Cloning and Function Analysis of ω-3-Fatty Acid Desaturase 8 Gene from Perilla frutescens / 中国生物化学与分子生物学报

ω-3-Fatty acid desaturase 8 (FAD8), as a dehydrogenase enzyme, plays a key role in the transformation of saturated fatty acids into unsaturated fatty acids, which is helpful to enhance the freezing tolerance of plants. However, it remains unclear whether the expression level of FAD8 in Perilla frutescens is regulated by low temperature. Based on transcriptome data, the FAD8 gene was cloned, characterized and then successfully expressed in tobacco Nicotiana tabacum. The gene was designated as PfFAD8 and has a full-length coding sequence of 1 317 bp coding for 438 amino acids with a predicted molecular weight of 50 kD and a theoretical isoelectric point of 9. 13. Our research indicated that the expression of PfFAD8 in Perilla frutescens was increased under the freezing stress. To further confirm this result, a 35S::PfFAD8 vector were constructed and transformed into N. tabacum by Agrobacterium tumefaciens-mediated transformation. Transgenic tobacco leaves that over-expressed the PfFAD8 gene exhibited significantly higher unsaturated fatty acids (UFA) such as linoleic (C18:2) and palmitic acid (C16:0) content and advanced freezing tolerance. Moreover, PfFAD8 overexpression in transgenic tobacco leaves increases malondialdehyde (MDA) and proline (PRO) content, and enhances defense enzymes activities of superoxide dismutase (SOD) and catalase (CAT) to some extent under the cold condition, which might prevent the decline of UFA. Taken together, PfFAD8 overexpression in Perilla frutescens might be involved in the desaturation process of lipids leading to increased membrane stability and/ or induction of other genes related to freezing tolerance by octadecanoid pathway or lipid peroxidation products. Thus, PfFAD8 overexpression could be useful in the production of freeze-tolerant varieties of N. tabacum.

Research Progress of Fatty Acid Desaturase 2 Gene in Glycolipid Metabolism / 中国医学科学院学报

The fatty acid desaturase 2 (FADS2) gene encodes delta-6 desaturase (D6D) and is a member of the fatty acid desaturase gene family.D6D is the key enzyme catalyzing the transformation of linoleic acid and α-linolenic acid to long-chain polyunsaturated fatty acid (LC-PUFA).LC-PUFA play a crucial role in regulating the glycolipid metabolism of living organisms.In recent years,the activity of D6D and the single nucleotide polymorphism (SNP) of FADS2 gene have become a hot topic in the research on glycolipid metabolism.This article reviews the role of FADS2 gene in glycolipid metabolism.

Construction of transgenic mice with Δ15 Des enzyme activity by using a PiggyBac transposon / 生物工程学报

Essential fatty acids are those that could not be synthesized by the body itself but crucial for health and life. Studies have shown that ω-3 fatty acids may facilitate human physiological functions. Mammals lack ω-3 desaturase gene, and the Δ15 fatty acid desaturase (Δ15 Des) from Caenorhabditis elegans can transform the ω-6 polyunsaturated fatty acids (PUFAs) into ω-3 PUFAs. Transgenic mice expressing Δ15 Des enzyme activity was constructed by using a PiggyBac transposon (PB). Homozygous transgenic mice with stable inheritance was bred in a short time, with a positive rate of 35.1% achieved. The mice were fed with 6% ω-6 PUFAs and the changes of fatty acids in mice were detected by gas chromatography (GC). The expression level of Δ15 Des in mice was detected by quantitative PCR (qPCR) and Western blotting (WB). qPCR and GC analysis revealed that the percentage of positive mice harboring the active gene was 61.53%. Compared with traditional methods, the transformation efficiency and activity of Δ15 Des were significantly improved, and homozygotes showed higher activity than that of heterozygotes. This further verified the efficient transduction efficiency of the PiggyBac transposon system.

Cloning and expression analysis of delta-12 fatty acid desaturase gene in Coix lacryma-jobi L / 药学学报

