Molecular characterization of two glutathione peroxidase genes of Panax ginseng and their expression analysis against environmental stresses

Glutathione peroxidases (GPXs) are a group of enzymes that protect cells against oxidative damage generated by reactive oxygen species (ROS). GPX catalyzes the reduction of hydrogen peroxide (H₂O₂) or organic hydroperoxides to water or alcohols by reduced glutathione. The presence of GPXs in plants has been reported by several groups, but the roles of individual members of this family in a single plant species have not been studied. Two GPX cDNAs were isolated and characterized from the embryogenic callus of Panax ginseng. The two cDNAs had an open reading frame (ORF) of 723 and 681 bp with a deduced amino acid sequence of 240 and 226 residues, respectively. The calculated molecular mass of the matured proteins are approximately 26.4 kDa or 25.7 kDa with a predicated isoelectric point of 9.16 or 6.11, respectively. The two PgGPXs were elevated strongly by salt stress and chilling stress in a ginseng seedling. In addition, the two PgGPXs showed different responses against biotic stress. The positive responses of PgGPX to the environmental stimuli suggested that ginseng GPX may help to protect against environmental stresses.     

A C. elegans homolog of the Cockayne syndrome complementation group A gene

Cockayne syndrome (CS) is a debilitating and complex disorder that results from inherited mutations in the CS complementation genes A and B, CSA and CSB. The links between the molecular functions of the CS genes and the complex pathophysiology of CS are as of yet poorly understood and are the subject of intense debate. While mouse models reflect the complexity of CS, studies on simpler genetic models might shed new light on the consequences of CS mutations. Here we describe a functional homolog of the human CSA gene in Caenorhabditis elegans. Similar to its human counterpart, mutations in the nematode csa-1 gene lead to developmental growth defects as a consequence of DNA lesions.     

苹果柠檬酸合酶3基因家族成员鉴定及表达分析

柠檬酸合酶(citrate synthase 3, CS3)是细胞代谢途径中的关键酶之一,其活性调节着生物体的物质和能量代谢过程。本研究旨在从苹果全基因组中鉴定CS3基因家族成员,并进行生物信息学和表达模式分析,为研究苹果CS3基因的潜在功能提供理论基础。利用BLASTp基于GDR数据库鉴定苹果CS3家族成员,通过Pfam、SMART、MEGA5.0、clustalx.exe、ExPASy Proteomics Server、MEGAX、SOPMA、MEME和WoLF PSORT等软件分析CS3蛋白序列基本信息、亚细胞定位情况、结构域组成、系统进化关系以及染色体定位情况。利用酸含量的测定和实时荧光定量PCR (real-time fluorescence quantitative polymerase chain reaction, qRT-PCR)技术检测苹果6个CS3的组织表达和诱导表达特性。苹果CS3基因家族包含6个成员,这些CS3蛋白包括473−608个不等的氨基酸残基,等电点分布在7.21−8.82。亚细胞定位结果显示CS3蛋白分别定位在线粒体和叶绿体。系统进化分析可将其分为3类,各亚家族基因数量分别为2个。染色体定位结果显示,CS3基因分布在苹果不同的染色体上。蛋白二级结构以a-螺旋为主,其次是无规则卷曲,b-转角所占比例最小。筛选的6个家族成员在不同苹果组织中均有表达,整体表达趋势从高到低依次为MdCS3.4相对表达含量最高,MdCS3.6次之,其他家族成员相对表达量依次为MdCS3.3>MdCS3.2>MdCS3.1>MdCS3.5。qRT-PCR结果显示,MdCS3.1和MdCS3.3基因在酸含量较低的‘成纪1号’果肉中相对表达量最高,酸含量较高的‘艾斯达’果肉中MdCS3.2和MdCS3.3基因相对表达量最高。因此,本研究对不同苹果品种中CS3基因相对表达量进行了检测,并分析了其在苹果果实酸合成过程中的作用。结果表明,CS3基因在不同苹果品种中的相对表达量存在差异,为后续研究苹果品质形成机制提供了参考。     

肠毒素大肠杆菌定居因子CS6抗原基因在痢疾杆菌中的表达

通过体外重组的方法,将asd基因插入重组表达质粒,使抗生素抗性失活,并与弗氏志贺氏菌FWL01构成宿主-载体平衡致死系统. 通过蛋白质印迹结果表明,在没有抗生素条件选择的情况下,可稳定表达肠毒素大肠杆菌定居因子抗原CS6. 重组菌通过口服和鼻饲免疫小鼠后,可以诱生CS6血清IgG抗体;同时可以检测到分泌型IgA产生,表明重组菌可以诱导相应的黏膜免疫反应.     

