American University, Department of Biology, 4400 Massachusetts Avenue NW, Washington DC, USA.
J Exp Bot. 2018 Sep 14;69(20):4757-4771. doi: 10.1093/jxb/ery239.
The shoot apical meristem (SAM) undergoes developmental transitions that include a shift from vegetative to reproductive growth. This transition is triggered by flowering time genes, which up-regulate floral meristem (FM) identity genes that, in turn, control flower development by activating floral organ identity genes. This cascade of transcriptional activation is refined by repression mechanisms that temporally and spatially restrict gene expression to ensure proper development. Here, we demonstrate that HISTONE DEACETYLASE 19 (HDA19) maintains the identity of the reproductive SAM, or inflorescence meristem (IM), late in Arabidopsis thaliana development. At late stages of growth, hda19 IMs display a striking patterning defect characterized by ectopic expression of floral organ identity genes and the replacement of flowers with individual stamenoid organs. We further show that the flowering time gene FD has a specific function in this regulatory process, as fd hastens the emergence of these patterning defects in hda19 growth. Our work therefore identifies a new role for FD in reproductive patterning, as FD regulates IM function together with HDA19 in an age-dependent fashion. To effect these abnormalities, hda19 and fd may accentuate the weakening of transcriptional repression that occurs naturally with reproductive meristem proliferation.
茎尖分生组织（SAM）经历发育转变，包括从营养生长向生殖生长的转变。这种转变由开花时间基因触发，这些基因上调花分生组织（FM）特征基因，进而通过激活花器官特征基因来控制花发育。这种转录激活级联反应受到抑制机制的精细调控，这些抑制机制在时间和空间上限制基因表达，以确保适当的发育。在这里，我们证明 HISTONE DEACETYLASE 19（HDA19）在拟南芥发育后期维持生殖 SAM 或花序分生组织（IM）的身份。在生长的后期阶段，hda19 IM 表现出明显的图案缺陷，其特征在于花器官特征基因的异位表达以及用单个雄蕊器官替代花。我们进一步表明，开花时间基因 FD 在这个调控过程中具有特定的功能，因为 fd 加速了这些图案缺陷在 hda19 生长中的出现。因此，我们的工作为 FD 在生殖图案形成中的新作用提供了证据，因为 FD 与 HDA19 一起以年龄依赖的方式调节 IM 功能。为了产生这些异常，hda19 和 fd 可能会加剧生殖分生组织增殖过程中自然发生的转录抑制的减弱。
