Auxin-induced WRKY23 activates PECTIN LYASE-LIKE1 and PECTIN LYASE-LIKE3 for apoplastic iron reutilization in Arabidopsis roots

• WRKY23 regulates the retention and reuse of apoplastic Fe in Arabidopsis roots. • WRKY23 expression is modulated by local auxin signaling under Fe deficiency. • WRKY23 directly binds to the promoters to activate the expression of PLL1 and PLL3 . • PLL1 and PLL3 regulate pectin metabolism and Fe-binding capacity in the cell wall. The retention and reutilization of apoplastic iron (Fe) are essential for Fe homeostasis in plants, yet the underlying molecular mechanisms remain largely unexplored. Here, we characterized the role of WRKY23, a nucleus-localized transcription factor, in regulating apoplastic Fe retention and reutilization in response to Fe deficiency in Arabidopsis thaliana . Under Fe deficiency, the induction of WRKY23 expression is modulated by local auxin signaling. Once activated, WRKY23 then influenced Fe homeostasis by regulating pectin metabolism and Fe-binding capacity in the cell wall. Notably, WRKY23 could directly bind to W-box motifs in the promoters of target genes, including PECTIN LYASE-LIKE1 ( PLL1 ) and PLL3 , activating their transcription. Collectively, our findings support a model in which WRKY23 functions as part of a transcriptional cascade, whereby auxin signaling promotes the role of WRKY23 in regulating pectin degradation and enhancing Fe retention and reutilization in the apoplast, thereby negatively modulating Fe deficiency responses in roots. This research deepens our understanding of plant responses to nutritional stress and may inform strategies for improving crop resilience.