Hepatocyte-Specific Fads1 Overexpression Attenuates Western Diet-Induced Metabolic Phenotypes in a Rat Model.

Fatty acid desaturase 1 (FADS1) is a rate-limiting enzyme in long-chain polyunsaturated fatty acid (LCPUFA) synthesis. Reduced activity of FADS1 was observed in metabolic dysfunction-associated steatotic liver disease (MASLD). The aim of this study was to determine whether adeno-associated virus serotype 8 (AAV8) mediated hepatocyte-specific overexpression of Fads1 (AAV8-Fads1) attenuates western diet-induced metabolic phenotypes in a rat model. Male weanling Sprague-Dawley rats were fed with a chow diet, or low-fat high-fructose (LFHFr) or high-fat high-fructose diet (HFHFr) ad libitum for 8 weeks. Metabolic phenotypes were evaluated at the endpoint. AAV8-Fads1 injection restored hepatic FADS1 protein levels in both LFHFr and HFHFr-fed rats. While AAV8-Fads1 injection led to improved glucose tolerance and insulin signaling in LFHFr-fed rats, it significantly reduced plasma triglyceride (by ~50%) and hepatic cholesterol levels (by ~25%) in HFHFr-fed rats. Hepatic lipidomics analysis showed that FADS1 activity was rescued by AAV8-FADS1 in HFHFr-fed rats, as shown by the restored arachidonic acid (AA)/dihomo-γ-linolenic acid (DGLA) ratio, and that was associated with reduced monounsaturated fatty acid (MUFA). Our data suggest that the beneficial role of AAV8-Fads1 is likely mediated by the inhibition of fatty acid re-esterification. FADS1 is a promising therapeutic target for MASLD in a diet-dependent manner.

Knockout of the delta11-desaturase SfruDES1 disrupts sex pheromone biosynthesis, mating and oviposition in the fall armyworm, Spodoptera frugiperda.

Moth insects rely on sex pheromones for long distance attraction and searching for sex partners. The biosynthesis of moth sex pheromones involves the catalytic action of multiple enzymes, with desaturases playing a crucial role in the process of carbon chain desaturation. However, the specific desaturases involved in sex pheromone biosynthesis in fall armyworm (FAW), Spodoptera frugiperda, have not been clarified. In this study, a Δ11 desaturase (SfruDES1) gene in FAW was knocked out using the CRISPR/Cas9 genome editing system. A homozygous mutant of SfruDES1 was obtained through genetic crosses. The gas chromatography-mass spectrometry (GC-MS) analysis results showed that the three main sex pheromone components (Z7-12:Ac, Z9-14:Ac, and Z11-16:Ac) and the three minor components (Z9-14:Ald, E11-14:Ac and Z11-14:Ac) of FAW were not detected in homozygous mutant females compared to the wild type. Furthermore, behavioral assay demonstrated that the loss of SfruDES1 resulted in a significant reduction in the attractiveness of females to males, along with disruptions in mating behavior and oviposition. Additionally, in a heterologous expression system, recombinant SfruDES1 could introduce a cis double bond at the Δ11 position in palmitic acid, which resulted in the changes in components of the synthesized products. These findings suggest desaturase plays a key role in the biosynthesis of sex pheromones, and knockout of the SfruDES1 disrupts sex pheromone biosynthesis and mating behavior in FAW. The SfruDES1 could serve as tool to develop a control method for S. frugiperda.

Metabolic engineering of omega-3 long chain polyunsaturated fatty acids in plants using different ∆6- and ∆5-desaturases co-expressed with LPCAT from the marine diatom Phaeodactylum tricornutum.

