Quiescin Sulfhydryl Oxidase‐Like 1 Positively Regulates Seed Dormancy in Rice

ABSTRACT Seed dormancy is an adaptive strategy that enables plants to survive adverse environmental conditions. In agricultural contexts, an optimal level of dormancy is essential: Insufficient dormancy can result in preharvest sprouting, while excessive dormancy may lead to uneven germination and poor stand establishment in subsequent crops. In this research, we cloned qSdn5 , a quantitative trait locus functioning as a positive regulator of seed dormancy in rice. The causal gene within qSdn5 encodes Quiescin sulfhydryl oxidase like 1 (QSOXL1). A critical amino acid polymorphism (K353E) in QSOXL1 between the varieties N22 and Nanjing35 (NJ35) significantly altered its enzymatic activity. The K‐E substitution at position 353 disrupted the cellular redox state and ultimately influenced seed dormancy. Furthermore, we identified COP9 Signalosome Subunit 5 (CSN5) as a central regulator of dormancy, promoting the proteasomal degradation of QSOXL1 , ABI5 and SLR1. Haplotype analysis revealed that Hap5 of QSOXL1 , originating from the aus subpopulation, confers elevated seed dormancy levels. This haplotype presents a promising genetic resource for enhancing seed dormancy in rice breeding programmes.