Distribution of 5S and 18S-28S rDNA loci in a tetraploid cotton (Gossypium hirsutum L) and its putative diploid ancestors
Distribution of 5S and 18S-28S rDNA loci in a tetraploid cotton (Gossypium hirsutum L) and its putative diploid ancestors
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DOI：
10.1007/bf02510039
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发表时间：
1996-07-01
期刊：
影响因子：
1.6
通讯作者：
Price, HJ
中科院分区：
文献类型：
--
作者：
Hanson, RE;IslamFaridi, MN;Price, HJ
栽培最广泛的棉花品种是陆地棉 (Gossypium hirsutum)，它是二体四倍体 (2n=4x=52)。先前有人提出，现存的 A 和 D 基因组物种与四倍体的二倍体祖先关系最为密切。我们使用荧光原位杂交（FISH）来确定 A 基因组物种 G. herbaceum 和 G. arboreum、D 基因组物种 G. raimondii 和 G. thurberi 以及 AD 四倍体 G. hirsutum 中 5S 和 18S-28S rDNA 位点的分布。使用高信噪比、单标记 FISH 来计数 rDNA 位点，同时使用双标记 FISH 来确定 5S rDNA 位点相对于 18S-28S rDNA 位点的同线关系。这些技术提供了比我们以前的方法更高的灵敏度，并允许检测 6 个新的陆地棉 18S-28S rDNA 位点，使观察到的位点总数达到 11 个。这些位点杂交信号强度的差异使我们能够将它们指定为主要、中间或次要 18S-28S 位点。使用带有标记的 A 基因组 DNA 的基因组绘制，五个 18S-28S 位点定位于 C. hirsutum A 亚基因组，六个定位于 D 亚基因组。陆地棉中的 11 个 18S-28S rDNA 位点中有 4 个无法在其假定的二倍体祖先中解释，因为两个 A 基因组物种都有 3 个基因座，而两个 D 基因组物种都有 4 个基因座。陆地棉有两个 5S rDNA 位点，这两个位点与主要 18S-28S rDNA 位点同线性。我们检查的所有四个二倍体基因组都包含一个 5S 基因座。在 G. herbaceum (A(1)) 和 G. thurberi (D-1) 中，5S 基因座与主要 18S-28S 基因座同线，但在 C. arboreum (A(2)) 和 G. raimondii (D-5)（拟议的陆地棉 D 基因组祖先）中，5S 基因座与次要和中间基因座同线分别为18S-28S基因座。四倍体物种及其假定的二倍体祖先之间的多样性、大小和位点数量的变化以及缺乏加和性表明，棉花中 rDNA 位点的行为是非教条性的，并且比以前想象的更加复杂和动态。 18S-28S rDNA 基因座与 5S rDNA 基因座的相对变异性表明串联重复的行为可能存在很大差异。
The most widely cultivated species of cotton, Gossypium hirsutum, is a disomic tetraploid (2n=4x=52). It has been proposed previously that extant A- and D-genome species are most closely related to the diploid progenitors of the tetraploid. We used fluorescent in situ hybridization (FISH) to determine the distribution of 5S and 18S-28S rDNA loci in the A-genome species G. herbaceum and G. arboreum, the D-genome species G. raimondii and G. thurberi, and the AD tetraploid G. hirsutum. High signal-to-noise, single-label FISH was used to enumerate rDNA loci, and simultaneous, dual-label FISH was used to determine the syntenic relationships of 5S rDNA loci relative to 18S-28S rDNA loci. These techniques provided greater sensitivity than our previous methods and permitted detection of six new G. hirsutum 18S-28S rDNA loci, bringing the total number of observed loci to 11. Differences in the intensity of the hybridization signal at these loci allowed us to designate them as major, intermediate, or minor 18S-28S loci. Using genomic painting with labeled A-genome DNA, five 18S-28S loci were localized to the C. hirsutum A-subgenome and six to the D-subgenome. Four of the 11 18S-28S rDNA loci in G. hirsutum could not be accounted for in its presumed diploid progenitors, as both A-genome species had three loci and both D-genome species had four. G. hirsutum has two 5S rDNA loci, both of which are syntenic to major 18S-28S rDNA loci. All four of the diploid genomes we examined contained a single 5S locus. In G. herbaceum (A(1)) and G. thurberi (D-1), the 5S locus is syntenic to a major 18S-28S locus, but in C. arboreum (A(2)) and G. raimondii (D-5), the proposed D-genome progenitor of G. hirsutum, the 5S loci are syntenic to minor and intermediate 18S-28S loci, respectively. The multiplicity, variation in size and site number, and lack of additivity between the tetraploid species and its putative diploid ancestors indicate that the behavior of rDNA loci in cotton is nondogmatic, and considerably more complex and dynamic than previously envisioned. The relative variability of 18S-28S rDNA loci versus 5S rDNA loci suggests that the behavior of tandem repeats can differ widely.