A LEA2 domain-containing protein PpLEA37 promotes seed germination under salinity and drought stresses through...

Seed germination is a pivotal developmental transition in the plant life cycle. The ability of seeds to germinate under abiotic stresses, such as salinity or drought condition, directly affects crop establishment and yield. Late embryogenesis abundant (LEA) proteins are recognized mediators of stress adaptation. Yet the molecular mechanisms by which they influence seed germination remain poorly understood. Here, we show that overexpression of PpLEA37 markedly improves germination rates. This effect is observed in both Arabidopsis and peach seeds, under normal, salinity, and drought stress conditions. Strikingly, enhanced germination coincides with transcriptional upregulation of 9-cis-epoxycarotenoid dioxygenase (NCED). NCED is the rate-limiting enzyme in abscisic acid (ABA) biosynthesis. Its induction leads to elevated endogenous ABA levels. Molecular interaction analyses further show that PpLEA37 physically associates with carotenoid cleavage dioxygenase 4 (PpCCD4). Functional characterization demonstrates that overexpression of either PpLEA37 or PpCCD4 potentiates NCED enzymatic activity. Based on these integrated results, we propose a new working model. Under stress, PpLEA37 and PpCCD4 assemble into a functional complex. This complex simultaneously drives ABA biosynthesis and initiates a pre-adaptive program. The program confers a basal level of stress resilience. As a result, an appropriate level of ABA synergistically promotes both germination and stress tolerance. Our findings identify PpLEA37 as a promising genetic target for improving stress-resilient germination. More broadly, they illuminate the mechanistic basis for context-dependent functional switching of ABA during seed germination. These results advance our understanding of how plants coordinate developmental transitions with stress adaptation. They also provide conceptual frameworks and genetic resources for breeding stress-tolerant crops.