Department of Biological Sciences and Temasek Life Sciences Laboratory, National University of Singapore, 10 Science Drive 4, Singapore.
Plant J. 2012 May;70(4):549-61. doi: 10.1111/j.1365-313X.2012.04919.x. Epub 2012 Mar 5.
Floral transition in Arabidopsis is tightly controlled by complex genetic regulatory networks in response to endogenous and environmental flowering signals. SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) and SHORT VEGETATIVE PHASE (SVP), two key MADS-domain transcription factors, perceive these signals and function as antagonistic flowering regulators. To understand how these factors mediate floral transition, we mapped in vivo binding sites of SOC1 and SVP using chromatin immunoprecipitation followed by hybridization to whole-genome tiling arrays (ChIP-chip). Genes that encoded proteins with transcription regulator activity and transcription factor activity were the most enriched groups of genes of those bound by SOC1 and SVP, which indicates their central roles in flowering regulatory networks. In combination with gene expression microarray studies, we further identified the genes whose expression was controlled directly by SOC1 or SVP. Among the common direct targets identified, APETALA2 (AP2)-like genes that repress FT and SOC1 expression were down-regulated by SOC1, but up-regulated by SVP, revealing a complex feedback regulation among the key genes that determine the integration of flowering signals. SOC1 regulatory regions were also accessed by SOC1 itself and SVP, suggesting that self-activation and repression by SVP contribute to the control of SOC1 expression. In addition, ChIP-chip analysis demonstrated that miR156e and miR172a, which are involved in the regulation of AP2-like genes, were direct targets of SOC1 and SVP, respectively. Taken together, these findings revealed that feedback regulatory loops mediated by SOC1 and SVP are essential components of the gene regulatory networks that underpin the integration of flowering signals during floral transition.
拟南芥的花发育是由复杂的遗传调控网络控制的，这些网络对内部和外部开花信号做出反应。SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1（SOC1）和SHORT VEGETATIVE PHASE（SVP）是两个关键的 MADS 结构域转录因子，它们感知这些信号并作为拮抗开花调节因子发挥作用。为了了解这些因子如何介导花发育转变，我们使用染色质免疫沉淀结合全基因组平铺芯片（ChIP-chip）来绘制 SOC1 和 SVP 的体内结合位点。SOC1 和 SVP 结合的基因中，编码转录调控因子和转录因子活性的基因是最丰富的一组，这表明它们在开花调控网络中具有核心作用。结合基因表达微阵列研究，我们进一步确定了 SOC1 或 SVP 直接调控表达的基因。在所鉴定的共同直接靶基因中，抑制 FT 和 SOC1 表达的 APETALA2（AP2）样基因被 SOC1 下调，但被 SVP 上调，这揭示了决定开花信号整合的关键基因之间的复杂反馈调控。SOC1 调节区域也被 SOC1 自身和 SVP 访问，表明 SVP 的自我激活和抑制有助于 SOC1 表达的控制。此外，ChIP-chip 分析表明，参与 AP2 样基因调控的 miR156e 和 miR172a 分别是 SOC1 和 SVP 的直接靶标。总之，这些发现表明，SOC1 和 SVP 介导的反馈调控环是构成花发育转变期间开花信号整合的基因调控网络的重要组成部分。
