45SrDNA和5SrDNA在南瓜、丝瓜和冬瓜染色体上的比较定位

Comparative analysis of rDNA distribution in metaphase chromosomes of Cucurbitaceae species

首次利用荧光原位杂交和双色荧光原位杂交技术对45S和5SrDNA在南瓜(Cucurbita moschata Duch)、丝瓜(Luffa cylindrical Roem)、冬瓜(Benincasa hispida Cogn)的有丝分裂中期染色体上进行了物理定位分析。南瓜有5对45SrDNA位点,2对5SrDNA位点;丝瓜具有5对45SrDNA位点,1对5SrDNA位点;冬瓜具有2对45SrDNA位点,1对5SrDNA位点,5SrDNA位点与其中一对45SrDNA位点都位于7号染色体短臂上,并在物理位置上紧密相邻。45SrDNA在这3种作物染色体上数目变化较大,但在染色体上都倾向分布在短臂末端,其分布模式较为一致。5SrDNA在这3种作物染色体上数目相对保守,但在染色体上分布的位置变化较大。文中讨论了45SrDNA和5SrDNA在植物基因组中不同的进化趋势。

Fluorescence in situ hybridization （FISH） and double FISH experiments were carded out to ascertain the chromosomal distribution patterns of the 45S and 5S ribosomal DNAs in the three species of Cucurbitaceae. Five pairs of 45S rDNA loci and two pairs of 5S rDNA signals were detected on chromosomes of Cucurbita moschata Duch. Luffa cylindrical Roem. contained five pairs of 45S rDNA loci and one pair of 5S rDNA loci. In Benincasa hispida Cogn., two pairs of 45S rDNA sites and one pair of 5S rDNA site were detected. In this species, 5S rDNA and one pair of the 45S loci were collocated closely in chromosome 7S. 45S rDNA chromosomal distribution patterns were highly conserved among the three species, althoufh their number varied markedly. The 5S rDNA sites on chromosomes among the three species were highly polymorphic. We further discussed differentially evolutionary processes of 45S and 5S rDNA in plant genomes.