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 En2core element, which was sufficient to promote the phyllotactic pattern, but was recalcitrant to further shortening. Here, we show that En2core 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, En2core 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, En2core enhancer activity in LOFCs correlates with an open chromatin structure at the DRNL transcription start. In combination, mutational and chromatin analyses imply that En2core 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.

中文翻译：

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DORNRÖSCHEN-LIKE 增强子 2 在胚胎和叶状排列模式中的功能解剖

拟南芥 DORNRÖSCHEN-LIKE 增强子 2 在 IM 外围包含一个高占用率目标区域，该区域整合了螺旋叶状结构和十字花科萼片排列的信号。DORNRÖSCHEN-LIKE (DRNL) 基因的转录标志着花序分生组织 (IM) 外围区域中的侧向器官形成细胞 (LOFC) 和 DRNL 启动子上游区域中的增强子 2 (En2) 基本上促成了这种叶序转录模式。进一步的分析集中在系统发育高度保守的 100 bp En2core 元件上，它足以促进叶序模式，但对进一步缩短是顽固的。在这里，我们展示了 En2core 的功能独立于方向，并创建了一系列突变来研究对转录模式的影响。他们的分析表明，首先，除了在花序顶端，En2core 还作用于胚胎；其次，顺式调节靶序列分布在整个 100 bp 元件中，尽管胚胎和 IM 之间的功能存在很大差异。第三，假定的核心生长素反应元件 (AuxREs) 在空间上激活或限制 DRNL 表达，第四，根据染色质配置数据，LOFCs 中的 En2core 增强子活性与 DRNL 转录开始时的开放染色质结构相关。结合起来，突变和染色质分析表明 En2core 包含一个转录因子的高占用目标 (HOT) 区域，该区域为 IM 外围的螺旋 LOFC 模式实施叶序信息并协调十字花科的花萼阵列。