【作者】 陆坤；

【导师】 徐柱； 张学勇；

【作者基本信息】 中国农业科学院 ， 草业科学， 2008， 硕士

【摘要】 小麦族(Triticeae)中十倍体长穗偃麦草(Thinopyrum ponticum)作为目前小麦育种中重要的抗病基因来源之一,一直倍受小麦育种家们的重视,但是对其基因组组成人们至今仍然没有明确统一的认识。为了鉴定其基因组,我们根据野生一粒小麦(Triticum boeoticum) CRW2-BAC5序列设计特异引物以二倍体拟鹅观草(Pseudoroegneria)基因组DNA为模板进行PCR扩增,通过回收产物、测序及比对,我们筛选到了一条来源于St基因组着丝粒反转录转座子长度为1755bp的相对特异序列,暂时命名为pStC1。这条序列有800bp的片段与野生一粒小麦CRW2-BAC5的LTR区高度同源,另有小部分片段与CRW2-BAC5的gag区部分同源,并且包含一段富含AGCAAC碱基的重复序列。序列比对显示,pStC1没有转座发生所必需的引物结合位点——PBS序列,它是源于一种已经失活的转座元件序列片段。以pStC1为探针对小麦、十倍体长穗偃麦草和中间偃麦草(Th. intermedium)等几个物种进行FISH检测,它在小麦A、B及D三个基因组着丝粒相关区域均有很强的杂交信号。对偃麦草属的检测结果显示十倍体长穗偃麦草的基因组明确的分成了两组:一组是28条染色体的着丝粒相关区域有清晰的杂交信号,另一组42条染色体上基本没有信号,我们推定十倍体长穗偃麦草的基因组组成为两个St组和三个E组,用(St1St2 EeEbEx)表示。pStC1在中间偃麦草中不仅St基因组上有强烈的荧光信号,而且E基因组一些染色体的近着丝粒区域也有较强的杂交信号;另外以pStC1下游与CRW2-BAC5的gag区部分同源的序列片段为探针对中国春进行FISH检测时发现,小麦B基因组部分染色体除在着丝粒及近着丝粒区域有较强的荧光信号外,在其常染色体上也发现了明显的信号。这些结果暗示我们在偃麦草属异源多倍体物种及六倍体小麦的物种形成及其基因组进化过程中,St和E基因组之间、A与B及D基因组之间在着丝粒相关区域可能存着在不平衡的整合与协调。更多还原

【Abstract】 Thinopyrum ponticum (2n=10x=70) in Triticeae is one of important sources of pathogen resistant genes in wheat breeding. Though it has attaracted mang concerns of wheat breeders, but its genome components is still in dispute. In order to characterize its chromosomes, according to the sequence of CRW2-BAC5 from Triticum boeoticum, six pair of specific primers were designed and several DNA fragments were amplified by PCR with the genome DNA of diploid Pseudoroegneria as the template. By purifying PCR products, sequencing and sequence alignment we screened a 1755bp DNA fragment originated from St Centromere-specific retrotransposon, we named it pStC1 (St genome centromeric associated sequence). There is a 800bp fragment of this sequence has highly homology with the LTR region of CRW2-BAC5, a less fragment share partial homology to the gag region, and also we have founded a AGCAAC-rich tandem repeat in this fragment. However, sequence comparison revealed that the primer binding site which is necessary for the activity of transposition was not found in pStC1. Therefore, this sequence might be a segment of an inactivating retrotransposon. Chinese Spring and several Elytrigia species were analysed by Fluorescent in situ hybridization (FISH) with this sequence as probe. Significant hybridization signals on the centromere related regions were observed among all the 42 chromosomes of Chinese Spring. The 70 chromosomes of Th. ponticum were definitely divided into two groups, 28 chromosomes were strongly hybridized at their centromeric regions, and the other 42 chromosome had nearly no signals, so we deduced the genomic compositions of Th. ponticum are two St genomes and three E genomes (St1St2EeEbEx). In Th. intermedium, strongest FISH signals existed on St genome chromosomes, but some E genome chromosomes also have strong signals at their pericentromeric regions. Also FISH of the 900bp downstream sequence of pStC1 was carried out in Chinese Spring, obvious signals were obversed on B genome chromosome arms. These results indicated that during the process of specation and genome evolution in allopolyploids of Thinopyrum genus, unbalanced coordination was existed between St genome and E genome at there centromeric and pericentromeric regions, and also these unbalanced coordination maybe existed among A, B and D genomes during the evolution of hexaploid wheat.更多还原