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 The EDFs were associated with repression of target genes, but this was superseded by activation when EIN3 bound the same genes.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. ChIP-seq and RNA-seq were applied to comprehensively profile the transcriptional regulation in response to ethylene in Col-0 and edf1234 mutants seedlings