Producing Designer Oils in Industrial Microalgae by Rational Modulation of Co-evolving Type-2 Diacylglycerol Acyltransferases

Microalgal oils, depending on their degree of unsaturation, can be utilized as either nutritional supplements or fuels; thus, a feedstock with genetically designed and tunable degree of unsaturation is desirable to maximize process efficiency and product versatility. Systematic profiling of ex vivo （in yeast）, in vitro, and in vivo activities of type-2 diacylglycerol acyltransferases in Nannochloropsis oceanica （NoDGAT2s or NoDGTTs）, via reverse genetics, revealed that NoDGAT2A prefers saturated fatty acids （SFAs）, NoDGAT2D prefers monounsaturated fatty acids （MUFAs）, and NoDGAT2C exhibits the strongest activity toward polyunsaturated fatty acids （PUFAs）. As NoDGAT2A, 2C, and 2D originated from the green alga, red alga, and eukaryotic host ancestral participants of secondary endosymbiosis, respectively, a mecha- nistic model of oleaginousness was unveiled, in which the indigenous and adopted NoDGAT2s formulated functional complementarity and specific transcript abundance ratio that underlie a rigid SFA：MUFA：PUFA hierarchy in triacylglycerol （TAG）. By rationally modulating the ratio of NoDGAT2A＇：2C^D transcripts, a bank of N. oceanica strains optimized for nutritional supplement or fuel production with a wide range of degree of unsaturation were created, in which proportion of SFAs, MUFAs, and PUFAs in TAG varied by 1.3-, 3.7-, and 11.2-fold, respectively. This established a novel strategy to simultaneously improve productivity and quality of oils from industrial microalgae.

Cloning, Characterization and Functional Analysis of Two Type 1 Diacylglycerol Acyltransferases (DGAT1s) from Tetraena mongolica

Two cDNAs encoding putative type 1 acyl-CoA： diacylglycerol acyltransferases （DGAT1, EC 2.3.1.20）, were cloned from Tetraena mongolica Maxim., an extreme xerophyte with high oil content in the stems. The 1,488-bp and 1,485-bp of the open reading frame （ORF） of the two cDNAs, designated as TmDGAT1a and TmDGAT1b, were both predicted to encode proteins of 495 and 494 amino acids, respectively. Southern blot analysis revealed that TmDGAT1a and TmDGAT1b both had low copy numbers in the T. mongolica genome. In addition to ubiquitous expression with different intensity in different tissues, including stems, leaves and roots, TmDGAT1a and TmDGAT1b, were found to be strongly induced by high salinity, drought and osmotic stress, resulting in a remarkable increase of triacylglycerol （TAG） accumulation in T. mongolica plantlets. TmDGAT1a and TmDGAT1b activities were confirmed in the yeast H1246 quadruple mutant （DGA1, LRO1, ARE1, ARE2） by restoring DGAT activity of the mutant host to produce TAG. Overexpression of TmDGAT1a and TmDGAT1b in soybean hairy roots as well as in T. mongolica calli both resulted in an increase in oil content （ranging from 37% to 108%）, accompanied by altered fatty acid profiles.

Lecithin-cholesterol acyltransferase is a potential tumor suppressor and predictive marker for hepatocellular carcinoma metastasis

