nisp基因在nisin生物合成终末成熟过程中的控制作用

本研究应用分子克隆和基因缺失突变技术首创了一个乳酸链球菌ｎｉｓｉｎ生物合成基因ｎｉｓｐ的突变株。此菌株能分泌完整的ｎｉｓｉｎ 前体肽链,却不能分泌有活性的ｎｉｓｉｎ。经生物活性、ＳＤＳ—ＰＡＧＥ和ＲＰ—ＨＰＬＣ等技术测定,ｎｉｓｉｎ 前体Ｎ—末端连接有先导序列,用胰酶或产活性ｎｉｓｉｎ的菌细胞膜蛋白处理ｎｉｓｉｎ前体,使之失去先导链,成为有活性的成熟的ｎｉｓｉｎ肽分子。此研究结果证明ｎｉｓｐ基因在ｎｉｓｉｎ生物合成最后阶段的成熟过程起决定作用。     

CEK2,一个白色念珠菌新的MAPK能互补fus3／kss1突变 …

在利用合成寡核苷酸片段和利用简并ＰＣＲ方法筛选白色念球菌ＭＡＰＫ相关蛋白激酶基因的过程中,都得到了一个新的ＭＡＰＫ基因ＣＥＫ２（Ｃａｎｄｉｄａ ａｌｂｉｃａｎｓ ｅｘｔｒａｃｅｌｌｕｌａｒ ｓｉｇｎａｌ－ｒｅｇｕｌａｔｅｄ ｋｉｎａｓｅ２）。ＣＥＫ２基因全长为１１１９ｂｐ,编码３７３个氨基酸,白色念珠菌ＣＥＫ１同源性达５６％。ＣＥＫ２与啤酒酵母ＦＵＳ３基因同源性很高,核苷酸的同源 达５７％,氨基酸     

增加复制起始区对基因表达的影响

我们在质粒ｐｕＢ１１０的基础上组建了ｐＤＲ质粒,它们具有双复制起始区而只有一个抗卡那霉素基因。携带了这些质粒的宿主细胞对卡那霉素的抗性明显高于亲本株（Ｂ,ｓｕｂｔｉｌｉｓ １５０（ｐｕＢ１１０））。经限制性酶切图谱分析新获得的转化株具有二个复制起始区及一个 Ｋｍ＆４基因。说明增加复制起始区是提高重组子表达能力的途径之一。     

白色念珠菌CRK1基因的敲除及其功能研究

在筛选白色念珠菌促分裂原活化蛋白激酶（ＭＡＰＫ）相关蛋白激酶基因的过程中,得到了ＣＲＫ１（ＣＤＣ２－ｒｅｌａｔｅｄ ｐｒｏｔｅｉｎ ｋｉｎａｓｅ １）基因。利用同源重组原理,敲除了ＣＲＫ１双拷贝基因片段,构建了ＣＲＫ１纯合缺失株,发现ＣＲＫ１基因的缺失影响到白色念珠菌的生长速度,絮凝生长和形态发生。     

大肠杆菌精氨酰－tRNA合成酶的Lys306为酶活力所必需

将大肠杆菌精氨酰ｔＲＮＡ合成酶（ＡｒｇＲＳ）上Ｌｙｓ３０６用基因点突变的方法分别变为Ａｌａ和Ａｒｇ的密码子;得到变种基因ａｒｇｓ３０６ＫＡ和ａｒｇｓ３０６ＫＲ。变种基因重组在ｐＵＣ１８上,转化到大肠杆菌ＴＧ１中,转化子中ＡｒｇＲＳ及其变种ＡｒｇＲＳ３０６ＫＡ和ＡｒｇＲＳ３０６ＫＲ所表达的蛋白量至少为ＴＧ１表达ＡｒｇＲＳ蛋白量的１００倍。细胞粗抽提液中ＡｒｇＲＳ的比活ＴＧ１、转化子ｐＵＣ１８－ａｒｇｓ、ｐＵＣ１８－ａｒｇｓ３０６ＫＡ和ｐＵＣ１８－ａｒｇｓ３０６ＫＲ分别为１．６５、２１０、１．８和３８单位／毫克。结果表明ＡｒｓＲＳ的Ｌｙｓ３０６为Ａｌａ取代使活力完全丧失;若被Ａｒｇ取代,则活力丧失８０％以上。Ｌｙｓ３０６为ＡｒｇＲＳ活力所必需。     

点状产气单胞菌脯氨酰内肽酶在大肠杆菌中的高效表达

采用ＰＣＲ分段克隆法将点状产气单胞菌点状亚种（Ａｅｒｏｍｏｎａｓ ｐｕｃｔａｔａ ｓｕｂｓｐ．ｊｐｕｃｔａｔａ）脯氨酰内肽酶（ｐｒｏｌｙｌ ｅｎｄｏｐｅｐｔｉｄａｓｅ,ａｐＰＥＰ）的编码区基因分成３段扩增并拼接成编码６９０个氨基酸的完整基因ａｐＰＥＰ,将其克隆在表达载体ｐＢＬ和ｐＫＫＨ上,构建成温度和ＩＰＴＧ诱导型高效表达ａｐＰＥＰ的重组大肠杆菌ＢＬ２１／ｐＢＬ－ＰＥＰ和ＢＬ２１／ｐＫＫＨ－ＰＥＰ     

