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1.
Allopolyploidy alters gene expression in the highly stable hexaploid wheat   总被引:31,自引:0,他引:31  
Hexaploid wheat (Triticum aestivum) contains triplicated genomes derived from three distinct species. To better understand how different genomes are coordinated in the same nucleus of the hexaploid wheat, we globally compared gene expression of a synthetic hexaploid wheat with its diploid (Aegilops tauschii) and tetraploid (T. turgidum) parents by cDNA-AFLP display. The results suggested that the expression of a significant fraction of genes was altered in the synthetic hexaploid; most appeared to be diminished and some were activated. We characterized nine cDNA clones in details. Cytogenetic as well as genomic sequence analyses indicated that the gene silencing was not due to chromosome/DNA loss but was caused by gene regulation. Northern and RT-PCR divided these genes into three groups: (I) four genes were down-regulated nonspecifically, likely involving both parental orthologues; (II) four genes were down-regulated in an orthologue-dependent manner; (III) one gene was activated specifically in the synthetic hexaploid wheat. These genes were often altered non-randomly in different synthetic hexaploids as well as natural hexaploid wheat, suggesting that many of the gene expression changes were intrinsically associated with polyploidy.  相似文献
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Wang X  Shi X  Hao B  Ge S  Luo J 《The New phytologist》2005,165(3):937-946
* Large-scale duplication events have been recently uncovered in the rice genome, but different interpretations were proposed regarding the extent of the duplications. * Through analysing the 370 Mb genome sequences assembled into 12 chromosomes of Oryza sativa subspecies indica, we detected 10 duplicated blocks on all 12 chromosomes that contained 47% of the total predicted genes. Based on the phylogenetic analysis, we inferred that this was a result of a genome duplication that occurred c. 70 million years ago, supporting the polyploidy origin of the rice genome. In addition, a segmental duplication was also identified involving chromosomes 11 and 12, which occurred c. 5 million years ago. * Following the duplications, there have been large-scale chromosomal rearrangements and deletions. About 30-65% of duplicated genes were lost shortly after the duplications, leading to a rapid diploidization. * Together with other lines of evidence, we propose that polyploidization is still an ongoing process in grasses of polyploidy origins.  相似文献
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PCR recombination describes a process of in vitro chimera formation from non-identical templates. The key requirement of this process is the inclusion of two partially homologous templates in one reaction, a condition met when amplifying any locus from polyploid organisms and members of multigene families from diploid organisms. Because polyploids possess two or more divergent genomes (”homoeologues”) in a common nucleus, intergenic chimeras can form during the PCR amplification of any gene. Here we report a high frequency of PCR-induced recombination for four low-copy genes from allotetraploid cotton (Gossypium hirsutum). Amplification products from these genes (Myb3, Myb5, G1262 and CesA1) range in length from 860 to 4,050 bp. Intergenomic recombinants were formed frequently, accounting for 23 of the 74 (31.1%) amplicons evaluated, with the frequency of recombination in individual reactions ranging from 0% to approximately 89%. Inspection of the putative recombination zones failed to reveal sequence-specific attributes that promote recombination. The high levels of observed in vitro recombination indicate that the tacit assumption of exclusive amplification of target templates may often be violated, particularly from polyploid genomes. This conclusion has profound implications for population and evolutionary genetic studies, where unrecognized artifactually recombinant molecules may bias results or alter interpretations. Received: 28 February 2001 / Accepted: 8 June 2001  相似文献
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热休克诱导鳙鱼四倍体的研究   总被引:19,自引:2,他引:17  
洪云汉 《动物学报》1990,36(1):70-75
采用热休克法研究了诱导鳙鱼四倍体的可能性和处理条件。结果表明:1)恰好在卵子开始第一次卵裂前用39—42℃水浴处理1—3分钟,可获得较高频率的四倍体;2)开始处理的时间至关重要,提前或推迟处理导致几乎全部死亡或四倍体频率大大下阵;3)热休克组的孵化率显著下降,畸形率明显升高;4)含高频率四倍体的热休克组的细胞分裂和胚胎发育延迟。  相似文献
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Ploidy induction and sex control in fish   总被引:19,自引:0,他引:19  
7.
木本植物多倍体育种研究进展   总被引:19,自引:0,他引:19  
李云  冯大领 《植物学通报》2005,22(3):375-382
本文从木本植物多倍体育种资源、多倍体育种途径和多倍体鉴定等方面,对国内外木本植物的多倍体育种研究进展进行了综述.与农作物相比,尽管木本植物在多倍体育种中有其缺陷,但木本植物丰富的物种资源及无性繁殖等特性较大程度地发挥了多倍体育种的优越性.  相似文献
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禾本科植物无融合生殖的研究进展   总被引:19,自引:0,他引:19       下载免费PDF全文
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