Faculty of Agriculture, Food and Natural Resources, University of Sydney, Sydney, New South Wales 2006, Australia.
Philos Trans R Soc Lond B Biol Sci. 2012 Feb 19;367(1588):556-64. doi: 10.1098/rstb.2011.0269.
Tectonic processes drive megacycles of atmospheric carbon dioxide (CO(2)) concentration, c(a), that force large fluctuations in global climate. With a period of several hundred million years, these megacycles have been linked to the evolution of vascular plants, but adaptation at the subcellular scale has been difficult to determine because fossils typically do not preserve this information. Here we show, after accounting for evolutionary relatedness using phylogenetic comparative methods, that plant nuclear genome size (measured as the haploid DNA amount) and the size of stomatal guard cells are correlated across a broad taxonomic range of extant species. This phylogenetic regression was used to estimate the mean genome size of fossil plants from the size of fossil stomata. For the last 400 Myr, spanning almost the full evolutionary history of vascular plants, we found a significant correlation between fossil plant genome size and c(a), modelled independently using geochemical data. The correlation is consistent with selection for stomatal size and genome size by c(a) as plants adapted towards optimal leaf gas exchange under a changing CO(2) regime. Our findings point to the possibility that major episodes of change in c(a) throughout Earth history might have selected for changes in genome size, influencing plant diversification.
构造过程驱动大气二氧化碳（CO(2)）浓度的巨周期，c(a)，这导致全球气候的剧烈波动。这些巨周期的周期为几亿年，与维管植物的进化有关，但由于化石通常无法保存这种信息，因此很难确定亚细胞尺度的适应。在这里，我们使用系统发育比较方法来解释进化上的亲缘关系后发现，在广泛的现存物种的分类范围内，植物核基因组大小（以单倍体 DNA 量衡量）和气孔保卫细胞的大小是相关的。这种系统发育回归被用来根据化石气孔的大小来估计化石植物的平均基因组大小。在过去的 4 亿年里，跨越了维管植物的整个进化历史，我们发现化石植物基因组大小与 c(a)之间存在显著的相关性，这是使用地球化学数据独立建模的。这种相关性与 c(a)对气孔大小和基因组大小的选择一致，因为植物在不断变化的 CO(2)环境下适应了最佳的叶片气体交换。我们的发现表明，地球历史上 CO(2)浓度的重大变化可能选择了基因组大小的变化，从而影响了植物的多样化。
