Development of a Brassica napus (Canola) Crop Containing Fish Oil-Like Levels of DHA in the Seed Oil

Abstract

Plant seeds have long been promoted as a production platform for novel fatty acids such as the ω3 long-chain (≥ C 20) polyunsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) commonly found in fish oil. In this article we describe the creation of a canola (Brassica napus) variety producing fish oil-like levels of DHA in the seed. This was achieved by the introduction of a microalgal/yeast transgenic pathway of seven consecutive enzymatic steps which converted the native substrate oleic acid to α-linolenic acid and, subsequently, to EPA, docosapentaenoic acid (DPA) and DHA. This paper describes construct design and evaluation, plant transformation, event selection, field testing in a wide range of environments, and oil profile stability of the transgenic seed. The stable, high-performing event NS-B50027-4 produced fish oil-like levels of DHA (9-11%) in open field trials of T 3 to T 7 generation plants in several locations in Australia and Canada. This study also describes the highest seed DHA levels reported thus far and is one of the first examples of a deregulated genetically modified crop with clear health benefits to the consumer.

n-3 Canola oil effectively replaces fish oil as a new safe dietary source of DHA in feed for juvenile Atlantic salmon

“…Ltd. The transgenic seeds were modified to produce the LC-PUFA -EPA and DHA; construct details are provided in Petrie et al (15) . The crop used in this trial was grown in Australia during 2015 and 2016.…”

“…In terrestrial GM plant oils, enriched levels of DHA have been achieved, combined with lower n-6 PUFA levels than occurs in conventional canola oils (12)(13)(14)(15) . Today, close to 70 % of the oil fraction in feeds for Atlantic salmon in Norway consists of canola oil, demonstrating that the fish already grow and perform well on canola oil-rich diets.…”

The Use of Genetic and Gene Technologies in Shaping Modern Rapeseed Cultivars (Brassica napus L.)

“…To maximize canola intake in both biofuel and feed industries, varieties with high oleic acid and extremely low glucosinolate content are targeted [ 12 ]. High oil yield (40–45% of the mass) and low production cost are features making canola a potential crop for producing high demand fatty acids [ 36 ].…”

“…High demand long chain-unsaturated fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which were once exclusively obtained from fish, are now novel components of transgenic B. napus lines [ 36 , 85 ]. In 2005, by transformation using A. tumefaciens containing 6 different constructs of desaturase genes from Thraustochytrium sp., Pythium irregular and Calendula officinalis , and fatty acid elongase from Physcomitrella patens in B. juncea , very long chain PUFAs such as arachidonic acid (AA) and EPA were produced at levels of up to 25% and 15% of total seed fatty acids, however, the DHA biosynthetic pathway needed further optimization [ 34 ].…”

“…Limitations in gene pool diversity [ 31 , 32 ], and the time and laborious constraints in canola breeding can now be overcome by using genetic modification [ 32 ] and genome editing technologies whereby transgenes or mutations can be directly introduced into plants, providing additional ways to investigate gene functions in biological processes [ 33 , 34 , 35 , 36 ]. The most commonly applied genome editing tool in eukaryotes in the last 8 years, the clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein (Cas) system [ 37 , 38 ], is gaining more interest compared to conventional genetic modification methods due to its high efficiency in targeted nucleotide modification and generation of a transgene-free end-product [ 39 ].…”