PaMYBS3 balances cold tolerance and growth inhibition as a cold acclimation strategy in Plumbago auriculata L.

Plumbago auriculata L., a tropical evergreen, developed enhanced cold tolerance through long-term field acclimation, yet its molecular mechanisms remained unclear. Here, we identified PaMYBS3, a MYB transcription factor, as a key dual-function regulator during cold acclimation. Short-term artificial cold treatment induced PaMYBS3 expression and improved cold resistance. Overexpression of PaMYBS3 in Arabidopsis promoted growth but reduced freezing tolerance, while domain-mutant and VIGS-silenced lines exhibited inhibited growth and enhanced cold adaptation. Physiological assays revealed that PaMYBS3 enhances cold tolerance by modulating ROS balance, photosynthetic performance, and osmotic regulators, while suppressing growth through downregulation of auxin- and sugar-related genes, supporting a cold acclimation strategy that prioritizes survival over growth. Notably, PaMYBS3 regulated cold-responsive pathways independently of the classical CBF/DREB1-COR module, suggesting a CBF-independent cold tolerance mechanism. Our findings highlight PaMYBS3 as a central integrator of cold response and growth restraint, offering new insights into the adaptive strategies of tropical perennials under prolonged low temperature.