Stress-induced mutagenesis in bacteria

The evolutionary significance of stress-induced mutagenesis was evaluated by studying mutagenesis in aging colonies (MAC) of Escherichia coli natural isolates. A large fraction of isolates exhibited a strong MAC, and the high MAC variability reflected the diversity of selective pressures in ecological niches. MAC depends on starvation, oxygen, and RpoS and adenosine 3',5'-monophosphate regulons; thus it may be a by-product of genetic strategies for improving survival under stress. MAC could also be selected through beneficial mutations that it generates, as shown by computer modeling and the patterns of stress-inducible and constitutive mutagenesis. We suggest that irrespective of the causes of their emergence, stress-induced mutations participate in adaptive evolution.     

水稻细菌性基腐病品种抗性鉴定

对42个水稻品种进行了基腐病抗性鉴定，结果表明：Ⅱ优128、特优63、培杂72、培杂77、博优713等5个水稻品种表现为高抗基腐病；培杂981、博优122、大丰占、博优903等21个水稻品种表现为中抗；三二矮、特籼13等10个水稻品种表现为中感；95占、雪花占、三七早占等6个水稻品种表现为高感．     

紫外线诱导大肠杆菌产生对鲎素抗药性菌株的研究

探讨经过紫外线诱变能否筛选出抗鲎素的大肠杆菌突变菌株以及突变菌株对抗生素敏感性的变化.以大肠杆菌JM109和ATCC25922为研究对象,通过紫外线诱变技术对出发菌株进行诱变,以相应的出发菌株作对照,并通过鲎素浓度梯度平板法对大肠杆菌进行初筛后,对初筛到的抗鲎素菌株进行亚抑菌浓度鲎素的连续传代诱导和抗生素对初筛到的抗鲎素菌株进行敏感性测定.结果表明,采用紫外诱变和鲎素浓度梯度筛选的方法,从中筛选到低抗鲎素的大肠杆菌ATCC25922 3株;通过抗生素对此3种低抗鲎素菌株进行敏感性测定,表明抗鲎素菌株对苄星青霉素有显著抗药性,而对盐酸左氧氟沙星仍然敏感.对于大肠杆菌JM109菌株,经过紫外线诱变后,未诱导出抗鲎素菌株.     

微波联合抗生素抗性诱变选育泰妙菌素高产菌株

为了获得泰妙菌素高产菌株,以泰妙菌素19-127为出发菌株,采用微波诱变对泰妙菌株进行诱变,并结合特比萘酚及制霉菌素两种抗生素抗性筛选法获得泰妙菌素高产菌株。结果表明,经过发酵验证最终选育出5株突变株20-016、20-029、20-048、20-072和20-088,相较于对照组效价分别增长19.9%、21.6%、20.2%、22.5%和23.1%,连续传代5次,遗传性状稳定。比较两种抗生素在泰妙菌素高产菌株选育中的作用,制霉菌素更有利于高产菌株的选育。     

烟草品种对青枯病抗病性及抗性机制的研究

为探讨烟草品种对青枯病的抗病性及抗性机制 ,为烟草的抗病育种提供抗源和鉴定方法 ,室内鉴定了 5 4个烟草品种对青枯病的抗性 ,发现不同品种间抗性有明显差异 ,抗病品种有 T144 8A,贵烟 ,CV 91,大晒烟 ,香烟 ,K32 6等 6个 ,中抗品种有大幅 ,D10 1,G2 8,安流晒烟 ,子州羊角大烟 ,G2 8× MD6 0 9,小样无烟 ,清间羊角大烟 ,N 32 6等 9个 ,其余均为感病品种 ,没有免疫品种 .选择 10个对烟青枯病抗、感性不同的品种进行了生化反应与抗性关系的研究 .结果表明 ,人工接种后 ,抗性品种的木质素、可溶性总糖、酚类物质含量、可溶性总糖 /淀粉及超氧化物歧化酶活性均高于感病品种 ;各品种的淀粉含量与抗性水平没有关系 .     

Improvement of megaprimer method for site-directed mutagenesis and its application to phytase

Site-directed mutagenesis is used extensively for probing gene function. In this paper we describe an improved megaprimer method to the site-directed mutagenesis of phytase from Aspergillus niger, which allowed the mutations to be performed more efficiently in less time than other traditional methods. Three rounds of PCR and two pairs of primers were required in this method, and additionally, the restriction enzyme Dpn I was used for the elimination of template instead of the gel purification in this process. The entire procedure was performed in one tube. Moreover, this method was easier for obtaining large mutant genes than other methods. We successfully carried out the site-directed mutagenesis of phytase by adopting this method.     

