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首页> 外文期刊>Protoplasma: An International Journal of Cell Biology >Karyotype structure and chromosome fragility in the grass Phleum echinatum Host
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Karyotype structure and chromosome fragility in the grass Phleum echinatum Host

机译：草紫茎泽兰寄主的核型结构和染色体易碎性

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摘要

Phleum echinatum Host (2n = 2x = 10) is an annual Mediterranean species which differs from other representatives of the genus Phleum by reduced chromosome number, asymmetric karyotype and unusually high amount of DNA in the genome. Chromosomes of this plant were studied using conventional acetic-orcein staining and fluorescence in situ hybridization (FISH). FISH showed the major 35S ribosomal DNA (rDNA) site at the secondary constriction of satellite chromosome (3) and the minor 35S rDNA site near 5S rDNA cluster in the monobrachial chromosome 5. Telomeric repeats were detected at all chromosome ends within secondary constriction in satellited chromosome 3 and at the centromeric regions of chromosomes 1 and 2. Intrachromosomally located telomeric repeats are probably traces of chromosomal rearrangements that have shaped P.echinatum genome; they were prone to breakage which was manifested in chromosome fragmentation. The most distinct telomeric signals, suggesting massive amplification of interstitial telomeric sequences (ITRs), were observed at the nucleolar organizer region (NOR) of the third chromosome pair. Double FISH confirmed co-localization of telomeric and 35S rDNA repeats in this locus characterized by the biggest fragility in the karyotype. Fragile sites of P.echinatum, composed of amplified telomeric repeats, may bear a resemblance to metazoan rare fragile sites enriched in microsatellite repeats.
机译：紫锥菊寄主（2n = 2x = 10）是一种一年生地中海物种，与它的其他代表不同，因为减少了染色体数，不对称核型和基因组中异常大量的DNA。使用常规的乙酸钙蛋白染色和荧光原位杂交（FISH）研究了该植物的染色体。 FISH显示单臂染色体5的主要35S核糖体DNA（rDNA）位点位于卫星染色体（3）和次要35S rDNA簇附近的5S rDNA簇中。染色体3以及染色体1和2的着丝粒区域。位于染色体内的端粒重复序列可能是塑造紫锥菊基因组的染色体重排的痕迹。它们易于断裂，这在染色体断裂中表现出来。在第三对染色体的核仁组织区（NOR）观察到最明显的端粒信号，表明间质端粒序列（ITR）大量扩增。双重FISH证实端粒和35S rDNA重复序列在该基因座中存在共定位，其特征是核型最大的脆弱性。由扩增的端粒重复序列组成的紫锥菊的易碎位点，可能类似于富含微卫星重复序列的后生动物罕见的易碎位点。

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