Transcription factor-promoter interactions for PSY/PSYR-mediated regulation of root growth

Precise cis-regulatory control of gene expression is essential for plant growth. In Arabidopsis thaliana, PLANT PEPTIDE CONTAINING SULFATED TYROSINE (PSY) peptides and their receptors (PSYRs) mediate growth-stress trade-offs, yet the transcriptional regulation of these genes remains poorly understood. Here, we mapped transcription factor (TF)-promoter interactions for nine PSY and three PSYR genes by combining high-throughput enhanced yeast one-hybrid screening with DNA Affinity Purification sequencing (DAP-seq) data, uncovering 1,207 interactions that reveal both shared and gene-specific regulatory relationships, defining the global TF-promoter interaction network of the PSY/PSYR pathway. Functional analysis of 25 TF mutants identified 12 regulators that significantly influence root growth, most acting as repressors. Of these, CYTOKININ RESPONSE FACTOR 10 (CRF10) emerged as a strong growth inhibitor. We identified a CRF10-binding motif in the PSYR3 promoter using DAP-seq data and validated it using eY1H. This motif is also located in the last 3' terminal exon of Topoisomerase 3A (TOP3A). Guided by these insights, we used CRISPR/Cas9-mediated promoter editing to delete a small region encompassing or flanking a functional TF-binding site (TFBS). Removal of this motif, or of its surrounding region, enhanced root growth, yielding variants that retained root length comparable to the crf10 mutant. Our results suggest that the observed root growth phenotype results either from disruption of the CRF10 binding motif or from the mutation in the TOP3A exon.