Identification and expression patterns of alcohol dehydrogenase genes involving in ester volatile biosynthesis in pear fruit

Alcohol dehydrogenase （ADH） catalyzes the interconversion of aldehydes and their corresponding alcohols, and is a key enzyme in volatile ester biosynthesis. However, little is known regarding ADH and ADH encoding genes （ADHs） in pear. We identified 8 ADHs in the pear＇s genome （PbrADHs） by multiple sequences alignment. The PbrADHs were highly ho- mologous in their coding regions, while were diversiform in structure. 9 introns were predicted in PbrADH3-PbrADH8, while 8 introns, generated through exon fusion and intron loss, were predicted in PbrADH1 and PbrADH2. To study the genetic regulation underlying aroma biogenesis in pear fruit, we determined the PbrADH transcripts, ADH activities and volatile contents of fruits during ripening stage for Nanguoli and Dangshansuli, two cultivars having different aroma characteristics. ADH activity was strongly associated with the transcription of ADH~ in the two cultivars during fruit ripening stage. The higher ester content paralleling to a higher ADH activity was detected in Nanguoli than in Dangshansuli, so it is induced that the lower ester content in Dangshansuli fruit may be the result of weak ADH activity. The present study revealed that total ADH activity and volatile ester production correlated with increased PbrADHstranscript levels. PbrADH6 may contribute to ADH activity catalyzing aldehyde reduction and ester formation in pear fruit.

Transcriptional Regulation of Expression of the Maize Aldehyde Dehydrogenase 7 Gene (ZmALDH7B6) in Response to Abiotic Stresses

Aldehyde dehydrogenases（ALDHs） represent a large protein family, which includes several members that catalyze the oxidation of an aldehyde to its corresponding carboxylic acid in plants. Genes encoding members of the ALDH7 subfamily have been suggested to play important roles in various stress adaptations in plants. In this study, quantitative RT-PCR analysis revealed that a maize ALDH7 subfamily member（ZmALDH7B6） was constitutively expressed in various organs, including roots, leaves, immature ears, tassels, and developing seeds. The abundance of ZmALDH7B6 mRNA transcripts in maize roots was increased by ammonium, NaCl, and mannitol treatments. To further analyze tissue-specific and stress-induced expression patterns, the 1.5-kb 5′-flanking ZmALDH7B6 promoter region was fused to the β-glucuronidase（GUS） reporter gene and introduced into maize plants. In roots of independent transgenic lines, there was significant induction of GUS activity in response to ammonium supply, confirming ammonium-dependent expression of ZmALDH7B6 at the transcript level. Histochemical staining showed that GUS activity driven by the ZmALDH7B6 promoter was mainly localized in the vascular tissues of maize roots. These results suggested that ZmALDH7B6 is induced by multiple environmental stresses in maize roots, and may play a role in detoxifying aldehydes, particularly in vascular tissue.

A Comparative Study Between Tumor Blood Vessels and Dynamic Contrast-enhanced MRI for Identifying Isocitrate Dehydrogenase Gene 1(IDH1)Mutation Status in Glioma

Objective Isocitrate dehydrogenase gene(IDH)mutations are associated with tumor angiogenesis and therefore play an important role in glioma management.This study compared the performance of tumor blood vessels counted from contrast-enhanced 3D brain volume(3D-BRAVO)sequence and dynamic contrast-enhanced(DCE)MRI in differentiating IDH1 status in gliomas.Methods Forty-four glioma patients[16 with IDH1 mutant-type(IDH1-MT),28 with IDH1 wild-type(IDH1-WT)]were retrospectively analyzed.A blood vessel entering a tumor was defined as an intratumoral vessel;a blood vessel adjacent to the edge of a tumor was defined as a peritumoral vessel.Combined vessels were defined as the sum of the intratumoral and peritumoral vessels.DCE-derived metrics of tumor were normalized to the contralateral normal-appearing white matter.Results Intratumoral,peritumoral,and combined tumor blood vessels were all significantly different between IDH1-MT and IDH1-WT gliomas,and the range of area under curves(AUCs)was 0.816–0.855.For DCE-derived parameters,cerebral blood volume,cerebral blood flow,mean transit time,and volume transfer constant were significantly different between IDH1-MT and IDH1-WT gliomas,and the range of AUCs was 0.703–0.756.Combined vessels possessed the best performance for identifying IDH1 mutations in gliomas(AUC:0.855,sensitivity:0.857,specificity:0.812,P<0.001).Conclusion The number of tumor blood vessels has comparable diagnostic performance with DCE-derived parameters for differentiating IDH1 mutations and can serve as a potential imaging biomarker to reflect IDH1 mutations in gliomas.