抗虫杂交棉丰产性、抗虫性鉴定研究

选择近期国内选育的抗虫杂交棉品种进行多点比较试验，鉴定其丰产性、抗虫性、适应性和纤维品质等。结果表明：综合表现较好的有皖抗杂3号、湘K-5、皖抗杂2号、中棉所29等。     

Directed mutagenesis of dihydrofolate reductase

Three mutations of the enzyme dihydrofolate reductase were constructed by oligonucleotide-directed mutagenesis of the cloned Escherichia coli gene. The mutations--at residue 27, aspartic acid replaced with asparagine; at residue 39, proline replaced with cysteine; and at residue 95, glycine replaced with alanine--were designed to answer questions about the relations between molecular structure and function that were raised by the x-ray crystal structures. Properties of the mutant proteins show that Asp-27 is important for catalysis and that perturbation of the local structure at a conserved cis peptide bond following Gly-95 abolishes activity. Substitution of cysteine for proline at residue 39 results in the appearance of new forms of the enzyme that correspond to various oxidation states of the cysteine. One of these forms probably represents a species cross-linked by an intrachain disulfide bridge between the cysteine at position 85 and the new cysteine at position 39.     

害虫抗药性及其治理

就害虫抗性机理、抗性监测、抗性治理几个方面对害虫抗性进行了综述.     

乙烯与植物抗逆性

乙烯是一种重要的植物激素,在植物对生物胁迫和非生物胁迫的耐受性和抗性中发挥重要作用。综述了近年来有关乙烯与植物抗逆性的一些最新研究进展,重点介绍了乙烯在植物响应干旱、高盐、低温、病害等逆境胁迫反应中所起的重要作用,以期为深入理解逆境胁迫下乙烯的调控方式奠定基础。     

大豆对SMV3号株系的抗性遗传分析

利用高抗东北SMV3号株系的大豆品系95-5383与4个感病品种(系)HB1、铁丰21、Amsoy、williams和抗病品种PI486355配制5个杂交组合,对各组合的F1、F2代接种SMV鉴定抗性.结果表明,95-5383与各感病品种杂交组合的F1代表现为感病,F2群体分离比例为3感(花叶+顶枯)1抗,表明95-5383对SMV3号株系的抗性受一对隐性基因控制.95-5383×PI486355的F2代接种后有感病植株分离,表明二者对SMV3的抗性基因不等位.利用BSA法对95-5383×HB1的F2代进行鉴定,筛选出RAPD引物OPN11在95-5383和抗池扩增出OPN11980片段,在HB1和感池扩增出OPN111070片段,在F1同时扩增出OPN11980和OPN111070.用该引物分析95-5383×HB1的F2个体,共显性的RAPD标记OPN11980/1070与95-5383抗病基因的遗传距离为2.1cM.     

大豆对SMV3号株系的抗性遗传分析及抗病基因的RAPD标记研究

 利用高抗东北 SMV3号株系的大豆品系 95 - 5 383与 4个感病品种 (系 ) HB1、铁丰 2 1、Am soy、William s和抗病品种 PI486 35 5配制 5个杂交组合 ,对各组合的 F1 、F2 代接种 SMV鉴定抗性。结果表明 ,95 - 5 383与各感病品种杂交组合的 F1 代表现为感病 ,F2 群体分离比例为 3感 (花叶 +顶枯 )∶ 1抗 ,表明 95 - 5 383对 SMV3号株系的抗性受一对隐性基因控制。 95 - 5 383× PI486 35 5的 F2 代接种后有感病植株分离 ,表明二者对 SMV3的抗性基因不等位。利用BSA法对 95 - 5 383× HB1的 F2 代进行鉴定 ,筛选出 RAPD引物 OPN11在 95 - 5 383和抗池扩增出 OPN11980 片段 ,在HB1和感池扩增出 OPN111 0 70 片段 ,在 F1 同时扩增出 OPN11980 和 OPN111 0 70 。用该引物分析 95 - 5 383× HB1的 F2 个体 ,共显性的 RAPD标记 OPN11980 /1 0 70 与 95 - 5 383抗病基因的遗传距离为 2 .1c M。     

水稻稻曲病抗性遗传机制

选用经多年接种鉴定,对水稻稻曲病有较强抗性的水稻地方品种早光头粳（P1）与感病品种粤B（P2）配置了P1、P2、F1、F2、BC1（F1×P1）和Bc2（F1×P2）6个世代。在水稻孕穗期,对这6个世代单株进行人工接种稻曲病病菌,调查各个单株对稻曲病的抗性表现,并进行遗传分析。结果表明：水稻稻曲病为2对主基因＋多基因的遗传,第1对主基因的效应以显性效应为主,加性作用次之;第2对主基因的效应以显性效应为主,加性作用不明显;对于该组合,按F2分离世代计算,水稻稻曲病抗性的遗传率为82．84％。