Similar patterns of rDNA evolution in synthetic and recently formed natural populations of Tragopogon (Asteraceae) allotetraploids.
Similar patterns of rDNA evolution in synthetic and recently formed natural populations of Tragopogon (Asteraceae) allotetraploids.
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DOI：
10.1186/1471-2148-10-291
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发表时间：
2010-09-22
影响因子：
3.4
通讯作者：
Kovarik A
中科院分区：
文献类型：
--
作者：
Malinska H;Tate JA;Matyasek R;Leitch AR;Soltis DE;Soltis PS;Kovarik A
Tragopogon mirus和T.miscellus是异源四倍体(2n=24)，在从欧洲引进二倍体T.dubius、T.porrifolius和T.pratensis(2n=12)后，在过去80年里在华盛顿东部和邻近的爱达荷州(美国)重复形成。在大多数自然种群中，杜比氏锥虫的35S rRNA基因(RDNA)远远少于另一个二倍体亲本(羊栖菜或草地早熟禾)。我们研究了从二倍体材料合成的异源四倍体中亲本rDNA座位的遗传。我们研究了这些rDNA丢失的动力学和方向性，以及亲本二倍体中的基因拷贝数变异对衍生四倍体中rDNA变异的贡献。应用Southern杂交和荧光原位杂交(FISH)技术，分析了7个人工合成毛滴虫品系(110个个体)和4个合成杂色毛滴虫品系(71个个体)中这些高重复基因的拷贝数和分布。二倍体亲本之间的变异解释了在F1杂交中检测到的大部分观察到的基因不平衡，但不能解释在异源四倍体品系中经常出现的重复相加偏离。含有相同二倍体亲本的多倍体谱系在rDNA基因型上存在差异，这表明基因组加倍后的条件对rDNA的变化至关重要。大约19%的人工合成的异源四倍体个体具有相同的二倍体亲本的rDNA贡献，74%的个体偏向T.porrifolius或T.pratens型单位，只有7%的个体拥有比其他两个亲本更多的T.dubius起源的rDNA拷贝。在自然人群中观察到相似的基因频率。尽管单位数定向减少，但在82%的合成品系和所有天然异源四倍体中，35S rDNA座位数的可加性保持不变。同源rRNA基因拷贝的单亲减少发生在异源多倍体的合成种群和自然种群中。这些rDNA变化的程度在自然种群中通常比在合成品系中高。我们推测，异源多倍体早期世代的位点特异性和染色体变化可能会影响后代的rDNA进化模式。
Tragopogon mirus and T. miscellus are allotetraploids (2n = 24) that formed repeatedly during the past 80 years in eastern Washington and adjacent Idaho (USA) following the introduction of the diploids T. dubius, T. porrifolius, and T. pratensis (2n = 12) from Europe. In most natural populations of T. mirus and T. miscellus, there are far fewer 35S rRNA genes (rDNA) of T. dubius than there are of the other diploid parent (T. porrifolius or T. pratensis). We studied the inheritance of parental rDNA loci in allotetraploids resynthesized from diploid accessions. We investigate the dynamics and directionality of these rDNA losses, as well as the contribution of gene copy number variation in the parental diploids to rDNA variation in the derived tetraploids. Using Southern blot hybridization and fluorescent in situ hybridization (FISH), we analyzed copy numbers and distribution of these highly reiterated genes in seven lines of synthetic T. mirus (110 individuals) and four lines of synthetic T. miscellus (71 individuals). Variation among diploid parents accounted for most of the observed gene imbalances detected in F1 hybrids but cannot explain frequent deviations from repeat additivity seen in the allotetraploid lines. Polyploid lineages involving the same diploid parents differed in rDNA genotype, indicating that conditions immediately following genome doubling are crucial for rDNA changes. About 19% of the resynthesized allotetraploid individuals had equal rDNA contributions from the diploid parents, 74% were skewed towards either T. porrifolius or T. pratensis-type units, and only 7% had more rDNA copies of T. dubius-origin compared to the other two parents. Similar genotype frequencies were observed among natural populations. Despite directional reduction of units, the additivity of 35S rDNA locus number is maintained in 82% of the synthetic lines and in all natural allotetraploids. Uniparental reductions of homeologous rRNA gene copies occurred in both synthetic and natural populations of Tragopogon allopolyploids. The extent of these rDNA changes was generally higher in natural populations than in the synthetic lines. We hypothesize that locus-specific and chromosomal changes in early generations of allopolyploids may influence patterns of rDNA evolution in later generations.
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