Developmental Biology, Biocenter, University of Cologne, Zülpicher Str 47b, 50674, Cologne, Germany.
Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829, Cologne, Germany.
Planta. 2020 Mar 31;251(4):90. doi: 10.1007/s00425-020-03381-7.
The Arabidopsis DORNRÖSCHEN-LIKE enhancer 2 comprises a high-occupancy target region in the IM periphery that integrates signals for the spiral phyllotactic pattern and cruciferous arrangement of sepals. Transcription of the DORNRÖSCHEN-LIKE (DRNL) gene marks lateral organ founder cells (LOFCs) in the peripheral zone of the inflorescence meristem (IM) and enhancer 2 (En2) in the DRNL promoter upstream region essentially contributes to this phyllotactic transcription pattern. Further analysis focused on the phylogenetically highly conserved 100-bp En2 element, which was sufficient to promote the phyllotactic pattern, but was recalcitrant to further shortening. Here, we show that En2 functions independent of orientation and create a series of mutations to study consequences on the transcription pattern. Their analysis shows that, first, in addition to in the inflorescence apex, En2 acts in the embryo; second, cis-regulatory target sequences are distributed throughout the 100-bp element, although substantial differences exist in their function between embryo and IM. Third, putative core auxin response elements (AuxREs) spatially activate or restrict DRNL expression, and fourth, according to chromatin configuration data, En2 enhancer activity in LOFCs correlates with an open chromatin structure at the DRNL transcription start. In combination, mutational and chromatin analyses imply that En2 comprises a high-occupancy target (HOT) region for transcription factors, which implements phyllotactic information for the spiral LOFC pattern in the IM periphery and coordinates the cruciferous array of floral sepals. Our data disfavor a contribution of activating auxin response factors (ARFs) but do not exclude auxin as a morphogenetic signal.
拟南芥 DORNRÖSCHEN-LIKE 增强子 2 包含一个高占有率的靶区，位于 IM 外围，整合了螺旋叶序模式和十字花科萼片排列的信号。DRNL 基因的转录标记了花序分生组织（IM）外围区的侧生器官起始细胞（LOFCs），而 DRNL 启动子上游区的增强子 2（En2）主要有助于这种叶序转录模式。进一步的分析集中在系统发育上高度保守的 100-bp En2 元件上，该元件足以促进叶序模式，但对进一步缩短有抗性。在这里，我们表明 En2 独立于定向起作用，并创建了一系列突变来研究对转录模式的影响。它们的分析表明，首先，除了在花序顶端，En2 在胚胎中起作用；其次，顺式调控靶序列分布在 100-bp 元件中，尽管胚胎和 IM 之间的功能存在显著差异。第三，假定的核心生长素响应元件（AuxREs）空间激活或限制 DRNL 的表达，第四，根据染色质构象数据，En2 增强子在 LOFCs 中的活性与 DRNL 转录起始处的开放染色质结构相关。综合起来，突变和染色质分析表明，En2 包含一个高占有率靶区（HOT），用于转录因子，它在 IM 外围的螺旋 LOFC 模式中实现叶序信息，并协调花萼的十字花科排列。我们的数据不支持激活生长素响应因子（ARFs）的贡献，但不排除生长素作为形态发生信号。
