Long-Term Experimental Evolution in Escherichia coli. XIII. Phylogenetic History of a Balanced Polymorphism

We investigated the phylogenetic history of a balanced polymorphism that evolved in an experimental population of Escherichia coli. Previous work showed that two ecologically and morphologically distinct types, designated L (large) and S (small), arose by generation 6000 and coexisted for more than 12,000 generations thereafter. Here, we performed RFLP analyses using Insertion Sequence elements to resolve the phylogenetic history of L and S. Specifically, we sought to determine whether the derived S morph was monophyletic, indicating a long history of coexistence with L or, alternatively, S was repeatedly regenerated from L, indicating a series of periods with only transiently stable coexistence. Phylogenetic analysis of some 200 clones collected throughout the history of this population demonstrates that S is monophyletic. We then performed competition assays using clones of both morphs from different generations to determine whether either or both lineages continued to undergo genetic adaptation. Indeed, both lineages continued to adapt, and their continued evolution contributed to fluctuations in their relative abundance over evolutionary time. Based on their phylogenetic history and independent evolutionary trajectories, S and L fulfill Cohan’s criteria for being different asexual species.[Reviewing Editor: Niles Lehman]     

Familial (11;21)(p13;q22)pat balanced reciprocal translocation in a female child with regression of milestones

The role of balanced translocations in the human morphogenesis is difficult to interpret. A balanced reciprocal translocation (BRT) was observed in a female child referred with a history of regression of milestones. The cytogenetic findings by GTG-banding and fluorescence in situ hybridization revealed a BRT involving chromosomes 11p and 21q, i.e. 46,XX, t(11;21)(p13;q22). The father was found to be a carrier of the same BRT. This is the first report of reciprocal translocation involving 11p and 21q. The possible reasons for the manifestation of clinical features in the proband due to inherited BRT are discussed.     

Genetic polymorphism at two linked loci,Sod and Est-6, in Drosophila melanogaster

We have examined the patterns of polymorphism at two linked loci, Sod and Est-6, separated by nearly 1000 kb on the left arm of chromosome 3 of Drosophila melanogaster. The evidence suggests that natural selection has been involved in shaping the polymorphisms. At the Sod locus, a fairly strong (s>0.01) selective sweep, started ≥2600 years ago, increased the frequency of a rare haplotype, F(A), to about 50% frequency in populations of Europe, Asia, and the Americas. More recently, an F(A) allele mutated to an S allele, which has increased to frequencies 5–15% in populations of Europe, Asia and North America. All S alleles are identical (or very nearly) in sequence and differ by one nucleotide substitution (which accounts for the F→S electrophoretic difference) from F(A) alleles. At the Est-6 locus, the evidence indicates both directional and balancing selection impacting separately the promoter and the coding regions of the gene, with linkage disequilibrium occurring within each region. Some linkage disequilibrium also exists between the two genes.     

Cytotoxicity of mitochondria-targeted resveratrol derivatives: Interactions with respiratory chain complexes and ATP synthase

We recently reported that mitochondria-targeted derivatives of resveratrol are cytotoxic in vitro, selectively inducing mostly necrotic death of fast-growing and tumoral cells when supplied in the low μM range (N. Sassi et al., Curr. Pharm. Des. 2014). Cytotoxicity is due to H₂O₂ produced upon accumulation of the compounds into mitochondria. We investigate here the mechanisms underlying ROS generation and mitochondrial depolarization caused by these agents. We find that they interact with the respiratory chain, especially complexes I and III, causing superoxide production. “Capping” free hydroxyls with acetyl or methyl groups increases their effectiveness as respiratory chain inhibitors, promoters of ROS generation and cytotoxic agents. Exposure to the compounds also induces an increase in the occurrence of short transient [Ca^2 +] “spikes” in the cells. This increase is unrelated to ROS production, and it is not the cause of cell death. These molecules furthermore inhibit the F₀F₁ ATPase. When added to oligomycin-treated cells, the acetylated/methylated ones cause a recovery of the cellular oxygen consumption rates depressed by oligomycin. Since a protonophoric futile cycle which might account for the uncoupling effect is impossible, we speculate that the compounds may cause the transformation of the ATP synthase and/or respiratory chain complex(es) into a conduit for uncoupled proton translocation. Only in the presence of excess oligomycin the most effective derivatives appear to induce the mitochondrial permeability transition (MPT) within the cells. This may be considered to provide circumstantial support for the idea that the ATP synthase is the molecular substrate for the MPT pore.     

“生态平衡施肥”的理论基础和技术体系

施肥是与产量、品质、成本、土壤培肥、污染等问题密切相关的复合生态系统物质循环调控的重要措施,以实现经济效益、生态效益和社会效益的综合效益最佳为目标,建立了“生态平衡施肥”的理论基础和技术体系,结合国情提出“生态平衡施肥’实现的关键条件和具体模式。“生态平衡施肥”是以施肥系统养分循环原理－－“通用施肥模型”为理论基础,以衫和和高新技术化组装的技术体系为实现手段,以“生态型肥料”为载体的新的施肥系统。     

不同保存方式下蝗虫组织DNA的提取及RAPD分析

为了开展蝗虫分子系统学研究,分别对冷冻、乙醇浸泡(100%、乙醇、70％乙醇)和干制蝗虫标本用饱和NaCl法进行了基因组DNA的提取,并用随机引物进行扩增,结果表明：70％乙醇固定的标本和部分干标本提取的总DNA得率较低,在琼脂糖凝胶电泳检测中大音琏分有明显降解,导致PCR扩增中信息缺失,甚至无扩增条带;而保存完好的干标本、-20℃冷冻标本和100%,乙醇浸泡标本提取的总DNA带型整齐,无拖尾,PCR扩增结果的稳定性好,成为蝗虫分子系统学研究中首选的三种保存方式。     

Estimation of Design and Genetic Components of Variance in Double Cross Mating Designs

The present paper deals with the estimation of design and genetic components of variance based on full double crosses and partial tetra-allel crosses. We have presented the explicit experissions for the symmetric sums estimators of design components of variance based on Hinkelmann's model. Consequently we have also presented explicitly the genetic components of variance based on full double crosses and partial tetra-allel crosses. The procedure is also illustrated with the help of a hypothetical data.     

The Probability of a Negative Linear Combination of Independent Mean Squares

SATTERTHWAITE'S (1941) approximation of the distribution of a linear combination, of independent mean squares is a commonly used technique in the analysis of variance. Confidence intervals and test statistics based on this approximation require that be positive. In this article, the probability that will be negative is considered in situations in which the mean squares are associated with a general balanced mixed model. Expressions are given for exact and approximate values of this probability in terms of the expected values and degrees of freedom of the mean squares. An example is presented to illustrate the implementation of the proposed methodology.