Knockout of OsSAP5 Improves Resistance to Pre-harvest Sprouting by Modulating OsSLR1 Protein Abundance in Rice.

Pre-harvest sprouting (PHS), defined as the premature germination of grains on the panicle before harvest, significantly compromises grain yield and seed quality. Optimizing seed dormancy is therefore crucial for mitigating PHS. Here, we report that loss of function in Stress-associated Protein 5 (OsSAP5) enhances resistance to PHS without grain yield reduction. Mechanistically, OsSAP5 participates in the GA-mediated modulation of the DELLA protein OsSLR1 abundance to orchestrate downstream responses; it accelerates GA signaling transduction to induce amylase gene expression and elevate soluble sugar content, while concurrently suppressing the expression of ABA signaling regulators, thereby collaboratively governing seed dormancy and germination. In ossap5 mutants, this bipartite control-manifested as intensified dormancy alongside delayed germination-acts in concert to repress PHS. We further confirm an interaction between OsSAP5 and OsSLR1, which likely plays a role in this regulatory process. Correspondingly, we also established that OsSLR1 positively regulates seed dormancy and negatively regulates seed germination, thereby further elaborating its biological functions. In conclusion, our findings identify OsSAP5 as a pivotal modulator of GA signaling, offering a new theoretical basis and genetic target for breeding PHS-resistant varieties.