Fatty Acid Desaturase Gene Family Research Articles

Transcriptional Analysis of Different Cultivars and Genome-Wide Identification of FAD Gene Family in Tree Peony

The tree peony (Paeonia ostii), a newly recognized woody oil plant endemic to China, is noteworthy for its high content of unsaturated fatty acids (UFA), particularly alpha-linolenic acid (ALA). Fatty acid desaturases (FADs) are integral to plant development and defense mechanisms. Nonetheless, there is limited understanding of (i) the molecular mechanism underlying FA biosynthesis in various varieties during seed maturation and (ii) a genome-wide analysis of FAD family genes within the tree peony. We selected three distinct cultivars of tree peony for transcriptome sequencing and performed an extensive analysis of PoFAD genes. In total, 67,542 unigenes were acquired and annotated with six protein databases available to the public. Forty-one differentially expressed genes (DEGs) pertinent to FA biosynthesis and lipid metabolism were identified in this study. Notably, genes such as PoFAD2, PoFAD6, and PoSAD were found to be significantly upregulated, contributing to a differential linolenic acid and linoleic acid content across the three cultivars. Herein, 24 PoFADs from the P. ostii genome were recognized and categorized into four distinct clusters according to their conserved structural features. The distribution of PoFADs was found to be random and uneven across five chromosomes, indicating a complex genomic architecture. Six colinear gene pairs were found between P. ostii and V. vinifera, indicating a potential link due to their close relationship. Together, these findings significantly enhance our knowledge of the molecular processes governing fatty acid synthesis, elucidate the functional roles of the FAD gene family, and lay the groundwork for using genetic manipulation to boost lipid levels.

Genome-wide analysis of fatty acid desaturase (FAD) gene family in Camellia sinensis: Identification, expression and their biochemical functions in low temperature resistance

Fatty acid desaturase (FAD) is critical for unsaturated fatty acids (UFAs) biosynthesis and plays crucial roles in plants' response to low temperature. Nevertheless, a comprehensive genomic analysis of the FAD gene family in Camellia sinensis remain unreported. This study employed bioinformatics to identify 17 CsFAD genes, which are unequally distributed across 9 chromosomes. CsFAD proteins are localized to chloroplasts and/or endoplasmic reticulum (ER) by subcellular localization predictions. Phylogenetic categorization divides CsFADs into six subfamilies. The cis-elements are related to hormonal regulation and adversity response. Additionally, differential expression patterns of CsFADs across various tissues were observed. qRT-PCR analysis revealed a marked upregulation in the expression of CsSLD3 and CsSLD4 (encoding sphingolipid Δ8 desaturase) under cold stress conditions. Moreover, subcellular localization assays in tobacco leaves confirmed the presence of CsSLD3 and CsSLD4 within ER. Yeast heterologous expression demonstrated the capacity of CsSLD3/4 to transform ceramide(t18:0) into ceramide(t18:1), and overexpression of CsSLD3/4 enhanced yeast tolerance to low temperature. Thus, this comprehensive analysis of the CsFAD gene family furnishes a robust foundation for future study into the biological functions of CsFAD genes, and offers a profound insight into their regulatory roles in stress resilience.

Comparative Genome-Wide Identification of the Fatty Acid Desaturase Gene Family in Tea and Oil Tea.

Camellia oil is valuable as an edible oil and serves as a base material for a range of high-value products. Camellia plants of significant economic importance, such as Camellia sinensis and Camellia oleifera, have been classified into sect. Thea and sect. Oleifera, respectively. Fatty acid desaturases play a crucial role in catalyzing the formation of double bonds at specific positions of fatty acid chains, leading to the production of unsaturated fatty acids and contributing to lipid synthesis. Comparative genomics results have revealed that expanded gene families in oil tea are enriched in functions related to lipid, fatty acid, and seed processes. To explore the function of the FAD gene family, a total of 82 FAD genes were identified in tea and oil tea. Transcriptome data showed the differential expression of the FAD gene family in mature seeds of tea tree and oil tea tree. Furthermore, the structural analysis and clustering of FAD proteins provided insights for the further exploration of the function of the FAD gene family and its role in lipid synthesis. Overall, these findings shed light on the role of the FAD gene family in Camellia plants and their involvement in lipid metabolism, as well as provide a reference for understanding their function in oil synthesis.