CS3菌毛抗原和霍乱毒素B亚基在人伤寒菌中的表达

通过体内外重组的方法,构建了人伤寒菌流行株Ｔｙ２的△ａｒｏＡ,△ａｒｏＣ和ａｓｄ＾－基因缺失突变体（ＲＳ４１７）作为抗原载体菌：同时,构建包含ａｓｄ基因的表达质粒ｐＹＸ１０２,与ＲＳ４１７一起,构成宿主－载全平衡致死系统,用于在没有抗生素条件选择的情况下,稳定表达克隆在表达质粒上的外源抗原基因,将肠毒素性大肠杆菌的菌毛抗原ＩＩＩ（ＣＳ３）基因和霍乱弧菌毒素Ｂ亚基（ＣＴＢ）基因分别克隆至ｐＹＸ１０２     

两种供氮水平下水稻生长后期相关性状的QTL定位

以特青为母本与Lemont杂交,然后用特青为轮回亲本回交,建立特青背景下的染色体片段置换系（CSSL）群体。在正常和低氮条件下分别在生长后期对株高（PH）、单株穗数（PN）、叶绿素含量（CC）、地上部干物重（SDW）和单株籽粒产量（YD）等性状进行了QTL分析,共检测到31个QTL。其中在正常供氮水平下控制PH、PN、CC、SDW和YD的QTL数目均为3个;在低氮水平下检测到5、4、5和2个影响PH、PN、CC和SDW的QTL,在低氮水平下没有检测到控制YD的位点。大部分QTL集中在第2、3、7、11和12染色体上,影响不同性状或在两种供氮水平下影响同一性状的QTL在染色体上成串或成簇分布。其中RM30-RM439、RM18-RM478、RM309-RM270、RM235-RM17等区域同时检测到控制两个以上性状的QTL,表现出明显的一因多效现象。推测仅在低氮水平下检测到的QTL可能跟水稻对低氮胁迫耐性有一定的关联。     

Mobilization of CS fimbriae-associated plasmids of enterotoxigenic Escherichia coli of serotype O6: K15: H16 or H- into various wild-type hosts

Abstract CS fimbriae-associated plasmids of two enterotoxigenic Escherichia coli strains of serotype O6: K15: H16 or H- (biotypes A and F) with M _r values of 51 × 10⁶ and 72 × 10⁶, respectively, were mobilized into various alternative host bacteria. Expression of CS1 or CS2 fimbriae was obtained when either of the CS fimbriae-associated plasmids was introduced into CS Fim⁻, O6: K15: H16 or H- recipients with rhamnose-negative and rhamnose-positive fermentation phenotypes, respectively, whereas CS3 fimbriae were expressed irrespective of the biotype of the recipient. On transfer into a CS Fim⁻ variant of an enterotoxigenic O8: H9 strain and into two K-12 strains, a CS3-fimbriae-only phenotype was conferred by the presence of either of the plasmids. When a CS Fim⁻ variant of a Rha⁺ CS2-fimbriae-only strain of serotype O6: K15: H16 harboured either of the plasmids, both CS2 and CS3 fimbriae were expressed, indicating that the rare CS2-fimbriae-only wild-type phenotype is probably due to the presence of a defective plasmid in such strains. Mobilization of the 51 MDa CS fimbriae-associated plasmid into five non-enterotoxigenic Rha⁺ porcine isolates of E. coli with O6 serotypes other than O6: K15: H16 or H- yielded CS3-fimbriae-only transconjugants. Thus the correlation between a Rha⁺ fermentation phenotype and expression of CS2 fimbriae does not hold in general for O-group 6 strains.