Calcium signaling-mediated phosphorylation controls zinc allocation in Arabidopsis

Zinc (Zn) deficiency in soil can directly result in Zn deficiency in crops, subsequently causing Zn deficiency in humans. Currently, the physiological adaptation mechanisms by which plants respond to Zn deficiency have been fairly well characterized. However, the regulatory mechanisms governing Zn transport in plants remain poorly understood. In this study, we found that CBL1/4/5/8/9-CIPK3/9/23/26 complexes interact with the Zn transporter ZIP2 and phosphorylate its Ser190 residue. Biochemical analyses and complementation experiments in yeast and plants demonstrated that the Ser190 site is essential for the transport activity of ZIP2, and that the Zn transporter ZIP2 is involved in the transport of Zn between the columnar sheath cells in the roots. Notably, the hybrid complementation lines carrying CBL-CIPK-mediated phosphorylation sites of ZIP2 and ZIP12 exhibited enhanced tolerance to Zn deficiency. Overall, these findings suggest that CBL-CIPK-ZIP2/ZIP12 phosphorylation network coordinates Zn allocation in Arabidopsis, providing a potential target for improving Zn deficiency and developing Zn-enriched crop varieties.