In this study, the fatty acid desaturase gene FAD2 was cloned from Coix lacryma-jobi L. and its molecular structure and function were studied. The results showed that the full-length cDNA sequence of FAD2 gene was 936 bp encoding 311 amino acid residues. Bioinformatics prediction results showed that the protein encoded by the FAD2 gene was an alkaline hydrophilic unstable protein with a molecular weight of 34.87 kDa. It contained three transmembrane helix domain, and did not contain the signal peptide splicing site, and was most likely to be located in plasmid membrane. Compared with other similar genes in plants, it has only a histidine conserved site, His Box Ⅲ histidine site (HXXHH), suggesting its activity may be reduced. Phylogenetic tree analysis showed that FAD2 was closely related to monocotyledonous plants, especially Maize and Oryza sativa japonica Group, but farther from dicotyledonous plants. Therefore, it was inferred that FAD2 might have similar functions with similar genes in Maize and Oryza sativa japonica Group. In addition, the expression of FAD2 gene could be detected in Coix lacryma-jobi L. with high oil content, but not in low oil content of Coix lacryma-jobi L. In order to clarify the function of FAD2, the gene was heterologously expressed in sporomyces cerevisiae. The results showed that the protein encoded by FAD2 gene did not catalyze the formation of C18∶1 unsaturated fatty acid into C18∶2 unsaturated fatty acid. Therefore, it was speculated that the deletion of histidinine conserved site of FAD2 gene might lead to the decrease of protein activity or even inactivation. This study provides reference value for further understanding the molecular structure characteristics of fatty acid desaturase. At the same time, it laid a foundation for elucidating the biosynthetic pathway of Coix lacryma-jobi L.

Analysis of the peanut transgenic offspring with depressing AhFAD2 gene / 生物工程学报

The delta-12 fatty acid desaturase (Δ¹² FAD or FAD2) is a key enzyme that catalyzes oleic acid to linoleic acid by dehydrogenation at Δ¹² position of fatty acid carbon chain. In peanut, reduction or loss of FAD2 activity could enhance the relative content of oleic acid in kernels, and improve the quality and oxidation stability of peanut kernels and products. RNA interference (RNAi) technology could lead to non-expression or down-regulated expression of AhFAD2 gene. We constructed two RNA interference expression vectors with the inverted repeat sequence of partial AhFAD2 gene, which were driven separately by cauliflower mosaic virus (CaMV) 35S promoter or soybean agglutinin lectin seed-specific promoter. Homozygous transgenic lines carrying the two constructs stably in genetics were developed by peanut genetic transformation. There were no significant differences between the transgenic lines and the control through investigating the main agronomic traits. We analyzed the transcriptional level expression of AhFAD2 gene in transgenic lines and the control by real-time fluorescence quantitative PCR (qRT-PCR). The results suggested that the target genes of transgenic lines were likely suppressed by RNA interference, but showed different transcriptional levels in different peanut transgenic lines. Compared with untransformed lines, the resulting down-regulation of AhFAD2 gene resulted in a 15.09% or 36.40% increase in oleic acid content in the seeds of transformed HY23 and FH1 lines respectively, and the content of linoleic acid decreased by 16.19% or 29.81%, correspondingly, the ratio of oleic acid and linoleic acid (O/L) improved by 38.02%, 98.10%. The oleic acid content had significant differences between the two transformation constructs, and also among different transgenic lines. Moreover, the inhibition effect of RNAi was more obvious in the transgenic lines with FH1 as the receptor, and with transformation structure driven by seed specific promoter. The suppressed expression of AhFAD2 gene enabled the development of peanut fatty acid, which indicated that RNA interference would be a reliable technique for the genetic modification of peanut seed quality and the potential for improvement of other traits as well.

Development and application of KASP marker for high throughput detection of AhFAD2 mutation in peanut

Background: Cultivated peanut (Arachis hypogaea L.) is a major oilseed crop worldwide. Fatty acid composition of peanut oil may affect the flavor and shelf life of the resulting food products. Oleic acid and linoleic acid are the major fatty acids of peanut oil. The conversion from oleic acid to linoleic acid is controlled by theΔ12 fatty acid desaturase (FAD) encoded byAhFAD2AandAhFAD2B, two homoeologous genes from A and B subgenomes, respectively. One nucleotide substitution (G:C→A:T) ofAhFAD2Aand an "A" insertion ofAhFAD2Bresulted in high-oleic acid phenotype. Detection ofAhFAD2mutation had been achieved by cleaved amplified polymorphic sequence (CAPS), real-time polymerase chain reaction (qRT-PCR) and allele-specific PCR (AS-PCR). However, a low cost, high throughput and high specific method is still required to detectAhFAD2genotype of large number of seeds. Kompetitive allele specific PCR (KASP) can detect both alleles in a single reaction. The aim of this work is to develop KASP for detectionAhFAD2genotype of large number of breeding materials. Results: Here, we developed a KASP method to detect the genotypes of progenies between high oleic acid peanut and common peanut. Validation was carried out by CAPS analysis. The results from KASP assay and CAPS analysis were consistent. The genotype of 18 out of 179 BC4F2seeds was aabb. Conclusions: Due to high accuracy, time saving, high throughput feature and low cost, KASP is more suitable fordeterminingAhFAD2genotype than other methods.

