含花生根瘤菌吸氢基因重组质粒pZ—55的特性分析

应用含豌豆根瘤菌部分吸氢基因的探讨及ＰＣＲ分析,从花生根瘤菌基因文库中筛选到含有吸氢基因的重组质粒ｐＺ－５５。用ＢａｍＨⅠ、ＥｃｏＲⅠ和ＫｐｎⅠ等内切酶对ｐＺ－５５进行酶切分析,构建了ｐＺ－５５的酶切物理图谱。经三亲本杂交分析,ｐＺ－５５能互补诱变株Ｌｎ－１（Ｈｕｐ＾－）,获得在自生条件下表达吸氢活性。     

根瘤菌吸氢酶基因转移的研究

通过三亲本杂交将含有花生根瘤菌吸氢基因的质粒pZ 55(Tcr)转入不吸氢的花生根瘤菌Ra 34等菌株 (Hup- ,Nif+,Apr)中 ,筛选到既具有吸氢又具有固氮能力的花生根瘤菌结合株Rz34 2。在自生和共生条件下 ,结合株均可表达高吸氢和高固氮活性。以结合株Rz34 2接种的花生植株叶片的干重比不接种的、接种受体株Ra34(Hup- )和接种对照菌株L8 3(Hup+,Nif+)的分别高 6.2 %、7.6%和 6.3% ;种子的含氮量分别高 8 9%、1.00 %和 6.0 % ;产量分别高 188%、1 0 5%和 1 0 7%。研究结果表明 ,以含吸氢基因的结合株接种花生能提高根瘤菌与花生的共生固氮效率 ,增加作物的产量。     

影响根瘤菌共生固氮效率的主要因素及遗传改造*

介绍了影响根瘤菌共生固氮效率的主要因素及遗传改造 :包括土壤因素、宿主植物、四碳二羧酸转移酶基因dct、固氮调节基因nifA、吸氢酶基因hup、共生质粒 (基因 )、缺陷型回复突变等。     

影响根瘤菌共生固氮效率的主要因素及遗传改造

介绍了影响根瘤菌共生固氮效率的主要因素及遗传改造,包括土壤因素,宿主植物,四碳二羟酸转移酶基因dct,固氮调节基因nifA,吸氢酶基因hup,共生质粒（基因）,缺陷型回复突变等。     

毛豆根瘤菌转吸氢基因的研究

通过三亲本杂交将携带豌豆根瘤菌吸氢基因的质粒pAL₆₁₈转移到台湾毛豆根瘤菌292-C中,经抗性筛选、质粒检测和吸氢活性测定,得到能稳定遗传的结合株292-C₂和292-C₃。在自生条件下结合株均表现较高的吸氢活性,而受体株292-C不吸氢,在共生条件下结合株表现为高吸氢,而受体株表现为放氢。     

毛豆根瘤菌转吸氢基因的研究

通过三亲本杂交将携带豌豆根瘤菌吸氢基因的质粒ｐＡＬ６１８转移到台湾毛豆根瘤菌２９２－Ｃ中,经抗性筛选、质粒检测和吸氢活性测定,得到能稳定遗传的结合株２９２－Ｃ２和２９２－Ｃ３。在自生条件下结合株均表现较高的吸氢活性,而受体株２９２－Ｃ不吸氢,在共生条件下结合株表现为高吸氢,而受体株表现为放氢。     

紫云英根瘤菌的吸氢与固氮的关系

用气相色谱和2,3,5-氯化三苯基四氮唑(TTC)还原测定,从8株紫云英、2株大豆,1株豇豆根瘤菌中检出二株在自生条件下具吸氢能力的紫云英根瘤菌菌株。观察到氢是诱导氢酶形成的必需条件。增加培养基中的碳底物浓度,菌株的吸氢活性受到抑制。乙炔和一氧化碳对吸氢活性具有不同程度的抑制作用。 从吸氢与不吸氢菌株的回接对比试验,似乎没有看到吸氢的菌株对寄主干物质积累有明显的影响。并发现自生条件下不吸氢的菌株所形成的根瘤具有吸氢的能力。     

巴西固氮螺菌中吸氢酶基因同源性的分子检测

通过TTC(2 ,3,5 氯化三苯基氮唑 )实验筛选出 12株能产生吸氢酶蛋白 (Hup+ )的巴西固氮螺菌 (Azospir rilumbrasilense)菌株。用Qiagen柱分离提纯含豌豆根瘤菌的hup基因片段的质粒 pHVT10 9和pHVT115 ,并用地高辛标记法标记pHVT115 ,与 12株Hup+ 巴西固氮螺菌的总DNA进行斑点杂交 ,结果显示pHVT115所含的吸氢酶基因 (hup基因 )片段与巴西固氮螺菌的大部分菌株的hup基因同源性不强。这一结果表明hup基因在固氮生物中存在着遗传多样性 ,异源hup基因探针不一定都适宜于探测hup基因。     

环境因子对根瘤菌吸氢活性表达的影响

自生条件下,测定准噶尔盆地南部的68株根瘤菌吸氢活力,获得一株Hup~+的冬箭筈豌豆根瘤菌C_(48)。经与紫云英根瘤菌株109及89比较,两者氢酶表达的最适pH相同;温度分别以20或30℃为宜;Ni~(2+)显著促进吸氢表达,但C_(48)还受Co~(2+ )、Mg~(2+)、Cu~(2+)的促进;紫云英根瘤菌的氨酶表达受碳水化合物抑制较冬箭筈豌豆根瘤菌明显。此外,自生条件下生长的Hup—菌株,经与宿主共生后,Hup~+的百分率大为增加。     

含吸氢酶基因（hup）嵌合质粒的构建和吸氢酶活性在阴沟肠杆菌中的表达

以质粒ｐＲＫ４０４为载体亚克隆含大豆根瘤菌吸氢酶结构基因（ｈｕｐ）的片段,构建成嵌合质粒ｐＨＲ１１、ｐＨＲ４和ｐＨＲ１０。通过三亲本杂交将这些嵌合质粒导入无吸氢活性的Ｒｈｏｄｏｂａｃｔｅｒｓｐｈａｅｒｏｉｄｅｓ２４１菌株（Ｈｕｐ－）,均获得Ｈｕｐ＋的接合子。利用启动子检测质粒ｐＭＰ２２０证明,在ｈｕｐ对结构基因上游１．２ｋｂ内存在ｈｕｐ启动基因片段。以ｐＲＫ２０１３为助质粒可将ｐＨＲ１１导入Ｅｎｔｅｒｏｂａｃｔｅｒｃｌｏａｃａｅ和Ｋｌｅｂｓｉｅｌｌａｏｘｙｔｏｃａ等土壤固氮菌株。本文以接合子Ｅ．ｃｌｏａｃａｅＥＨ１１１３为例,通过对基因组ＤＮＡＳｏｕｔｈｅｒｎ杂交分析证明,嵌合质粒ｐＨＲ１１在ＥＨ１１１３中稳定贮存和复制。Ｈ２诱导接合子ＥＨ１１１３吸氢酶活性高表达,吸氢活性与放氢活性比值约为对照的两倍。当以延胡索酸为电子受体时,吸氢酶的吸氢作用支持菌株固氮酶活性的提高。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细