BACKGROUND Hepatocellular carcinoma(HCC)is a major cause of cancer mortality worldwide,and metastasis is the main cause of early recurrence and poor prognosis.However,the mechanism of metastasis remains poorly understood.AIM To determine the possible mechanism affecting HCC metastasis and provide a possible theoretical basis for HCC treatment.METHODS The candidate molecule lecithin-cholesterol acyltransferase(LCAT)was screened by gene microarray and bioinformatics analysis.The expression levels of LCAT in clinical cohort samples was detected by quantitative realtime polymerase chain reaction and western blotting.The proliferation,migration,invasion and tumor-forming ability were measured by Cell Counting Kit-8,Transwell cell migration,invasion,and clonal formation assays,respectively.Tumor formation was detected in nude mice after LCAT gene knockdown or overexpression.The immunohistochemistry for Ki67,E-cadherin,N-cadherin,matrix metalloproteinase 9 and vascular endothelial growth factor were performed in liver tissues to assess the effect of LCAT on HCC.Gene set enrichment analysis(GSEA)on various gene signatures were analyzed with GSEA version 3.0.Three machine-learning algorithms(random forest,support vector machine,and logistic regression)were applied to predict HCC metastasis in The Cancer Genome Atlas and GEO databases.RESULTS LCAT was identified as a novel gene relating to HCC metastasis by using gene microarray in HCC tissues.LCAT was significantly downregulated in HCC tissues,which is correlated with recurrence,metastasis and poor outcome of HCC patients.Functional analysis indicated that LCAT inhibited HCC cell proliferation,migration and invasion both in vitro and in vivo.Clinicopathological data showed that LCAT was negatively associated with HCC size and metastasis(HCC size≤3 cm vs 3-9 cm,P<0.001;3-9 cm vs>9 cm,P<0.01;metastatic-free HCC vs extrahepatic metastatic HCC,P<0.05).LCAT suppressed the growth,migration and invasion of HCC cell lines via PI3K/AKT/mTOR signaling.Our results indicated that the logistic regression model based on LCAT,TNM stage and the serum level of α-fetoprotein in HCC patients could effectively predict high metastatic risk HCC patients.CONCLUSION LCAT is downregulated at translational and protein levels in HCC and might inhibit tumor metastasis via attenuating PI3K/AKT/mTOR signaling.LCAT is a prognostic marker and potential therapeutic target for HCC.

GSTM1,GSTT1,GSTP1 and CYP1A1 genetic polymorphisms and susceptibility to esophageal cancer in a French population:Different pattern of squamous cell carcinoma and adenocarcinoma

AIM:To evaluate the association between CYP1A1 and GSTs genetic polymorphisms and susceptibility to esophageal squamous cell carcinoma(SCC)and esophageal adenocarcinoma(ADC)in a high risk area of northwest of France. METHODS:A case-control study was conducted to investigate the genetic polymorphisms of these enzymes (CYPIAI*2C and GSTP1 exon 7 Val alleles,GSTMI*2/*2 and GSTTl *2/*2 null genotypes).A total of 79 esophageal cancer cases and 130 controls were recruited. RESULTS:GSTMI*2/*2 and CYPIAI*IA/*2C genotype frequencies were higher among squamous cell carcinomas at a level dose to statistical significance(OR =1.83,95% CI 0.88-3.83,P=0.11;OR=3.03,95% CI 0.93-9.90,P=0.07, respectively).For GSTP1 polymorphism,no difference was found between controls and cases,whatever their histological status.Lower frequency of GSTT1 deletion was observed in ADC group compared to controls with a statistically significant difference(OR=13.31,95% CI 1.66-106.92,P<0.01). CONCLUSION:In SCC,our results are consistent with the strong association of this kind of tumour with tobacco exposure.In ADC,our results suggest 3 distinct hypotheses: (1)activation of exogenous procarcinogens,such as small halogenated compounds by GSTT1;(2)contribution of GSTT1 to the inflammatory response of esophageal mucosa,which is known to be a strong risk factor for ADC, possibly through leukotriene synthesis;(3)higher sensitivity to the inflammatory process associated with intracellular depletion of glutathione.

Identification and Comparative Analysis of DGAT1 Genes among Cotton and Other Model Plants

Diacylglycerol acyltransferase （DGAT） is the key enzyme that catalyzes the triacylglycerol biosynthesis. The comparative analysis was performed on the DGAT1 genes of cotton and other model plants. Sequence analysis showed that most of the DGAT1 genes,with high variation of intron length and high conservation of intron phrase,from the cotton and other model plants had 16 exons. Additionally, 7 conserved motifs were present in these DGAT1 proteins. The core motifs were overlapped with the functional domain of DGAT1 protein. Phylogenetic analysis demonstrated that gene tree was highly consistent to species tree,suggesting that the evolutionary history of species was revealed by gene tree. There was single copy of DGAT1 gene in cotton,but at least two duplicated DGAT1 genes were iden- tified in rice,maize,poplar and moss genomes. The selective pressure analysis showed that the PtDGATla/PtDGATlb was under positive selection,but other four pairs of homologous genes were under negative selection. 17 positively selected sites were identified at subgroup level （P〉0.05）,suggesting these subgroups under relaxed functional constraint. The findings provide a basis for further studying func- tion and evolution of DGAT1 genes in cotton and other model plants.