Genome-wide identification and characterization of FAD family genes in barley.

Fatty acid desaturases (FADs) play pivotal roles in determining plant stress tolerance. Barley is the most salt-tolerant cereal crop. In this study, we performed genome-wide identification and characterization analysis of the FAD gene family in barley (Hordeum vulgare). A total of 24 HvFADs were identified and divided into four subfamilies based on their amino acid sequence similarity. HvFADs unevenly distributed on six of seven barley chromosomes, and three clusters of HvFADs mainly occurred on the chromosome 2, 3 and 6. Segmental duplication events were found to be a main cause for the HvFAD gene family expansion. The same HvFAD subfamily showed the relatively consistent exon-intron composition and conserved motifs of HvFADs. Cis-element analysis in HvFAD promoters indicated that the expression of HvFADs may be subject to complex regulation, especially stress-responsive elements that may involve in saline-alkaline stress response. Combined transcriptomic data with quantitative experiments, at least five HvFADs highly expressed in roots under salt or alkali treatment, suggesting they may participate in saline or alkaline tolerance in barley. This study provides novel and valuable insights for underlying salt/alkali-tolerant mechanisms in barley.

Genome-Wide Characterization of Tomato FAD Gene Family and Expression Analysis under Abiotic Stresses.

The fatty acid desaturase (FAD) gene family plays a crucial regulatory role in the resistance process of plant biomembranes. To understand the role of FADs in tomato growth and development, this study identified and analyzed the tomato FAD gene family based on bioinformatics analysis methods. In this study, 26 SlFADs were unevenly distributed on 10 chromosomes. Phylogenetic analysis showed that the SlFAD gene family was divided into six branches, and the exon-intron composition and conserved motifs of SlFADs clustered in the same branch were quite conservative. Several hormone and stress response elements in the SlFAD promoter suggest that the expression of SlFAD members is subject to complex regulation; the construction of a tomato FAD protein interaction network found that SlFAD proteins have apparent synergistic effects with SPA and GPAT proteins. qRT-PCR verification results show that SlFAD participates in the expression of tomato root, stem, and leaf tissues; SlFAD8 is mainly highly expressed in leaves; SlFAD9 plays a vital role in response to salt stress; and SlFAB5 regulates all stages of fruit development under the action of exogenous hormones. In summary, this study provides a basis for a systematic understanding of the SlFAD gene family. It provides a theoretical basis for in-depth research on the functional characteristics of tomato SlFAD genes.

Analysis of Delta(9) fatty acid desaturase gene family and their role in oleic acid accumulation in Carya cathayensis kernel.

Carya cathayensis, commonly referred to as Chinese hickory, produces nuts that contain high-quality edible oils, particularly oleic acid (18:1). It is known that stearoyl-ACP desaturase (SAD) is the first key step converting stearic acid (C18:0, SA) to oleic acid (C18:1, OA) in the aminolevulinic acid (ALA) biosynthetic pathway and play an important role in OA accumulation. Thus far, there is little information about SAD gene family in C. cathayensis and the role of individual members in OA accumulation. This study searched the Chinese Hickory Genome Database and identified five members of SAD genes, designated as CcSADs, at the whole genome level through the comparison with the homologous genes from Arabidopsis. RNA-Seq analysis showed that CcSSI2-1, CcSSI2-2, and CcSAD6 were highly expressed in kernels. The expression pattern of CcSADs was significantly correlated with fatty acid accumulation during the kernel development. In addition, five full-length cDNAs encoding SADs were isolated from the developing kernel of C. cathayensis. CcSADs-green fluorescent protein (GFP) fusion construct was infiltrated into tobacco epidermal cells, and results indicated their chloroplast localization. The catalytic function of these CcSADs was further analyzed by heterologous expression in Saccharomyces cerevisiae, Nicotiana benthamiana, and walnut. Functional analysis demonstrated that all CcSADs had fatty acid desaturase activity to catalyze oleic acid biosynthesis. Some members of CcSADs also have strong substrate specificity for 16:0-ACP to synthesize palmitoleic acid (C16:1, PA). Our study documented SAD gene family in C. cathayensis and the role of CcSSI2-1, CcSSI2-2, and CcSAD6 in OA accumulation, which could be important for future improvement of OA content in this species via genetic manipulation.

