Laboratoire de Reproduction et Développement des Plantes, UMR 5667, CNRS-INRA-Université de Lyon, Ecole Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France.
Ann Bot. 2011 Sep;108(4):589-98. doi: 10.1093/aob/mcr088. Epub 2011 Apr 12.
The angiosperms, or flowering plants, diversified in the Cretaceous to dominate almost all terrestrial environments. Molecular phylogenetic studies indicate that the orders Amborellales, Nymphaeales and Austrobaileyales, collectively termed the ANA grade, diverged as separate lineages from a remaining angiosperm clade at a very early stage in flowering plant evolution. By comparing these early diverging lineages, it is possible to infer the possible morphology and ecology of the last common ancestor of the extant angiosperms, and this analysis can now be extended to try to deduce the developmental mechanisms that were present in early flowering plants. However, not all species in the ANA grade form convenient molecular-genetic models.
The present study reviews the genus Cabomba (Nymphaeales), which shows a range of features that make it potentially useful as a genetic model. We focus on characters that have probably been conserved since the last common ancestor of the extant flowering plants. To facilitate the use of Cabomba as a molecular model, we describe methods for its cultivation to flowering in the laboratory, a novel Cabomba flower expressed sequence tag database, a well-adapted in situ hybridization protocol and a measurement of the nuclear genome size of C. caroliniana. We discuss the features required for species to become tractable models, and discuss the relative merits of Cabomba and other ANA-grade angiosperms in molecular-genetic studies aimed at understanding the origin of the flowering plants.
被子植物，或开花植物，在白垩纪多样化，以主导几乎所有的陆地环境。分子系统发育研究表明，Amborellales、Nymphaeales 和 Austrobaileyales 这三个目，统称为 ANA 级，在开花植物进化的早期就从一个剩余的被子植物分支中分离出来成为独立的谱系。通过比较这些早期分化的谱系，可以推断出现存被子植物最后共同祖先的可能形态和生态，而这种分析现在可以进一步扩展，试图推断早期开花植物中存在的发育机制。然而，ANA 级的并非所有物种都形成方便的分子遗传模型。
本研究回顾了水鳖属（Nymphaeales），该属表现出一系列特征，使其成为潜在有用的遗传模型。我们专注于可能自现存开花植物最后共同祖先以来就一直保守的特征。为了促进水鳖作为分子模型的使用，我们描述了在实验室中培养其开花的方法、一个新颖的水鳖花表达序列标签数据库、一个适应性良好的原位杂交方案以及卡罗来纳水鳖核基因组大小的测量。我们讨论了物种成为可行模型所需的特征，并讨论了水鳖和其他 ANA 级被子植物在旨在理解开花植物起源的分子遗传研究中的相对优点。
