnt1 has amplified rapidly and independently after Nicotiana speciation. We compare patterns of Tnt1 insertion in allotetraploid tobacco ( N. tabacum ) with those in the diploid species that are most closely related to the progenitors of tobacco, N. sylvestris (S-genome donor) and N. tomentosiformis (T-genome donor). We found no evidence for Tnt1 insertion sites of N. otophora origin in tobacco. Nicotiana sylvestris has a higher Tnt1 content than N. tomentosiformis and the elements are distributed more uniformly across the genome. This is reflected in tobacco where there is a higher Tnt1 content in S-genome chromosomes. However, the total Tnt1 content of tobacco is not the sum of the two modern-day parental species. We also observed tobacco-specific Tnt1 insertions and an absence of tobacco Tnt1 insertion sites in the diploid relatives. These data indicate Tnt1 evolution subsequent to allopolyploidy. We explore the possibility that fast evolution of Tnt1 is associated with 'genomic-shock' arising out of interspecific hybridization and allopolyploidy.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 639–649.     

Karyotype differentiation of four Cestrum species (Solanaceae) revealed by fluorescent chromosome banding and FISH

The karyotypes of four South American species of Cestrum (C. capsulare,C. corymbosum,C. laevigatum and C. megalophylum) were studied using conventional staining, C-CMA/DAPI chromosome banding and FISH with 45S and 5S rDNA probes. The karyotypes showed a chromosome number of 2n = 2x = 16, with metacentric chromosomes, except for the eighth submeta- to acrocentric pair. Several types of heterochromatin were detected, which varied in size, number, distribution and base composition. The C-CMA(+) bands and 45S rDNA were located predominantly in terminal regions. The C-CMA (+) /DAPI (+) bands appeared in interstitial and terminal regions, and the C-DAPI (+) bands were found in all chromosome regions. The 5S rDNA sites were observed on the long arm of pair 8 in all species except C. capsulare, where they were found in the paracentromeric region of the long arm of pair 4. The differences in band patterns among the species studied here, along with data from other nine species reported in the literature, suggest that the bands are dispersed in an equilocal and non-equilocal manner and that structural rearrangements can be responsible for internal karyotype diversification. However, it is important to point out that the structural changes involving repetitive segments did not culminate in substantial changes in the general karyotype structure concerning chromosome size and morphology.     

Programmed DNA Degradation and Nucleolar Biogenesis Occur in Distinct Organelles During Macronuclear Development in Tetrahymena

ABSTRACT. Programmed DNA rearrangements, including DNA degradation, characterize the development of the soma from the germline in a number of developmental systems. Pddl p (programmed DNA degradation 1 protein), a development-specific polypeptide in Tetrahymena , is enriched in developing macronuclei (anlagen) and has been implicated in DNA elimination and nucleolar biogenesis. Here, immunocytochemistry and fluorescent in situ hybridization (FISH) were employed to follow Pddl p and two nucleolar markers (Nopp52 and rDNA) during macronuclear development. Both Pdd 1p and Nopp52 localize to subnuclear structures, each of which resemble nucleoli. However, while true nucleoli form and persist during development, Pdd 1p-positive structures are only present for a brief period of macronuclear differentiation. Accordingly, two distinct organelles can be recognized in anlagen: (1) Pdd 1p-positive structures, which lack Nopp52 and rDNA, and (2) developing nucleoli which contain rDNA and Nopp52 but lack Pdd 1p. Taken together with recent data corroborating Pdd 1p's role in DNA elimination, we favor the hypothesis that Pdd 1p structures are unique, short-lived organelles, likely to function in programmed DNA degradation and not in nucleolar biogenesis.     

