Ultrastructural Changes of the Mitochondrion During the Life Cycle of Trypanosoma brucei

The mitochondrion is crucial for ATP generation by oxidative phosphorylation, among other processes. Cristae are invaginations of the mitochondrial inner membrane that house nearly all the macromolecular complexes that perform oxidative phosphorylation. The unicellular parasite Trypanosoma brucei undergoes during its life cycle extensive remodeling of its single mitochondrion, which reflects major changes in its energy metabolism. While the bloodstream form (BSF) generates ATP exclusively by substrate-level phosphorylation and has a morphologically highly reduced mitochondrion, the insect-dwelling procyclic form (PCF) performs oxidative phosphorylation and has an expanded and reticulated organelle. Here, we have performed high-resolution 3D reconstruction of BSF and PCF mitochondria, with a particular focus on their cristae. By measuring the volumes and surface areas of these structures in complete or nearly complete cells, we have found that mitochondrial cristae are more prominent in BSF than previously thought and their biogenesis seems to be maintained during the cell cycle. Furthermore, PCF cristae exhibit a surprising range of volumes in situ, implying that each crista is acting as an independent bioenergetic unit. Cristae appear to be particularly enriched in the region of the organelle between the nucleus and kinetoplast, the mitochondrial genome, suggesting this part has distinctive properties.     

Hybridization and speciation

Hybridization has many and varied impacts on the process of speciation. Hybridization may slow or reverse differentiation by allowing gene flow and recombination. It may accelerate speciation via adaptive introgression or cause near‐instantaneous speciation by allopolyploidization. It may have multiple effects at different stages and in different spatial contexts within a single speciation event. We offer a perspective on the context and evolutionary significance of hybridization during speciation, highlighting issues of current interest and debate. In secondary contact zones, it is uncertain if barriers to gene flow will be strengthened or broken down due to recombination and gene flow. Theory and empirical evidence suggest the latter is more likely, except within and around strongly selected genomic regions. Hybridization may contribute to speciation through the formation of new hybrid taxa, whereas introgression of a few loci may promote adaptive divergence and so facilitate speciation. Gene regulatory networks, epigenetic effects and the evolution of selfish genetic material in the genome suggest that the Dobzhansky–Muller model of hybrid incompatibilities requires a broader interpretation. Finally, although the incidence of reinforcement remains uncertain, this and other interactions in areas of sympatry may have knock‐on effects on speciation both within and outside regions of hybridization.     

马铃薯实生群体遗传多样性的SSR分析

以云南马铃薯品种‘剑川红’植株1个浆果中的天然实生种子产生的70个单株以及B20[CIP010(♀)×CIP004(♂)]杂交组合后代100个实生苗单株为材料,采用12对SSR引物对自交种和杂交实生群体的遗传差异性进行分析,旨在从后代群体中找到与母本(亲本)在分子水平上表现一致的植株,为种质资源的长期保存提供依据。结果表明:(1)‘剑川红’自交群体的多态性比率为81.6%,比杂交组合B20实生群体的多态性比率72.8%略高,说明2个群体的多态性比率均较高。(2)聚类分析结果显示,自交后代和杂交后代群体的遗传相似系数均较高,变化范围均在0.74~0.96之间,说明2个群体均发生了不同程度的遗传分离,但分离的程度较小,绝大多数条带表现一致。(3)在所有供试材料中,同一浆果中均未发现与‘剑川红’母株在分子水平上表现完全一致的单株。研究认为,在分子水平上寻找完全不分离的实生群体难度非常大,需进一步评价与母株(亲本)在分子水平上相似株系的田间表现,从而确定是否可以通过相近或极相近株系来恢复种源。     

How reticulated are species?

Many groups of closely related species have reticulate phylogenies. Recent genomic analyses are showing this in many insects and vertebrates, as well as in microbes and plants. In microbes, lateral gene transfer is the dominant process that spoils strictly tree‐like phylogenies, but in multicellular eukaryotes hybridization and introgression among related species is probably more important. Because many species, including the ancestors of ancient major lineages, seem to evolve rapidly in adaptive radiations, some sexual compatibility may exist among them. Introgression and reticulation can thereby affect all parts of the tree of life, not just the recent species at the tips. Our understanding of adaptive evolution, speciation, phylogenetics, and comparative biology must adapt to these mostly recent findings. Introgression has important practical implications as well, not least for the management of genetically modified organisms in pest and disease control.     

