ETHYLENE RESPONSE DNA-BINDING FACTORs are transcriptional repressors responsible for hormone cross-regulation during the ethylene response

Ethylene is a gaseous plant hormone that regulates plant growth and development. Broad reprogramming of gene expression is required for ethylene responses. The primary ethylene transcription factor (TF) ETHYLENE INSENSITIVE3 (EIN3) drives expression of secondary TFs including the ETHYLENE RESPONSE DNA-BINDING FACTORS (EDFs), but the role of the EDFs within the ethylene genome regulatory network is not understood. Here, we describe an investigation into the function of the EDFs in ethylene signalling and hormonal cross-regulation. We determined the target genes and binding dynamics of EDFs 1, 2, 3 during an ethylene response and the effects of edf1234 quadruple mutation on gene expression. The EDFs and EIN3 shared a large proportion of their target genes but had different functions. The EDFs were associated with repression of target genes, but this was superseded by activation when EIN3 bound the same genes. Genes important in other hormone signalling pathways, in particular abscisic acid (ABA), were targets of the EDFs. This demonstrates how ethylene engages hormonal cross-regulation to repress genes in competing signalling pathways and prioritize itself. Overall design: ChIP-seq and RNA-seq were applied to comprehensively profile the transcriptional regulation in response to ethylene in Col-0 and edf1234 mutants seedlings

乙烯是一类调控植物生长发育的气态植物激素。乙烯响应过程需对基因表达进行广泛重编程。乙烯初级转录因子（Transcription Factor, TF）乙烯不敏感3（EIN3）可介导包括乙烯响应DNA结合因子（EDFs）在内的次级转录因子的表达，但目前学界尚未明确EDFs在乙烯基因组调控网络中的具体功能。本研究围绕EDFs在乙烯信号转导及激素交叉调控中的功能开展探究：我们解析了乙烯响应进程中EDF1、EDF2、EDF3的靶基因及结合动态，并分析了edf1234四突变体对基因表达的影响。EDFs与EIN3共享大量靶基因，但二者功能存在显著差异。EDFs通常介导靶基因的转录抑制，但若EIN3结合同一靶基因，则该抑制效应会被激活效应所替代。此外，包括脱落酸（abscisic acid, ABA）在内的其他激素信号通路中的关键基因均为EDFs的靶基因，这一结果揭示了乙烯如何通过激素交叉调控，抑制竞争信号通路中的靶基因并确立自身的调控优先级。实验设计：本研究采用染色质免疫共沉淀测序（ChIP-seq）与RNA测序（RNA-seq）技术，全面解析野生型Col-0及edf1234四突变体幼苗在乙烯响应过程中的转录调控模式。