Genetic manipulation of gamma-linolenic acid (GLA) synthesis in a commercial variety of evening primrose (Oenothera sp.)

Engineering and fermenter production of fungi GLA in Pichia pastoris GS115 using oil waste

γ-Linolenic acid (GLA) is an essential n-6 polyunsaturated fatty acid (PUFA) that has received considerable attention in human and animal feed. GLA is used in many nutritional and medicinal applications, such as the treatment of cancer, inflammatory disorders, and diabetes. Currently, plant seed is the primary dietary source of GLA that is not enough to utilize on an industrial scale. To generate a sustainable novel source of GLA, the gene of delta-6 desaturase, one of the essential enzymes in the GLA production pathway, was isolated from Mucor rouxii DSM1194 and expressed in P. pastoris GS115 by pPICZC vector. The recombinant yeast expressed the GLA up to 19.2% (72 mg/g) of total fatty acids. GLA production of recombinant yeast was studied in a fermenter by oil waste for 5 days, and results detected 6.3 g/l lipid, and 103 mg/g GLA was produced in 72 h. The present study may provide an opportunity to develop an alternative host for manufacturing GLA on an industrial scale.

Engineering Trienoic Fatty Acids into Cottonseed Oil Improves Low-Temperature Seed Germination, Plant Photosynthesis and Cotton Fiber Quality

Alpha-linolenic acid (ALA, 18:3Δ9,12,15) and γ-linolenic acid \ (GLA, 18:3Δ6,9,12) 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, 18:2Δ9,12) by the microsomal ω-3 fatty acid desaturase (FAD3) and Δ6 desaturase (D6D), respectively. Cotton (Gossypium hirsutum L.) seed oil composition was modified by transforming with an 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 fiber 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.

Screening and molecular identification of overproducing γ-linolenic acid fungi and cloning the delta 6-desaturase gene

This research aims at isolating and identifying γ-linolenic acid (GLA)-producing fungi in the traditional Chinese salt-fermented soybean food, Douchi, from Yongchuan, People's Republic of China. In this study, Rhizopus oryzae DR3 was identified as a novel fungal species that produces large amounts of GLA. A full-length cDNA, designated as RoD6 D, with high homology to fungal △6 fatty acid desaturase genes was isolated from R. oryzae by using the rapid amplification of cDNA ends method. It had an open reading frame of 1,176 bp encoding a deduced polypeptide of 391 amino acids. Bioinformatics analysis characterized the putative RoD6 D protein as a typical membrane-bound desaturase, including three conserved histidine-rich motifs, a hydropathy profile, and a cytochrome b5 -like domain in the N-terminus. When the coding sequence was expressed in the Saccharomyces cerevisiae strain INVScl, the encoded product of RoD6 D exhibited △6 fatty acid desaturase activity that led to the accumulation of GLA. The results show that Douchi contains a large natural diverse composition, and some strains could be selected as starters for functional fermented foods. This study has also laid a foundation for developing functional Douchi products for further research.

Targeted mutation of Δ12 and Δ15 desaturase genes in hemp produce major alterations in seed fatty acid composition including a high oleic hemp oil

We used expressed sequence tag library and whole genome sequence mining to identify a suite of putative desaturase genes representing the four main activities required for production of polyunsaturated fatty acids in hemp seed oil. Phylogenetic-based classification and developing seed transcriptome analysis informed selection for further analysis of one of seven Δ12 desaturases and one of three Δ15 desaturases that we designate CSFAD2A and CSFAD3A, respectively. Heterologous expression of corresponding cDNAs in Saccharomyces cerevisiae showed CSFAD2A to have Δx+3 activity, while CSFAD3A activity was exclusively at the Δ15 position. TILLING of an ethyl methane sulphonate mutagenized population identified multiple alleles including non-sense mutations in both genes and fatty acid composition of seed oil confirmed these to be the major Δ12 and Δ15 desaturases in developing hemp seed. Following four backcrosses and sibling crosses to achieve homozygosity, csfad2a-1 was grown in the field and found to produce a 70 molar per cent high oleic acid (18:1(Δ9) ) oil at yields similar to wild type. Cold-pressed high oleic oil produced fewer volatiles and had a sevenfold increase in shelf life compared to wild type. Two low abundance octadecadienoic acids, 18:2(Δ6,9) and 18:2(Δ9,15), were identified in the high oleic oil, and their presence suggests remaining endogenous desaturase activities utilize the increased levels of oleic acid as substrate. Consistent with this, CSFAD3A produces 18:2(Δ9,15) from endogenous 18:1(Δ9) when expressed in S. cerevisiae. This work lays the foundation for the development of additional novel oil varieties in this multipurpose low input crop.

