FLOWERING LOCUS T (FT) protein, physiologically florigen, has been identified as a system integrator of numerous flowering time pathways in many studies, and its homologs are found throughout the plant lineage. It is important to uncover how precisely florigenic homologs contribute to flowering initiation and how these factors interact genetically. Here we dissected the function of Brachypodium FT orthologs BdFTL1 and BdFTL2 using overexpression and gene-editing experiments. Transgenic assays showed that both BdFTL1 and BdFTL2 could promote flowering, whereas BdFTL2 was essential for flowering initiation. Notably, BdFTL1 is subject to alternative splicing (AS), and its transcriptional level and AS are significantly affected by BdFTL2. Additionally, BdFTL2 could bind with the PHD-containing protein BdES43, an H3K4me3 reader. Furthermore, BdES43 was antagonistic to BdFTL2 in flowering initiation in a transcription-dependent manner and significantly affected BdFTL1 expression. BdFTL2, BdES43 and H3K4me3 also had highly similar distribution patterns within the BdFTL1 locus, indicating their interplay in regulating target genes. Taken together, florigen BdFTL2 functions as a potential epigenetic effector of BdFTL1 by interacting with a BdES43-H3K4me3 complex. This finding provides an additional insight for the regulatory mechanism underlying the multifaceted roles of florigen.

中文翻译：

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在模型温带草Brachypodium distachyon中，荧光原相互作用物BdES43抑制开花。

FLOWERING LOCUS T（FT）蛋白是一种生理上的荧光素，在许多研究中已被确定为多种开花时间途径的系统整合者，并且其同源物遍布整个植物谱系。重要的是要揭示出致花同源物如何精确地促进开花的开始以及这些因素如何在遗传上相互作用。在这里我们使用过表达和基因编辑实验解剖了腕足鱼FT直系同源基因BdFTL1和BdFTL2的功能。转基因试验表明，BdFTL1和BdFTL2均可促进开花，而BdFTL2对于开花开始是必不可少的。值得注意的是，BdFTL1受到其他剪接（AS）的影响，其转录水平和AS受到BdFTL2的显着影响。此外，BdFTL2可以与包含PHD的蛋白BdES43（H3K4me3阅读器）结合。此外，BdES43在开花初期以转录依赖性方式拮抗BdFTL2，并显着影响BdFTL1的表达。BdFTL2，BdES43和H3K4me3在BdFTL1基因座中也具有高度相似的分布模式，表明它们在调节靶基因中相互作用。综上所述，荧光原BdFTL2通过与BdES43-H3K4me3复合体相互作用，作为BdFTL1的潜在表观遗传效应子。这一发现为氟里昂多方面作用的潜在调控机制提供了新的见解。florigen BdFTL2通过与BdES43-H3K4me3复合体相互作用而充当BdFTL1的潜在表观遗传效应子。这一发现为氟里昂多方面作用的潜在调控机制提供了新的见解。florigen BdFTL2通过与BdES43-H3K4me3复合体相互作用而充当BdFTL1的潜在表观遗传效应子。这一发现为氟里昂多方面作用的潜在调控机制提供了新的见解。