Continuous research on obtaining an even more efficient production of very long-chain polyunsaturated fatty acids (VLC-PUFAs) in plants remains one of the main challenges of scientists working on plant lipids. Since crops are not able to produce these fatty acids due to the lack of necessary enzymes, genes encoding them must be introduced exogenously from native organisms producing VLC-PUFAs. In this study we reported, in tobacco leaves, the characterization of three distinct ∆6-desaturases from diatom Phaeodactylum tricornutum, fungi Rhizopus stolonifer and microalge Osterococcus tauri and two different ∆5-desaturases from P. tricornutum and single-celled saprotrophic eukaryotes Thraustochytrium sp. The in planta agroinfiltration of essential ∆6-desaturases, ∆6-elongases and ∆5-desaturases allowed for successful introduction of eicosapentaenoic acid (20:5∆5,8,11,14,17) biosynthesis pathway. However, despite the desired, targeted production of ω3-fatty acids we detected the presence of ω6-fatty acids, indicating and confirming previous results that all tested desaturases are not specifically restricted to neither ω3- nor ω6-pathway. Nevertheless, the additional co-expression of acyl-CoA:lysophosphatidylcholine acyltransferase (LPCAT) from Phaeodactylum tricornutum boosted the proportion of ω3-fatty acids in newly synthesized fatty acid pools. For the most promising genes combinations the EPA content reached at maximum 1.4% of total lipid content and 4.5% of all fatty acids accumulated in the TAG pool. Our results for the first time describe the role of LPCAT enzyme and its effectiveness in alleviating a bottleneck called 'substrate dichotomy' for improving the transgenic production of VLC-PUFAs in plants.

Targeted Knockdown of Hepatic Δ-5 Fatty Acid Desaturase FADS1 Aggravates Atherosclerosis in ApoE-/- Mice.

BACKGROUND: The endogenous metabolism of polyunsaturated fatty acids is regulated by the fatty acid desaturase (FADS) gene cluster and is strongly associated with diseases such as atherosclerosis, dyslipidemia, and type 2 diabetes. However, the association between FADS and atherosclerosis remains a subject of debate. METHODS: In this study, we specifically investigated the physiological role of Δ-5 fatty acid desaturase (FADS1) in aortic and peripheral vessel (namely, the femoral artery) atherosclerosis by targeting the selective knockdown of hepatic Fads1 in apolipoprotein E-null (ApoE-⁣/-) mice with antisense oligonucleotides (ASOs). RESULTS: Knockdown of hepatic Fads1 in ApoE-⁣/- mice exacerbated aortic atherosclerosis and non-alcoholic fatty liver disease (NAFLD), resulting in weight loss. Upregulation of FADS1 mRNA expression in more severe atherosclerosis vascular tissues potentially caused the upregulation of angiopoietin-like 4 expression. CONCLUSIONS: Our study demonstrated that knockdown of hepatic Fads1 in ApoE-⁣/- mice aggravates spontaneous atherosclerosis and NAFLD but does not affect peripheral atherosclerosis (femoral artery) induced by vascular cuff combined with tandem stenosis.

Impact of FADS genotype on polyunsaturated fatty acid content in human milk extracellular vesicles: A genetic association study.

BACKGROUND: Extracellular vesicles in human milk are critical in supporting newborn growth and development. Bioavailability of dietary extracellular vesicles may depend on the composition of membrane lipids. Single-nucleotide polymorphisms (SNPs) in the fatty acid desaturase gene cluster impact the content of long-chain polyunsaturated fatty acids in human milk phospholipids. This study investigated the relation between variation in FADS1 and FADS2 with the content of polyunsaturated fatty acids in extracellular vesicles from human milk. METHODS: Milk was obtained from a cohort of mothers (N = 70) at 2-4 weeks of lactation. SNPs in the FADS gene locus were determined using pyrosequencing for rs174546 in FADS1 and rs174575 in FADS2. Quantitative lipidomic analysis of polyunsaturated fatty acids in human milk and extracellular vesicles from human milk was completed by gas chromatography-mass spectrometry. RESULTS: The rs174546 and rs174575 genotypes were independent predictors of the arachidonic acid content in extracellular vesicles. The rs174546 genotype also predicted eicosapentaenoic acid and docosahexaenoic acid in extracellular vesicles. The reduced content of long-chain polyunsaturated fatty acids in extracellular vesicles in human milk may be due to lower fatty acid desaturase activity in mothers who are carriers of the A allele in rs174546 or the G allele in rs174575. CONCLUSION: The polyunsaturated fatty acid composition of milk extracellular vesicles is predicted by the FADS genotype. These findings yield novel insights regarding extracellular vesicle content and composition that can inform the design of future research to explore how lipid metabolites impact the bioavailability of human milk extracellular vesicles.