Genome-wide identification and characterization of the fatty acid desaturase gene family in Vanilla planifolia

• We identify and characterize 18 FAD genes in the Vanilla planifolia genome. • FAD expression differs between different plant tissues and development stages. • Some VpFAD genes were found to participate in the interaction between Vanilla planifolia and Fusarium oxysporium . Fatty acid desaturase (FAD) plays an essential role in plants; however, FAD genes have not previously been characterized in orchids. Vanilla planifolia is a valuable natural spice in the family Orchidaceae. In this study, we identified 18 FAD genes in this species and analyzed their protein characteristics, chromosome distribution, phylogeny, gene structure, and conserved motifs. Transcriptome data analysis showed that the 18 genes showed different expression patterns in six tissues (seed, placental laminae, mesocarp, hair, stem, and leaf) and various stages of seed development (6 weeks, 8 weeks, 10 weeks, 3 months, 5 months, and 6 months). In addition, the expression profile of infected Fusarium oxysporum indicated that the FAD genes play an essential role in dealing with pathogen invasion. This study provides a comprehensive understanding of the FAD family in Vanilla planifolia as well as information on pathogen immunity, which can provide a reference for further functional research.

Genome-Wide Characterization and Expression Analysis of Fatty acid Desaturase Gene Family in Poplar.

Fatty acid desaturases (FADs) modulate carbon–carbon single bonds to form carbon–carbon double bonds in acyl chains, leading to unsaturated fatty acids (UFAs) that have vital roles in plant growth and development and their response to environmental stresses. In this study, a total of 23 Populus trichocarpa FAD (PtFAD) candidates were identified from the poplar genome and clustered into seven clades, including FAB2, FAD2, FAD3/7/8, FAD5, FAD6, DSD, and SLD. The exon–intron compositions and conserved motifs of the PtFADs, clustered into the same clade, were considerably conserved. It was found that segmental duplication events are predominantly attributable to the PtFAD gene family expansion. Several hormone- and stress-responsive elements in the PtFAD promoters implied that the expression of the PtFAD members was complicatedly regulated. A gene expression pattern analysis revealed that some PtFAD mRNA levels were significantly induced by abiotic stress. An interaction proteins and gene ontology (GO) analysis indicated that the PtFADs are closely associated with the UFAs biosynthesis. In addition, the UFA contents in poplars were significantly changed under drought and salt stresses, especially the ratio of linoleic and linolenic acids. The integration of the PtFAD expression patterns and UFA contents showed that the abiotic stress-induced PtFAD3/7/8 members mediating the conversion of linoleic and linolenic acids play vital roles in response to osmotic stress. This study highlights the profiles and functions of the PtFADs and identifies some valuable genes for forest improvements.

Genome-wide identification of FAD gene family and their contributions to the temperature stresses and mutualistic and parasitic fungi colonization responses in banana

Fatty acid desaturase (FAD) plays important roles in plant growth and development and plant defense processes. In this study, we identified 27 MaFAD genes from the banana genome. According to the amino acid sequence similarities, their encoded proteins could be classified into five subfamilies. This classification is consistently supported by their gene and protein structures, conserved motifs and subcellular localizations. Segmental duplication events were found to play predominant roles in the MaFAD gene family expansion. Thirty miRNAs targeting MaFADs were identified and many hormone- and stress-responsive cis-acting elements and transcription factor binding sites (TFBSs) were identified in their promoters, indicating that the MaFADs expression regulation was very complicated. Gene expression analysis showed that some MaFADs showed significant differential expression in response to high and low temperature. FocTR4 influenced greatly the expression of several MaFADs and greatly induced the fatty acid (FA) accumulations in roots. Although S. indica showed no significant influence on the expression of most MaFADs, it could greatly alleviate the influence of FocTR4 on several MaFADs and FA biosynthesis. Our study revealed that MaFADs contributed greatly to the responses of high and low temperature stresses and mutualistic and parasitic fungi colonization in banana.

Genome-Wide Analysis of the Fatty Acid Desaturase Gene Family Reveals the Key Role of PfFAD3 in α-Linolenic Acid Biosynthesis in Perilla Seeds.