Genome-wide identification and analysis of cytokinin dehydrogenase/oxidase(CKX) family genes in Brassica oleracea L.reveals their involvement in response to Plasmodiophora brassicae infections

Cytokinins are a class of phytohormones that promote cell division and differentiation and are thought to affect plant immunity to multiple pathogens.However,a comprehensive analysis of cytokinin dehydrogenase/oxidase(CKX)family genes in cabbage has not been reported.In this study,a total of 36 CKX genes were identified using a genome-wide search method.Phylogenetic analysis classified these genes into three groups.They were distributed unevenly across nine chromosomes in B.oleracea,and 15 of them did not contain any introns.The results of colinearity analysis showed that 36 CKX gene in Arabidopsis was present in several copies in the Brassica oleracea genome.An analysis of cisacting elements indicated that all genes possessed at least one stress or hormone responsive cis-acting element.A heatmap of CKX gene expression showed the patterns of expression of these genes in various tissues and organs.Three genes(Bol028363,Bol031036 and Bol018140)were relatively highly expressed in all of the investigated tissues under normal conditions,showing the expression profile of housekeeping genes.Generally,the expression patterns of CKX genes in Jingfeng 1 and Xiangan 336 were quite different under the same treatment.Notably,three genes(Bol020547,Bol028392 and Bol045724)were significantly down-regulated and up-regulated in the susceptible and resistant material,respectively,after inoculation,which may indicate their crucial roles in resistance to clubroot disease.The results provide insights for better understanding the roles of CKX genes in the B.oleracea–P.brassicae interaction.

Relationship Between Polymorphism of Methylenetetrahydrofolate Dehydrogenase and Congenital Heart Defect

To investigate the relationship between G1958A gene polymorphism of methylenetetrahydrofolate dehydrogenase (MTHFD) and occurrence of congenital heart disease (CHD) in North China. Methods One hundred and ninety-two CHD patients and their parents were included in this study as case group in Liaoning Province by birth defect registration cards, and 124 healthy subjects (age and gender matched) and their parents were simultaneously selected from the same geographic area as control. Their gene polymorphism of MTHFD G1958A locus was examined with PCR-RFLP, and serum folic acid and homocysteine (Hcy) levels were tested with radio-immunoassay and fluorescence polarization immunoassay (FPIA). Results There existed gene polymorphism at MTHFD G1958A locus in healthy subjects living in North China. The percentages of GG, GA, and AA genotype were 57.98%, 35.57%, and 6.45% respectively, and the A allele frequency was 24.23%, which was significantly different from Western population. No difference was observed when comparing genotype distribution and allele frequency between the case and control groups, so was the result from the comparison between genders. The A allele frequency of arterial septal defect patients’ mothers (10.87%) was significantly lower than that of controls (28.15%) (P=0.014), with OR=0.31 (95% CI: 0.09-0.84), and no difference in the other subgroups. The percentage of at least one parent carrying A allele in arterial septal defect subgroup (43.48%) was significantly lower than that in controls (69.64%) (P=0.017), with OR=0.34 (95% CI: 0.12-0.92). The analysis of genetic transmission indicated that there was no transmission disequillibrium in CHD nuclear families. Their serum folic acid level was significantly higher than that of controls (P=0.000), and Hcy level of the former was higher than that of the latter with no statistical significance (P>0.05). Serum Hcy and folic acid levels of mothers with gene mutation were lower than those of mothers with no mutation. Conclusion No significant difference of genotype distribution and allele frequency existed between CHD patients and healthy population. MTHFD G1958A mutation in parents (particularly in mother) can decrease the risk of arterial septal defect in offspring. The possible mechanism of protection might be mutation, which can increase MTHFD enzyme activity, folic acid metabolism and homocysteine remethylation, and decrease Hcy level.

