The regulation of signalling capacity, combined with the spatiotemporal distribution of developmental signals themselves, is pivotal in setting developmental responses in both plants and animals 1 . The hormone auxin is a key signal for plant growth and development that acts through the AUXIN RESPONSE FACTOR (ARF) transcription factors 2 – 4 . A subset of these, the conserved class A ARFs 5 , are transcriptional activators of auxin-responsive target genes that are essential for regulating auxin signalling throughout the plant lifecycle 2 , 3 . Although class A ARFs have tissue-specific expression patterns, how their expression is regulated is unknown. Here we show, by investigating chromatin modifications and accessibility, that loci encoding these proteins are constitutively open for transcription. Through yeast one-hybrid screening, we identify the transcriptional regulators of the genes encoding class A ARFs from Arabidopsis thaliana and demonstrate that each gene is controlled by specific sets of transcriptional regulators. Transient transformation assays and expression analyses in mutants reveal that, in planta, the majority of these regulators repress the transcription of genes encoding class A ARFs. These observations support a scenario in which the default configuration of open chromatin enables a network of transcriptional repressors to regulate expression levels of class A ARF proteins and modulate auxin signalling output throughout development. Genes encoding the class A auxin-response factor group of plant transcriptional activators reside in constitutively open chromatin, enabling their continual regulation by transcriptional repressors to modulate auxin signalling throughout development.

中文翻译：

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转录抑制因子网络调节生长素反应

信号能力的调节，结合发育信号本身的时空分布，对于植物和动物 1 的发育反应至关重要。生长素激素是植物生长和发育的关键信号，通过 AUXIN RESPONSE FACTOR (ARF) 转录因子 2 – 4 发挥作用。其中的一个子集，即保守的 A 类 ARFs 5 ，是生长素响应靶基因的转录激活因子，这些靶基因对于在整个植物生命周期中调节生长素信号传导至关重要 2 、 3 。尽管 A 类 ARF 具有组织特异性表达模式，但它们的表达是如何被调节的却是未知的。在这里，我们通过研究染色质修饰和可及性表明，编码这些蛋白质的基因座对转录是组成性开放的。通过酵母一杂交筛选，我们从拟南芥中鉴定出编码 A 类 ARF 的基因的转录调节因子，并证明每个基因都受特定的转录调节因子组控制。突变体中的瞬时转化测定和表达分析表明，在植物中，这些调节剂中的大多数抑制编码 A 类 ARF 的基因的转录。这些观察结果支持这样一种情况，即开放染色质的默认配置使转录抑制子网络能够调节 A 类 ARF 蛋白的表达水平并在整个发育过程中调节生长素信号输出。编码植物转录激活因子 A 类生长素反应因子组的基因存在于组成型开放染色质中，