淹水胁迫下江南牡丹生长及光合特性研究

以3年生江南牡丹品种‘凤丹白’为材料,利用盆栽淹水法,设置正常管理、轻度胁迫和重度胁迫3个水平,研究不同淹水胁迫水平对牡丹生长和光合特性的影响。结果表明：经过30 d胁迫后,正常管理、轻度胁迫和重度胁迫下的江南牡丹苗高生长量分别为3.6、1.1和0.73 cm,地径生长量分别为0.21、0.11和0.06 cm,植株总生物量增加量分别为7.0、3.0和2.75 g,淹水胁迫和正常生长差异显著,淹水胁迫严重影响了江南牡丹的生长。同时,在正常管理时,牡丹总叶绿素含量升高,而在淹水胁迫下呈下降趋势。淹水胁迫不同时间根系活力均呈下降趋势且随着胁迫程度的增加下降越大。正常管理下光合速率逐渐增加而胁迫条件下光合速率逐渐降低。同时胁迫条件下,牡丹蒸腾速率、气孔导度均明显下降;轻度淹水胁迫下胞间CO2浓度先升高后降低;而重度胁迫下胞间CO2浓度呈现逐渐升高的变化趋势。淹水胁迫对牡丹根系活力、茎段生长和叶片光合特性影响较大。该研究结果为江南牡丹耐涝胁迫机理研究奠定了理论基础。     

2018年感染病领域十大进展

2018年已缤纷落幕,2019年带着对未来的期许纷至沓来。回顾过去,展望未来,本文整理了2018年世界乃至中国感染病界的几项重大事件与进展,并进一步梳理了该领域的发展趋势。     

子痫前期患者血清APN、TNF-α、Apelin水平的表达及相关性研究

目的:探讨子痫前期患者血清脂联素(APN)、肿瘤坏死因子-α(TNF-α)、Apelin水平的表达及相关性。方法:选取2015年10月到2017年8月在辽河油田总医院妇产科就诊的子痫前期患者86例,根据患者的病情严重程度将其分为轻度子痫前期组(46例)和重度子痫前期组(40例),另选取同期在我院进行产检的健康孕妇40例作为对照组,比较三组受试者血清中APN、TNF-α、Apelin、低密度脂蛋白胆固醇(LDL-C)、甘油三酯(TG)、高密度脂蛋白胆固醇(HDL-C)和总胆固醇(TC)水平,并分析子痫前期患者血清中APN、TNF-α、Apelin、LDL-C、TG、HDL-C、TC的相关性。结果:重度子痫前期组血清中APN水平低于轻度子痫前期组和对照组,TNF-α、Apelin水平高于轻度子痫前期组和对照组(P0.05);轻度子痫前期组血清中APN水平低于对照组,TNF-α、Apelin水平高于对照组(P0.05)。重度子痫前期组血清中LDL-C、TG、TC水平高于轻度子痫前期组和对照组,HDL-C水平低于轻度子痫前期组和对照组(P0.05);轻度子痫前期组LDL-C、TC水平高于对照组,HDL-C水平低于对照组(P0.05)。Pearson相关性分析结果显示,子痫前期患者血清中APN与TNF-α、Apelin、LDL-C、TG呈负相关,与HDL-C呈正相关(P0.05);TNF-α与Apelin、LDL-C、TG、TC呈正相关,与HDL-C呈负相关(P0.05);Apelin与LDL-C、TG、TC呈正相关,与HDL-C呈负相关(P0.05)。结论:子痫前期患者血清中APN水平明显下降,TNF-α、Apelin明显升高,三种指标可相互影响,且均可影响机体的脂质代谢水平,共同调节子痫前期患者的疾病进展。     

七姊妹山常绿落叶阔叶混交林物种多样性格局及其环境解释

依托七姊妹山自然保护区6 hm²森林动态监测样地研究平台,基于样地和物种基本信息数据,采用多元回归树和冗余分析研究方法,探讨地形因子对生境的塑造作用及物种分布特征,分析不同群丛类型下物种多样性的变化规律。结果表明：(1)依据“1 SE”规则,4次分割依次以海拔(1 453 m)、坡度(23.13°)、海拔(1 398 m)、凹凸度(4.094)为分界点可将150个样地分为5个群丛。(2)冗余分析表明地形因子对物种分布解释量为0.077 6,解释率为16.36%,各环境因子对物种分布的解释力度依次为：海拔>坡度>凹凸度;坡向与物种的分布无显著相关性。(3)5个群丛中立木密度与胸高截面积最高的均为群丛5(527.4株/400 m²;3.495 cm²/株),立木密度与平均胸高截面积最低为群丛4(225.4株/400 m²;3.057 cm²/株)。(4)5个群丛中Shannon Winener丰富度指数与Simpson优势度指数最高的均为群丛2,最低的为群丛5,物种多样性尺度效应明显;Pielou均匀度指数最高为群丛4,最低为群丛5。(5)两两群丛间Jaccard相似性系数最低为群丛1 群丛2(0.331),最高的为群丛4 群丛5(0.645),海拔对β多样性格局影响较大。研究认为,七姊妹山自然保护区6 hm²样地地形因子对该区域生境的塑造具有一定作用,海拔、坡度、凹凸度组成的“环境筛”影响了该区域的物种分布及多样性格局。     

嗜热链球菌胞外多糖EPS333对酸乳品质的影响

本研究以酸乳为基质,通过测试酸乳酸化速率曲线、脱水收缩敏感性、持水力、水分迁移、质构及流变特性等参数,研究了嗜热链球菌胞外多糖与市场常规应用多糖对酸乳品质的影响。研究结果表明:嗜热链球菌胞外多糖EPS333在酸乳凝胶过程中较其他几种多糖能明显减缓酸化趋势,后熟及储藏阶段减少"自由水"含量,降低流动性,改善其流变特性。