OsS40-14 regulates rice seed germination by modulating ABA responsiveness and inhibiting dormancy release.

Abstract

Seed germination is a complex process influenced by various physical and biochemical factors, and dormancy release upon imbibition is essential for germination. However, the specific regulators controlling dormancy release in rice remain largely unknown. Here, we identified OsS40-14, a member of the senescence-associated S40 gene family, as a negative regulator of seed germination in rice. Using CRISPR/Cas9 gene editing and transgenic overexpression (OE) lines, we found that the oss40-14 mutant lines exhibit pre-harvest sprouting (PHS) and accelerated germination, while the OE-OsS40-14 lines show delayed germination. Notably, dormancy-breaking treatments largely eliminated these phenotypic differences. Analysis of endogenous abscisic acid (ABA) levels and the response to exogenous ABA revealed that OsS40-14 regulates germination by modulating ABA signaling. Transcriptomic and CUT & Tag-seq analyses demonstrated that OsS40-14 directly represses the transcription of two ABA catabolic genes, OsABA8ox1 and OsABA8ox3, thereby preventing the reduction of ABA levels during seed dormancy release. These findings establish OsS40-14 as a key regulator of seed germination through its control of ABA homeostasis, providing potential targets for breeding PHS-resistant varieties.