5S rDNA在百合染色体上的定位及其联会特点研究

利用FISH技术追踪不同倍性百合中5S rDNA在染色体上的位置,发现5S rDNA位点稳定位于3号染色体长臂近端部。通过观察铁炮百合小孢子母细胞减数分裂过程中染色体的联会配对特点,发现不同染色体联会特点不同,以5S rDNA重复序列为探针的FISH结果可发现铁炮百合3号染色体上5S rDNA区域在减数分裂过程中不发生联会,这是5S rDNA能稳定在3号染色体遗传的主要原因。

12个竹种的45S rDNA和5S rDNA分布特性比较

【目的】分析12个竹种的45S rDNA和5S rDNA分布特征,并调查这些竹种的染色体数目和结构,为竹类植物系统分类和染色体结构等研究提供相应的细胞遗传学资料,为相关的染色体识别提供相应的染色体物理标记。【方法】以毛竹、花毛竹、龟甲竹、早竹、金镶玉竹、白哺鸡竹、紫竹、斑竹、黄秆乌哺鸡竹、人面竹、大明竹和茶秆竹为材料,以45S rDNA和5S rDNA为探针,采用双色荧光原位杂交技术分析45S rDNA和5S rDNA在这些竹种染色体上的分布。【结果】1)12个竹种的染色体数目均为2 n=48,45S rDNA在12个竹种染色体上展现出一定的多态性分布。①毛竹、花毛竹、龟甲竹、早竹、黄秆乌哺鸡竹和斑竹均具有2个45S rDNA位点,且2个45S rDNA位点信号强度和分布位置表现一致。②茶秆竹、人面竹、白哺鸡竹和金镶玉竹也具有2个45S rDNA位点,其中1个位点较为稳定,位于染色体末端,另外1个位点断裂严重,经常脱离分布位置。③紫竹和大明竹具有2个45S rDNA位点,这对位点在信号强度上存在较大差异,特别是紫竹表现更明显。2)5S rDNA在12个竹种染色体上展现出了一定的多态性分布。①毛竹、花毛竹和龟甲竹的5S rDNA分布模式相似,具有2对信号强度不同的5S rDNA位点,其中1对5S rDNA位点信号很强,位于染色体末端,另外1对5S rDNA位点信号微弱,位于染色体近中间区域。②早竹、白哺鸡竹和黄秆乌哺鸡竹的5S rDNA分布模式较为相似,具有2对较强的5S rDNA信号,且2对信号强度差异不大,以成对形式位于2对同源染色体近中间区域。③金镶玉竹、紫竹和大明竹的5S rDNA分布模式比较特殊,均有3个位点,明显不对称,其中紫竹的3个5S rDNA位点,2个位于染色体末端,1个位于染色体近中间区域,金镶玉竹的3个5S rDNA,2个强弱不同的信号位于染色体中间,还有1个位于染色体末端,而大明竹的3个5S rDNA均位于染色体近中间区域。④斑竹与人面竹的5S rDNA分布模式非常相似,具有2对5S rDNA位点,且信号较弱,均位于染色体近中间区域。⑤茶秆竹具有1对较弱的5S rDNA位点,位于染色体短臂近着丝粒区域。【结论】1)根据45S rDNA和5S rDNA在金镶玉竹、紫竹、人面竹、白哺鸡竹、大明竹和茶秆竹染色体上的分布特征,推测这些竹种的染色体可能发生过断裂、易位、删除或插入等遗传重组。2)毛竹、花毛竹和龟甲竹3个竹种的45S rDNA和5S rDNA分布模式非常相似,该分布模式与3个竹种系统分类地位具有一定的一致性。

Chromosomal Localization of the 5S and 45S rDNA Sites and 5S rDNA Sequence Analysis in Nelumbo Species

The physical location of 45S and 5S rDNA sites by double-target fluorescence in situ hybridization （FISH） and 5S rDNA non-transcribed spacer （NTS） sequences was studied in five accessions of Nelumbo nucifera Gaertn.and one accession of N.nucifera subsp.lutea （Willd.）.The chromosome number of all tested materials was 2n=16.The loci of 5S rDNA were close to the centromere regions of chromosome 3,and the loci of 45S rDNA were found on chromosomes 7 and 8 in all the six tested accessions,respectively.Similarly,45S rDNAs were also located on chromosome 4 in four tested accessions.The 5S rRNA gene sequences were conserved and the NTS sequences were variable among the samples.N.nucifera subsp.lutea was the longest branch in the phylogenetic tree and clustered with N.nucifera cv.Liangzihu.N.nucifera cv.Heilongjiang and N.nucifera cv.Weishanhu showed a close relationship with each other.N.nucifera cv.Dahe Lian was closer to N.nucifera cv.Nihelu Lian than to other tested accessions.Analysis of the molecular karyotype and the 5S rRNA gene spacer sequence suggested the genetic diversity was limited within Nelumbo species and it seems suitable that American lotus was considered as the subspecies of N.nucifera.

