Laboratori de Botànica, Facultat de Farmàcia, Universitat de Barcelona, Barcelona, Catalonia, Spain.
Plant Biol (Stuttg). 2010 Sep 1;12(5):820-30. doi: 10.1111/j.1438-8677.2009.00268.x.
Polyploidy is a key factor in the evolution of higher plants and plays an important role in the variation of plant genomes, leading to speciation in some cases. During polyploidisation, different balancing processes take place at the genomic level that can promote variation in nuclear DNA content. We estimated genome size using flow cytometry in 84 populations of 67 Artemisia species and one population of Crossostephium chinense. A total of 73 sequences of nrDNA ITS and 3'-ETS were newly generated and analysed, together with previously published sequences, to address the evolution of genome size in a phylogenetic framework. Differences in 2C values were detected among some lineages, as well as an increase of genome size heterogeneity in subgenera whose phylogenetic relationships are still unclear. We confirmed that the increase in 2C values in Artemisia polyploids was not proportional to ploidy level, but 1Cx genome size tended to decrease significantly when high ploidy levels were reached. The results lead us to hypothesise that genome size in polyploids tends to a maximum as it follows saturation behaviour, in agreement with the Michaelis-Menten model. We tested different arithmetic functions with our dataset that corroborated a non-linear relationship of genome size increase in polyploids, allowing us to suggest a theoretical upper limit for the DNA content of this genus.
多倍体是高等植物进化的关键因素，在植物基因组的变异中起着重要作用，在某些情况下导致物种形成。在多倍体化过程中，不同的平衡过程发生在基因组水平上，可以促进核 DNA 含量的变异。我们使用流式细胞术在 67 种青蒿属的 84 个种群和一个中华苦荬菜种群中估算了基因组大小。总共生成并分析了 73 个 nrDNA ITS 和 3'-ETS 序列，以及以前发表的序列，以在系统发育框架内解决基因组大小的进化问题。在一些谱系中检测到 2C 值的差异，以及在其系统发育关系仍不清楚的亚属中基因组大小异质性的增加。我们证实，青蒿多倍体中 2C 值的增加与多倍体水平不成比例，而是当达到高多倍体水平时，1Cx 基因组大小明显减小。结果使我们假设，随着多倍体达到饱和行为，基因组大小趋于最大值，这与米氏-门坦模型一致。我们用我们的数据集测试了不同的算术函数，证实了多倍体中基因组大小增加的非线性关系，使我们能够为该属的 DNA 含量建议一个理论上限。
