Flowering time is a critical developmental trait in crops that significantly influences yield. MicroRNAs (miRNAs), a class of small endogenous RNAs processed from MIR gene transcripts, regulate gene expression by mediating transcript cleavage. In this study, we identified a novel miRNA—novel-Bna-miR1040—in rapeseed (Brassica napus), whose biological function had not been previously characterized. Transgenic rapeseed plants overexpressing Bna-miR1040 exhibited delayed flowering compared to wild-type plants. Degradome sequencing identified BnaEIF3A as a potential target of Bna-miR1040. This interaction was validated by 5′RACE and transient expression assays in tobacco leaves, which confirmed that Bna-miR1040 cleaves BnaEIF3A, significantly reducing its transcript levels. Evolutionary analysis showed that BnaEIF3A is highly conserved across diverse plant species. Subcellular localization analysis revealed that the BnaEIF3A protein is exclusively localized in the nucleus. To further investigate its function, we generated BnaEIF3A loss-of-function mutants using CRISPR/Cas9 genome editing. These mutants also exhibited delayed flowering phenotypes compared to wild-type controls. Together, our findings demonstrate that Bna-miR1040 regulates flowering time in rapeseed by suppressing BnaEIF3A expression, providing novel insights for molecular breeding strategies aimed at optimizing flowering time in rapeseed.
Ma et al. (2025) studied this question.