A genetic demographic analysis of Lake Malawi rock‐dwelling cichlids using spatio‐temporal sampling

We estimated the effective population sizes (N_e) and tested for short‐term temporal demographic stability of populations of two Lake Malawi cichlids: Maylandia benetos, a micro‐endemic, and Maylandia zebra, a widespread species found across the lake. We sampled a total of 351 individuals, genotyped them at 13 microsatellite loci and sequenced their mitochondrial D‐loop to estimate genetic diversity, population structure, demographic history and effective population sizes. At the microsatellite loci, genetic diversity was high in all populations. Yet, genetic diversity was relatively low for the sequence data. Microsatellites yielded mean N_e estimates of 481 individuals (±99 SD) for M. benetos and between 597 (±106.3 SD) and 1524 (±483.9 SD) individuals for local populations of M. zebra. The microsatellite data indicated no deviations from mutation–drift equilibrium. Maylandia zebra was further found to be in migration–drift equilibrium. Temporal fluctuations in allele frequencies were limited across the sampling period for both species. Bayesian Skyline analyses suggested a recent expansion of M. zebra populations in line with lake‐level fluctuations, whereas the demographic history of M. benetos could only be estimated for the very recent past. Divergence time estimates placed the origin of M. benetos within the last 100 ka after the refilling of the lake and suggested that it split off the sympatric M. zebra population. Overall, our data indicate that micro‐endemics and populations in less favourable habitats have smaller N_e, indicating that drift may play an important role driving their divergence. Yet, despite small population sizes, high genetic variation can be maintained.     

Assessment of Preparation Methods for Organic Phosphorus Analysis in Phosphorus-Polluted Fe/Al-Rich Haihe River Sediments Using Solution 31P-NMR

Fe/Al-rich river sediments that were highly polluted with phosphorus (P) were used in tests to determine the optimum preparation techniques for measuring organic P (Po) using solution ³¹P nuclear magnetic resonance spectroscopy (³¹P-NMR). The optimum pre-treatment, extraction time, sediment to solution ratio and sodium hydroxide-ethylenediaminetetraacetic acid (NaOH-EDTA) extractant solution composition were determined. The total P and Po recovery rates were higher from freeze- and air-dried samples than from fresh samples. An extraction time of 16 h was adequate for extracting Po, and a shorter or longer extraction time led to lower recoveries of total P and Po, or led to the degradation of Po. An ideal P recovery rate and good-quality NMR spectra were obtained at a sediment:solution ratio of 1∶10, showing that this ratio is ideal for extracting Po. An extractant solution of 0.25 M NaOH and 50 mM EDTA was found to be more appropriate than either NaOH on its own, or a more concentrated NaOH-EDTA mixture for ³¹P-NMR analysis, as this combination minimized interference from paramagnetic ions and was appropriate for the detected range of Po concentrations. The most appropriate preparation method for Po analysis, therefore, was to extract the freeze-dried and ground sediment sample with a 0.25 M NaOH and 50 mM EDTA solution at a sediment:solution ratio of 1∶10, for 16 h, by shaking. As lyophilization of the NaOH-EDTA extracts proved to be an optimal pre-concentration method for Po analysis in the river sediment, the extract was lyophilized as soon as possible, and analyzed by ³¹P-NMR.     

黑河中游主要农作物灌溉制度优化

科学的灌溉制度是干旱半干旱地区农业生产的重要保障。黑河位于西北干旱区,是我国第二大内陆河,且当地中游农业灌溉和下游生态需水矛盾十分突出。利用DSSAT （Decision Support for Agro-technology Transfer）模型模拟了黑河中游地区玉米、小麦、油菜、马铃薯的生长情况,对比分析了四种作物生育期内需水量变化与当地降水条件、现行灌溉制度之间的差异。通过设置灌溉组合探究了四种作物最适宜的灌溉制度,并计算了优化灌溉制度下的节水潜力。结果表明：DSSAT模型通过参数校正与验证后,对四种作物生长过程模拟性能较好,产量标准化均方根误差（nRMSE）均低于15.0%,决定系数（R²）均达到0.65以上。缺水量模拟结果表明,四种作物生长季平均水分亏缺介于122.5-367.0 mm。通过调整灌溉制度,可使玉米、小麦、油菜、马铃薯的水分利用效率分别提高54.8%、25.0%、18.3%和51.3%,且产量变幅均低于5.0%,实现了高产节水的目的。在研究区实施最优灌溉制度,中游农业灌区每年可以节省8.1×10⁸ m³的水资源量,用于支持下游生态保护。     