Assessment of liver fibrosis by a noninvasive method of transient elastography and biochemical markers

AIM： To assess the correlation between the fibrotic area （FA） as calculated by a digital image analysis （DIA）, and to compare the diagnostic accuracy of FibroScan to the other existing Liver fibrosis （LF） markers using the receiver operating curve analysis.METHODS： We recruited 30 patients who underwent a liver resection for three different etiologies including normal liver, hepatitis B, and hepatitis C. Liver stiffness was measured by using a FibroScan. The FA was then calculated by DIA to evaluate LF in order to avoid any sampling bias. RESULTS： The FA negatively correlated with Prothrombin time （PT）, platelet count, lecithin-cholesterol acyltransferase （LCAT）, and pre-albumin （ALB）. On the other hand, the findings of FibroScan correlated with similar markers. The FA positively correlated with FibroScan, serum hyaluronate level, and type Ⅳ collagen level, and aspartate transaminase to platelet ratio index （APRI）. The area under the receiver operating curve for FibroScan was higher than that for the other markers, even though the statistical significance was minimal. CONCLUSION： Our findings suggest that FibroScan can initially be used to assess LF as an alternative to a liver biopsy （LB） and serum diagnosis, because it is a safe method with comparable diagnostic accuracy regarding the existing LF markers.

PNPLA3,the triacylglycerol synthesis/hydrolysis/storage dilemma,and nonalcoholic fatty liver disease

Genome-wide and candidate gene association studies have identified several variants that predispose indi- viduals to developing nonalcoholic fatty liver disease （NAFLD）. However, the gene that has been consis- tently involved in the genetic susceptibility of NAFLD in humans is patatin-like phospholipase domain contain- ing 3 （PNPLA3, also known as adiponutrin）. A nonsyn- onymous single nucleotide polymorphism in PNPLA3 （rs738409 C/G, a coding variant that encodes an amino acid substitution I148M） is significantly associated with fatty liver and histological disease severity, not only in adults but also in children. Nevertheless, how PNPLA3 influences the biology of fatty liver disease is still an open question. A recent article describes new aspects about PNPLA3 gene/protein function and suggests that the I148M variant promotes hepatic lipid synthesis due to a gain of function. We revise here the published data about the role of the I148M variant in lipogen- esis/lipolysis, and suggest putative areas of future research. For instance we explored in silico whether the rs738409 C or G alleles have the ability to modify miRNA binding sites and miRNA gene regulation, and we found that prediction of PNPLA3 target miRNAs shows two miRNAs potentially interacting in the 3＇ UTR region （hsa-miR-769-3p and hsa-miR-516a-3p）. In addition, interesting unanswered questions remain to be explored. For example, PNPLA3 lies between two CCCTC-binding factor-bound sites that could be tested for insulator activity, and an intronic histone 3 lysine 4 trimethylation peak predicts an enhancer element, cor- roborated by the DNase I hypersensitivity site peak. Finally, an interaction between PNPLA3 and glycerol- 3-phosphate acyltransferase 2 is suggested by data miming.

Regulation of Acyl-coenzyme A:Cholesterol Acyltransferase 2 Expression by Saturated Fatty Acids

Objective To verify the regulation of acyl-coenzyme A:cholesterol acyltransferase 2 (ACAT 2), which is associated with cholesterol metabolism, by saturated fatty acids (SFAs). Methods Palmitic acid (PA), the most abundant saturated fatty acid in plasma, and oleic acid (OA), a widely distributed unsaturated fatty acid, were used to treat hepatic cells HepG2, HuH7, and mouse primary hepatocytes. In addition, PA at different concentrations and PA treatment at different durations were applied in HepG2 cells. In in vivo experiment, three-month male C57/BL6 mice were fed with control diet and SFA diet containing hydrogenated coconut oil rich of SFAs. The mRNA level of ACAT2 in those hepatic cells and the mouse livers was detected with real-time polymerase chain reaction (PCR). Results In the three types of hepatic cells treated with PA, that SFA induced significant increase of ACAT2 expression (P<0.01), whereas treatment with OA showed no significant effect. That effect of PA was noticed gradually rising along with the increase of PA concentration and the extension of PA treatment duration (both P<0.05). SFA diet feeding in mice resulted in a short-term and transient increase of ACAT2 expression in vivo, with a peak level appearing in the mice fed with SFA diet for two days (P<0.05). Conclusion SFA may regulate ACAT2 expression in human and mouse hepatic cells and in mouse livers.

