Transcriptional repression of K+ uptake by ARF2

HAK5 is a high-affinity potassium transporter that is transcriptionally repressed in high K+ conditions. Zhao et al. identified hormone-related cis-elements in the HAK5 promoter. They screened mutants deficient in transcription factors associated with these cis-elements and found that arf2 mutants show enhanced K+ uptake and root growth on low-K medium, whereas ARF2 overexpression lines showed decreased K+ uptake, indicating that ARF2 acts as a transcriptional repressor. The authors further showed that under low K conditions, ARF2 is phosphorylated, relieving its repressive function. Plant Cell 10.1105/tpc.16.00684