BIN2 phosphorylation of GRF5 suppresses low nitrate root foraging by inhibiting transcriptional activity and UBP12/13-mediated deubiquitination

Under low nitrate conditions, enhanced exploratory root growth—characterized by increased primary and lateral root elongation—facilitates nutrient foraging. Although nitrate-hormone crosstalk regulates this process, the underlying molecular mechanisms remain poorly understood.

Here, we identify a BIN2-GRF5-UBP12/13 module governing root foraging responses to low nitrate in Arabidopsis. We demonstrate that BIN2 phosphorylates GRF5 at Ser-205, reducing its stability and transcriptional activity. Integrative DAP-seq and transcriptome analyses revealed that GRF5 directly regulates key nitrate-responsive genes, including the dual-affinity transporter NRT1.1 and the high-affinity uptake gene NRT2.1.