The BASIC PENTACYSTEINE (BPC) GAGA (C-box) binding proteins belong to a small plant transcription factor family. We previously reported that class I BPCs bind directly to C-boxes in the SEEDSTICK (STK) promoter and the mutagenesis of these cis-elements affects STK expression in the flower. The MADS-domain factor SHORT VEGETATIVE PHASE (SVP) is another key regulator of STK. Direct binding of SVP to CArG-boxes in the STK promoter are required to repress its expression during the first stages of flower development. Here we show that class II BPCs directly interact with SVP and that MADS-domain binding sites in the STK promoter region are important for the correct spatial and temporal expression of this homeotic gene. Furthermore, we show that class I and class II BPCs act redundantly to repress STK expression in the flower, most likely by recruiting TERMINAL FLOWER 2/LIKE HETEROCHROMATIN PROTEIN 1 (TFL2/LHP1) and mediating the establishment and the maintenance of H3K27me3 repressive marks on DNA. We investigate the role of LHP1 in the regulation of STK expression. In addition to providing a better understanding of the role of BPC transcription factors in the regulation of STK expression, our results suggest the existence of a more general regulatory complex composed of BPCs, MADS-domain factors and Polycomb Repressive Complexes that co-operate to regulate gene expression in reproductive tissues. We believe that our data along with the molecular model described here could provide significant insights for a more comprehensive understanding of gene regulation in plants.

中文翻译：

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BPC转录因子和Polycomb Group蛋白限制了胚珠同一性基因SEEDSTICK在拟南芥中的表达。

基本的PENTACYSTEINE（BPC）GAGA（C-box）结合蛋白属于小植物转录因子家族。我们以前报道过，I类BPC直接与SEEDSTICK（STK）启动子中的C-boxs结合，这些顺式元件的诱变影响花中STK的表达。MADS域因子简短植物阶段（SVP）是STK的另一个关键调节器。SVP与STK启动子中的CArG-boxs直接结合是抑制其在花发育初期的表达所必需的。在这里，我们显示II类BPC直接与SVP相互作用，并且STK启动子区域中的MADS域结合位点对于该同源基因的正确时空表达很重要。此外，我们显示I类和II类BPC可以多余地抑制花中STK的表达，最有可能通过募集TERLOWAL FLOWER 2 / Like Heterochromotinatin Protein 1（TFL2 / LHP1）并介导DNA上H3K27me3阻抑标记的建立和维持来进行。我们调查LHP1在调节STK表达中的作用。除了更好地了解BPC转录因子在STK表达调控中的作用外，我们的研究结果还表明存在由BPC，MADS域因子和Polycomb Repressive Complexes组成的更一般的调控复合物，它们可以协同调控基因在生殖组织中的表达。我们相信，我们的数据以及此处描述的分子模型可以为更全面地了解植物中的基因调控提供重要的见识。