ABA synthesis gene OsNCED3 regulates pre-harvest sprouting through embryo-controlled seed dormancy in rice

Pre-harvest sprouting (PHS) is an unfavorable trait in cereal crops that could seriously productivity and economic losses. However, the molecular mechanism underlying PHS remains largely elusive. Here, we identified a member of 9-cisepoxycarotenoid dioxygenase family (NCED), OsNCED3, which regulates PHS in rice. OsNCED3 encodes a chloroplast- localized ABA synthesis enzyme, which is highly expressed in embryo of developing seeds. Disruption of OsNCED3 by CRISPR/Cas9-mediated mutagenesis lead to decreased seed dormancy, thus increased PHS in rice. Histological observation and hormone content analysis indicated that decreased seed dormancy was caused by reduced ABA levels and increased GA levels, resulting in unbalanced ABA/GA ratio in the embryos, thus faster embryos growth at seed dormancy stage in the Osnced3 mutants. In addition, OsNCED3 and OsNCED5 function synergistically in PHS in rice. These findings indicate that OsNCED3 regulates PHS through embryo-controlled seed dormancy in rice, which shed light on the control of seed dormancy aimed at preventing PHS and provide a potential target gene for improving PHS resistance in rice.