Divashuk M G, Alexandrov O S, Kroupin P Yu, Karlov G I
Center for Molecular Biotechnology, Russian State Agrarian University-MTAA, Moscow, Russia.
Cytogenet Genome Res. 2011;134(3):213-9. doi: 10.1159/000328831. Epub 2011 Jun 29.
Dioecy is relatively rare in plants and sex determination systems vary among such species. A good example of a plant with heteromorphic sex chromosomes is hop (Humulus lupulus). The genotypes carrying XX or XY chromosomes correspond to female and male plants, respectively. Until now no clear cytogenetic markers for the sex chromosomes of hop have been established. Here, for the first time the sex chromosomes of hop are clearly identified and characterized. The high copy sequence of hop (HSR1) has been cloned and localized on chromosomes by fluorescence in situ hybridization. The HSR1 repeat has shown subtelomeric location on autosomes with the same intensity of the signal. The signal has been present in the subtelomeric region of the long arm and in the near-centromeric region but absent in the telomeric region of the short arm of the X chromosome. At the same time the signal has been found in the telomeric region only of the long arm of the Y chromosome. This finding indicates that the sex chromosomes of hop have evolved from a pair of autosomes via ancient translocation or inversion. The observation of the meiotic configuration of the sex bivalents shows the location of a pseudoautosomal region on the long arms of X and Y chromosomes.
雌雄异株在植物中相对罕见，并且性别决定系统在这类物种中各不相同。具有异形性染色体的植物的一个很好的例子是啤酒花（Humulus lupulus）。携带XX或XY染色体的基因型分别对应雌性和雄性植株。到目前为止，尚未建立啤酒花性染色体的明确细胞遗传学标记。在此，首次明确鉴定并表征了啤酒花的性染色体。啤酒花的高拷贝序列（HSR1）已被克隆，并通过荧光原位杂交定位在染色体上。HSR1重复序列在常染色体上显示出亚端粒位置，信号强度相同。该信号存在于X染色体长臂的亚端粒区域和近着丝粒区域，但在短臂的端粒区域不存在。同时，该信号仅在Y染色体长臂的端粒区域被发现。这一发现表明，啤酒花的性染色体是通过古老的易位或倒位从一对常染色体进化而来的。对性二价体减数分裂构型的观察显示了X和Y染色体长臂上假常染色体区域的位置。
