Restricted gene flow within and between rapidly diverging Neotropical plant species

Speciation involves the evolution of traits and genetic differences that contribute to reproductive isolation and the cessation of gene flow, and studying closely related species and divergent populations gives insight into how these phenomena proceed. Here, we document patterns of gene flow within and between two members of a rapid Neotropical species radiation, Costus pulverulentus and Costus scaber (Costaceae). These species co‐occur in the tropical rainforest and share pollinators, but are reproductively isolated by a series of prezygotic barriers, some of which show evidence of reinforcement at sympatric sites. Here, we genotype microsatellite markers in plants from eight sites that span the geographical range of both species, including four sympatric sites. We also genotype putative hybrids found at two sympatric sites. We find high levels of genetic isolation among populations within each species and low but detectable levels of introgression between species at sympatric sites. Putative hybrids identified by morphology are consistent with F1 or more advanced hybrids. Our results highlight the effectiveness of prezygotic isolating mechanisms at maintaining species boundaries in young radiations and provide empirical data on levels of gene flow consistent with reinforcement.     

流式细胞术的发展及在植物研究中的应用

流式细胞术是通过对液流中各种荧光标记的颗粒进行多参数快速高效的定性或定量测定的方法,在科学研究的多个领域发挥重要作用。然而,由于植物组织及细胞壁和次生代谢产物等细胞的特殊成分和结构,限制了其在植物研究领域的应用。本文在介绍流式细胞仪发展和组成分类的基础上,着重讨论了流式细胞术在植物领域的应用、研究进展及应用限制,进而展望该研究领域的发展趋势,为拓宽植物流式细胞术的潜在应用范围提供新的思考方向。     

干旱胁迫下胡杨茎流日变化分析——以塔里木河下游英苏断面为例

用PHYTALK植物生理生态监测系统对塔里木河下游英苏断面胡杨的茎流和相关环境因子的日变化进行了监测.结果表明:在极端干旱区塔里木河下游的胡杨茎流日变化表现多峰值,且夜晚仍保持一定流速;主枝与侧枝茎流日变化趋势相似,主枝流速高于侧枝;侧枝对环境变化响应更加灵敏,波动强烈,主枝相对侧枝,茎流变化响应迟钝且有明显滞后效应;茎流变化受太阳辐射、风速和大气温度影响明显,而其它环境因子如空气湿度、土壤湿度等影响则不大,气温与叶温表现出极佳相关性,气温与空气湿度呈显著负相关;同时,日变化中,不同时段起主导作用的因子不尽相同.     

花苜蓿小尺度空间遗传结构研究

以花苜蓿（Medicago ruthenica Trautv.）为材料,在内蒙古克什克腾旗建立两个25 m×50 m的样方（山谷YF1和山坡YF2）,采集该范围内的所有个体,利用8对SSR分子标记对其遗传变异特性进行分析。结果显示,克什克腾旗花苜蓿居群遗传多样性较高。两个居群个体的空间自相关分析结果表明,9 m内的个体间为非随机邻近交配,且在同距离范围内,山谷居群的个体间遗传相似性更低,推测此区域可能是历史和地理因素塑造了花苜蓿丰富的遗传多样性,两个小尺度空间格局的个体间基因流模式主要受地形影响。     

塔玛亚历山大藻遗传多样性的微卫星分析

应用12个微卫星标记对9株来自欧洲和中国等不同海域的塔玛亚历山大藻(Alexandrium tamarense)进行了遗传多样性分析,探讨了不同地理藻株之间的遗传分化程度和基因流水平,分析了我国沿海塔玛亚历山大藻的遗传多样性。结果表明：9株塔玛亚历山大藻共检测出26个等位基因,其中9个位点具有多态性,多态比率75%。有效等位基因数1.3243～3.2667,平均为1.8774。塔玛亚历山大藻种内基因多样性为0.3630。9株塔玛亚历山大藻大致可以分为3个进化支,进化支与藻株的地理位置相关联。其中,中国海域的塔玛亚历山大藻至少可分为2个进化支。不同地理分布的塔玛亚历山大藻的遗传分化水平较高,达0.7522。种群间的基因流估算水平较低,提示3个种群间可能不存在基因交流。     

Effects of changing climate on aquatic habitat and connectivity for remnant populations of a wide‐ranging frog species in an arid landscape

Amphibian species persisting in isolated streams and wetlands in desert environments can be susceptible to low connectivity, genetic isolation, and climate changes. We evaluated the past (1900–1930), recent (1981–2010), and future (2071–2100) climate suitability of the arid Great Basin (USA) for the Columbia spotted frog (Rana luteiventris) and assessed whether changes in surface water may affect connectivity for remaining populations. We developed a predictive model of current climate suitability and used it to predict the historic and future distribution of suitable climates. We then modeled changes in surface water availability at each time period. Finally, we quantified connectivity among existing populations on the basis of hydrology and correlated it with interpopulation genetic distance. We found that the area of the Great Basin with suitable climate conditions has declined by approximately 49% over the last century and will likely continue to decline under future climate scenarios. Climate conditions at currently occupied locations have been relatively stable over the last century, which may explain persistence at these sites. However, future climates at these currently occupied locations are predicted to become warmer throughout the year and drier during the frog's activity period (May – September). Fall and winter precipitation may increase, but as rain instead of snow. Earlier runoff and lower summer base flows may reduce connectivity between neighboring populations, which is already limited. Many of these changes could have negative effects on remaining populations over the next 50–80 years, but milder winters, longer growing seasons, and wetter falls might positively affect survival and dispersal. Collectively, however, seasonal shifts in temperature, precipitation, and stream flow patterns could reduce habitat suitability and connectivity for frogs and possibly other aquatic species inhabiting streams in this arid region.     

