Department of Agricultural Sciences, Latokartanonkaari 7, University of Helsinki, Helsinki, Finland.
Mol Biol Evol. 2012 Apr;29(4):1155-66. doi: 10.1093/molbev/msr283. Epub 2011 Nov 18.
Plant-specific TCP domain transcription factors have been shown to regulate morphological novelties during plant evolution, including the complex architecture of the Asteraceae inflorescence that involves different types of flowers. We conducted comparative analysis of the CYCLOIDEA/TEOSINTE BRANCHED1 (CYC/TB1) gene family in Gerbera hybrida (gerbera) and Helianthus annuus (sunflower), two species that represent distant tribes within Asteraceae. Our data confirm that the CYC/TB1 gene family has expanded in Asteraceae, a condition that appears to be connected with the increased developmental complexity and evolutionary success of this large plant family. Phylogenetic analysis of the CYC/TB1 gene family revealed both shared and lineage-specific duplications in gerbera and sunflower, corresponding to the three gene lineages previously identified as specific to core eudicots: CYC1, CYC2, and CYC3. Expression analyses of early stages of flower primordia development indicated that especially within the CYC2 clade, with the greatest number of secondary gene duplications, gene expression patterns are conserved between the species and associated with flower and inflorescence development. All sunflower and gerbera CYC2 clade genes showed differential expression between developing flower types, being upregulated in marginal ray (and trans) flowers. One gene in gerbera (GhCYC3) and two in sunflower (HaCYC2d and HaCYC2c) were indicated to be strong candidates as regulators of ray flower identity, a function that is specific for Asteraceae. Our data further showed that other CYC2 clade genes are likely to have more specialized functions at the level of single flowers, including the late functions in floral reproductive organs that may be more conserved across plant families. The expression patterns of CYC1 and CYC3 clade genes showed more differences between the two species but still pointed to possible conserved functions during vegetative plant development. Pairwise protein-protein interaction assays gave the first molecular evidence that CYC/TB1-like proteins function in complexes. Compared with sunflower, the gerbera proteins showed higher capacity for dimerization, between as well as within CYC clades. Our data from two distant species within the Asteraceae suggest that the expansion and the apparent conservation of especially the CYC2 clade CYC/TB1-like genes are associated with the evolution of the increased complexity of the Asteraceae inflorescence architecture.
植物特有的 TCP 结构域转录因子已被证明在植物进化过程中调节形态新颖性，包括菊科花序的复杂结构，涉及不同类型的花。我们对两种代表菊科不同族的物种，即杂种天人菊（gerbera）和向日葵（sunflower）中的 CYCLOIDEA/TEOSINTE BRANCHED1（CYC/TB1）基因家族进行了比较分析。我们的数据证实，CYC/TB1 基因家族在菊科中已经扩张，这种情况似乎与该大型植物家族的发育复杂性和进化成功有关。对 CYC/TB1 基因家族的系统发育分析揭示了杂种天人菊和向日葵中存在共享和谱系特异性的复制，这与先前确定的核心真双子叶植物特有的三个基因谱系相对应：CYC1、CYC2 和 CYC3。对花原基发育早期的表达分析表明，特别是在 CYC2 分支中，由于发生了最多的次级基因复制，物种之间的基因表达模式是保守的，并且与花和花序的发育有关。所有向日葵和杂种天人菊的 CYC2 分支基因在不同的花类型之间表现出差异表达，在边缘射线（和转）花中上调表达。在杂种天人菊中（GhCYC3）的一个基因和向日葵中的两个基因（HaCYC2d 和 HaCYC2c）被认为是调控射线花身份的强有力候选基因，这是菊科特有的功能。我们的数据还表明，其他 CYC2 分支基因在单个花的水平上可能具有更专门的功能，包括在花的生殖器官中的晚期功能，这些功能可能在植物科之间更保守。CYC1 和 CYC3 分支基因的表达模式在两个物种之间表现出更多的差异，但仍然指向营养植物发育过程中可能保守的功能。成对的蛋白-蛋白相互作用测定首次提供了分子证据，证明 CYC/TB1 样蛋白在复合物中起作用。与向日葵相比，杂种天人菊的蛋白表现出更高的二聚化能力，在 CYC 分支内和分支之间都可以。我们对菊科两个不同物种的数据表明，尤其是 CYC2 分支 CYC/TB1 样基因的扩张和明显的保守性与菊科花序结构复杂性的增加进化有关。