Lipopolysaccharide triggers nuclear import of Lpcat1 to regulate inducible gene expression in lung epithelia

AIM:To report that Lpcat1 plays an important role in regulating lipopolysaccharide (LPS) inducible gene tran-scription. METHODS:Gene expression in Murine Lung Epithelial MLE-12 cells with LPS treatment or Haemophilus influenza and Escherichia coli infection was analyzed by employing quantitative Reverse Transcription Polymerase Chain Reaction techniques. Nucleofection was used to deliver Lenti-viral system to express or knock down Lpcat1 in MLE cells. Subcellular protein fractionation and Western blotting were utilized to study Lpcat1 nuclear relocation. RESULTS:Lpcat1 translocates into the nucleus from thecytoplasm in murine lung epithelia (MLE) after LPS treatment. Haemophilus influenza and Escherichia coli , two LPS-containing pathogens that cause pneumonia, triggered Lpcat1 nuclear translocation from the cytoplasm. The LPS inducible gene expression profile was determined by quantitative reverse transcription polymerase chain reaction after silencing Lpcat1 or overexpression of the enzyme in MLE cells. We detected that 17 out of a total 38 screened genes were upregulated, 14 genes were suppressed, and 7 genes remained unchanged in LPS treated cells in comparison to controls. Knockdown of Lpcat1 by shRNA dramatically changed the spectrum of the LPS inducible gene transcription, as 18 genes out of 38 genes were upregulated, of which 20 genes were suppressed or unchanged. Notably, in Lpcat1 overex-pressed cells, 25 genes out of 38 genes were reduced in the setting of LPS treatment.CONCLUSION:These observations suggest that Lpcat1 relocates into the nucleus in response to bacterial infection to differentially regulate gene transcriptional repression.

Effect of Tumor Necrosis Factor-α on Acyl Coenzyme A: Cholesteryl Acyltransferase Activity and ACAT1 Gene Expression in THP-1 Macrophages

In order to explore the effect and mechanisms of tumor necrosis factor-α （TNF-α） on the activity of the acyl coenzyme A： cholesteryl acyltransferase （ACAT）, THP-I monocytes were cul- tured and induced to differentiate into macrophages with phorbol ester. TNF-α （60 ng/mL） was added at different time points into the macrophage-containing medium and the ACAT enzyme activity was measured by quantifying the incorporation of [1-^14C] oleoyl CoA into cholesteryl esters. The expression of ACAT-1 protein and mRNA was respectively detected by Western blotting and RT-PCR in THP-1 macrophages 24 h after treatment with TNF-α （60 ng/mL）. The results indicated that ACAT activity in THP-I macrophages treated with TNF-α was increased in a time-dependent manner. The expression levels of ACAT-1 protein and mRNA were significantly increased in THP-I macrophages after treatment with TNF-α （P〈0.05）. It was suggested that TNF-α could increase the activity of ACAT in THP-1 macrophages by up-regulating the expression of ACAT-1 gene.

Characterization and expression analysis of genes encoding Taxol biosynthetic enzymes in Taxus spp.

Taxol(Paclitaxel),an important anticancer drug,is derived at very low yields from Taxus(yew)species that grow very slowly.In the present study,thirteen genes that encode enzymes involved in Taxol biosynthesis in Taxus spp.were analyzed with bioinformatics methods,and their expression levels in different tissues and after cold and hormone treatments were also analyzed.The results indicated that many cis-elements related to abiotic stresses and hormones were found in the promoter sequences of the 8 genes involved in Taxol biosynthesis.Moreover,the 13 enzymes encoded by the target genes were located in different organelles and had many phosphorylation sites in the response proteins.The 13 genes were expressed highly either in roots or in stems,with lower transcripts in needles,and they were highly expressed after treatment with cold,gibberellin,methyl jasmonate or coronatine,consistent with predictions based on the bioinformatics analysis.These results suggest that the factors such as hormones and abiotic stresses stimulate taxane biosynthesis in yews,providing an important way to sustainably generate taxanes from yew trees or their cell cultures to improve Taxol yields.

