Soltis Douglas E, Chanderbali André S, Kim Sangtae, Buzgo Matyas, Soltis Pamela S
Department of Botany, University of Florida, Gainesville, FL 32611, USA.
Ann Bot. 2007 Aug;100(2):155-63. doi: 10.1093/aob/mcm117. Epub 2007 Jul 6.
Although the flower is the central feature of the angiosperms, little is known of its origin and subsequent diversification. The ABC model has long been the unifying paradigm for floral developmental genetics, but it is based on phylogenetically derived eudicot models. Synergistic research involving phylogenetics, classical developmental studies, genomics and developmental genetics has afforded valuable new insights into floral evolution in general, and the early flower in particular.
Genomic studies indicate that basal angiosperms, and by inference the earliest angiosperms, had a rich tool kit of floral genes. Homologues of the ABCE floral organ identity genes are also present in basal angiosperm lineages; however, C-, E- and particularly B-function genes are more broadly expressed in basal lineages. There is no single model of floral organ identity that applies to all angiosperms; there are multiple models that apply depending on the phylogenetic position and floral structure of the group in question. The classic ABC (or ABCE) model may work well for most eudicots. However, modifications are needed for basal eudicots and, the focus of this paper, basal angiosperms. We offer 'fading borders' as a testable hypothesis for the basal-most angiosperms and, by inference, perhaps some of the earliest (now extinct) angiosperms.
尽管花是被子植物的核心特征，但其起源及后续的多样化却鲜为人知。长期以来，ABC模型一直是花发育遗传学的统一范式，但它是基于系统发育衍生的真双子叶植物模型。涉及系统发育学、经典发育研究、基因组学和发育遗传学的协同研究，为花的进化，尤其是早期花的进化，提供了宝贵的新见解。
基因组研究表明，基部被子植物，由此推断最早的被子植物，拥有丰富的花基因工具包。ABCE花器官特征基因的同源物也存在于基部被子植物谱系中；然而，C、E，尤其是B功能基因在基部谱系中表达更为广泛。不存在适用于所有被子植物的单一花器官特征模型；根据所讨论类群的系统发育位置和花结构，有多种适用模型。经典的ABC（或ABCE）模型可能对大多数真双子叶植物适用。然而，基部真双子叶植物以及本文的重点——基部被子植物，需要进行修正。我们提出“边界渐消”作为最基部被子植物，由此推断或许还有一些最早（现已灭绝）被子植物的一个可检验假说。