cDNA Fragment Cloning of L-Galactono-1,4-Lactone Dehydrogenase andIt＇s Expression in Different Organs of R. roxburghii Tratt

A 855 bp cDNA encoding L-galactono-1,4-lactone dehydrogenase (GalLDH) fragment was cloned from fruit of R. roxburghii Tratt by the method of RT-PCR, on the basis of the homologous genes of Arabidopsis thaliana, cauliflower, sweet potato, strawberry, etc. in GenBank. Sequence analysis showed 79-92% identity in nucleotide sequence and 75-87% identity in amino acid sequence to that of strawberry and Arabidopsis thaliana, etc. Northern blot showed that the expression of GalLDH was significantly different in different organs. The transcription level of GalLDH in fruit was significantly higher than that in leaf, stem and root respectively. Furthermore, this expression mode was highly correlated with AsA levels.

Polymorphisms of alcohol dehydrogenase 2 and aldehyde dehydrogenase 2 and colorectal cancer risk in Chinese males

AIM: To evaluate the relationship between drinking and polymorphisms of alcohol dehydrogenase 2 (ADH2) and/or aldehyde dehydrogenase 2 (ALDH2) for risk of colorectal cancer (CRC) in Chinese males. METHODS: A case-control study was conducted in 190 cases and 223 population-based controls. ADH2 Arg47His (G-A) and ALDH2 Glu487Lys (G-A)genotypes were identified by PCR and denaturing high-performance liquid chromatography (DHPLC). Information on smoking and drinking was collected and odds ratio (OR) was estimated. RESULTS: The ADH2 A/A and ALDH2 G/G genotypes showed moderately increased CRC risk. The age- and smoking-adjusted OR for ADH2 A/A relative to G/A and G/G was 1.60 (95% CI=1.08-2.36), and the adjusted OR for ALDH2 G/G relative to G/A and A/A was 1.79 (95% CI=1.19-2.69). Signif icant interactions between ADH2, ALDH2 and drinking were observed. As compared to the subjects with ADH2 G and ALDH2 A alleles, those with ADH2 A/A and ALDH2 G/G genotypes had a signif icantly increased OR (3.05, 95% CI= 1.67-5.57). The OR for CRC among drinkers with the ADH2 A/A genotype was increased to 3.44 (95% CI= 1.84-6.42) compared with non-drinkers with the ADH2 G allele. The OR for CRC among drinkers with the ALDH2 G/G genotype was also increased to 2.70 (95% CI= 1.57-4.66) compared with non-drinkers with the ALDH2 A allele. CONCLUSION: Polymorphisms of the ADH2 and ALDH2 genes are significantly associated with CRC risk. There are also signifi cant gene-gene and gene- environment interactions between drinking and ADH2 and ALDH2 polymorphisms regarding CRC risk in Chinese males.

Glutamate dehydrogenase and Na^+-K^+ ATPase expression and growth response of Litopenaeus vannamei to different salinities and dietary protein levels

Improvement in the osmoregulation capacity via nutritional supplies is vitally important in shrimp aquaculture.The effects of dietary protein levels on the osmoregulation capacity of the Pacific white shrimp(L.vannamei) were investigated.This involved an examination of growth performance,glutamate dehydrogenase(GDH) and Na+-K+ ATPase mRNA expression,,and GDH activity in muscles and gills.Three experimental diets were formulated,containing 25%,40%,and 50% dietary protein,and fed to the shrimp at a salinity of 25.After 20 days,no significant difference was observed in weight gain,though GDH and Na+-K+ ATPase gene expression and GDH activity increased with higher dietary protein levels.Subsequently,shrimp fed diets with 25% and 50% dietary protein were transferred into tanks with salinities of 38 and 5,respectively,and sampled at weeks 1 and 2.Shrimp fed with 40% protein at 25 in salinity(optimal conditions) were used as a control.Regardless of the salinities,shrimp fed with 50% dietary protein had significantly higher growth performance than other diets;no significant differences were found in comparison with the control.Shrimp fed with 25% dietary protein and maintained at salinities of 38 and 5 had significantly lower weight gain values after 2 weeks.Ambient salinity change also stimulated the hepatosomatic index,which increased in the first week and then recovered to a relatively normal level,as in the control,after 2 weeks.These findings indicate that in white shrimp,the specific protein nutrient and energy demands related to ambient salinity change are associated with protein metabolism.Increased dietary protein level could improve the osmoregulation capacity of L.vannamei with more energy resources allocated to GDH activity and expression.