Fusion to Mistic improved fatty acid desaturase Fat-1 overexpression in E .coli / 重庆医学

Objective To construct a highly efficient expression plasmid of eukaryotic nuclear membrane protein Omega 3 fatty acid desaturase gene Fat‐1 in E .coli .Methods Using molecular cloning technology to construct the recombinant prokaryotic expression plasmid pET32a Fat‐1 and pET32a‐Mistic‐Fat‐1 fused with Membrane proteins expression chaperon mistic ;the two re‐combinant plasmids were transformed into E .coli strain BL21 (DE3) ,the expression of Fat‐1 protein and M110 Fat‐1 protein in‐duced by IPTG were identified by SDS‐PAGE and gray degree analysed the amount of expression ,further identified by Western blot .Results The results of enzyme digestion and sequencing demonstrated that we successfully constructed the prokaryotic ex‐pression vectors pET32a Fat‐1 and pET32a‐Mistic‐Fat‐1;SDS‐PAGE and Western blot showed that Fat‐1 fatty acid desaturase wasn′t significantly induced ,but the overexpression of M110 Fat‐1 fusion protein was obtained in E .coli ,accounting for 15% of the total amount of whole cell proteins .Conclusion The fusion with Mistic proteins to express the Fat‐1 gene has realized the overex‐pression of eukaryotic nuclear membrane integrated protein Omega 3 fatty acid desaturase in prokaryotic host .

Gene transfer of Chlorella vulgaris n-3 fatty acid desaturase optimizes the fatty acid composition of human breast cancer cells

Chlorella vulgaris has the gene of n-3 fatty acid desaturase (CvFad3), which can synthesize the precursor of n-3 polyunsaturated fatty acids (PUFAs) or convert n-6 to n-3 PUFAs. The objective of the present study was to examine whether the CvFad3 gene from C. vulgaris can be functionally and efficiently expressed in human breast cancer cells and whether its expression can exert a significant effect on cell fatty acid composition. We inserted the CvFad3 gene into the plasmid pEGFP-C3 to construct the eukaryotic expression vector pEGFP-C3-n-3 and to express the n-3 Fad gene in human breast cancer cells (MCF-7 cells). Transfection of MCF-7 cells with the recombinant vector resulted in a high expression of n-3 fatty acid desaturase. Lipid analysis indicated that the ratio of n-6/n-3 PUFAs was decreased from 6:1 in the control cells to about 1:1 in the cells expressing the n-3 fatty acid desaturase. Accordingly, the CvFad3 gene significantly decreased the ratio of n-6/n-3 PUFAs of the MCF-7 cell membrane. The expression of the CvFad3 gene can decrease cell proliferation and promote cell apoptosis. This study demonstrates that the CvFad3 gene can dramatically balance the ratio of n-6/n-3 PUFAs and may provide an effective approach to the modification of the fatty acid composition of mammalian cells, also providing a basis for potential applications of its transfer in experimental and clinical settings.

Transgenic Production of Polyunsaturated Fatty Acids in Mammalian Cells / 生物化学与生物物理进展

Linoleic acid (C18∶2n-6) and ?-linolenic acid (C18∶3n-3) are found widely in fungi, plants and some lower animals. However, they can not be synthesized in mammals due to lack of △12 and ?-3 fatty acid desaturases. To enable endogenous production of essential fatty acids in mammalian cells, here the stable expression of a Caenorhabditis elegans gene FAT-2 encoding △12 fatty acid desaturase in CHO cells was reported. First, the FAT-2 coding sequence was cloned by RT-PCR. To facilitate high level synthesis of heterogeneous protein, the codon usage of the fatty acid desaturase genes was optimized according to the codon preference of mouse by site-directed mutagenesis, 2 synonymous mutations were introduced into FAT-2 gene by overlapping PCR. The codon-modified gene was finally fused to pBudCE4.1 vector (Invitrogen) under the control of CMV promoter. The expression vector pBudCE-FAT2 was linearized with NheⅠ, and then transfected CHO cells, the cells were under Zeocin selection for nine days and then propagated, then the transfected cells were harvested. The genome and total RNA were isolated for PCR and Norhern blot ananlysis. The results revealed that FAT-2 gene has been integrated into the genome of CHO cells and expressed properly. Fatty acids of total cellular lipids were analyzed by gas chromatography. The results indicate that the expression and function of △-12 fatty acid desaturase resulted in accumulation of linoleic acid. The levels of linoleic acid in transgenic cells were 2.4-fold higher than those in wild-type cells. The moderate linoleic acid in CHO cells was derived from cell culture media uptaken by cell membrane. The results demonstrate that a heterogenous desaturase gene can function well in mammalian cells and prove that transgenic approach is an efficient strategy for changing fatty acid composition of mammals.