Positive Effects of Isopropanol as a Co-Precipitant in Glycerol-3-Phosphate Acyltransferase Crystallization

Glycerol-3-phosphate acyltransferase(GPAT) is considered as the rate-limiting enzyme of glycerolipid synthesis pathway and the core element in lysophosphatidic acid(LPA) synthesis. For understanding its catalytic mechanism, the structural biology study is expected, but is always hindered by obtaining crystals for X-ray diffraction analysis. In this study, a progressive strategy to optimize the crystal of microalgae plastidial GPAT was presented. After the expression and purification of GPAT, the crystals were screened by hanging-drop and only clusters were obtained. The crystals were optimized by adjusting temperature, pH, protein concentration, or precipitant, but little improvement. To improve the interaction between protein and precipitant, the isopropanol was applied as co-precipitant. The qualified crystals formed. It's suggested that isopropanol is critical to affect protein crystallization by altering polyethylene glycol(PEG)-water-protein interaction when PEG serves as precipitant. The resulting crystal diffracted to a resolution of 2.75 ? and belonged to space group P1, with unit-cell parameters a = 50.79, b = 80.09, c = 88.21 ?, and α = 62.85, β = 73.04, γ = 80.53?. This work introduced a new strategy to optimize the crystal of the heterogeneous catalysis enzymes like GPAT and provided the fundamental structural information for the oriented synthesis of marine microalgae glycerolipid.

Characterization of a broad substrates specificity acyl-CoA:diacylglycerol acyltransferase 1 from the green tide alga Ulva prolifera

Triacylglycerols(triglycerides,TAGs)are the major carbon and energy storage forms in various organisms,and important components of cellular membranes and signaling molecules;they have essential functions in multiple physiological processes and stress regulation.Acyl-CoA:diacylglycerol acyltransferase(DGAT)catalyzes the final and only committed acylation step in the synthesis of TAGs in eukaryotes.The present work identified and isolated a novel gene,UpDGAT1,from the green tide alga Ulva prolifera.The activity of UpDGAT1 was confirmed by heterologous expression in a Saccharomyces cerevisiae TAG-deficient quadruple mutant.Results of thin-layer chromatography and BODIPY staining indicated that UpDGAT1 was able to restore TAG synthesis and lipid body formation in the yeast.Lipid analysis of yeast cells revealed that UpDGAT1 showed broad substrate specificity,accepting saturated as well as mono-and polyunsaturated acyl-CoAs as substrates.High salinity and high temperature stresses increased UpDGAT1 expression and TAG accumulation in U.prolifera.The present study provides clues to the functions of UpDGAT1 in TAG accumulation in,and stress adaptation of,U.prolifera.

Conjugated Linoleic Acid and Dietary Fats Differentially Affect Hepatic ACAT Activity and LDL-Cholesterol in Postweanling Pigs Fed Low-Fat Diets

ABSTRACT：Two separate studies tested the hypoth- esis that plasma low-density lipoprotein cholesterol LDL-C ） can be decreased by conjugated linoleic acid （CLA） by depressing hepatic acyl-coenzyme A： cholesterol acyltransferase （ACAT） activity. In the first experiment, 3 groups of 6 early-weaned piglets were fed low-fat diets containing either 1.5% CLA, 1.5% corn oil or 1.5% beef tallow;fat provided 8% of the energy intake. In the second experiment, 4 groups of 6 early-weaned piglets were fed high-fat di- ets containing either 15% beef tallow, 12% beef tal- low plus 3% CLA, 15% corn oil, or 12% corn oil plus 3% CLA; fat provided 29% of energy intake. Cholesterol was balanced across diets in both experi-ments. In pigs fed the low-fat diets, all dietary fats in- creased LDL-C and triacylglycerols and decreased high-density lipoprotein cholesterol （ HDL-C ） and very low-density lipoprotein cholesterol （VLDL-C）. LDL-C was the same in pigs fed low-fat tallow or low-fat CLA diets. However, ACAT activity was near- ly 80% higher in pigs fed the low-fat tallow diet than in pigs fed the low-fat CLA diets. All high-fat diets increased LDL-C, HDL-C and triacylglycerols equally with no effect on VLDL-C. There were no unique fat- ty acid effects of the high-fat diets on ACAT activity. We conclude that supplemental fats had differential effects on hepatic ACAT activity and LDL-C, but on- ly in pigs fed low-fat diets.

