High level accumulation of gamma linolenic acid (C18:3Δ6.9,12 cis) in transgenic safflower (Carthamus tinctorius) seeds

Abstract

Gamma linolenic acid (GLA; C18:3Δ6,9,12 cis), also known as γ-Linolenic acid, is an important essential fatty acid precursor for the synthesis of very long chain polyunsaturated fatty acids and important pathways involved in human health. GLA is synthesized from linoleic acid (LA; C18:2Δ9,12 cis) by endoplasmic reticulum associated Δ6-desaturase activity. Currently sources of GLA are limited to a small number of plant species with poor agronomic properties, and therefore an economical and abundant commercial source of GLA in an existing crop is highly desirable. To this end, the seed oil of a high LA cultivated species of safflower (Carthamus tinctorius) was modified by transformation with Δ6-desaturase from Saprolegnia diclina resulting in levels exceeding 70% (v/v) of GLA. Levels around 50% (v/v) of GLA in seed oil was achieved when Δ12-/Δ6-desaturases from Mortierella alpina was over-expressed in safflower cultivars with either a high LA or high oleic (OA; C18:1Δ9 cis) background. The differences in the overall levels of GLA suggest the accumulation of the novel fatty acid was not limited by a lack of incorporation into the triacylgylcerol backbone (>66% GLA achieved), or correlated with gene dosage (GLA levels independent of gene copy number), but rather reflected the differences in Δ6-desaturase activity from the two sources. To date, these represent the highest accumulation levels of a newly introduced fatty acid in a transgenic crop. Events from these studies have been propagated and recently received FDA approval for commercialization as Sonova™400.

Progress in modification of sunflower oil to expand its industrial value

“…γ ‐Linolenic acid is also important fatty acid and considered as precursor of very‐long‐chain fatty acids in human body. The gene encoding Δ6‐desaturases was isolated from the Saprolegnia diclina and used to transform safflower which increased γ ‐linolenic acid to 50% . The Δ6‐desaturase gene was cloned along with the embryo‐specific promoter β ‐conglycinin in soybean.…”

“…The gene encoding Δ6-desaturases was isolated from the Saprolegnia diclina and used to transform safflower which increased -linolenic acid to 50%. 56 The Δ6-desaturase gene was cloned along with the embryo-specific promoter -conglycinin in soybean. Transgenic soybean contained 3.4% to 28.7% of -linolenic acid and 0.6% to 4.2% stearidonic acid.…”

Improved γ-linolenic acid production in Mucor circinelloides by homologous overexpressing of delta-12 and delta-6 desaturases

“…However, GLA production from plant seeds is easily influenced by region, climate and seasons, resulting in variable quantities and qualities of the oils. Genetically-engineered safflower seeds are now available in which GLA may now be up to 70% of the total fatty acids [8, 9] but, because of the uncertainties surrounding the acceptability of genetically modified (GM) materials as neutraceuticals, there is continued interest in developing microbial oils over conventional sources. Thus, a promising alternative source comes from oleaginous microorganisms with high GLA contents [5, 10–12].…”

“…Thus, three desaturases, the delta-9, delta-12 and delta-6, accomplish the desaturation processes in GLA synthesis [5, 13, 14]. Genes coding for those desaturases have been cloned from diverse organisms ranging from prokaryotes to higher eukaryotes, and overexpressed in several hosts, including microalgae, yeasts and plants [8, 13–16]. However, few researches on homologous expression of fungal desaturases have been reported.…”

A new <i>O</i>-methyltransferase for monolignol synthesis in <i>Carthamus tinctorius</i>

“…In addition, several protocols for Agrobacterium-mediated genetic transformation of the plant have been reported (Belide et al 2011;Motamedi et al 2011;Nykiforuk et al 2012;Shilpa et al 2010). This species can therefore be used for comparative studies of lignin and lignan biosynthesis.…”