植物通过测量白天或夜晚的长度，以协调特定的发展变化与有利的季节。在水稻（Oryza sativa）中，通过在叶片中诱导表达HEADING DATE 3a（Hd3a）和RICE FLOWERING LOCUS T 1（RFT1）的短日照而开始繁殖阶段。同源蛋白是成花信号的组分，并通过韧皮部系统地移动到达顶端分生组织（SAM）。在SAM中，它们与bZIP转录因子OsFD1形成转录激活复合物以启动穗发育。本文研究表明，Hd3a和RFT1可以形成转录激活或抑制复合物也在叶子和反馈调节自己的转录。激活复合物依赖于OsFD1来促进开花。然而，包括Hd3a结合表达因子1（HBF1）和HBF2在内的其他bZIPs形成阻遏物复合物，其减少Hd3a和RFT1表达以延迟开花。我们认为Hd3a和RFT1也在叶片本地活动，微调光周期开花反应。Antagonistic Transcription Factor Complexes Modulate the Floral Transition in Rice.
Brambilla V,et alPlant Cell Nov
1Department of Biosciences, University of Milan, 3 Milan, Italy.
2Department of Agricultural and Environmental Sciences, University of Milan,3 Milan, Italy.
3Institute for Developmental Genetics and Cluster of Excellence on PlantSciences, Heinrich Heine University, D-40225 Düsseldorf, Germany.
4CNR-Biophysics Institute, 3 Milan, Italy.
5Department of Biosciences, University of Milan, 3 Milan, Italyfabio.fornara@unimi.it.
Plants measure day or night lengths to coordinate specific developmental changes with a favorable season. In rice (Oryza sativa), the reproductive phase is initiated by exposure to short days when expression of HEADING DATE 3a (Hd3a) and RICE FLOWERING LOCUS T 1 (RFT1) is induced in leaves. The cognate proteins are components of the florigenic signal and move systemically through the phloem to reach the shoot apical meristem (SAM). In the SAM, they form a transcriptional activation complex with the bZIP transcription factor OsFD1 to start panicle development. Here, we show that Hd3a and RFT1 can form transcriptional activation or repression complexes also in leaves and feed back to regulate their own transcription. Activation complexes depend on OsFD1 to promote flowering. However, additional bZIPs, including Hd3a BINDING REPRESSOR FACTOR1 (HBF1) and HBF2, form repressor complexes that reduce Hd3a and RFT1 expression to delay flowering. We propose that Hd3a and RFT1 are also active locally in leaves to fine-tune photoperiodic flowering responses.