Molecular cloning and functional characterization of a Δ6-fatty acid desaturase gene from Rhizopus oryzae

The objective was to screen for and isolate a novel enzyme with the specific activity of a Δ6-fatty acid desaturase from Rhizopus oryzae. In this study, R. oryzae was identified as a novel fungal species that produces large amounts of γ-linolenic acid. A full-length cDNA, designated here as RoD6D, with high homology to fungal Δ6-fatty acid desaturase genes was isolated from R. oryzae by using the rapid amplification of cDNA ends method. It had an open reading frame of 1176 bp encoding a deduced polypeptide of 391 amino acids. Bioinformatics analysis characterized the putative RoD6D protein as a typical membrane-bound desaturase, including three conserved histidine-rich motifs, a hydropathy profile, and a cytochrome b5 -like domain in the N terminus. When the coding sequence was expressed in the Saccharomyces cerevisiae strain INVScl, the encoded product of RoD6D exhibited Δ6-fatty acid desaturase activity that led to the accumulation of γ-linolenic acid. The corresponding genomic sequence of RoD6D was 1565 bp in length, with five introns. This is the first report on the characterization and gene cloning of a Δ6-fatty acid desaturase of R. oryzae from Douchi.

Molecular marker systems for Oenothera genetics

The genus Oenothera has an outstanding scientific tradition. It has been a model for studying aspects of chromosome evolution and speciation, including the impact of plastid nuclear co-evolution. A large collection of strains analyzed during a century of experimental work and unique genetic possibilities allow the exchange of genetically definable plastids, individual or multiple chromosomes, and/or entire haploid genomes (Renner complexes) between species. However, molecular genetic approaches for the genus are largely lacking. In this study, we describe the development of efficient PCR-based marker systems for both the nuclear genome and the plastome. They allow distinguishing individual chromosomes, Renner complexes, plastomes, and subplastomes. We demonstrate their application by monitoring interspecific exchanges of genomes, chromosome pairs, and/or plastids during crossing programs, e.g., to produce plastome-genome incompatible hybrids. Using an appropriate partial permanent translocation heterozygous hybrid, linkage group 7 of the molecular map could be assigned to chromosome 9.8 of the classical Oenothera map. Finally, we provide the first direct molecular evidence that homologous recombination and free segregation of chromosomes in permanent translocation heterozygous strains is suppressed.

Seed-specific heterologous expression of a nasturtium FAE gene in Arabidopsis results in a dramatic increase in the proportion of erucic acid

The fatty acid elongase [often designated FAE or beta-(or 3-) ketoacyl-CoA synthase] is a condensing enzyme and is the first component of the elongation complex involved in synthesis of erucic acid (22:1) in seeds of garden nasturtium (Tropaeolum majus). Using a degenerate primers approach, a cDNA of a putative embryo FAE was obtained showing high homology to known plant elongases. This cDNA contains a 1,512-bp open reading frame that encodes a protein of 504 amino acids. A genomic clone of the nasturtium FAE was isolated and sequence analyses indicated the absence of introns. Northern hybridization showed the expression of this nasturtium FAE gene to be restricted to the embryo. Southern hybridization revealed the nasturtium beta-ketoacyl-CoA synthase to be encoded by a small multigene family. To establish the function of the elongase homolog, the cDNA was introduced into two different heterologous chromosomal backgrounds (Arabidopsis and tobacco [Nicotiana tabacum]) under the control of a seed-specific (napin) promoter and the tandem 35S promoter, respectively. Seed-specific expression resulted in up to an 8-fold increase in erucic acid proportions in Arabidopsis seed oil, while constitutive expression in transgenic tobacco tissue resulted in increased proportions of very long chain saturated fatty acids. These results indicate that the nasturtium FAE gene encodes a condensing enzyme involved in the biosynthesis of very long chain fatty acids, utilizing monounsaturated and saturated acyl substrates. Given its strong and unique preference for elongating 20:1-CoA, the utility of the FAE gene product for directing or engineering increased synthesis of erucic acid is discussed.