IRD, UMR DIAPC, IRD/CIRAD Palm Development Group, Montpellier Cedex, France.
Mol Biol Evol. 2011 Apr;28(4):1439-54. doi: 10.1093/molbev/msq328. Epub 2010 Dec 6.
In order to understand how the morphology of plant species has diversified over time, it is necessary to decipher how the underlying developmental programs have evolved. The regulatory network controlling shoot meristem activity is likely to have played an important role in morphological diversification and useful insights can be gained by comparing monocots and eudicots. These two distinct monophyletic groups of angiosperms diverged 130 Ma and are characterized by important differences in their morphology. Several studies of eudicot species have revealed a conserved role for NAM and CUC3 genes in meristem functioning and pattern formation through the definition of morphogenetic boundaries during development. In this study, we show that NAM- and CUC3-related genes are conserved in palms and grasses, their diversification having predated the radiation of monocots and eudicots. Moreover, the NAM-miR164 posttranscriptional regulatory module is also conserved in palm species. However, in contrast to the CUC3-related genes, which share a similar expression pattern between the two angiosperm groups, the expression domain of the NAM-miR164 module differs between monocot and eudicot species. In our studies of spatial expression patterns, we compared existing eudicot data with novel results from our work using two palm species (date palm and oil palm) and two members of the Poaceae (rice and millet). In addition to contrasting results obtained at the gene expression level, major differences were also observed between eudicot and monocot NAM-related genes in the occurrence of putative cis-regulatory elements in their promoter sequences. Overall, our results suggest that although NAM- and CUC3-related proteins are functionally equivalent between monocots and eudicots, evolutionary radiation has resulted in heterotopy through alterations in the expression domain of the NAM-miR164 regulatory module.
为了理解植物物种的形态是如何随时间多样化的，有必要解码潜在的发育程序是如何进化的。控制茎分生组织活性的调控网络可能在形态多样化中发挥了重要作用，通过比较单子叶植物和双子叶植物可以获得有用的见解。这两个截然不同的被子植物单系群在 1.3 亿年前分化，其形态有重要差异。对双子叶植物物种的几项研究表明，NAM 和 CUC3 基因在分生组织功能和形态发生中发挥保守作用，通过在发育过程中定义形态发生边界。在这项研究中，我们表明，NAM 和 CUC3 相关基因在棕榈科和禾本科中是保守的，它们的多样化发生在单子叶植物和双子叶植物辐射之前。此外，NAM-miR164 转录后调控模块在棕榈科物种中也是保守的。然而，与 CUC3 相关基因不同的是，后者在这两个被子植物群之间具有相似的表达模式，而 NAM-miR164 模块的表达域在单子叶植物和双子叶植物物种之间存在差异。在我们对空间表达模式的研究中，我们将现有的双子叶植物数据与我们使用两种棕榈科物种（枣椰树和油棕）和两种禾本科物种（水稻和小米）的新工作结果进行了比较。除了在基因表达水平上得到的对比结果外，在 Eudicot 和 Monocot NAM 相关基因的启动子序列中，推测的顺式调控元件的发生也存在显著差异。总的来说，我们的结果表明，尽管 NAM 和 CUC3 相关蛋白在单子叶植物和双子叶植物中具有功能等效性，但进化辐射导致了 NAM-miR164 调控模块表达域的异位，从而产生了异质性。
