Genetic and functional analysis of tocopherol biosynthesis pathway genes from rapeseed (Brassica napus L.)

Brassica napus L. is one of the most important oilseed crops in the world. Improving oil quality by increasing vitamin E content is a major target of rapeseed breeding. Vitamin E compounds, or tocopherols, are lipid‐soluble antioxidants that are essential nutrients for mammals. In this study, we report the characterization of rapeseed orthologs of the Arabidopsis tocopherol genes VTE1, VTE2 and PDS1. For each gene, at least two homologous sequences were found, and their expression was analysed in different tissues from three rapeseed genotypes. Genetic complementation experiments demonstrated that BnaX.VTE1.b and BnaA.VTE2.b homologs are capable of recovering seed γ‐tocopherol in Arabidopsis mutants. Overexpression of the genes in Arabidopsis Col‐0 shifted the seed tocopherol composition towards higher α‐tocopherol without increasing the total tocopherol content. To address the functionality of BnPDS1 sequences, we performed overexpression tests in Escherichia coli and enzymatic activity analyses. Overall, our results show that the identified sequences from rapeseed are functional orthologs of the Arabidopsis VTE genes and thus have considerable potential as molecular markers for selecting rapeseed with improved seed oil quality.