Characterization and Functional Analysis of Fads Reveals Δ5 Desaturation Activity during Long-Chain Polyunsaturated Fatty Acid Biosynthesis in Dwarf Surf Clam Mulinia lateralis.

Fatty acid desaturases (Fads), as key enzymes in the biosynthesis of long-chain polyunsaturated fatty acids (LC-PUFAs), catalyze the desaturation between defined carbons of fatty acyl chains and control the degree of unsaturation of fatty acids. In the present study, two Fads genes, designated MulFadsA and MulFadsB, were identified from the genome of the dwarf surf clam Mulinia lateralis (Mollusca, Mactridae), and their spatiotemporal expression was examined. MulFadsA and MulFadsB contained the corresponding conserved functional domains and clustered closely with their respective orthologs from other mollusks. Both genes were expressed in the developmental stages and all tested adult tissues of M. lateralis, with MulFadsA exhibiting significantly higher expression levels in adult tissues than MulFadsB. Subsequently, the effects of dietary microalgae on Fads expressions in the dwarf surf clam were investigated by feeding clams with two types of unialgal diets varying in fatty acid content, i.e., Chlorella pyrenoidosa (Cp) and Platymonas helgolandica (Ph). The results show that the expressions of MulFads were significantly upregulated among adult tissues in the Cp group compared with those in the Ph group. In addition, we observed the desaturation activity of MulFadsA via heterologous expression in yeasts, revealing Δ5 desaturation activity toward PUFA substrates. Taken together, these results provide a novel perspective on M. lateralis LC-PUFA biosynthesis, expanding our understanding of fatty acid synthesis in marine mollusks.

Identification of Conjugated Dienes of Fatty Acids in Vischeria sp. IPPAS C-70 under Oxidative Stress.

The microalgae Vischeria sp. IPPAS C-70 produces eicosapentaenoic acid. Several stresses cause the formation of fatty acid peaks that resemble hexadecadienoic acids. We used the integrated technique including TLC, HPLC, and GC-MS to search and determine these fatty acids. Double bond positioning in these fatty acids indicated that they were conjugated dienes and allenes. We identified and described natural nine isomers of C16 polyunsaturated fatty acids, including common methylene-interrupted dienes (Δ6,9-16:2, Δ7,10-16:2, Δ9,12-16:2), and unusual conjugated dienes (Δ6,8-, Δ7,9-, Δ8,10-, Δ9,11-, and Δ10,12-16:2), as well as allenic diene (Δ9,10-16:2). We hypothesize that the formation of conjugated dienes and allenes among fatty acids is the result of oxidative stress caused by H2O2. Hydrogen peroxide also caused an increase in saturated at the expense of unsaturated fatty acids, suggesting inhibition either fatty acid desaturases activities or the corresponding gene expression.

Maternal and Offspring Fatty Acid Desaturase Variants, Prenatal DHA Supplementation, and Dietary n-6:n-3 Fatty Acid Ratio in Relation to Cardiometabolic Health in Mexican Children.

BACKGROUND: Single-nucleotide polymorphisms (SNPs) in fatty acid desaturase (FADS) genes may modify dietary fatty acid requirements and influence cardiometabolic health (CMH). OBJECTIVES: We evaluated the role of selected variants in maternal and offspring FADS genes on offspring CMH at the age of 11 y and assessed interactions of genotype with diet quality and prenatal docosahexaenoic acid (DHA) supplementation. METHODS: We used data from offspring (n = 203) born to females who participated in a randomized controlled trial of DHA supplementation (400 mg/d) from midgestation to delivery. We generated a metabolic syndrome (MetS) score from body mass index, high-density lipoprotein cholesterol, triglycerides, systolic blood pressure, and fasting glucose and identified 6 distinct haplotypes from 5 offspring FADS SNPs. Dietary n-6 (ω-6):n-3 fatty acid ratios were derived from 24-h recall data (n = 141). We used generalized linear models to test associations of offspring diet and FADS haplotypes with MetS score and interactions of maternal and offspring FADS SNP rs174602 with prenatal treatment group and dietary n-6:n-3 ratio on MetS score. RESULTS: Associations between FADS haplotypes and MetS score were null. Offspring SNP rs174602 did not modify the association of prenatal DHA supplementation with MetS score. Among children with TT or TC genotype for SNP rs174602 (n = 88), those in the highest n-6:n-3 ratio tertile (>8.61) had higher MetS score relative to the lowest tertile [<6.67) (Δ= 0.36; 95% confidence interval (CI): 0.03, 0.69]. Among children with CC genotype (n = 53), those in the highest n-6:n-3 ratio tertile had a lower MetS score relative to the lowest tertile (Δ= -0.23; 95% CI: -0.61, 0.16). CONCLUSIONS: There was evidence of an interaction of offspring FADS SNP rs174602 with current dietary polyunsaturated fatty acid intake, but not with prenatal DHA supplementation, on MetS score. Further studies may help to determine the utility of targeted supplementation strategies and dietary recommendations based on genetic profile.