Perilla (Perilla frutescens), a traditional medicinal and oilseed crop in Asia, contains extremely high levels of polyunsaturated α-linolenic acid (ALA) (up to 60.9%) in its seeds. ALA biosynthesis is a multistep process catalyzed by fatty acid desaturases (FADs), but the FAD gene family in perilla has not been systematically characterized. Here, we identified 42 PfFADs in the perilla genome and classified them into five subfamilies. Subfamily members of PfFADs had similar exon/intron structures, conserved domain sequences, subcellular localizations, and cis-regulatory elements in their promoter regions. PfFADs also possessed various expression patterns. PfFAD3.1 was highly expressed in the middle stage of seed development, whereas PfFAD7/8.3 and PfFAD7/8.5 were highly expressed in leaf and later stages of seed development, respectively. Phylogenetic analysis revealed that the evolutionary features coincided with the functionalization of different subfamilies of PUFA desaturase. Heterologous overexpression of PfFAD3.1 in Arabidopsis thaliana seeds increased ALA content by 17.68%–37.03%. These findings provided insights into the characteristics and functions of PfFAD genes in perilla.

Based on the whole genome clarified the evolution and expression process of fatty acid desaturase genes in three soybeans

Soybean is an important oil crop cultivated worldwide. With the increasing global population crossed with growing challenging cultivation conditions, improving soybean breeding by selecting important traits is urgent needed. Genes coding for plant fatty acid desaturases (FADs) genes are major candidates for that, because they are involving in controlling fatty acid composition and holding membrane fluidity under abiotic stress. Here, 75 FADs were found in three soybean genomes, which were further classified into four sub-groups. Phylogenetic tree, gene structure, motif and promoter analysis showed that the FAD gene family was conserved in the three soybeans. In addition, the numbers of omega desaturase from Chinese cultivated varieties were significantly higher than those in Chinese wild soybean and ancient polyploid soybean, respectively. However, it was the opposite for the sphingolipid subfamily. These results indicated that each subfamily was subjected to different selection pressures during cultivation and domestication. As the extra genes of the subfamily were very close to other family members' positions on chromosomes, they should be produced by duplication. The cis-element analysis of FAD promoter sequences revealed that upstream sequences of FAD contained abundant light, hormone and abiotic stress responsive cis-elements, suggesting that the quality of soybean could be improved by regulating these stresses. Expression analysis of Chinese wild soybean under salt stress showed that GsDES1.1, GsDES1.2, GsFAD2.1 and GsSLD1 in leaves and GsSLD2, GsSLD5 and GsSLD6 in roots were not closely related to salt stress response. Therefore, we explored the significant role of conserved, duplicated and neofunctionalized FAD in the domestication of soybean, which contributes to the importance of soybean as a global oil crop.

Evolution of the codling moth pheromone via an ancient gene duplication

BackgroundDefining the origin of genetic novelty is central to our understanding of the evolution of novel traits. Diversification among fatty acid desaturase (FAD) genes has played a fundamental role in the introduction of structural variation in fatty acyl derivatives. Because of its central role in generating diversity in insect semiochemicals, the FAD gene family has become a model to study how gene family expansions can contribute to the evolution of lineage-specific innovations. Here we used the codling moth (Cydia pomonella) as a study system to decipher the proximate mechanism underlying the production of the ∆8∆10 signature structure of olethreutine moths. Biosynthesis of the codling moth sex pheromone, (E8,E10)-dodecadienol (codlemone), involves two consecutive desaturation steps, the first of which is unusual in that it generates an E9 unsaturation. The second step is also atypical: it generates a conjugated diene system from the E9 monoene C12 intermediate via 1,4-desaturation.ResultsHere we describe the characterization of the FAD gene acting in codlemone biosynthesis. We identify 27 FAD genes corresponding to the various functional classes identified in insects and Lepidoptera. These genes are distributed across the C. pomonella genome in tandem arrays or isolated genes, indicating that the FAD repertoire consists of both ancient and recent duplications and expansions. Using transcriptomics, we show large divergence in expression domains: some genes appear ubiquitously expressed across tissue and developmental stages; others appear more restricted in their expression pattern. Functional assays using heterologous expression systems reveal that one gene, Cpo_CPRQ, which is prominently and exclusively expressed in the female pheromone gland, encodes an FAD that possesses both E9 and ∆8∆10 desaturation activities. Phylogenetically, Cpo_CPRQ clusters within the Lepidoptera-specific ∆10/∆11 clade of FADs, a classic reservoir of unusual desaturase activities in moths.ConclusionsOur integrative approach shows that the evolution of the signature pheromone structure of olethreutine moths relied on a gene belonging to an ancient gene expansion. Members of other expanded FAD subfamilies do not appear to play a role in chemical communication. This advises for caution when postulating the consequences of lineage-specific expansions based on genomics alone.