Chromosome investigations in annual Medicago species (Fabaceae) with emphasis on the origin of the polyploid Medicago rugosa and M. scutellata

Chromosome number variations play an important role in the genus Medicago. In addition to polyploidy there are cases of dysploidy as evidenced by two basic numbers, x = 8 and x = 7, the latter limited to five annual species having 2n = 14. Annuals are diploid with the exception of Medicago scutellata and Medicago rugosa which have 2n = 30 and are considered the result of crosses between the 2n = 16 and 2n = 14 species. However, this hypothesis has never been tested. This study was carried out to investigate the 2n = 14 and 2n = 30 karyotypes and verify the allopolyploid origin of M. scutellata and M. rugosa. Fluorescence in situ hybridization (FISH) of rDNA probes and genomic in situ hybridization (GISH) were performed. FISH showed that all five diploids with 2n = 14 have one pair of 45S and one pair of 5S rDNA sites. M. scutellata displayed four sites of 45S and four sites of 5S rDNA, while in M. rugosa only one pair of each of these sites was found. GISH did not produce signals useful to identify the presumed progenitors with 14 chromosomes. This result suggests alternative evolutionary pathways, such as the formation of tetraploids (2n = 32) and subsequent dysploidy events leading to the chromosome number reduction.     

The evolutionary origin of a novel karyotype in Timarcha (Coleoptera, Chrysomelidae) and general trends of chromosome evolution in the genus

In this work, we have analysed the karyotypes of six species of Timarcha for the first time and updated the cytological information for two additional taxa, for one of them confirming previous results ( Timarcha erosa vermiculata ), but not for the other ( T. scabripennis ). We describe the remarkable karyotype of T. aurichalcea , the lowest chromosome number in the genus (2 n  = 18), distinctive as well for the presence of an unusual chiasmatic sexual bivalent hitherto unreported for Timarcha . This study increases the number of species studied cytologically in this genus to forty. Additional cytogenetic analyses are performed on several species, including Ag-NOR staining and fluorescent in situ hybridization (FISH) studies with ribosomal DNA probes. Karyotype evolution is analysed by tracing different karyotype coding strategies on a published independent phylogenetic hypothesis for Timarcha based on the study of three genetic markers. The implementation of a likelihood model of character change optimized onto the phylogeny is tentatively used to detect possible drifts in chromosome changes. These analyses show that karyotype is conservative in the evolution of the genus and that there is an apparent trend to reducing chromosome number. Cytological and phylogenetic data are used to explain the evolutionary origin of the karyotype of T. aurichalcea by two centric fusions involving one pair of acrocentric autosomes and the sexual chromosomes.     

莲C_0t-1 DNA的荧光原位杂交分析

为分析中国莲C_0t-1 DNA在其中期染色体上的分布,从中国莲基因组DNA中分离出C_0t-1 DNA,将基因组和所分离的C_0t-1 DNA用生物素标记后作探针,对中国莲染色体进行原位杂交。杂交结果用耦联有荧光素Cy3的生物素抗体检测,发现在每对染色体上均显示出特定的荧光原位杂交带。同时分析了FISH和GISH信号分布的异同。基于C_0t-1 DNA荧光原位杂交带型及染色体型,构建了中国莲核型。     

苜蓿种质间染色体多态性的荧光原位杂交检测

利用染色体荧光原位杂交技术(FISH),将3种重复序列5S rDNA、45S rDNA和C0t-1 DNA用不同荧光物进行标记,对我国10个不同地理来源的苜蓿种质(Medicago sativa L.;2n=4X=32)进行了染色体多态性检测。结果表明,利用以上重复序列可以较好地将苜蓿32条染色体区分为16对特征不同的染色体,10份不同种质材料FISH带纹特征表现高度相似,比较不同种质间同源染色体重复序列杂交特征,揭示出种质群体内和群体间多态性染色体的存在,其中不同的同源染色体多态性表现不尽一致,1号染色体(随体染色体)多态性最高,10份材料中检出7个多态型,3、4、15号染色体保守性较强,在不同种质间表现为单态,其他染色体多态性居中。对在地理分布上自西向东的10个材料进行染色体多态性比较,结果显示分布于西藏、新疆以及分布在辽宁的材料部分染色体多态型显著区别于其他材料。     

莲C0t-1 DNA的荧光原位杂交分析

为分析中国莲Cot-1DNA在其中期染色体上的分布,从中国莲基因组DNA中分离出Cot-1DNA,将基因组和所分离的Cot-1DNA用生物素标记后作探针,对中国莲染色体进行原位杂交。杂交结果用耦联有荧光素Cy3的生物素抗体检测,发现在每对染色体上均显示出特定的荧光原位杂交带。同时分析了FISH和GISH信号分布的异同。基于Cot-1DNA荧光原位杂交带型及染色体型,构建了中国莲核型。     