Brain tissue- and cell type-specific eQTL Mendelian randomization reveals efficacy of FADS1 and FADS2 on cognitive function.

Epidemiological studies suggested an association between omega-3 fatty acids and cognitive function. However, the causal role of the fatty acid desaturase (FADS) gene, which play a key role in regulating omega-3 fatty acids biosynthesis, on cognitive function is unclear. Hence, we used two-sample Mendelian randomization (MR) to estimate the gene-specific causal effect of omega-3 fatty acids (N = 114,999) on cognitive function (N = 300,486). Tissue- and cell type-specific effects of FADS1/FADS2 expression on cognitive function were estimated using brain tissue cis-expression quantitative trait loci (cis-eQTL) datasets (GTEx, N ≤ 209; MetaBrain, N ≤ 8,613) and single cell cis-eQTL data (N = 373), respectively. These causal effects were further evaluated in whole blood cis-eQTL data (N ≤ 31,684). A series of sensitivity analyses were conducted to validate MR assumptions. Leave-one-out MR showed a FADS gene-specific effect of omega-3 fatty acids on cognitive function [ß = -1.3 × 10-2, 95% confidence interval (CI) (-2.2 × 10-2, -5 × 10-3), P = 2 × 10-3]. Tissue-specific MR showed an effect of increased FADS1 expression in cerebellar hemisphere and FADS2 expression in nucleus accumbens basal ganglia on maintaining cognitive function, while decreased FADS1 expression in nine brain tissues on maintaining cognitive function [colocalization probability (PP.H4) ranged from 71.7% to 100.0%]. Cell type-specific MR showed decreased FADS1/FADS2 expression in oligodendrocyte was associated with maintaining cognitive function (PP.H4 = 82.3%, respectively). Increased FADS1/FADS2 expression in whole blood showed an effect on cognitive function maintenance (PP.H4 = 86.6% and 88.4%, respectively). This study revealed putative causal effect of FADS1/FADS2 expression in brain tissues and blood on cognitive function. These findings provided evidence to prioritize FADS gene as potential target gene for maintenance of cognitive function.

Fatty acid desaturase 1/2 (FADS1 and FADS2), fatty acid desaturase indices, and their relationships with metabolic syndrome in female adults with first-episode schizophrenia after antipsychotic medications.