Lipids-induced Apoptosis Is Aggravated by Acyl-coenzyme A:Cholesterol Acyltransferase Inhibitor

Objective To investigate the role of acyl-coenzyme A:cholesterol acyltransferase inhibitor(ACATI) in apoptosis induced by lipids and whether lipids-induced apoptosis is accompanied by increase of free cholesterol in endoplasmic reticulum(ER),in order to further understand the mechanism of lipids-induced apoptosis in advanced atherosclerosis.Methods Human vascular smooth muscle cells(VSMCs) and phorbol 12-myristate 13-acetate(PMA) differentiated THP-1 macrophages were used.Tritiated thymidine incorporation was applied to detect cell proliferation.Cytotoxicity was assessed by lactate dehydrogenase(LDH) release.4',6-diamidino-2-phenylindole(DAPI) staining,caspase-3,-7 assay,and Annexin-V/propidium iodide(PI) staining were used to detect apoptosis.High performance liquid chromatography was used in intracellular free cholesterol and cholesterol ester assay.ER free cholesterol was quantified.Results Different lipids had different effects on proliferation and cytotoxicity of VSMCs.25-hydroxycholesterol(25OHC) had biphasic effects on the proliferation of VSMCs.At low concentration,it stimulated cell proliferation,but turned to proliferation inhibition as concentration reached 15 μg/mL.25OHC and acetylated low density lipoprotein(AcLDL) could respectively induce apoptosis in human VSMCs and PMA differentiated THP-1 macrophages,which was aggravated by ACATI,accompanied by increase of intracellular free cholesterol content.There was also an increase of cholesterol content in ER with AcLDL-induced apoptosis in THP-1 macrophages.Conclusions Lipids could induce apoptosis,accompanied by increase of intracellular free cholesterol content,which could be augmented by ACATI,suggesting that insults resulting in ER free cholesterol rise might be the initiator of apoptosis.

An acyltransferase gene that putatively functions in anthocyanin modification was horizontally transferred from Fabaceae into the genus Cuscuta

Horizontal gene transfer(HGT) refers to the flow of genetic materials to non-offspring,and occasionally HGT in plants can improve the adaptation of organisms in new niches due to expanded metabolic capability.Anthocyanins are an important group of water-soluble red,purple,or blue secondary metabolites,whose diversity results from modification after the main skeleton biosynthesis.Cuscuta is a stem holoparasitic genus,whose members form direct connection with hosts to withdraw water,nutrients,and macromolecules.Such intimate association is thought to increase the frequency of HGT.By transcriptome screening for foreign genes in Cuscuta australis,we discovered that one gene encoding a putative anthocyanin acyltransferase gene of the BAHD family,which is likely to be involved in anthocyanin modification,was acquired by C.australis from Fabaceae through HGT.The anthocyanin acyltransferase-like(AT-like) gene was confirmed to be present in the genome assembly of C.australis and the transcriptomes of Cuscuta pentagona.The higher transcriptional level in old stems is consistent with its putative function in secondary metabolism by stabilizing anthocyanin at neutral pH and thus HGT of this AT-like gene may have improved biotic and abiotic resistance of Cuscuta.

Suppression of Sebum Production and Accumulation by <i>β</i>-Cryptoxanthin Due to the Inhibition of the Expression of Diacylglycerol Acyltransferase-1 and Perilipin in Hamster Sebocytes