Genome-wide characterization and expression analysis of fatty acid desaturase gene family in Camelina sativa

Camelina is a flexible crop with several positive properties such as resistant to adverse environmental conditions, high potential for biodiesel production that make it distinctive among oilseed crops. Fatty acid desaturases (FADs) play a crucial role in regulating FA compositions, but there are no well characteristics and comprehensive genome-wide study of the FAD gene family in Camelina sativa. An exhaustive analysis was fulfilled to identify the FAD genes from Camelina sativa genome and described their phylogenetic relationship, the conserved motifs and histidine boxes, expression profile, co-expression analysis, physical and chemical properties, prediction of post-translation modifications and promoter analysis. In the present study, 24 desaturase genes were identified from Camelina sativa genome. The conserved histidine boxes were observed at deduced FAD proteins with various sequences, the four histidine boxes were figured out at omega desaturase genes, and it seems that the conserved histidine box, HHHGH, was detected for the first time. Also, three SAD genes were identified in camelina genome. Moreover, the result of the expression profile revealed that FAD genes have the tissue-specific expression pattern and diverse function in response to adverse conditions. In addition, 55 genes with high expression correlation were identified as co-expression genes with FAD genes in camelina. Besides, the studied FAD proteins varied based on predicted phosphorylation and N-glycosylation site. For instance, LOC104699734 protein showed the highest N-glycosylation site, while the LOC104765502, LOC104776214, LOC104734563, and LOC104745425 had the highest predicted phosphorylation sites. This study was the first report that widely analyzes the FAD gene family in the genome of Camelina sativa using available bioinformatics tools that will be used in future functional analyses related to molecular mechanisms of FAD genes in camelina.

Identification and analysis of the FAD gene family in walnuts (Juglans regia L.) based on transcriptome data

BackgroundWalnut kernels contain a large amount of unsaturated fatty acids, such as linoleic acid and linolenic acid, which are essential fatty acids for humans and have important effects on growth and health. The main function of fatty acid desaturase (FAD), which is widely distributed in organisms, is to remove hydrogen from carbon chains in the biosynthesis of unsaturated fatty acids to generate C=C bonds.ResultsBy performing a series of bioinformatics analysis, 24 members of the JrFAD gene family were identified from the genome database of walnut, and then compared with the homologous genes from Arabidopsis. Phylogenetic analysis showed that JrFADs were classified into four subfamilies: the SAD desaturase subfamily, Δ7/Δ9 desaturase subfamily, Δ12/ω-3 desaturase subfamily and “front-end” desaturase subfamily. Meanwhile, the expression of fatty acid synthesis genes in walnut kernels at different developmental stages was analysed by transcriptome sequencing, with expression of JrFAD3-1, which encodes an enzyme involved in linolenic acid synthesis, being particularly prominent. The relative expression level of JrFAD3-1 changed dramatically with the kernel development stages and exhibited a Bell-Shaped Curve. A significant positive correlation was observed between the expression of JrFAD3-1 during 70–100 DAF (Days after flowering) and the content of alpha-linolenic acid during 100–130 DAF, with a correlation coefficient of 0.991. Additionally, JrFAD3-1 was proved closely related to homologous genes in Betula pendula and Corylus heterophylla, indicating that the conserved structure of FADs is consistent with classical plant taxonomy.ConclusionTwenty-four members JrFADs in walnut were identified and classified into four subfamilies. JrFAD3-1 may play significant roles in the biosynthesis of polyunsaturated fatty acids in walnut.

