Abstract
BackgroundTraditional canola (Brassica napus L.; AACC, 2n = 38) cultivars yield seed oil with a relatively high proportion of α-linolenic acid (ALA; C18:3cis∆9,12,15), which is desirable from a health perspective. Unfortunately, due to the instability of this fatty acid, elevated levels also result in oils that exhibit a short shelf life and problems associated with use at high temperatures. As a result, the development of cultivars bearing reduced amounts of ALA in their seeds is becoming a priority. To date, several low ALA B. napus cultivars (~2-3% ALA of total fatty acids) have been developed and molecular analyses have revealed that the low ALA phenotype of lines tested thus far is a result of mutations within two ‘class b’ FATTY ACID DESATURASE 3 (FAD3) genes. Since B. napus possesses six FAD3 genes (two ‘class a’, two ‘class b’ and two ‘class c’) and ALA levels of approximately 2-3% remain in these low ALA lines, it is likely that the mutation of additional FAD3 genes could further decrease the content of this fatty acid.ResultsIn this study, we generated low ALA (≤2%) lines of B. oleracea, which is the C genome progenitor species of B. napus, via ethyl methanesulphonate (EMS) mutagenesis. We identified a novel nonsense mutation within the ‘class a’ FAD3 gene (BoFAD3-2) in these lines, which would result in the production of an encoded protein lacking 110 amino acids at its C terminus. When expressed in Saccharomyces cerevisiae, this mutant protein exhibited a drastic decline in its Δ-15 desaturase activity compared to the wild-type (wt) protein. Furthermore, we demonstrated that the expression of the mutant BoFAD3-2 gene was significantly reduced in developing seeds of low ALA lines when compared to expression in wt plants.ConclusionsGiven the additive nature of FAD3 mutations on ALA content and the ease with which B. napus can be re-synthesized from its progenitor species, the mutant isolated here has the potential to be used for the future development of B. napus cultivars exhibiting further reductions in ALA content.
Highlights
Traditional canola (Brassica napus L.; AACC, 2n = 38) cultivars yield seed oil with a relatively high proportion of α-linolenic acid (ALA; C18:3cisΔ9,12,15), which is desirable from a health perspective
While treated seeds only demonstrated a 3% reduction in viability when compared to wt B. oleracea, ethyl methanesulphonate (EMS) treatment had a significant effect on M1 plants (Table 1)
The ALA content in seeds harvested from these M3 plants ranged from 2.28 to 11.13%, which was significantly lower than wt B. oleracea (Figure 2, Additional file 1: Table S1)
Summary
The seed oil of traditional canola cultivars is characterized by a low amount of saturated fatty acids (FAs; ~7%) and high contents of it is the proportions of the three major unsaturated FAs (oleic acid, LA and ALA) that largely determine the usefulness of this oil from both food and industrial perspectives. It follows that decreasing the level of ALA in canola seeds would be of value to enhance shelf life and stability of its oil at high temperatures [7,8,9]. To this effect, the development of low ALA (≤2-3%) cultivars has recently become one of the major breeding goals for the improvement of B. napus [10]. FAD3.c, BnaC.FAD3.a, BnaC.FAD3.b and BnaC.FAD3.c) can be phylogenetically grouped into three classes (a, b and c), with each class comprising a single gene from the A and C genomes, respectively [14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
