The stigma is an angiosperm-specific tissue that is essential for pollination. In the last two decades, several transcription factors with key roles in stigma development in Arabidopsis thaliana have been identified. However, genetic analyses have thus far been unable to unravel the precise regulatory interactions among these transcription factors or the molecular basis for their selective roles in different spatial and temporal domains. Here, we show that the NGATHA (NGA) and HECATE (HEC) transcription factors, which are involved in different developmental processes but are both essential for stigma development, require each other to perform this function. This relationship is likely mediated by their physical interaction in the apical gynoecium. NGA/HEC transcription factors subsequently upregulate INDEHISCENT (IND) and SPATULA and are indispensable for the binding of IND to some of its targets to allow stigma differentiation. Our findings support a nonhierarchical regulatory scenario in which the combinatorial action of different transcription factors provides exquisite temporal and spatial specificity of their developmental outputs.

中文翻译：

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NGATHA 和 bHLH 转录因子的转录复合物指导拟南芥的柱头发育

柱头是被子植物特有的组织，对授粉至关重要。在过去的二十年中，已经确定了几种在拟南芥柱头发育中起关键作用的转录因子。然而，迄今为止，遗传分析无法揭示这些转录因子之间的精确调控相互作用或它们在不同空间和时间域中的选择性作用的分子基础。在这里，我们表明 NGATHA (NGA) 和 HECATE (HEC) 转录因子参与不同的发育过程，但对于柱头发育都是必不可少的，它们需要彼此来执行此功能。这种关系可能是由它们在顶端雌蕊中的物理相互作用介导的。NGA/HEC 转录因子随后上调 INDEHISCENT (IND) 和 SPATULA，并且对于 IND 与其一些靶标的结合以允许柱头分化是必不可少的。我们的研究结果支持了一种非等级调控情景，其中不同转录因子的组合作用为其发育输出提供了精细的时间和空间特异性。