Molecular Weight of Cytoplasmic Malate Dehydrogenase,Mitochondrial Malate Dehydrogenase and Lactate Dehydrogenase of a Freshwater Catfish

The multiple molecular forms of cytoplasmic malate dehydrogenase (cMDH), mitochondrial malate dehydrogenase (mMDH ) and lactate dehydrogenase (LDH ) were studied in the liver and skeletal muscle of the freshwater catfish, Clarias batrachus. There were two electrophoretically distinguishable bands (AA andBB) of cMDH and mMDH which suggests that they are apparently encoded at two gene loci (A and B) in both the tissues.However, the presence of a single band (LDH-1 ) of LDH in liver and double bands (LDH-1and LDH-2) in skeletal muscle in which LDH-2 was predominant reflects the differential expression of LDH genes in different metabolic tissues to meet the requirement of energy production. The AA isoform (74 kd) of liver cMDH was smaller than those of the AA form (110 kd) of skeletal muscle. In contrast, the BB isoform of liver (42 kd) and skeletal muscle (54 kd) were more or less similar in size. Unlike the case of cMDH, the molecular weight of AA isoform (115 kd) of liver mMDH was higher than those of the AA form (87kd) of skeletal muscle. Whereas the molecular weight of BB isoform (58 kd) of liver was in proximity to the weight of BB form (44 kd) of skeletal muscle mMDH. The size of AA isoform (74 kd) of liver cMDH was smaller, while the AA isoform (110 kd) of skeletal muscle was larger as compared to AA form of mMDH in the liver (115 kd) and skeletal muscle (87 kd). But the size of BB isoform of both the isozymes was almost equal in these metabolic tissues. The molecular weight of liver LDH-1 (96 kd) was close to the weight of LDH-1 (82 kd) in skeletal muscle. The molecular weight of skeletal muscle LDH-2 was deduced as 37 kd which is much more lower than the weight of LDH-1 in liver and skeletal muscle. The smaller size of LDH-2 in skeletal muscle may be of a physiological significance in this anaerobic tissue

Expression and characterization of mouse lactate dehydrogenase subunit C in Escherichia coli.

Objective: To construct a prokaryotic recombinant vector for mouse lactate dehydrogenase-C and to detect its expression in BL21. Methods: The coding sequence of mouse lactate dehydrogenase subunit C was amplified from mouse testis RNA with specific primers and cloned into pGEX-2T after restriction digestion with BamH I and EcoR I. GST fusion protein was expressed after induction with IPTG. Results: Sequencing and restriction digestion of the recombinant plasmid revealed the coding sequence for mouse lactate dehydrogenase subunit C. A protein band of about 60 000 could be induced by IPTG in the recombinant plasmid. Conclusion: The coding sequence of mouse lactate dehydrogenase subunit C was introduced into the pGEX-2T plasmid and a GST-fused protein could be induced at a high level.

Affiliation of Dihydrolipoyl Dehydrogenase Allozymes in Mycorrhizae of European Forest Trees and Characterization of the Enzyme of the Matt Bolete (<i>Xerocomus pruinatus</i>) and the Bay Bolete (<i>X. badius</i>)

