变铅青链霉菌DNA的研究——Ⅱ.位点特异性降解与DNA修饰的关系

变铅青链霉菌的DNA上存在着一种异常的修饰,使其在含有微量Fe~(++)的缓冲液中电泳时,双链DNA遭到降解。DNA的切割是位点特异性的。与已知修饰特征的DNA进行同步试验发现,变铅青链霉菌的这种特异性修饰与目前所发现的修饰系统(如DNA甲基化)均不相同,很可能是一种新的修饰系统。     

Extensive dispersal of Roanoke logperch (Percina rex) inferred from genetic marker data

The dispersal ecology of most stream fishes is poorly characterised, complicating conservation efforts for these species. We used microsatellite DNA marker data to characterise dispersal patterns and effective population size (N_e) for a population of Roanoke logperch Percina rex, an endangered darter (Percidae). Juveniles and candidate parents were sampled for 2 years at sites throughout the Roanoke River watershed. Dispersal was inferred via genetic assignment tests (ATs), pedigree reconstruction (PR) and estimation of lifetime dispersal distance under a genetic isolation‐by‐distance model. Estimates of N_e varied from 105 to 1218 individuals, depending on the estimation method. Based on PR, polygamy was frequent in parents of both sexes, with individuals spawning with an average of 2.4 mates. The sample contained 61 half‐sibling pairs, but only one parent–offspring pair and no full‐sib pairs, which limited our ability to discriminate natal dispersal of juveniles from breeding dispersal of their parents between spawning events. Nonetheless, all methods indicated extensive dispersal. The AT indicated unrestricted dispersal among sites ≤15 km apart, while siblings inferred by the PR were captured an average of 14 km and up to 55 km apart. Model‐based estimates of median lifetime dispersal distance (6–24 km, depending on assumptions) bracketed AT and PR estimates, indicating that widely dispersed individuals do, on average, contribute to gene flow. Extensive dispersal of P. rex suggests that darters and other small benthic stream fishes may be unexpectedly mobile. Monitoring and management activities for such populations should encompass entire watersheds to fully capture population dynamics.     

转基因植物非预期效应检测评价技术的发展

检测和评价转基因植物非预期效应是转基因植物安全评价不可或缺的重要内容之一。介绍了转基因植物非预期效应的定义、成因及其检测评价技术的发展，指出了转基因植物非预期效应检测评价技术的难点和存在的问题。阐述了基因芯片分析技术在检测和评价转基因植物非预期效应中的应用前景，特别介绍了转基因植物在不同发育阶段和生长条件下差异表达基因的分布模型，并提出了利用基因芯片分析技术，从差异基因到代谢途径，再到非预期效应的转基因植物安全评价模式。这一评价模式可为今后创建高效、全面、客观、公正的转基因植物非预期效应检测和评价技术提供可能的实验模型和理论依据。     

盐藻DNA对水稻幼苗在低盐中生长的影响

[目的]分析盐藻DNA对水稻幼苗在低盐中生长的影响。[方法]将刚萌发的水稻幼苗根系浸入5 mg/L盐藻DNA溶液中培养2d,以蒸馏水培养为对照,处理后的水稻幼苗栽于含有氯化钠3 g/L的MS培养液中培养,分析盐藻DNA对水稻幼苗在低盐中生长的影响。[结果]水稻幼苗用5 mg/L盐藻DNA处理后,在含氯化钠3 g/L的MS培养液中培养15 d,其平均株重为150.7 mg,比对照增加了10.3%;平均株高为15.28 cm,比对照增加了6.1%;平均存活率为45.0%,比对照增加了125.0%;平均根数为7.15条,比对照减少了2.8%;平均根长为3.83 cm,比对照缩短了8.4%。说明盐藻DNA提高了水稻幼苗的耐盐适应性。[结论]盐藻DNA可提高水稻的耐盐适应性。     

一种用于桑RAD-Seq高通量测序的基因组DNA提取方法

[目的]筛选一种能够得到高质量桑树基因组DNA的方法。[方法]采用天根试剂盒法(Plant Genomic DNA Kit离心柱型),并稍加改进,从11个桑种的新鲜嫩叶中提取DNA。[结果]该方法简单快速,不需要复杂仪器,且能有效地除去桑叶中的多糖、多酚、蛋白质等杂质,得到的DNA能够满足RAD-Seq高通量的测序要求。[结论]建立了一种用于桑RAD-Seq高通量测序的基因组DNA提取方法。     

