Gibberellic acid (GA) is a major plant hormone involved in several biological processes from the flowering to the symbiosis with microorganisms. Thus, the GA regulation is crucial for plant biology. This regulation occurs via the DELLA proteins that belong to the GRAS transcription factor family. DELLA proteins are characterised by a DELLA N-terminal and a GRAS C-terminal domains. It is well known that DELLA activity appears after the bryophytes divergence and then evolved in the vascular plant lineages. Here we present the phylogeny of DELLA across 75 species belonging to various lineages from algae, liverworts and angiosperms. Our study confirmed two main duplication events, the first occurring before the angiosperms divergence and the other specific to the eudicots lineage. Comparative analysis of DELLA subclades in angiosperms revealed the loss in Poaceae and strong alteration in other species of the DELLA functional domain in the DELLA2 clade. In addition, molecular evolution analysis suggests that each of the clades (named DELLA1.1, DELLA1.2 and DELLA2) evolved differently but copies of each subclade are under strong purifying selection. This also suggests that, although the DELLA functional domain is altered in DELLA2, DELLA2 orthologs are still functional and operate in a different way compared to DELLA1 copies. In angiosperms, additional duplication events occurred and led to duplicate copies in species, genus or family such as in the Fabaceae subfamily Papilionoideae. This duplication led to the formation of additional paralogs in the DELLA1.2 subclade (DELLA1.2.1 and DELLA1.2.2). Interestingly, both copies appeared to be under relaxing selection revealing different evolutionary fate of the DELLA duplicated copies.

中文翻译：

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DELLA 家族重复事件导致被子植物的不同选择约束

赤霉酸 (GA) 是一种主要的植物激素，参与从开花到与微生物共生的几个生物过程。因此，GA 调控对植物生物学至关重要。这种调节通过属于 GRAS 转录因子家族的 DELLA 蛋白发生。DELLA 蛋白的特征在于 DELLA N 端和 GRAS C 端结构域。众所周知，DELLA 活性出现在苔藓植物分化之后，然后在维管植物谱系中进化。在这里，我们展示了来自藻类、地衣和被子植物的 75 种不同谱系的 DELLA 的系统发育。我们的研究证实了两个主要的重复事件，第一个发生在被子植物分化之前，另一个特定于双子叶植物谱系。被子植物中 DELLA 亚支的比较分析揭示了禾本科的丧失和 DELLA2 支中 DELLA 功能域的其他物种的强烈改变。此外，分子进化分析表明，每个进化枝（命名为 DELLA1.1、DELLA1.2 和 DELLA2）进化不同，但每个子进化枝的副本都受到强烈的纯化选择。这也表明，尽管 DELLA2 中的 DELLA 功能域发生了改变，但与 DELLA1 副本相比，DELLA2 直向同源物仍然具有功能并且以不同的方式运作。在被子植物中，发生了额外的复制事件并导致物种、属或科（例如豆科亚科蝶形花亚科）中的复制。这种重复导致在 DELLA1.2 分支（DELLA1.2.1 和 DELLA1.2.2）中形成了额外的旁系同源物。有趣的是，