Mycorrhizal roots of the deciduous trees European beech (Fagus sylvatica (L.)) and Sessile oak (Quercus petraea (MattuschkaLiebl.)) and the conifers Norway spruce (Picea abies (L.) H. Karst.) and European larch (Larix decidua (Mill.)) associated with the ectomycorrhizal fungi matt bolete (Xerocomus pruinatus (Fries 1835)) or bay bolete (X. badius (Fries 1818)) were analysed with respect to the occurrence of dihydrolipoyl dehydrogenase (EC 1.8.1.4) allozymes. In root tissues of the two deciduous trees, two gene loci could be visualized after cellulose acetate electrophoresis while three loci were expressed in root tissues of the two coniferous species. The two fungal species and further ectomycorrhizal fungi expressed exclusively one dihydrolipoyl dehydrogenase gene. In Xerocomus pruinatus and X. badius, the dihydrolipoyl dehydrogenase gene consists of 1460 bp and 1370 bp, respectively, including five introns each consisting of 52 bp. Their DNA sequences correspond to 70 to 90% to other fungal dihydrolipoyl dehydrogenase genes. One monomer of the dimeric dihydrolipoyl dehydrogenase enzyme consists of 486 (X. pruinatus) or 454 (X. badius) amino acids which sum up to a molecular mass of 55 kDa (X. pruinatus), respectively 52 kDa (X. badius). The number of positively charged amino acid residues makes 79 (X. pruinatus) and 68 (X. badius) and the number of negatively charged amino acid residues was calculated to make 46 (X. pruinatus) and 48 (X. badius);isoelectric points make 9.99 (X. pruinatus) and 9.68 (X. badius). Calculated three dimensional structures reveal a short NADH binding site being part of a larger FAD-binding site and a binding/dimerization domain.

云南松PyCADs基因的克隆与表达分析

【目的】研究云南松肉桂醇脱氢酶的表达特性及其在木质素生物合成过程中的作用。【方法】以一年生云南松苗木为材料,通过测定嫩茎、嫩芽和针叶中18种木质素通路小分子的相对含量,并结合转录组数据联合分析,对云南松CAD基因进行筛选、克隆和生物信息学分析,同时利用RT-qPCR技术分析其在不同组织中的表达模式。【结果】在检测的18种木质素通路小分子中,嫩芽以5-O-咖啡酰莽草酸、5-O-对香豆酰莽草酸和咖啡酸3种小分子的相对含量较高,嫩茎以3-O-对香豆酰奎宁酸、4-香豆酸、阿魏酸、松柏醛、L-苯丙氨酸、松柏醇、对-香豆醇、L-酪氨酸和芥子醛9种小分子的相对含量较高,而在针叶中则以松柏苷、香豆醛、咖啡醛和紫丁香苷4种小分子的相对含量较高。云南松转录组中筛选出4个CAD家族成员,通过系统进化分析发现云南松PyCAD-3与AtCAD1同源,PyCAD-1、PyCAD-2和PyCAD-4与松属类CAD、拟南芥AtCAD4、AtCAD5亲缘关系最近。相关性分析表明PyCAD-1和PyCAD-2与上下游木质素通路小分子相关性较强。PyCAD-1和PyCAD-2开放阅读框全长分别为570和1083 bp,编码蛋白分子量分别为20.38和39.30 kDa。实时荧光定量PCR结果分析显示,PyCAD-1基因的相对表达量在嫩芽、嫩茎中最高;PyCAD-2基因的相对表达量在嫩茎中最高。【结论】PyCAD-2可能直接参与云南松木质素的生物合成,而PyCAD-1则可能存在一定的功能冗余。研究结果为云南松CAD基因家族及木质素代谢途径相关基因研究提供参考。