三种葱莲属植物的倍性及FISH核型分析

本研究以5S rDNA为探针,利用FISH技术对3种葱莲属栽培品种有丝分裂中期染色体上的rDNA位点进行物理定位,分析3种葱莲属栽培品种的倍性及FISH核型。结果表明:3个品种存在两种倍性,其中‘Lily Pies’和‘Fragrance’为二倍体、‘King′s ramson’为四倍体。它们的核型特点表现为:(1)‘Lily Pies’核型公式2n=2x=24=6 m+18 sm,染色体相对长度范围为6.17%~12.80%,属于2B型;(2)‘Fragrance’核型公式2n=2x=24=14 m+10 sm,染色体相对长度范围为6.36%~12.08%,属于2A型;(3)‘King’ s ramson’核型公式2n=4x=48=28 m+20 sm,染色体相对长度范围为5.68%~13.55%,属于2B型。3种葱莲属植物的FISH位点均位于染色体的长臂末端,分别为‘Lily Pies’含有4个5S rDNA位点,在6号和8号的两条染色上;‘Fragrance’含有3个5S rDNA位点,在两条6号染色体以及一条8号染色上;‘King′s ramson’含有4个5S rDNA位点,分别在一条2号染色体、两条6号染色体和一条8号染色体上。本研究对葱莲属3个栽培品种的倍性和FISH核型的分析,将为该物种的遗传多样性分析和基因组结构解析提供新的信息。

Chromosomal mapping of 5S and 18S-5.8S-25S rRNA genes in Saccharina japonica(Phaeophyceae)as visualized by dual-color fluorescence in situ hybridization

It has been reported that there was a linkage of 5S rRNA gene to 18S-5.8S-25S rRNA gene in a few of species in Ochrophyta.In regard to the usual two positions of linked 5S rDNA to the 3′end of 25S rDNA,two pairs of primers were designed for amplification to verify this linkage of two genes in a kelp cultivar of Saccharina japonica,one of species in Ochrophyta.This result supplemented the previous report that 5S rDNA was unlinked to 25S rDNA in this kelp.In order to simultaneously visualize this unlinkage of two genes,dual-color fluorescence in situ hybridization(FISH)technique was applied to the cytogenetics of S.japonica.Dual-color FISH images showed that two and four hybridization signals were present in the kelp gametophyte and sporophyte,respectively,metaphase nuclei hybridized simultaneously with the labeled probes of 18S rDNA and 5S rDNA.Both haploid and diploid karyotypes in decreasing length of chromosomes showed that 18S-5.8S-25S rDNA was localized at the interstitial region of Chromosome 23,whereas 5S rDNA resided at the sub-telomeric region of Chromosome 27.These karyotypes suggested that the kelp nuclear genome had only one locus of each rRNA gene,and their loci on different chromosomes indicated the physical unlinkage of 5S rDNA to 18S-5.8S-25S rDNA in this kelp.Therefore,dual-color FISH seems to be a powerful technique for the discrimination and pairing of chromosomes featured in both small size and nearly identical shape in S.japonica.

荧光原位杂交法分析肥披碱草的染色体核型

以肥披碱草为材料,用45S rDNA和5S rDNA做探针,通过荧光原位杂交(FISH)法,借助肥披碱草染色体内45S rDNA、5S rDNA的分布特性,分析其染色体核型。结果表明,检测到45S rDNA中第2号、第20号染色体短臂的末端及第17号染色体短臂次缢痕上有杂交信号,并检测到5S rDNA中第2号、第7号和第14号染色体短臂上及第17号染色体短臂次缢痕上有杂交信号。肥披碱草的核型公式为2n=6x=42=30 m+12 sm(4 sat);染色体平均长度为12.68μm,染色体长度范围为9.19~17.39μm,染色体组总长度为266.29μm,根据Stebbins核型分类原则,肥披碱草核型属于2A型。

Evolutionary relationship of three mitten crabs(Eriocheir sp)revealed by mitogenome and 5S ribosomal DNA analysis

To reveal the evolutionary relationship of three mitten crabs(Eriocheir sinensis,E.hepuensis,and E.japonica),complete mitogenomes and nuclear 5S rDNA sequences were analyzed.Sequencing revealed that the mitogenomes analyzed shared conserved organization of the coding and non-coding regions but genetic variation was identified.Among the three mitten crabs distinct tandem repeats were identified in the mitochondrial D-loop region.The 5S gene(5S rDNA)sequence was highly conserved across the three species,whereas non-transcribed spacer(NTS)region exhibit high levels of variation including insertions,deletions and point mutations.Cluster analysis suggested that the three mitten crabs had their own independent 5S rDNA sequence variation and evolutionary pattern.Both mitogenome and 5S rDNA sequence analysis revealed significant genetic variation across the mitten crabs species.Phylogenetic analysis using mitogenome and 5S rDNA sequences demonstrated that E.japonica was relatively more distant from E.sinensis and E.hepuensis.This study extended our previous knowledge and confirmed that the three mitten crabs are likely to be genetically differentiated species.In addition,our study also provided insights into the conservation of pure natural resources of E.sinensis,an important aquaculture species.

黑格尔(Symphysodon discus Heckel)×松石七彩神仙鱼(Symphysodon discus Turquoise)杂交后代的遗传变异

以雄性黑格尔七彩神仙(Symphysodon discus Heckel)和雌性松石七彩神仙(S.discus Turquoise)为亲本进行杂交,获得两种表现型的杂交F1代,一种继承了亲本的花纹与黑色纵带(全色花纹组),一种仅继承了黑色纵带(黑色花纹组)。对该杂交F1代及其亲本的形态特征和5S rDNA进行研究,根据主成分分析得出全色花纹组与黑色花纹组外形特征相似,尾柄与背鳍两处性状更接近松石,下颌骨末端到臀鳍起点之间长度更接近黑格尔;松石、全色花纹组和黑色花纹组的5S rDNA长度210 bp,黑格尔具有210 bp和300 bp两种5S rDNA,包括编码区和非编码区(NTS),编码区长度均为120 bp,全色花纹组偏向黑格尔,黑色花纹组偏向松石,杂交子代序列具有明显的重组和突变特征,是品种改良和新品系形成的遗传基础。本研究证明了F1代在体型参数和遗传基因方面都与其亲本有本质区别,是一种有杂种特性的后代。该杂交品种的研究对七彩神仙鱼新品系、纯系和种鱼筛选标准的建立具有重要意义。