OBJECTIVE: Although antipsychotics constitute the best treatment for patients with schizophrenia, this treatment class carries a high risk of metabolic disarrangements thus developing metabolic syndrome (MetS). Altered fatty acid (FA) composition and desaturase indices have been associated with several metabolic diseases, including MetS. Herein, we determined fatty acid desaturase 1 (FADS1) and FADS2 gene expressions, serum delta-5 desaturase (D5D) and D6D indices in female adults with first-episode schizophrenia after olanzapine medication, as well as their relationship with the incidence of MetS. METHODS: This study prospectively recruited 120 female patients with first-episode schizophrenia who completed 6-month olanzapine medication. Among these female patients, 31 patients developed MetS and 89 patients did not. RESULTS: The mRNA expression levels of FADS1 and FADS2 in patients were analyzed according to the presence of MetS and evaluation times with results of two-way ANOVAs (FADS1: PMetS = 0.0006, Ptime = 0.004, Pinteraction = 0.010; FADS2: PMetS = 0.012, Ptime < 0.0001, Pinteraction = 0.001). The D5D and D6D indices in patients were analyzed according to the presence of MetS and evaluation times with results of two-way ANOVAs (D5D: PMetS = 0.002, Ptime = 0.009, Pinteraction = 0.014; D6D: PMetS = 0.011, Ptime = 0.006, Pinteraction = 0.0001). The SCD-16 and SCD-18 indices in patients were analyzed according to the presence of MetS and evaluation times (SCD-16: PMetS = 0.005, Ptime = 0.009, Pinteraction = 0.016; SCD-18: PMetS = 0.037, Ptime = 0.382, Pinteraction = 0.163). The following multiple comparisons test showed the MetS exhibited reduced FADS1 mRNA expression and D5D index, increased FADS2 mRNA expression and D6D index, concomitant with an enhanced SCD-16 index, compared to the non-MetS did not after 6-month olanzapine medication. CONCLUSION: The study suggests changes of FADS1, FADS2 expressions, and fatty acid desaturase indices including D5D, D6D, and SCD-16 may be associated with the development of MetS in female adults with first-episode schizophrenia after olanzapine medication.

Loss of function and reduced levels of sphingolipid desaturase DEGS1 variants are both relevant in disease mechanism.

The last step of ex novo ceramide biosynthesis consists of the conversion of dihydroceramide into ceramide catalyzed by sphingolipid Δ4-desaturase DEGS1. DEGS1 variants were found to be responsible for heterogeneous clinical pictures belonging to the family of hypomyelinating leukodystrophies. To investigate the mechanisms making such variants pathogenic, we designed a procedure for the efficient detection of desaturase activity in vitro using LC-MS/MS and prepared a suitable cell model knocking out DEGS1 in HEK-293T cells through CRISPR-Cas9 genome editing (KO-DES-HEK). Transfecting KO-DES-HEK cells with DEGS1 variants, we found that their transcripts were all overexpressed as much as the WT transcripts, while the levels of cognate protein were 40%-80% lower. In vitro desaturase activity was lost by many variants except L175Q and N255S, which maintain a catalytic efficiency close to 12% of the WT enzyme. Metabolic labeling of KO-DES-HEK with deuterated palmitate followed by LC-MS/MS analysis of the formed sphingolipids revealed that the ceramide/dihydroceramide and sphingomyelin/dihydrosphingomyelin ratios were low and could be reverted by the overexpression of WT DEGS1 as well as of L175Q and N255S variants, but not by the overexpression of all other variants. Similar analyses performed on fibroblasts from a patient heterozygous for the N255S variant showed very low variant DEGS1 levels and a low ratio between the same unsaturated and saturated sphingolipids formed upon metabolic labeling, notwithstanding the residual activity measured at high substrate and homogenate protein concentrations. We conclude that loss of function and reduced protein levels are both relevant in disease pathogenesis.

Contiguous identity between entire coding regions of transgenic and native genes rather than special regions is essential for a strong co-suppression.

The discovery of co-suppression in plants has greatly boosted the study of gene silencing mechanisms, but its triggering mechanism has remained a mystery. In this study, we explored its possible trigger mechanism by using Fatty acid desaturase 2 (FAD2) and Fatty acid elongase 1 (FAE1) strong co-suppression systems. Analysis of small RNAs in FAD2 co-suppression lines showed that siRNAs distributed throughout the coding region of FAD2 with an accumulated peak. However, mutations of the peak siRNA-matched site and siRNA derived site had not alleviated the co-suppression of its transgenic lines. Synthetic FAD2 (AtFAD2sm), which has synonymous mutations in the entire coding region, failed to trigger any co-suppression. Furthermore, 5' and 3' portions of AtFAD2 and AtFAD2sm were swapped to form two hybrid genes, AtFAD2-3sm and AtFAD2-5sm. 80 % and 92 % of their transgenic lines exhibited co-suppression, respectively. Finally, FAE1s with different degrees of the continuous sequence identity compared with AtFAE1 were tested in their Arabidopsis transgenic lines, and the results showed the co-suppression frequency was reduced as their continuous sequence identity stepped down. This work suggests that contiguous identity between the entire coding regions of transgenic and native genes rather than a special region is essential for a strong co-suppression.

