Manganese (Mn) is essential for plants, but its fluctuating soil availability—deficiency in alkaline soils and toxicity in acidic soils—challenges crop productivity. Breakthroughs in Arabidopsis have uncovered Ca2+ signaling as a key integrator of Mn status. This review synthesizes these discoveries into an emerging Arabidopsis-centered framework. Under Mn deficiency, sustained Ca2+ oscillations activate CPK21/23, which phosphorylate the importer NRAMP1 at Thr498 to enhance Mn uptake. Under Mn excess, a rapid Ca2+ transient triggers a multi-layered cascade: CPK4/5/6/11 activates MTP8 (Ser31/32) for vacuolar sequestration, while CBL2/3–CIPK3/9/26 sequentially suppresses MTP8 (Ser35, peak 24 h) and MTP11 (Ser194/201, peak 36 h)—a multi-tiered “brake” system. Concurrently, CBL1/9–CIPK23 induces NRAMP1 endocytosis (Ser20/22) to limit Mn uptake. The IRT1 transporter directly binds cytoplasmic Mn2+ and triggers its own degradation via CIPK23, thereby converging with Ca2+ signaling. The BRI1–CNGC12 module generates Mn-induced Ca2+ signals. By organizing current knowledge into a hierarchical framework, this review provides a working model for future research and outlines translational opportunities for engineering Mn-resilient crops.
Zhang et al. (Sat,) studied this question.