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The floral meristem (FM), which develops from the inflorescence meristem upon completion of the floral transition, terminates after producing a defined number of floral organs. This is in contrast to the shoot apical meristem, which is active throughout the entire life span of plants. WUSCHEL (WUS) encodes a homeodomain-containing protein and plays a critical role in shoot apical meristem, inflorescence meristem, and FM establishment and maintenance as well as FM determinacy. Although many genes have been implicated in FM determinacy through the regulation of WUS expression, precisely how these genes are coordinated to regulate WUS and consequently dictate FM fate remains unclear. Emerging lines of evidence indicate that epigenetic mechanisms, such as histone modification, chromatin remodeling, noncoding RNAs, and DNA methylation, play vital roles in meristem maintenance and termination. Here, recent findings demonstrating the involvement of the epigenetic network in the regulation of WUS expression in the context of FM determinacy are summarized and discussed. [ABSTRACT FROM AUTHOR]

Plant meristems are responsible for the generation of all plant tissues and organs. Here we show that the transcription factor (TF) FAR-RED ELONGATED HYPOCOTYL3 (FHY3) plays an important role in both floral meristem (FM) determinacy and shoot apical meristem maintenance in Arabidopsis, in addition to its well-known multifaceted roles in plant growth and development during the vegetative stage. Through genetic analyses, we show that WUSCHEL (WUS) and CLAVATA3 (CLV3), two central players in the establishment and maintenance of meristems, are epistatic to FHY3. Using genome-wide ChIP-seq and RNA-seq data, we identify hundreds of FHY3 target genes in flowers and find that FHY3 mainly acts as a transcriptional repressor in flower development, in contrast to its transcriptional activator role in seedlings. Binding motif-enrichment analyses indicate that FHY3 may coregulate flower development with three flowerspecific MADS-domain TFs and four basic helix-loop-helix TFs that are involved in photomorphogenesis. We further demonstrate that CLV3, SEPALLATA1 (SEP1), and SEP2 are FHY3 target genes. In shoot apical meristem, FHY3 directly represses CLV3, which consequently regulates WUS to maintain the stem cell pool. Intriguingly, CLV3 expression did not change significantly in fhy3 and phytochrome B mutants before and after light treatment, indicating that FHY3 and phytochrome B are involved in light-regulated meristem activity. In FM, FHY3 directly represses CLV3, but activates SEP2, to ultimately promote FM determinacy. Taken together, our results reveal insights into the mechanisms of meristem maintenance and determinacy, and illustrate how the roles of a single TF may vary in different organs and developmental stages. [ABSTRACT FROM AUTHOR]