A research team led by Academician Peisong Hu from the China National Rice Research Institute, Chinese Academy of Agricultural Sciences, has successfully identified a key gene that controls seed dormancy and confers resistance to pre-harvest sprouting (PHS) in rice. The findings, published in Science Bulletin , reveal a novel molecular mechanism that regulates seed dormancy at the post-translational level via the abscisic acid (ABA) signaling pathway, and demonstrate that natural variation in this gene provides valuable resources for breeding PHS resistance in rice and other cereal crops.
By screening for PHS mutants, the researchers cloned a key gene, OsSD7 , that controls seed dormancy and PHS resistance in rice. Further investigation revealed that OsSD7 encodes an F-box protein that interacts with SKP1 to form an SCF (Skp1-Cullin-F-box) E3 ubiquitin ligase complex. This complex specifically targets the jasmonate signaling repressor OsJAZ9 for ubiquitination and subsequent proteasomal degradation.
The study found that ABA induces the expression of the transcription factor OsTRAB1, which directly binds to the OsSD7 promoter and activates its transcription. OsSD7 then promotes the degradation of OsJAZ9, thereby relieving the suppression of the ABA signaling pathway. In the absence of OsSD7, OsJAZ9 accumulates and interacts with OsJAZ6, inhibiting the transcriptional activity of the key ABA signaling regulators OsABI3/OsABI5, ultimately leading to reduced seed dormancy and increased susceptibility to PHS. “Our study reveals a complete signaling cascade from ABA to the transcriptional regulation of OsSD7 , and then to the post-translational degradation of a repressor that otherwise blocks ABA signaling,” said corresponding author Academician Peisong Hu. “This dual-layer regulatory mechanism ensures robust control of seed dormancy.”
The research team also identified a natural SNP (3,744,951) in the promoter region of OsSD7 that significantly correlates with seed dormancy among rice varieties: the Hap A type (with high OsSD7 expression) exhibits strong seed dormancy and PHS resistance, while the Hap G type (with low OsSD7 expression) shows the opposite. This SNP is enriched in modern Xian varieties, suggesting it has been subjected to artificial selection during breeding. By using CRISPR technology to convert Hap G to Hap A, the researchers successfully improved PHS resistance in several rice varieties.
More excitingly, overexpression of OsSD7 in the wheat cultivar Fielder also significantly enhanced seed dormancy and PHS resistance, indicating that the mechanism by which OsSD7 regulates dormancy is highly conserved across monocot crops and holds cross-species potential for breeding applications.
This study not only elucidates the molecular mechanism by which rice precisely regulates seed dormancy and PHS resistance through a single F-box protein, but also provides valuable genetic resources and a theoretical foundation for stress tolerance genetic improvement in rice, wheat, and other crops. In the future, introducing the superior allele Hap A of OsSD7 into elite varieties through marker-assisted selection or gene editing is expected to significantly improve PHS resistance without compromising yield, thereby reducing losses caused by rainy weather.
Science Bulletin
Experimental study