恢复演替中草地斑块动态及尺度转换分析

研究了９ａ草地恢复油潜系列中斑块边界形状和斑块面积分布动态,并进行了凡度转换分析。獐茅斑块的边界分维数和斑块化指数最高,羊草斑块的较低,碱蓬斑块的斑块化指数略小于羊草斑块,边界分维数大于洋草斑块。共他类型斑块的两种指数基本上介于獐茅斑块之间,斑块化指数的年限变动滞后于斑块边界分维数,斑块边发维数在整个试验的尺度范围内符合同一自相似规律,斑块的面积分布格局在不同的尺度上有不同的自相似规律。     

植物DNA条形码技术

DNA条形码技术是利用标准的、具有足够变异的、易扩增且相对较短的DNA片段在物种内的特异性和种间的多样性而创建的一种新的生物身份识别系统, 从而实现对物种的快速自动鉴定。尽管这一技术在理论上和具体应用上仍存在很多争论, 但DNA条形码概念自2003年由加拿大分类学家Paul Hebert首次提出后就在世界范围内受到了广泛关注。在植物类群中条形码的研究和应用尚处于探索阶段, 稍落后于对动物类群的研究, 这主要表现在: (1) DNA条形码的选择及其评价仍没有统一的标准; (2) 对类群较全面的形态分类学修订和植物DNA条形码研究的结合十分缺乏; (3) 以往研究在取样上尺度较大, 而对具体类群的研究较少, 一个科或一个属只用有限的种类作为代表, 同一种内的取样个体数量也不足, 这样虽然表面上看来利用选定的DNA条形码可以较容易地把代表物种区分开, 但实际上目前建议的植物DNA条形码(例如由生命条形码咨询委员会植物工作组最近提出的rbcL和matK)由于其分子进化速率较慢, 在种级水平上, 特别是对于那些经历了适应辐射或快速进化的属来说, 分辨率较低。而DNA条形码的应用主要集中在属内物种水平的鉴别, 因此只有针对具体类群进行探索研究, 发现进化速率较快、分辨率高且通用性好的条形码, 才可能为建立完整的条形码数据库起到积极有效的作用。     

microRNA-193b protects against myocardial ischemia-reperfusion injury in mouse by targeting mastermind-like 1

The current study aimed to explore the functions and roles of microRNA-193b (miR-193b) in the myocardium with ischemia-reperfusion (I/R) injury and a potential therapeutic method for myocardial I/R injury. The mice were subjected to myocardial I/R with or without miR-193b pretreatment. The infarct size and myocardial enzymes were detected. The terminal deoxynucleotidyl transferase dUTP nick-end labeling assay was conducted to investigate the effect of miR-193b on cardiomyocyte apoptosis. The expression levels of miR-193b and mastermind-like 1 (MAML1) were validated by quantitative real-time polymerase chain reaction and Western blot analysis. The results suggested that the miR-193b expression level was significantly downregulated in the myocardium with I/R injury compared with control group. miR-193b overexpression is able to reduce infarct size and myocardial enzymes after myocardial I/R injury. Furthermore, overexpression of miR-193b could alleviate the apoptosis level after myocardial I/R injury. Taken together, the present study demonstrated that upregulated miRNA-193b alleviated myocardial I/R injury via targeting MAML1.     

Scanning mutagenesis studies reveal multiple distinct regions within the human protein kinase C alpha regulatory domain important for phorbol ester-dependent activation of the enzyme

While phorbol ester-binding sites within protein kinase C alpha (PKCalpha) have been identified and characterized utilizing fragments of the enzyme, it remains unclear whether additional regions within the enzyme may play an important role in its ability to be activated by phorbol ester. To examine this hypothesis, we generated 20 glutathione-S-transferase-tagged, V1-deficient, human PKCalpha holoenzyme constructs in which tandem six or 12 amino acid residue stretches along the full regulatory domain were changed to alanine residues. Each protein was assessed for its ability to bind phorbol ester and to induce growth repression when its catalytic activity was activated by phorbol ester upon expression in yeast cells. Mutagenesis of residues 99-158 potently reduced phorbol binding, consistent with previously published findings on the importance of the C1b region in phorbol binding. In addition, we identified a number of regions within the PKC regulatory domain that, when mutagenized, blocked the activation of PKC-mediated growth repression by phorbol ester while actually enhancing phorbol ester binding in vitro (residues 33-62, and 75-86). This study thus helps distinguish regions important for phorbol binding from regions important for the ability of phorbol ester to activate the enzyme. Our findings also suggest that multiple regions within C2 are necessary for full activation of the enzyme by phorbol ester, in particular residues 231-254. Finally, three regions, when mutagenized, completely, blocked catalytic domain activity in vivo (residues 33-62, 75-86, and 123-146), underscoring the important role of regulatory domain sequences in influencing catalytic domain function, even in the absence of the V1 region containing the pseudosubstrate sequence. This is the first tandem mutagenesis study for PKC that assesses the importance of regions for both phorbol binding and for phorbol-dependent activation in the context of the entire holoenzyme.