A mutation in CsDWF7 gene encoding a delta7 sterol C-5(6) desaturase leads to the phenotype of super compact in cucumber (Cucumis sativus L.).

KEY MESSAGE: A novel super compact mutant, scp-3, was identified using map-based cloning in cucumber. The CsDWF7 gene encoding a delta7 sterol C-5(6) desaturase was the candidate gene of scp-3. Mining dwarf genes is important in understanding stem growth in crops. However, only a small number of dwarf genes have been cloned or characterized. Here, we characterized a cucumber (Cucumis sativus L.) dwarf mutant, super compact 3 (scp-3), which displays shortened internodes and dark green leaves with a wrinkled appearance. The photosynthetic rate of scp-3 is significantly lower than that of the wild type. The dwarf phenotype of scp-3 mutant can be partially rescued by the exogenous brassinolide (BL) application, and the endogenous brassinosteroids (BRs) levels in the scp-3 mutant were significantly lower compared to the wild type. Microscopic examination revealed that the reduced internode length in scp-3 resulted from a decrease in cell size. Genetic analysis showed that the dwarf phenotype of scp-3 was controlled by a single recessive gene. Combined with bulked segregant analysis and map-based cloning strategy, we delimited scp-3 locus into an 82.5 kb region harboring five putative genes, but only one non-synonymous mutation (A to T) was discovered between the mutant and its wild type in this region. This mutation occurred within the second exon of the CsGy4G017510 gene, leading to an amino acid alteration from Leu156 to His156. This gene encodes the CsDWF7 protein, an analog of the Arabidopsis DWF7 protein, which is known to be involved in the biosynthesis of BRs. The CsDWF7 protein was targeted to the cell membrane. In comparison to the wild type, scp-3 exhibited reduced CsDWF7 expression in different tissues. These findings imply that CsDWF7 is essential for both BR biosynthesis as well as growth and development of cucumber plants.

Association of the Arabidopsis oleoyl Δ12-desaturase FAD2 with pre-cis-Golgi stacks at endoplasmic reticulum-Golgi-exit sites.

The unsaturation of phospholipids influences the function of membranes. In Arabidopsis thaliana, the oleoyl Δ12-desaturase FAD2 converts oleic (18:1Δ9 ) to linoleic acid (18:2Δ9,12 ) and influences phospholipid unsaturation in different cellular membranes. Despite its importance, the precise localization of Arabidopsis FAD2 has not been unambiguously described. As FAD2 is thought to modify phospholipid-associated fatty acids at the endoplasmic reticulum (ER), from where unsaturates are distributed to other cellular sites, we hypothesized that FAD2 locates to ER subdomains enabling trafficking of lipid intermediates through the secretory pathway. Fluorescent FAD2 fusions used to test this hypothesis were first assessed for functionality by heterologous expression in yeast (Saccharomyces cerevisiae), and in planta by Arabidopsis fad2 mutant rescue upon ectopic expression from an intrinsic FAD2 promoter fragment. Light sheet fluorescence, laser scanning confocal or spinning disc microscopy of roots, leaves, or mesophyll protoplasts showed the functional fluorescence-tagged FAD2 variants in flattened donut-shaped structures of ~0.5-1 µm diameter, in a pattern not resembling mere ER association. High-resolution imaging of coexpressed organellar markers showed fluorescence-tagged FAD2 in a ring-shaped pattern surrounding ER-proximal Golgi particles, colocalizing with pre-cis-Golgi markers. This localization required the unusual C-terminal retention signal of FAD2, and deletion or substitutions in this protein region resulted in relaxed distribution and diffuse association with the ER. The distinct association of FAD2 with pre-cis-Golgi stacks in Arabidopsis root and leaf tissue is consistent with a contribution of FAD2 to membrane lipid homeostasis through the secretory pathway, as verified by an increased plasma membrane liquid phase order in the fad2 mutant.

Protein concentrations and activities of fatty acid desaturase and elongase enzymes in liver, brain, testicle, and kidney from mice: Substrate dependency.