Whole-genome mining and in silico analysis of FAD gene family in Brassica juncea

Brassica juncea is one of important oilseed crops, and FA compositions determine quality of vegetable oil. Although fatty acid desaturases (FADs) are mainly responsible for modifying seed FA compositions, genome-wide analysis of FAD gene family in B. juncea (BjuFAD) is not reported. Here, we identified 57 BjuFAD genes in B. juncea genome using homology searches. These FAD genes were unevenly distributed in 16 chromosomes and 3 scaffolds. Phylogenetic analysis showed that BjuFAD genes were divided into seven subfamilies. Exon–intron organizations, intron patterns and MEME motifs were highly conserved within each of BjuFAD subfamilies. Moreover, subcellular locations of deduced BjuFAD proteins and cis-acting elements in BjuFAD promoters were predicted and analyzed using online software. In addition, 16 SSR loci were totally found in BjuFAD genes/promoters. This work provides a basis for further function study of BjuFAD genes in quality improvement of B. juncea seed oil and in plant development as well as stress response.

Genome-wide identification of the fatty acid desaturases gene family in four Aspergillus species and their expression profile in Aspergillus oryzae

Fatty acid desaturases play a key role in producing polyunsaturated fatty acids by converting single bonds to double bonds. In the present study, a total of 13, 12, 8 and 8 candidate fatty acid desaturases genes were identified in the Aspergillus oryzae, Aspergillus flavus, Aspergillus fumigatus and Aspergillus nidulans genomes through database searches, which were classified into five different subfamilies based on phylogenetic analysis. Furthermore, a comprehensive analysis was performed to characterize conserved motifs and gene structures, which could provide an intuitive comprehension to learn the relationship between structure and functions of the fatty acid desaturases genes in different Aspergillus species. In addition, the expression pattern of 13 fatty acid desaturases genes of A. oryzae was tested in different growth stages and under salt stress treatment. The results revealed that the fatty acid desaturases genes in A. oryzae were highly expressed in adaptive phase growth and up-regulated under salt stress treatment. This study provided a better understanding of the evolution and functions of the fatty acid desaturases gene family in the four Aspergillus species, and would be useful for seeking methods to improve the production of unsaturated fatty acids and enhance efforts for the genetic improvement of strains to adapt to the complex surrounding environment.

Omega-3 fatty acid desaturase gene family from two ω-3 sources, Salvia hispanica and Perilla frutescens: Cloning, characterization and expression.

Omega-3 fatty acid desaturase (ω-3 FAD, D15D) is a key enzyme for α-linolenic acid (ALA) biosynthesis. Both chia (Salvia hispanica) and perilla (Perilla frutescens) contain high levels of ALA in seeds. In this study, the ω-3 FAD gene family was systematically and comparatively cloned from chia and perilla. Perilla FAD3, FAD7, FAD8 and chia FAD7 are encoded by single-copy (but heterozygous) genes, while chia FAD3 is encoded by 2 distinct genes. Only 1 chia FAD8 sequence was isolated. In these genes, there are 1 to 6 transcription start sites, 1 to 8 poly(A) tailing sites, and 7 introns. The 5’UTRs of PfFAD8a/b contain 1 to 2 purine-stretches and 2 pyrimidine-stretches. An alternative splice variant of ShFAD7a/b comprises a 5’UTR intron. Their encoded proteins harbor an FA_desaturase conserved domain together with 4 trans-membrane helices and 3 histidine boxes. Phylogenetic analysis validated their identity of dicot microsomal or plastidial ω-3 FAD proteins, and revealed some important evolutionary features of plant ω-3 FAD genes such as convergent evolution across different phylums, single-copy status in algae, and duplication events in certain taxa. The qRT-PCR assay showed that the ω-3 FAD genes of two species were expressed at different levels in various organs, and they also responded to multiple stress treatments. The functionality of the ShFAD3 and PfFAD3 enzymes was confirmed by yeast expression. The systemic molecular and functional features of the ω-3 FAD gene family from chia and perilla revealed in this study will facilitate their use in future studies on genetic improvement of ALA traits in oilseed crops.

Genome-Wide Survey and Characterization of Fatty Acid Desaturase Gene Family in Brassica napus and Its Parental Species.

