Li Dongming, Fu Xing, Guo Lin, Huang Zhigang, Li Yongpeng, Liu Yang, He Zishan, Cao Xiuwei, Ma Xiaohan, Zhao Meicheng, Zhu Guohui, Xiao Langtao, Wang Haiyang, Chen Xuemei, Liu Renyi, Liu Xigang
State Key Laboratory of Plant Cell and Chromosome Engineering, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang 050021, China; Hebei Collaboration Innovation Center for Cell Signaling, College of Life Sciences, Hebei Normal University, Shijiazhuang 050024, China; School of Life Sciences, Lanzhou University, Lanzhou 730000, China;
Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 201602, China;
Proc Natl Acad Sci U S A. 2016 Aug 16;113(33):9375-80. doi: 10.1073/pnas.1602960113. Epub 2016 Jul 28.
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 flower-specific 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.
植物分生组织负责生成所有的植物组织和器官。我们在此表明，转录因子（TF）远红光下胚轴伸长3（FHY3）在拟南芥花分生组织（FM）的确定性和茎尖分生组织维持中发挥重要作用，此外它在营养生长阶段的植物生长和发育中还具有众所周知的多方面作用。通过遗传分析，我们发现WUSCHEL（WUS）和CLAVATA3（CLV3）这两个在分生组织建立和维持中起核心作用的基因，相对于FHY3是上位性的。利用全基因组染色质免疫沉淀测序（ChIP-seq）和RNA测序（RNA-seq）数据，我们在花中鉴定出数百个FHY3靶基因，并发现FHY3在花发育中主要作为转录抑制因子起作用，这与其在幼苗中的转录激活因子作用形成对比。结合基序富集分析表明，FHY3可能与三个花特异性MADS结构域转录因子和四个参与光形态建成的基本螺旋-环-螺旋转录因子共同调节花发育。我们进一步证明CLV3、SEPALLATA1（SEP1）和SEP2是FHY3靶基因。在茎尖分生组织中，FHY3直接抑制CLV3，进而调节WUS以维持干细胞库。有趣的是，在光处理前后，fhy3和phytochrome B突变体中CLV3的表达没有显著变化，这表明FHY3和phytochrome B参与光调节的分生组织活性。在FM中，FHY3直接抑制CLV3，但激活SEP2，最终促进FM的确定性。综上所述，我们的结果揭示了分生组织维持和确定性的机制，并阐明了单个转录因子在不同器官和发育阶段的作用可能如何变化。