The synthesis rates of n-3 and n-6 polyunsaturated fatty acids (PUFAs) in rodents and humans are not agreed upon and depend on substrate availability independently of the capacity for synthesis. Therefore, we aimed to assess the activities of the enzymes for n-3 and n-6 PUFA synthesis pathways in liver, brain, testicle, kidney, heart, and lung, in relation to their protein concentration levels. Eight-week-old Balb/c mice (n = 8) were fed a standard chow diet (6.2% fat, 18.6% protein, and 44.2% carbohydrates) until 14 weeks of age, anesthetized with isoflurane and tissue samples were collected (previously perfused) and stored at -80°C. The protein concentration of the enzymes (Δ-6D, Δ-5D, Elovl2, and Elovl5) were assessed by ELISA kits; their activities were assayed using specific PUFA precursors and measuring the respective PUFA products as fatty acid methyl esters by gas chromatographic analysis. The liver had the highest capacity for PUFA biosynthesis, with limited activity in the brain, testicles, and kidney, while we failed to detect activity in the heart and lung. The protein concentration and activity of the enzymes were significantly correlated. Furthermore, Δ-6D, Δ-5D, and Elovl2 have a higher affinity for n-3 PUFA precursors compared to n-6 PUFA. The capacity for PUFA synthesis in mice mainly resides in the liver, with enzymes having preference for n-3 PUFAs.

The influence of first desaturase subfamily genes on fatty acid synthesis, desiccation tolerance and inter-caste nutrient transfer in the termite Coptotermes formosanus.

Desaturase enzymes play an essential role in the biosynthesis of unsaturated fatty acids (UFAs). In this study, we identified seven "first desaturase" subfamily genes (Cfor-desatA1, Cfor-desatA2-a, Cfor-desatA2-b, Cfor-desatB-a, Cfor-desatB-b, Cfor-desatD and Cfor-desatE) from the Formosan subterranean termite Coptotermes formosanus. These desaturases were highly expressed in the cuticle and fat body of C. formosanus. Inhibition of either the Cfor-desatA2-a or Cfor-desatA2-b gene resulted in a significant decrease in the contents of fatty acids (C16:0, C18:0, C18:1 and C18:2) in worker castes. Moreover, we observed that inhibition of most of desaturase genes identified in this study had a negative impact on the survival rate and desiccation tolerance of workers. Interestingly, when normal soldiers were reared together with dsCfor-desatA2-b-treated workers, they exhibited higher mortality, suggesting that desaturase had an impact on trophallaxis among C. formosanus castes. Our findings shed light on the novel roles of desaturase family genes in the eusocial termite C. formosanus.

Exogenous alpha-linolenic acid and Vibrio parahaemolyticus induce EPA and DHA levels mediated by delta-6 desaturase to enhance shrimp immunity.

Globally, penaeid shrimp are the most farmed and traded aquatic organisms, although they are easily susceptible to microbial pathogens. Moreover, there is a desire to increase the nutritional value of shrimp, especially the levels of n-3 polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which also possess immunomodulatory and anti-inflammatory properties. Some aquatic animals can synthesize EPA and DHA from dietary plant-sourced alpha-linolenic acid (ALA), but penaeid shrimps' ability to synthesize these n-3 PUFAs is unknown. Here, molecular biology techniques, including gas chromatography-mass spectrometry, qPCR, ELISA, etc., were used to demonstrate that exogenous ALA or Vibrio parahaemolyticus could modulate EPA and DHA levels and immune genes in Penaeus vannamei by inducing key enzymes involved in n-3 PUFAs biosynthesis, such as delta desaturases and elongation of very long-chain fatty acid (ELOVLs). Most importantly, knockdown or inhibition of ∆6 desaturase significantly decreased EPA and DHA levels and immune gene expression even with exogenous ALA treatment, consequently affecting shrimp antibacterial immunity and survival. This study provides new insight into the potential of P. vannamei to synthesize n-3 PUFAs from exogenous ALA or upon bacteria challenge, which could be leveraged to increase their nutritional content and antimicrobial immunity.

Engineering the synthesis of unsaturated fatty acids by introducing desaturase improved the stress tolerance of yeast.

