PubMed · 2026-02-19
Scientists discovered a three-protein molecular switch in apple trees that controls how cells flood with calcium during cold stress — a key early alarm signal that helps the plant survive freezing. The system is self-regulating: it turns on when temperatures drop and automatically dials back once calcium levels get too high.
MdCNGC1C, a calcium channel, is activated by the kinase MdOST1 via phosphorylation at a specific site (Serine-47), directly enhancing calcium influx and freezing tolerance in apple.
The calcium sensor protein MdCaM7.1 competes with MdOST1 for binding to the same region (N-terminus) of MdCNGC1C, and when it wins, it inhibits calcium entry and reduces cold tolerance.
Elevated cytoplasmic calcium concentrations promote MdCaM7.1 binding and suppress MdOST1 activity, revealing a calcium-dependent negative feedback loop that self-limits cold-induced calcium signaling.