大豆Kunitz型胰蛋白酶抑制剂基因的分离及其在抗虫植物基因工程中的应用

大豆Ｋｕｎｉｔｚ型胰蛋白酶抑制剂属于丝氨酸蛋白酶抑制剂,具有抗虫特性。从未成熟的大豆（ＧｌｙｃｉｎｅｍａｘＬ．）子叶中提取总ＲＮＡ,然后反转录成单链ｃＤＮＡ,以此为模板,用ＰＣＲ方法扩增出大豆Ｋｕｎｉｔｚ型胰蛋白酶抑制剂基因,并克隆到ｐＢｌｕｅｓｃｒｉｐｔＫＳ（＋）的ＳｍａⅠ位点上。序列分析表明：克隆片段大小为６６３ｂｐ,包含了基因完整的编码序列。编码多肽由２１７个氨基酸组成,其中包括Ｎ端２５个氨基酸组成的信号肽序列,１８１个氨基酸组成的成熟蛋白序列和Ｃ端１１个氨基酸组成的液泡定位信号序列。构建了此基因的一系列植物表达载体,用于烟草（ＮｉｃｏｔｉａｎａｔａｂａｃｕｍＬ．）、水稻（ＯｒｙｚａｓａｔｉｖａＬ．）、棉花（ＧｏｓｙｐｉｕｍｈｉｒｓｕｔｕｍＬ．）等作物的转化。利用棉铃虫（ＨｅｌｉｏｔｈｉｓａｒｍｉｇｅｒａＨｕｂｎｅｒ）对经ＰＣＲＳｏｕｔｈｅｒｎ杂交验证获得的转基因烟草进行了抗虫测试,结果表明,转基因烟草和对照烟草相比,具有明显的抗虫能力。     

痢疾福氏2a asd基因的克隆及其序列分析

本文根据大肠杆菌（Ｅ．ｃｏｌｉ）Ｋ１２ａｓｄ基因两侧序列设计了一对引物,用全菌ＰＣＲ扩增了福氏２ａ Ｔ３２株的ａｓｄ基因及其两侧序列。对ＰＣＲ产物的初步结果表明,在ａｓｄ基因两端存在ＢａｍＨ Ｉ位点。为了防止由ＰＣＲ扩增带来的差错,我们又从福氏２ａ Ｔ３２株染色体中克隆了全长的ａｓｄ基因。序列分析了结果表明,福氏２ａＴ３２株ａｓｄ基因的序列与Ｅ．ｃｏｌｉ Ｋ１２的完全一致,全长１６８０ｂｐ,其两侧     

遗传转化花粉长成单倍体植株

日本Ｈｉｒｏｓｈｉｍａ大学和Ｋａｇａｗａ大学的Ｍ．Ｎｉｓｈｉｈａｒａ和Ｈ．Ｍｏｒｉｋａｗａ及其同事报道,他们从用粒子轰击法转化的花粉第一次获得了稳定的转基因单倍体植株。Ｎｉｓｈｉｈａｒａ等人用含有新霉素转移酶Ⅱ（ＮＰＴⅡ）和β－葡糖苷酸酶（ＧＵＳ）基因的质粒ＤＮＡ包被的金粒,转化烟草属Ｎｉｃｏｔｉａｎａｒｕｓｔｉｃａｎａ的未成熟花粉。从被轰击的花粉再生了卡那霉素抗性花粉胚胎,并从总数为２×１０６个被轰击细胞中获得两个独立的转基因株系。一个同时具有ＮＰＴⅡ和ＧＵＳ活性,另一个只有ＮＰＴⅡ活性。两个…     

黄瓜花叶病毒（CMV）运动蛋白基因介导的抗病性

利用Ｆｎｙ＿ＣＭＶ株系ＲＮＡ３ｃＤＮＡ克隆,构建了含有全长和编码区缺失５０１个核苷酸的运动蛋白（ＭＰ）基因植物表达载体ｐＢＭＰＲ和ｐＢＭＰＫ。在土壤农杆菌（Ａｇｒｏｂａｃｔｅｒｉｕｍｔｕｍｅｆａｃｉｅｎｓ（ＳｍｉｔｈｅｔＴｏｗｎｓｅｎｄ）Ｃｏｎｎ）ＬＢＡ４４０４介导下转化烟草（ＮｉｃｏｔｉａｎａｔａｂａｃｕｍＬ．）品种“ＮＣ８９”,分别经Ｓｏｕｔｈｅｒｎｂｌｏｔｉｎｇ、ＲＴ＿ＰＣＲ或Ｗｅｓｔｅｒｎｂｌｏｔｉｎｇ分析,外源基因已整合到再生植株中并得到表达。抗病性分析表明,含有缺失型ＭＰ基因的Ｒ０代转基因植株抗性较好,接种５０ｄ后,１０株转化植株中仍有５株不表现症状。在自然发病条件下,这５个含有缺失型ＭＰ基因转基因株系在Ｒ１代都表现了一定的抗病性。抗性主要表现为症状出现推迟,严重度减轻。利用ＰＣＲ筛选、种子卡那霉素抗性试验和温室抗病性测定等方法,初步认为Ｒ２代转基因烟草Ｋ＿６＿５株系为转基因抗病纯合系。而含有全长ＭＰ基因的Ｒ０代转化植株,前期没有表现明显的抗病性,但在接种４０ｄ后部分发病植株有恢复健康的趋势。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

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     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.