Background: Acne vulgaris is characterized by the enhancement of sebaceous lipogenesis and sebum secretion, and apart from retinoids and some natural products there are few effective antiacne agents that directly suppress sebum production and accumulation in sebaceous glands. Objective: We examined the effects of β-cryptoxanthin (β-CRX), which is a carotenoid pigment most abundant in Citrus unshiu Marcovich (Satsuma mandarin orange) and plays a role as a vitamin A precursor on sebum production and accumulation in hamster sebaceous gland cells (sebocytes). Materials and methods: The regulation of sebum production was examined by the measurement of triacylglycerols (TGs), the major sebum component, and oil red O staining in insulindifferentiated hamster sebocytes. The expression of diacylglycerol acyltransferase-1 (DGAT-1), a rate-limiting enzyme of TG biosynthesis, and perilipin 1 (PLIN1), a lipid storage droplet protein, was analyzed using real-time PCR and Western blotting. Results: Hamster sebocytes constitutively produced TGs during cultivation and the production of TGs was enhanced by insulin treatment. Both constitutive and insulin-enhanced TG productions were dose- and time-dependently inhibited by β-CRX as well as 13-cis retinoic acid. In addition, the gene expression of DGAT-1 was suppressed by β-CRX in the sebocytes. Furthermore, the insulin-en- hanced sebum accumulation as lipid droplets was reduced in the β-CRX-treated cells. Moreover, β-CRX was found to suppress the gene expression and production of PLIN1 in insulin-differentiated hamster sebocytes. Conclusions: These results provide novel evidence that β-CRX is an effective candidate for acne therapy by its ability to exert dual inhibitory actions against DGAT-1-dependent TG production and PLIN1-mediated lipiddroplet formation in hamster sebocytes.

Research progress on unusual acetyl triacylglycerol

Acetyl triacylglycerol (acetyl-TAG) containing acetyl at sn-3 position is rare in nature. It is optically active asymmetric TAG with low viscosity, having improved cold temperature property and low calorific content compared to regular TAGs. It gains increasingly attentions due to its potential applications. Metabolic engineering of plant or microorganism for production of acetyl-TAG is currently attractive. Here we summarize the researches on acetyl-TAG, with emphasis on gene discovery, protein analysis and its potential applications. Comprehensive understanding of current development in acetyl-TAG biosynthesis pathway may contribute to the increase of production and more applications.

Gomparative analysis of DGAT3（diacylglycerol acyltraiisferase 3） gene from different peanut （Arachis hypogaea L.） varieties

Cultivated peanut is one of the primary sources of vegetable oil and protein in developing countries. DG〉A73 family in peanut cotyledons has no membrane-bound regions suggesting that cytosol is one of the sites for triacylglycerol （TAG） biosynthesis in oilseeds. According to functional annotation and classification of 5 cDNA libraries, 12 unigenes were found with relation of peanut DGAT3 in different organs. Three clones of unigenes, OCP- contig168t OCPcontig12101-3 and OCPcontigl2388-1 were selected for sequencing. Full length sequence of DGAT3 was obtained, showing over 98% sequence similarity with peanut DGAT3 gene AY875644 or EU183333. Upon cluster analysis, DGAT3 of 40 culti- vars were divided into 3 types, namely AhDGATS-1, AhDGAT3-2 and AhDGAT3-3. Coding regions are 1023, 1038 and 1026 base pairs which encoded proteins with 340-, 345- and 341-amino acids, respectively. DGAT3-3 might be a novel gene type among the DGAT3 family which provides great help for studying DGAT3 gene evolution in peanut.

Classification,biosynthesis,and biological functions of triterpene esters in plants

Triterpene esters comprise a class of secondary metabolites that are synthesized by decorating triterpene skeletons with a series of oxidation,glycosylation,and acylation modifications.Many triterpene esters with important bioactivities have been isolated and identified,including those with applications in the pesticide,pharmaceutical,and cosmetic industries.They also play essential roles in plant defense against pests,dis-eases,physical damage(as part of the cuticle),and regulation of root microorganisms.However,there has been no recent summary of the biosynthetic pathways and biological functions of plant triterpene esters.Here,we classify triterpene esters intofive categories based on their skeletons andfind that C-3 oxidation may have a significant effect on triterpenoid acylation.Fatty acid and aromatic moieties are common li-gands present in triterpene esters.We further analyze triterpene ester synthesis-related acyltransferases(TEsACTs)in the triterpene biosynthetic pathway.Using an evolutionary classification of BAHD acyltrans-ferases(BAHD-ATs)and serine carboxypeptidase-like acyltransferases(SCPL-ATs)in Arabidopsis thaliana and Oryza sativa,we classify 18 TEsACTs with identified functions from 11 species.All the triterpene-skel-eton-related TEsACTs belong to BAHD-AT clades IIIa and I,and the only identified TEsACT from the SCPL-AT family belongs to the CP-I subfamily.This comprehensive review of the biosynthetic pathways and bioactivities of triterpene esters provides a foundation for further study of their bioactivities and applica-tions in industry,agricultural production,and human health.