Instituto de Biología Molecular y Celular de Plantas (CSIC-Universidad Politécnica de Valencia), Valencia, Spain.
PLoS One. 2011;6(8):e23918. doi: 10.1371/journal.pone.0023918. Epub 2011 Aug 31.
The hormones gibberellins (GAs) control a wide variety of processes in plants, including stress and developmental responses. This task largely relies on the activity of the DELLA proteins, nuclear-localized transcriptional regulators that do not seem to have DNA binding capacity. The identification of early target genes of DELLA action is key not only to understand how GAs regulate physiological responses, but also to get clues about the molecular mechanisms by which DELLAs regulate gene expression. Here, we have investigated the global, early transcriptional response triggered by the Arabidopsis DELLA protein GAI during skotomorphogenesis, a developmental program tightly regulated by GAs. Our results show that the induction of GAI activity has an almost immediate effect on gene expression. Although this transcriptional regulation is largely mediated by the PIFs and HY5 transcription factors based on target meta-analysis, additional evidence points to other transcription factors that would be directly involved in DELLA regulation of gene expression. First, we have identified cis elements recognized by Dofs and type-B ARRs among the sequences enriched in the promoters of GAI targets; and second, an enrichment in additional cis elements appeared when this analysis was extended to a dataset of early targets of the DELLA protein RGA: CArG boxes, bound by MADS-box proteins, and the E-box CACATG that links the activity of DELLAs to circadian transcriptional regulation. Finally, Gene Ontology analysis highlights the impact of DELLA regulation upon the homeostasis of the GA, auxin, and ethylene pathways, as well as upon pre-existing transcriptional networks.
植物激素赤霉素（GAs）控制着植物的多种过程，包括应激和发育反应。这一任务主要依赖于 DELLA 蛋白的活性，DELLA 蛋白是一种定位于核内的转录调节剂，似乎没有 DNA 结合能力。鉴定 DELLA 作用的早期靶基因不仅对于理解 GAs 如何调节生理反应至关重要，而且对于了解 DELLAs 如何调节基因表达的分子机制也很重要。在这里，我们研究了拟南芥 DELLA 蛋白 GAI 在暗形态发生过程中触发的全局早期转录反应，暗形态发生是一个受 GAs 严格调控的发育程序。我们的结果表明，GAI 活性的诱导对基因表达几乎立即产生影响。尽管这种转录调控主要基于靶基因荟萃分析由 PIFs 和 HY5 转录因子介导，但其他证据表明，其他转录因子可能直接参与 DELLA 对基因表达的调控。首先，我们在 GAI 靶基因启动子中富集的序列中鉴定了 Dofs 和 B 型 ARR 识别的顺式作用元件；其次，当将此分析扩展到 DELLA 蛋白 RGA 的早期靶基因数据集时，出现了其他顺式作用元件的富集：CArG 盒，由 MADS 盒蛋白结合，以及 E 盒 CACATG，将 DELLA 的活性与昼夜节律转录调控联系起来。最后，基因本体分析强调了 DELLA 调节对 GA、生长素和乙烯途径以及现有转录网络的稳态的影响。
