Identification of candidate genes involved in fatty acids degradation at the late maturity stage in Brassica napus based on transcriptomic analysis

In rapeseed (Brassica napus), the reduction of seed oil content (SOC) at the late maturity stage is widely observed in most rapeseed cultivars. However, the molecular mechanism relevant to the SOC reduction (i.e. fatty acids degradation) at the late stage is not clearly understood. In this study, we investigated dynamic accumulation of the SOC in the developing seeds of a cultivar Zhongyou-511 using gas chromatography and changes of transcriptomic profile in the seeds at different stages using RNA-seq respectively. The total SOC of Zhongyou-511 was decreased by 14% at 55 days after pollination (DAP) in comparison with that at 40 DAP. Transcriptomic analysis revealed that the majority of genes involved in fatty acids biosynthesis as well as β-oxidation for lipids degradation were significantly up-regulated at the late maturity stage, including BnaA09g32380D and BnaC08g23150D homologous genes of acyl-CoA oxidase 4 and BnaA03g15290D and BnaC04g11470D homologous genes of 3-ketoacyl-CoA thiolase 2. These results indicate that the increased expression of candidate genes in the β-oxidation pathway maybe cause the SOC reduction at the late maturity stage. The current study would be helpful for increasing our knowledge on the molecular mechanism of the SOC reduction and for utilizing candidate genes for high SOC breeding in rapeseed.