禾谷镰刀菌醛脱氢酶(ALDH)基因敲除突变体的转录组分析

【目的】对野生型PH-1菌株和醛脱氢酶(ALDH)基因FGSG_04194敲除突变体(ΔFg04194)进行转录组测序,分析禾谷镰刀菌ALDH调控菌丝生长和脱氧雪腐镰刀菌烯醇(DON)生成情况,为深入探究禾谷镰刀菌ALDH的生物学功能、DON生成机制及致病机理提供了理论依据。【方法】接种禾谷镰刀菌野生型PH-1、ΔFg04194突变体和基因回补突变体(ΔFg04194-C)菌株至CM培养基和小麦基质中,分析FGSG_04194基因对菌丝生长和DON生成的影响。利用高通量转录组测序技术对野生型PH-1菌株和ΔFg04194突变菌株在CM培养基中培养72 h的菌丝进行转录组测序,对筛选出的差异表达基因(DEGs)进行GO功能注释和KEGG信号通路富集分析,利用实时荧光定量PCR对转录组测序结果进行验证。【结果】ΔFg04194突变体的菌落直径和生成的DON含量较野生型PH-1和ΔFg04194-C突变体菌株显著减少(P<0.05,下同)。野生型PH-1和ΔFg04194突变体转录组原始数据经过滤后获得34.9 Gb Clean data,共鉴定出329个DEGs,其中263个基因表达显著上调,66个基因表达显著下调。GO功能注释结果显示,DEGs显著富集在质膜成分、碳水化合物代谢和物质转运过程等条目上。KEGG信号通路富集分析显示,DEGs显著富集在碳水化合物代谢通路、氨基酸代谢通路、脂质代谢、能量代谢、生物降解代谢通路、细胞生长和死亡相关途径、信号转导途径等。将FGSG_04194基因调控下有代表性的DEGs分成五大类:几丁质合成相关的基因、跨膜转运蛋白相关的基因、转录因子相关基因、脂质代谢相关基因和能量代谢相关的基因。ΔFg04194突变体的ATP含量显著高于野生型PH-1和ΔFg04194-C突变体。运用实时荧光定量PCR检测7个DEGs的表达情况,其结果与转录组测序结果基本一致。【结论】FGSG_04194影响禾谷镰刀菌的菌丝生长和DON生成,并在ATP生成中起负调控作用,其机制可能与调控转录因子的表达、调控脂类代谢、氨基酸代谢和能量代谢等通路有关。

强化厌氧表达dld基因以提高大肠杆菌工程菌发酵产L-乳酸的光学纯度

为去除廉价发酵原料中的D-乳酸从而提高发酵最终产物L-乳酸的光学纯度,该研究通过构建带有不同厌氧诱导启动子(pflBp6、pnirB、pflBp6-pnirB)的D-乳酸脱氢酶基因(dld)的表达质粒,并将其分别转入大肠杆菌(Escherichia coli)HBUT-L,加强其在发酵产L-乳酸的同时消除外源D-乳酸的能力。通过装液量与转速的单因素试验筛选最优的质粒表达条件及菌株,并在无机盐培养基与玉米浆培养基中进行发酵验证。结果表明,在装液量为200 mL/250 mL、转速为150 r/min的条件下,含有启动子pflBp6-pnirB的表达质粒的工程菌株HBUT-L4发酵18 h时D-乳酸脱氢酶活力最高,为81.1 U/g。在此条件下进行无机盐培养基和玉米浆培养基发酵时,工程菌株HBUT-L4相对于出发菌株HBUT-L,D-乳酸消耗速率分别提高250%、217%,L-乳酸的光学纯度分别从96.32%、98.48%提升至99.95%、99.98%。在大肠杆菌工程菌发酵L-乳酸的过程中,带有厌氧诱导启动子pflBp6-pnirB的表达质粒可提高D-乳酸脱氢酶活力,强化菌株消除外源D-乳酸,进而提高L-乳酸的光学纯度的能力,具有重要的工业化应用价值。

分形维数对高级别胶质瘤异柠檬酸脱氢酶-1基因突变状态和Ki-67指数的评估价值

目的:探讨分形维数(FD)评估高级别胶质瘤(HGG)异柠檬酸脱氢酶-1(IDH-1)基因突变状态和肿瘤细胞的增殖活跃程度的价值。方法:收集经病理证实为HGG并测定IDH-1突变状态和Ki-67指数的患者75例,其中,IDH-1野生型52例,IDH-1突变型23例。术前在T_(1)WI、T_(2)WI、DWI图像最大层面及其上下2个层面上自动勾画肿瘤边界及瘤周水肿范围,测定外边缘FD值,取3个层面的平均值为测定值。比较IDH-1突变型和野生型组间FD值的差异;使用ROC曲线分析不同FD值对评估IDH-1突变的效能;使用logistic回归分析评估FD是否为IDH-1突变的独立危险因素;使用Pearson相关分析评估不同FD值与Ki-67指数之间的关系。结果:IDH-1野生型T_(1(肿瘤))-FD、T_(2(肿瘤))-FD、T_(2(水肿))-FD、DWI_((肿瘤))-FD均低于IDH-1突变型(均P<0.05);且在DWI上的FD值诊断效能最高,AUC为0.868,特异度为0.696,敏感度为0.923,且DWI_((肿瘤))-FD是IDH-1突变预测的独立危险因素;各FD值与Ki-67指数均呈正相关,T_(2(肿瘤))-FD与Ki-67指数相关性最高(r=0.4853,P<0.0001)。结论:基于HGG患者MRI图像测定的FD值可评估患者IDH-1基因突变状态,且与Ki-67指数呈正相关。

