The florigen interactor BdES43 represses flowering in the model temperate grass Brachypodium distachyon

• Published in: The Plant journal : for cell and molecular biology 2020-04, Vol.102 (2), p.262-275
• Main Authors: Cao, Shuanghe, Luo, Xumei, Xie, Li, Gao, Caixia, Wang, Daowen, Holt, Ben F., Lin, Hao, Chu, Chengcai, Xia, Xianchun
• Format: Article
• Language: English
• Subjects: Alternative splicing; BdES43; Brachypodium; Brachypodium - genetics; Brachypodium - growth & development; Epigenetics; florigen; Florigen - metabolism; Flowering; flowering time; Flowers - genetics; Flowers - growth & development; gene editing; H3K4me3; Histones - genetics; Histones - metabolism; Homology; Loci; Plant Proteins - genetics; Plant Proteins - metabolism; Proteins; Regulatory mechanisms (biology); Splicing; Time Factors; Transcription initiation
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/tpj.14622

Summary 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. Significance Statement FLOWERING LOCUS T (FT) protein, physiologically florigen, is a signal integrator in flowering pathways and function in multiple other development processes. Here we achieved the functional dissection of Brachypodium FT homologs BdFTL1 and BdFTL2 by gene‐editing technology, observed their epistatic interaction, and revealed that a BdES43 and H3K4me3 complex might mediate BdFTL2 in regulating BdFTL1. These findings provide an additional entry point to explore the molecular basis for florigen’s pleiotropic effects on plant development.