Engineering trienoic fatty acids into cottonseed oil improves
low-temperature seed germination, plant photosynthesis and cotton fibre
quality
Abstract
Alpha-linolenic acid (ALA, 18:3∆9,12,15) and γ-linolenic acid (GLA,
18:3∆6,9,12) are important trienoic fatty acids which are beneficial for
human health in their own right, or as precursors for the biosynthesis
of long chain polyunsaturated fatty acids. ALA and GLA in seed oil are
synthesized from linoleic acid (LA, 18:2∆9,12) by the microsomal ω-3
fatty acid desaturase (FAD3) and ∆6 desaturase (D6D), respectively.
Cotton (Gossypium hirsutum L.) seed oil composition was modified by
transforming with a FAD3 gene from Brassica napus and a D6D gene from
Echium plantagineum, resulting in approximately 30% ALA and 20% GLA,
respectively. The total oil content in transgenic seeds remained
unaltered relative to parental seeds. Despite the use of a seed-specific
promoter for transgene expression, low levels of GLA and increased
levels of ALA were found in non-seed cotton tissues. At low temperature
the germinating cottonseeds containing the linolenic acid isomers
elongated faster than the untransformed controls. ALA-producing lines
also showed higher photosynthetic rates at cooler temperature and better
fibre quality compared to both untransformed controls and GLA-producing
lines. The oxidative stability of the novel cottonseed oils was
assessed, providing guidance for potential food, pharmaceutical and
industrial applications of these oils.