自杀质粒同源重组介导阴沟肠杆菌adh基因缺失突变体构建及其生物学特性

本研究旨在探究敲除阴沟肠杆菌(Enterobacter cloacae)代谢通路上乙醇脱氢酶基因对乙偶姻代谢合成的影响,进一步提高乙偶姻产量。实验基于E.cloacae SDM中的乙醇脱氢酶adh基因序列设计特异性引物,并构建adh基因自杀质粒pKR6K-∆adh。利用热激法将自杀质粒转入E.cloacae∆budCldh,成功得到多基因缺失菌株E.cloaca∆budC-ldh-adh,并进行发酵性能测试。研究结果显示,与出发菌株相比,新构建的重组菌株在敲除了负责乙醇合成的关键酶乙醇脱氢酶adh基因后,其乙偶姻的生产强度提高了20.6%,产量提高了22.6%,同时乙醇产量提高了92.8%。此外,由于通过基因改造阻断了多条分支代谢路径,流向丁二酸代谢路径的碳通量明显变多,丁二酸产量提高101.3%。本研究成果不仅为构建高效乙偶姻生产菌株提供了有价值的参考,也为乙偶姻的大规模工业生产奠定了基础。

谷氨酸脱氢酶gdhA基因缺失对单增李斯特菌抗氧化应激的影响

【目的】旨在阐明谷氨酸脱氢酶gdhA基因对单增李斯特菌抗氧化应激能力的影响,并探明glnR基因对gdhA基因的调控作用。【方法】采用同源重组技术构建单增李斯特菌gdhA基因缺失株;通过生长曲线测定亲本株10403S、缺失株10403S-ΔgdhA和回补株10403S-CΔgdhA菌株的生长能力;利用抗氧化应激存活试验检测gdhA基因缺失对单增李斯特菌抗氧化应激能力的影响。诱导GdhA蛋白表达并纯化,制备兔多克隆抗体,并通过Western blotting检测抗体特异性。通过构建携带gdhA基因启动子区域的GFP报告质粒,测定氧化应激条件下glnR基因缺失对gdhA基因转录水平的影响。使用Western blotting检测氧化应激条件下glnR基因缺失对GdhA蛋白表达水平的影响,并检测glnR基因缺失对菌株存活能力的影响。【结果】生长曲线结果显示,gdhA基因缺失不影响单增李斯特菌在正常条件下的生长能力。在20 mmol/L H 2O 2条件下,缺失株10403S-ΔgdhA存活能力极显著高于亲本株10403S(P<0.01)。Western blotting结果显示,GdhA兔多克隆抗体制备成功。GFP荧光分析结果显示,glnR基因缺失后,gdhA基因转录水平极显著上调(P<0.01);在氧化应激条件下glnR基因缺失后GdhA蛋白表达水平极显著升高(P<0.01);glnR基因缺失菌株存活能力显著下降(P<0.05)。【结论】谷氨酸脱氢酶编码基因gdhA缺失不影响单增李斯特菌10403S正常生长,但显著提高其氧化应激条件下的存活能力,gdhA基因转录水平及GdhA蛋白表达水平受glnR基因负调控。

柠檬明串珠菌KM20中D-乳酸脱氢酶的特性

目的:分析柠檬明串珠菌中D-乳酸脱氢酶(D-LDH)的酶学特性。方法:对柠檬明串珠菌KM20中D-乳酸脱氢酶基因进行克隆表达并构建表达质粒,转化至Escherichia coli BL21(DE3)中实现过表达。结果:经Ni-NTA柱亲和层析纯化后,D-LDH-1与D-LDH-2编码的蛋白分子质量分别为40.0,38.5 kDa;比活力分别为2.18,153.10 U/mg;在丙酮酸还原中两种酶的最适pH值与最适温度均为8.0与40℃;而乳酸氧化时D-LDH-2的最适pH值与最适温度分别为12.0与30℃。D-LDH-1与D-LDH-2对草酰乙酸、苯丙酮酸和2-酮戊二酸具有较强的催化能力,且Ca^(2+)、Cu^(2+)和Na+对其酶活性均具有促进作用,Zn^(2+)与SDS对酶活性有极高的抑制作用。此外,两种酶对丙酮酸的Km值分别为2.98,6.11 mmol/L,对丙酮酸的K_(cat)/K_(m)分别为6.04×10^(2),2.28×10^(4)L/(mol·s),LDH-2对D-乳酸的K_(cat)/K_(m)为65.0 L/(mol·s)。结论:D-LDH-1与D-LDH-2为柠檬酸明串珠菌中催化D-乳酸合成的关键酶。