DNA折纸术的研究进展

为了帮助广大研究者在短时间内了解DNA折纸术的最新研究现状,掌握DNA折纸术相关软件的应用,本论文将DNA折纸术的相关内容进行了归纳。首先介绍了DNA折纸术的起源与基本原理;然后综述了近几年国内外的研究进展与取得的成果;接下来对DNA折纸术相关软件-Tiamat和Cadnano的应用和功能进行了简单的介绍,并对不同的软件进行了比较;最后对DNA折纸术的应用前景进行了展望。DNA折纸术虽然取得了一定的研究进展,但其未来的发展和应用前景将更广阔。     

Comparison of DNA probe test and cultivation methods for detection of Mycobacterium avium subsp paratuberculosis in caprine and ovine faeces

OBJECTIVE: To compare a DNA probe test with two cultivation methods for the detection of Mycobacterium avium subsp paratuberculosis in goat and sheep faeces. DESIGN: Comparison of the results of the three methods with histological examination as the reference standard. PROCEDURE: Faecal specimens were obtained from goats and sheep originating from flocks known to be affected with paratuberculosis and tested for Mycobacterium avium subsp paratuberculosis with a DNA probe test and two cultivation methods (old conventional culture and new double incubation method in Herrold's and Lowenstein-Jensen medium). RESULTS: In goats, the sensitivity of the various tests were for the DNA probe test 17.2%, for the double incubation culture method 25.4% and for the old conventional culture method 22.8% using the histopathological results as reference. In sheep the sensitivity of the various tests were for the DNA probe test 13.2%, for the double incubation culture method 8.8% and for the old conventional culture method 5.9% using the histopathological results as reference. The specificity of the above tests was 100% in goats and sheep and the specificity of the double incubation culture method in goats was 91%. CONCLUSIONS: The DNA probe test is a rapid and specific test that could be used in a control program if the sensitivity of the test were improved and possibly in combination with another test.     

Demonstration of Heterogeneous Genotypes of Taylorella equigenitalis Isolated from Horses in Six European Countries by Pulsed-Field Gel Electrophoresis

Forty-six isolates of Taylorella equigenitalis were analysed by pulsed-field gel electrophoresis (PFGE) after separate digestion of the genomic DNA with ApaI and with NotI. The isolates had been obtained from horses in six European countries and were classified into 18 genotypes. In Belgium, 2 genotypes were detected in 2 isolates, in England 9 among 15, in Finland 2 in 2, in France 2 among 10, in Sweden 3 among 5, and in Switzerland 3 among 12. Two English isolates and 4 French isolates gave identical PFGE profiles to those of Kentucky 188 from the United States. A common genotype was found in 5 isolates from Belgium and England and also in 10 isolates from France and Switzerland. The analysis of genomic DNA from 12 isolates of T. equigenitalis obtained from male horses in France, Sweden and Switzerland gave no evidence of a sex-related difference in the genomic DNA. Genomic DNA from 11 streptomycin (STM)-susceptible isolates obtained in Sweden and Switzerland were classified into four genotypes by PFGE. Each of the six genotypes determined among the 17 isolates from these two countries had single phenotypes for resistance or susceptibility to STM.     

Genetic relationships between the dominant genotypes of Phytophthora infestans in Hokkaido, Japan

The genetic characteristics of the dominant genotypes of Phytophthora infestans in Japan (US-1, JP-1, Japanese A1-A, A1-B) were compared. Differences were evident in the peptidase genotype, amplified fragment length polymorphism, and RG57 DNA fingerprints. Almost all of the fingerprint bands for the Japanese genotype A1-B were also present in JP-1 and Japanese A1-A, and few bands were unique to Japanese A1-B. These results suggest that the Japanese A1-B genotype was generated from sexual reproduction involving Japanese A1-A and JP-1 or related genotypes.     

Random amplified polymorphic DNA markers reveal low genetic variation and a single dominant genotype in Eichhornia crassipes populations throughout China

Genetic variation within and between 34 populations of Eichhornia crassipes (water hyacinth) in China was surveyed using random amplified polymorphic DNA (RAPD) markers. A total of 1009 individuals were analysed, for which 12 RAPD primers amplified 69 reproducible bands, with 22 (32%) being polymorphic. The percentage of polymorphic loci (p) within a population ranged from 4.4% to 17.4%, and the mean Nei's gene diversity (H_e) was 0.046 ± 0.0145, indicating a low genetic diversity of E. crassipes in China. Each population contained at least four RAPD phenotypes (genotypes), and the same particular genotype was invariably dominant in all the populations sampled. The mean proportion of distinguishable genotypes was 0.29. Analysis of molecular variance revealed a large proportion of genetic variation (83.9%) residing within populations and a slightly larger proportion (88.1%) within localities, indicating a low genetic differentiation of E. crassipes populations, both locally and regionally. Human-mediated dispersal, vigorous clonal growth, and a generally low level of sexual reproduction were thought to be responsible for such a pattern of genetic structure.