BACKGROUND: Yeast is often used to build cell factories to produce various chemicals or nutrient substances, which means the yeast has to encounter stressful environments. Previous research reported that unsaturated fatty acids were closely related to yeast stress resistance. Engineering unsaturated fatty acids may be a viable strategy for enhancing the stress resistance of cells. RESULTS: In this study, two desaturase genes, OLE1 and FAD2 from Z. rouxii, were overexpressed in S. cerevisiae to determine how unsaturated fatty acids affect cellular stress tolerance of cells. After cloning and plasmid recombination, the recombinant S. cerevisiae cells were constructed. Analysis of membrane fatty acid contents revealed that the recombinant S. cerevisiae with overexpression of OLE1 and FAD2 genes contained higher levels of fatty acids C16:1 (2.77 times), C18:1 (1.51 times) and C18:2 (4.15 times) than the wild-type S. cerevisiae pY15TEF1. In addition, recombinant S. cerevisiae cells were more resistant to multiple stresses, and exhibited improved membrane functionality, including membrane fluidity and integrity. CONCLUSION: These findings demonstrated that strengthening the expression of desaturases was beneficial to stress tolerance. Overall, this study may provide a suitable means to build a cell factory of industrial yeast cells with high tolerance during biological manufacturing. © 2023 Society of Chemical Industry.

Loss of function mutations at the tomato SSI2 locus impair plant growth and development by altering the fatty acid desaturation pathway.

The stearoyl-ACP desaturase (SACPD) is a key enzyme in the regulation of saturated to unsaturated fatty acid ratio, playing a crucial role in regulating membrane stability and fluidity, as well as photosynthesis efficiency, which makes it an important research focus in crop species. This study reports the characterization and molecular cloning of pale dwarf (pad), a new tomato (Solanum lycopersicum L.) T-DNA recessive mutant, which exhibits a dwarf and chlorotic phenotype. Functional studies of the T-DNA tagged gene were conducted, including phylogenetic analysis, expression and metabolomic analyses, and generation of CRISPR/Cas9 knockout lines. The cloning of T-DNA flanking genomic sequences and a co-segregation analysis found the pad phenotype was caused by a T-DNA insertion disrupting the tomato homologue of the Arabidopsis SUPPRESSOR OF SALICYLIC ACID INSENSITIVITY 2 (SlSSI2), encoding a plastid localized isoform of SACPD. The phenotype of CRISPR/Cas9 SlSSI2 knockout lines confirmed that the morphological abnormalities in pad plants were due to SlSSI2 loss of function. Functional, metabolomic and expression analyses proved that SlSSI2 disruption causes deficiencies in 18:1 fatty acid desaturation and leads to diminished jasmonic acid (JA) content and increased salicylic acid (SA) levels. Overall, these results proved that SSI2 plays a crucial role in the regulation of polyunsaturated fatty acid profiles in tomato, and revealed that SlSSI2 loss of function results in an inhibited JA-responsive signalling pathway and a constitutively activated SA-mediated defence signalling response. This study lays the foundation for further research on tomato SACPDs and their role in plant performance and fitness.

A Horizontally Transferred Plant Fatty Acid Desaturase Gene Steers Whitefly Reproduction.

Polyunsaturated fatty acids (PUFAs) are essential nutrients for all living organisms. PUFA synthesis is mediated by Δ12 desaturases in plants and microorganisms, whereas animals usually obtain PUFAs through their diet. The whitefly Bemisia tabaci is an extremely polyphagous agricultural pest that feeds on phloem sap of many plants that do not always provide them with sufficient PUFAs. Here, a plant-derived Δ12 desaturase gene family BtFAD2 is characterized in B. tabaci and it shows that the BtFAD2-9 gene enables the pest to synthesize PUFAs, thereby significantly enhancing its fecundity. The role of BtFAD2-9 in reproduction is further confirmed by transferring the gene to Drosophila melanogaster, which also increases the fruit fly's reproduction. These findings reveal an extraordinary evolutionary scenario whereby a phytophagous insect acquired a family of plant genes that enables it to synthesize essential nutrients, thereby lessening its nutritional dependency and allowing it to feed and reproduce on many host plants.