普通小麦与东方旱麦草异附加系和异代换系的选育与原位杂交检测

旱麦草属（Ｅｒｅｍｏｐｙｒｕｍ）是用于小麦品种改良的又－潜在的植物资源。为了筛选小麦－旱麦草异附加系、异代换系,对普通小麦品种 Ｆｕｋｏｈｏ×东方旱麦草属间杂种的 ＢＣ２Ｆ３代材料的９６粒种子进行了染色体数目的检测,共检出１５粒２ｎ＝４３的种子, ８粒 ２ｎ＝ ４４的种子,进一步对以上材料进行的基因组ＤＮＡ原位杂交,共鉴定出３个单体附加系,２个二体附加系,１个双单体附加,１个小麦三体单体附加,１个附加３条东方旱麦草染色体的小麦单体,在染色体数为４２的个体中,检测出１个单体代换,１个双单体代换。根据ＢＣ２Ｆ３代自交品系来源的不同,初步认为由双单体附加自交比单体附加自交选择异附加系的效率高。     

一种栉孔扇贝丝氨酸蛋白酶基因的染色体定位及其内部SNP的研究

病害问题是制约我国扇贝养殖业发展的关键, 因此贝类的先天免疫也成为当前研究的热点。丝氨酸蛋白酶是先天免疫中至关重要的酶类,在许多通路中起信号放大作用。目前对栉孔扇贝丝氨酸蛋白酶的研究主要集中于基因序列分析和表达谱研究, 基因定位方面的研究尚未开展。文章以包含一种栉孔扇贝丝氨酸蛋白酶基因的BAC克隆为探针, 利用BAC-FISH技术将其定位到一对同源染色体的长臂上, 为丝氨酸蛋白酶基因的后续研究提供了基础; 同时, 利用PCR产物直接测序法筛选了该基因内部的6个SNP标记, 这些SNP标记可供遗传图谱定位使用, 从而可以实现遗传图谱与染色体间的锚定与初步整合     

Karyotype analysis and physical mapping of 45S rDNA in eight species of Sophora,Robinia, and Amorpha

The karyotype analysis and physical locations of 45S rDNA were carried out by means of fluorescence in situ hybridization in three species,and two forms of Sophora,two species of Robina,and one species of Amorpha.S.japonica L.,S.japonica L.f.oligophylla Franch.,S.japonica L.f.pendula Loud.,and S.xanthantha C.Y.Ma.are all tetraploids with 2n=28.There were four 45S rDNA sites in pericentromeric regions of two Pairs of chromosomes in each of them.S.rubriflora Tsoong.is a triploid with 2n=21,and three sites were located in each satellite of group 5 chromosomes.In R.pseudoacacia L.(2n=2x=22),we examined four intensive signals in telomeric regions of two pairs of satellite chromosomes.In R.hispida L.(2n=2x=30),there were four other signals in centromeric regions besides those like in R.pseudoacacia.Amorpha fruticosa L.has most chromosomes(2n=40)among the eight materials,however,there were only six 45S rDNA loci and they laid in centromeric regions,and satellites of three pairs of chromosomes.45S rDNA is a valuable chromosomal landmark in karyotype analysis.The distribution and genomic organization Of rDNA in the three genera were also discussed.     

普通小麦三个基因组之间的遗传关系及原位杂交分析

以普通小麦（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍＬ．）的３个可能的二倍体供体种（乌拉尔图小麦（Ｔ．ｕｒａｒｔｕＴｈｕｍ．）拟斯卑尔脱山羊草（ＡｅｇｉｌｏｐｓｓｐｅｌｔｏｉｄｅｓＴａｕｓｃｈ）和粗山羊草（Ａｅ．ｔａｕｓｃｈｉｉＣｏｓｓ．）的基因组ＤＮＡ为研究对象,通过它们之间的相互杂交,比较杂交强度以及泳道中带纹的不同,并结合部分ＤＮＡ重复序列在基因组间含量差异的数据,得出结论：Ａ＾ｕ和Ｄ基因组的关系