Journal of Integrative Agriculture (Dec 2023)
Biotechnology of α-linolenic acid in oilseed rape (Brassica napus) using FAD2 and FAD3 from chia (Salvia hispanica)
Abstract
α-Linolenic acid (ALA, 18:3Δ9,12,15) is an essential fatty acid for humans since it is the precursor for the biosynthesis of omega-3 long-chain polyunsaturated fatty acids (LC-PUFA). Modern people generally suffer from deficiency of ALA because most staple food oils are low or lack ALA content. Biotechnological enrichment of ALA in staple oil crops is a promising strategy. Chia (Salvia hispanica) has the highest ALA content in its seed oil among known oil crops. In this study, the FAD2 and FAD3 genes from chia were engineered into a staple oil crop, oilseed rape (Brassica napus), via Agrobaterium tumefaciens-mediated transformation of their LP4-2A fusion gene construct driven by the seed-specific promoter PNapA. In seeds of T0, T1, and T2 lines, the average ALA contents were 20.86, 23.54, and 24.92%, respectively, which were 2.21, 2.68, and 3.03 folds of the non-transformed controls (9.42, 8.78, and 8.22%), respectively. The highest seed ALA levels of T0, T1, and T2 plants were 38.41, 35.98, and 39.19% respectively, which were 4.10–4.77 folds of the respective controls. FA-pathway enzyme genes (BnACCD, BnFATA, BnSAD, BnSCD, BnDGAT1, BnDGAT2, and BnDGAT3) and positive regulatory genes (BnWRI1, BnLEC1, BnL1L, BnLEC2, BnABI3, BnbZIP67, and BnMYB96) were all significantly up-regulated. In contrast, BnTT1, BnTT2, BnTT8, BnTT16, BnTTG1, and BnTTG2, encoding negative oil accumulation regulators but positive secondary metabolism regulators, were all significantly down-regulated. This means the foreign ShFAD2-ShFAD3 fusion gene, directly and indirectly, remodeled both positive and negative loci of the whole FA-related network in transgenic B. napus seeds.