番茄FAD基因家族的鉴定与表达分析

【目的】脂肪酸脱氢酶(fatty acid desaturase,FAD)是一类催化植物不饱和脂肪酸合成的关键酶,在植物生长发育及逆境胁迫响应中起重要作用。鉴定番茄SlFAD基因家族,为番茄SlFAD基因家族功能研究及遗传改良提供理论依据。【方法】采用生物信息学方法,对其基因家族成员进行鉴定,并对其理化性质、基因结构、系统发育树和表达模式等方面进行研究。【结果】在番茄基因组中共鉴定出26个SlFAD基因,可分为4个亚族;理化性质分析显示SlFAD蛋白的氨基酸个数在119-912个之间,分子量介于13288.27-102522.25 Da,SlFAD蛋白在番茄中主要以碱性蛋白的性质存在,大部分SlFAD家族成员为稳定蛋白和亲水性蛋白;亚细胞定位预测SlFAD基因家族成员主要存在于内质网;基因特征分析显示同一亚族间的成员具有较为相似的基因结构和保守基序;启动子顺式作用元件分析显示数量最多的是光响应与激素响应相关的元件;染色体定位显示26个SlFAD家族成员共分布在10条染色体上,6号和12号染色体上成员最多;二级结构预测显示26个SlFADs家族成员均以α-螺旋和β-转角为主;转录组数据及RT-qPCR分析表明SlFAD1、SlFAD4和SlFAD18基因在成熟花药中高度表达,SlFAD23在根尖中高度表达,说明SlFAD1、SlFAD4和SlFAD18可能参与花药发育,SlFAD23可能参与根尖发育;低温胁迫下,SlFAD6和SlFAD21表达量被抑制,说明SlFAD6和SlFAD21可能与低温响应有关系,SlFAD1和SlFAD14在低温胁迫初期显著上调,随后又被抑制,说明该基因在低温胁迫初期发挥重要作用。【结论】SlFAD基因家族在番茄根尖、叶片、花药的生长发育过程及低温胁迫中发挥重要作用。

外源添加VB_(12)对肺炎克雷伯氏菌代谢3-羟基丙酸的影响

为了探究外源添加维生素B12(Vitamin B12,VB_(12))对Klebsiella pneumoniae HD79和K.pneumoniae HD79-T利用甘油还原途径生产3-羟基丙酸(3-hydroxypropionic acid,3-HP)的影响以及摸索VB_(12)对K.pneumoniae HD79和K.pneumoniae HD79-T的阈值上限,将不同浓度(0.01、0.02、0.03、0.04、0.05 g/L)的VB_(12)添加到K.pneumoniae HD79及K.pneumoniae HD79-T的发酵培养基中,利用HPLC检测其底物消耗及产物产生情况、qRT-PCR检测还原途径相关基因的mRNA表达情况以及酶联免疫试剂盒检测代谢相关酶活性。结果表明,VB_(12)对K.pneumoniae HD79和K.pneumoniae HD79-T的阈值为0.01 g/L和0.03 g/L。与未添加VB_(12)相比,菌株K.pneumoniae HD79和K.pneumoniae HD79-T的3-HP产量分别提高了24.39%,8.86%;醛脱氢酶基因puuC表达量分别提高了2.49倍和1.68倍;ALDH、GDHt和PDOR的酶活力分别提高了50.24%、40.36%和18.29%,及30.49%、37.84%和13.56%。说明通过外源添加辅酶因子VB_(12)对肺炎克雷伯氏菌高产3-HP是可行策略。