OsCPN10a, cooperating with OsCPN20 and OsHSP60-3B negatively regulate ABA signaling and enhance seed storability in rice.

Seed storability is crucial for maintaining vigor at the sowing stage and ensuring agricultural sustainability. Although molecular chaperones are well characterized in protein homeostasis, their roles in regulating ABA receptor stability and starch integrity during seed aging remain unclear. Here, we demonstrate that OsCPN10a enhances storability by maintaining ABA homeostasis, suppressing ROS accumulation, and preserving starch granule structure. Genetic and biochemical analyses reveal that OsCPN10a functions upstream of the OsCPN20-OsHSP60-3B cascade, directly interacts with both partners to promote complex assembly, and negatively regulates ABA signaling. The resulting trimeric complex interacts with OsPYL10, facilitating receptor dissociation and high-affinity association with the PP2C phosphatase OsABIL1 to attenuate signaling. This study reveals a non-canonical function of molecular chaperones in directly modulating hormone receptor signaling, establishing a mechanistic link between protein homeostasis and ABA sensitivity in seeds.