Multi-Omics Analysis Revealed the overexpression of BnNCED2 inhibits preharvest sprouting in Brassica napus
Brassica napus is one of the most important oilseed crops in China. Preharvest sprouting (PHS) was a frequently observed phenomenon in the later seed developmental stages when the seeds met high temperatures and high humidity, decreasing crop yield and quality. However, the mechanism underlying PHS in B. napus needed to be better understood. To explore the mechanism of PHS, quantitative trait locus (QTL) mapping on the PHS rate was first analyzed by using the KN DH population, and 28 identified QTL for PHS were detected (the phenotypic variation ranged from 0.76% to 8.94%). After meta-analysis, 25 consensus QTLs were obtained, and three could be detected in multiple environments. Forty-three genes related to ABA synthesis and signal transduction in confidence interval (CI) were identified. Transcriptomics analysis showed that the differentially expressed genes (DEGs) between the rapeseeds with high and low PHS rates were related to carotenoid biosynthesis and fatty acid metabolism. Combining the genes in the CI of QTL, DEGs revealed by the transcriptome and genome resequencing data of two mapping parents, the BnaC01g10770D (BnNCED2) was identified as the candidate gene for PHS in B. napus. Transgenetic analysis showed that BnNCED2 could complement the phenotype of nced2 mutants, and the seeds of overexpression lines exhibited delayed seed germination in Arabidopsis. Further analysis showed that RNA interference lines of BnNCED2 in B. napus could lead to PHS, and the overexpression of BnNCED2 could delay seed germination. The present research lays the foundation for improving and cultivating new rapeseed varieties with low PHS rates in the future.