Rapeseed (Brassica napus) is an important oilseed crop worldwide, and fatty acid (FA) compositions determine the nutritional and economic value of its seed oil. Fatty acid desaturases (FADs) play a pivotal role in regulating FA compositions, but to date, no comprehensive genome-wide analysis of FAD gene family in rapeseed and its parent species has been reported. In this study, using homology searches, 84, 45, and 44 FAD genes were identified in rapeseed, Brassica rapa, and Brassica oleracea genomes, respectively. These FAD genes were unevenly located in 17 chromosomes and 2 scaffolds of rapeseed, 9 chromosomes and 1 scaffold of B. rapa, and all the chromosomes of B. oleracea. Phylogenetic analysis showed that the soluble and membrane-bound FADs in the three Brassica species were divided into four and six subfamilies, respectively. Generally, the soluble FADs contained two conserved histidine boxes, while three highly conserved histidine boxes were harbored in membrane-bound FADs. Exon-intron structure, intron phase, and motif composition and position were highly conserved in each FAD subfamily. Putative subcellular locations of FAD proteins in three Brassica species were consistent with those of corresponding known FADs. In total, 25 of simple sequence repeat (SSR) loci were found in FAD genes of the three Brassica species. Transcripts of selected FAD genes in the three species were examined in various organs/tissues or stress treatments from NCBI expressed sequence tag (EST) database. This study provides a critical molecular basis for quality improvement of rapeseed oil and facilitates our understanding of key roles of FAD genes in plant growth and development and stress response.

Evening primrose (Oenothera biennis) Δ6 fatty acid desaturase gene family: cloning, characterization, and engineered GLA and SDA production in a staple oil crop

γ-Linolenic acid (GLA), stearidonic acid (SDA), and other polyunsaturated fatty acids (PUFAs) play important roles in human health, and Δ6 fatty acid desaturase (D6D) is a key enzyme for PUFA biosynthesis. Oenothera biennis is a traditional GLA-producing oil crop. Here we report the cloning, characterization, and metabolic engineering of its D6D gene family. The intronless 1922-bp ObD6D1 and 1752-bp ObD6D2 both have alternative transcription start sites, alternative polyadenylation sites, and repeated stop codons. Phylogenetic study revealed five large groups of front-end desaturases which are not simply correlated with desaturase types or organism origins. Any type of front-end enzyme has independently originated for multiple times. “Higher plants,” “higher animals,” and cyanobacteria each has front-end enzymes of single ancient origin, but other taxa are contrary. ObD6D1 and ObD6D2 are most abundantly expressed in bud and root, respectively. In yeast expression, ObD6D1 and ObD6D2 both catalyzed linoleic acid into GLA, and α-linolenic acid into SDA. Based on a newly constructed double-selection vector system, four constructs of ObD6D1 and ObD6D2 both individually driven by double CaMV35S promoter PD35S and seed-specific promoter PNAP were transformed into Brassica napus via Agrobacterium. T1 plants, T2 elite lines, and homozygous T3 elite lines accumulated average GLA + SDA levels of 6.04, 15.77, and 21.56% of seed fatty acids, respectively. ObD6D2 showed higher effect than ObD6D1. PD35S-D6D engineering has little side effect but is weaker than PNAP-D6D engineering in terms of GLA + SDA productivity.

Genomic structural analysis of porcine fatty acid desaturase cluster on chromosome 2.

Fatty acid composition is an economically important trait in meat-producing livestock. To gain insight into the molecular genetics of fatty acid desaturase (FADS) genes in pigs, we investigated the genomic structure of the porcine FADS gene family on chromosome 2. We also examined the tissue distribution of FADS gene expression. The genomic structure of FADS family in mammals consists of three isoforms FADS1, FADS2 and FADS3. However, porcine FADS cluster in the latest pig genome assembly (Sscrofa 10.2) containing some gaps is distinct from that in other mammals. We therefore sought to determine the genomic structure, including the FADS cluster in a 200-kbp range by sequencing gap regions. The structure we obtained was similar to that in other mammals. We then investigated the porcine FADS1 transcription start site and identified a novel isoform named FADS1b. Phylogenetic analysis revealed that the three members of the FADS cluster were orthologous among mammals, whereas the various FADS1 isoforms identified in pigs, mice and cattle might be attributable to species-specific transcriptional regulation with alternative promoters. Porcine FADS1b and FADS3 isoforms were predominantly expressed in the inner layer of the subcutaneous adipose tissue. Additional analyses will reveal the effects of these functionally unknown isoforms on fatty acid composition in pig fat tissues.