The response of giant phospholipid vesicles to pore-forming peptide melittin

The interaction between the pore-forming peptide melittin (MLT) and giant phospholipid vesicles was explored experimentally. Micromanipulation and direct optical observation of a vesicle (loaded with sucrose solution and suspended in isomolar glucose solution) enabled the monitoring of a single vesicle response to MLT. Time dependences of the vesicle size, shape and the composition of the inner solution were examined at each applied concentration of MLT (in the range from 1 to 60 μg/ml). The response varied with MLT concentration from slight perturbation of the membrane to disintegration of the vesicle. A model for MLT-vesicle interaction is proposed that explains the observed phenomena in the entire span of MLT concentrations and is consistent with deduced underlying mechanisms of MLT action: trans-membrane positioning and dimerization of MLT, the lipid flow from the outer to the inner membrane leaflet induced by MLT translocation, formation of pores and the consequent transport of small molecules through the membrane. The results of the theoretical analysis stress the role of dimers in the MLT-membrane interaction and demonstrate that the MLT-induced membrane permeability for sugar molecules in this experimental set-up depends on both MLT concentration and time.     

Neurohormonal and cytokine fluctuations following transcatheter closure for an atrial septal defect

Introduction

Inflammation and neurohormonal activation are considered to be involved in the development of earlier and/or later complications in congenital heart disease patients, even after a successful repair of the lesion. It is not yet clarified what is the role of the therapeutic interventions in the occurrence of such a response and how it could be associated with possible postoperative complications.

Aim

We sought to assess the inflammatory and neurohormonal response to transcatheter closure of secundum type atrial septal defects (ASD) over a six-month follow-up period. We also evaluated the association between the respective markers and catheterization data as well as echocardiographic measurements.

Methods

Plasma concentrations of interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), interleukin-10 (IL-10), N-terminal-proatrial natriuretic peptide (NT-proANP) and N-terminal-probrain natriuretic peptide (NT-proBNP) were assessed and echocardiographic measurements were performed in twenty-eight patients with atrial septal defect prior to, and at the first, second and sixth months post transcatheter closure. Thirty-three age-matched healthy volunteers were also enrolled.

Results

IL-6 plasma levels, although higher preoperatively, [physical logarithm (ln) IL-6: 3.37 ± 0.66 vs 2.92 ± 0.44 pg/ml, p = 0.015], reached control levels postoperatively, at the end of the third month, whereas TNF-α and IL-10 were not influenced by the procedure. NT-proANP levels were elevated preoperatively compared to the control group (ln NT-proANP 3.78 ± 0.572 vs 3.48 ± 0.30, p = 0.031), with a further significant increase during the 1st month (ln NT-proANP 3.78 ± 0.572 vs 4.2 ± 0.42, p = 0.006), following the pattern of the left atrial volume enlargement, and remained high even 6 months after the procedure .On the other hand, the initially normal concentrations of NT-proBNP, after a transient significant increase during the first month postoperatively (ln NT-proBNP 3.56 ± 0.94 vs 4.58 ± 0.91, p < 0.0001) returned to the controls’ levels at the end of the third month. Preoperative concentrations of NT-proANP positively correlated with NT-proBNP concentrations and pulmonary to systemic flow ratio (Qp/Qs).

Conclusions

Transcatheter closure could improve, on a mid- term basis, the inflammatory process but natriuretic peptides’ secretion continues in parallel with left atrial volume increase. Further follow up is required to determine the long-term progress of the inflammatory and neurohormonal response to the procedure.     

Development of an apparatus for rapid release of oligosaccharides at the glycosaminoglycan-protein linkage region in chondroitin sulfate-type proteoglycans

An apparatus, AutoGlycoCutter (AGC), was developed as a tool for rapid release of O-linked-type glycans under alkaline conditions. This system allowed rapid release of oligosaccharides at the glycosaminoglycan-protein linkage region in proteoglycans (PGs). After digestion of PGs with chondroitinase ABC, the oligosaccharides at the linkage region were successfully released from the protein core by AGC within 3 min. The reducing ends of the released oligosaccharides were labeled with 2-aminobenzoic acid and analyzed by a combination of capillary electrophoresis (CE) and matrix-assisted laser desorption time-of-flight mass spectrometry. In addition, the unsaturated disaccharides produced by chondroitinase ABC derived from the outer parts of the glycans were labeled with 2-aminoacridone and analyzed by CE to determine the disaccharide compositions. We evaluated AGC as a method for structural analysis of glycosaminoglycans in some chondroitin-sulfate-type PGs (urinary trypsin inhibitor, bovine nasal cartilage PG, bovine aggrecan, bovine decorin, and bovine biglycan). Recoveries of the released oligosaccharides were 57-73% for all PGs tested in the present study. In particular, we emphasize that the use of AGC achieved ca. 1000-fold rapid release of O-glycans compared with the conventional method.