植物种群分子进化中对生境的适应——对荒漠植物遗传多样性研究结果的初步分析

长期以来,自然选择理论与中性理论对生物分子进化中的环境适应机理存在着激烈争论。目前,在植物种群分子进化中对生境适应的研究中正面临着一些难题：中性突变是分子水平进化的唯一原因,自然选择发挥主要作用的适应性进化是否存在于分子水平,选择与中性两种学说两种机制完全不同,如何才能将两者联系和统一起来,部分学者利用建立各种模型来描述自然选择对分子标记位点以及连锁序列的直接作用,如生态位宽度变异假设等。本研究小组以新疆阜康荒漠植物为研究对象,通过对两种重要荒漠植物遗传多样性的研究,分析两种植物各亚种群不同生境的生态因子与其遗传变异的关系,讨论生态位宽度变异假设,揭示遗传变异的产生与维持。中性论者与选择论者都试图解释生物环境适应与分子变异之间的关系。中性论和选择论是反映进化的两个侧面,它们不是绝对的,可以相互转化。     

鞘磷脂酶通路与紫外线诱导的细胞凋亡

紫外线是一种重要的环境因素,对人类日常生活起着广泛的影响效应。大量的非保护的日光暴露不仅可以导致皮肤炎症、过度老化甚至皮肤癌症的发生,而且还能够诱导多种细胞凋亡。鞘磷脂酶-神经酰胺信号通路的激活与细胞凋亡关系密切,本文旨在探讨该通路在介导紫外线诱导细胞凋亡中的地位,重点描述了第二信使神经酰胺代谢的研究进展、鞘磷脂酶通路参与紫外线诱导细胞凋亡的机制。深入了解和研究紫外线诱导细胞凋亡的过程及其相关信号转导途径,有助于指导紫外线辐射的防护,开发新的治疗策略。     

Words as alleles: connecting language evolution with Bayesian learners to models of genetic drift

Scientists studying how languages change over time often make an analogy between biological and cultural evolution, with words or grammars behaving like traits subject to natural selection. Recent work has exploited this analogy by using models of biological evolution to explain the properties of languages and other cultural artefacts. However, the mechanisms of biological and cultural evolution are very different: biological traits are passed between generations by genes, while languages and concepts are transmitted through learning. Here we show that these different mechanisms can have the same results, demonstrating that the transmission of frequency distributions over variants of linguistic forms by Bayesian learners is equivalent to the Wright–Fisher model of genetic drift. This simple learning mechanism thus provides a justification for the use of models of genetic drift in studying language evolution. In addition to providing an explicit connection between biological and cultural evolution, this allows us to define a ‘neutral’ model that indicates how languages can change in the absence of selection at the level of linguistic variants. We demonstrate that this neutral model can account for three phenomena: the s-shaped curve of language change, the distribution of word frequencies, and the relationship between word frequencies and extinction rates.     

Field theory for biogeography: a spatially explicit model for predicting patterns of biodiversity

Predicting the variation of biodiversity across the surface of the Earth is a fundamental issue in ecology, and in this article we focus on one of the most widely studied spatial biodiversity patterns: the species–area relationship (SAR). The SAR is a central tool in conservation, being used to predict species loss following global climate change, and is striking in its universality throughout different geographical regions and across the tree of life. In this article we draw upon the methods of quantum field theory and the foundation of neutral community ecology to derive the first spatially explicit neutral prediction for the SAR. We find that the SAR has three phases, with a power law increase at intermediate scales, consistent with decades of documented empirical patterns. Our model also provides a building block for incorporating non-neutral biological variation, with the potential to bridge the gap between neutral and niche-based approaches to community assembly.
Ecology Letters (2010) 13: 87–95     

Epidermal sphingolipids: metabolism, function, and roles in skin disorders

Mammalian epidermis produces and delivers large quantities of glucosylceramide and sphingomyelin precursors to stratum corneum extracellular domains, where they are hydrolyzed to corresponding ceramide species. This cycle of lipid precursor formation and subsequent hydrolysis represents a mechanism that protects the epidermis against potentially harmful effects of ceramide accumulation within nucleated cell layers. Prominent skin disorders, such as psoriasis and atopic dermatitis, have diminished epidermal ceramide levels, reflecting altered sphingolipid metabolism, that may contribute to disease severity/progression. Enzymatic processes in the hydrolysis of glucosylceramide and sphingomyelin, and the roles of sphingolipids in skin diseases, are the focus of this review.     

Phospholipase D protects ECV304 cells against TNFalpha-induced apoptosis

Tumor necrosis factor alpha (TNFalpha), a pleiotropic cytokine, activates both apoptotic and pro-survival signals depending on the cell model. Using ECV304 cells, which can be made TNFalpha-sensitive by cycloheximide (CHX) co-treatment, we evaluated the potential roles of ceramide and phospholipase D (PLD) in TNFalpha-induced apoptosis. TNFalpha/CHX induced a robust increase in ceramide levels after 16 h of treatment when cell death was maximal. PLD activity was increased at early time point (1h) whereas both PLD activity and PLD1 protein were strongly decreased after 24h. TNFalpha/CHX-induced cell death was significantly lowered by exogenous bacterial PLD and phoshatidic acid, and in cells overexpressing PLD1. Conversely, cells depleted in PLD proteins by small interference RNA (siRNA) treatment exhibited higher susceptibility to apoptosis. These results show that PLD exerts a protective role against TNFalpha-induced cell death.     

The cellular resistance against oxidative stress (H2O2) is independent of neutral trehalase (Ntc1p) activity in Candida albicans

The protective role of trehalose against oxidative stress caused by hydrogen peroxide in Candida albicans has been investigated in the homozygous mutant ntc1Delta/ntc1Delta, disrupted in the NTC1 gene, which encodes the neutral (cytosolic) trehalase (Ntc1p). After a severe oxidative exposure (50 mM H(2)O(2)), both parental (CAI-4) and ntc1Delta/ntc1Delta exponential-phase cells stored large amounts of intracellular trehalose. In turn, the degree of cell survival was roughly equivalent in both strains, although slightly higher in ntc1Delta/ntc1Delta cultures. The mechanism of 'adaptive tolerance' was functional in the two strains. Thus, a gently oxidative pretreatment (5 mM H(2)O(2)) increased the recovery of cellular viability when it was followed by a severe challenge (50 mM H(2)O(2)); this phenomenon was accompanied by a significant elevation of the endogenous trehalose content. Oxidative stress also induced specific activation of the antioxidant enzymes catalase and glutathione reductase upon gentle oxidative treatment (5 mM H(2)O(2)), whereas superoxide dismutase activity was only activated upon prolonged exposure. Taken together, these results strongly suggest that in C. albicans neutral trehalase activity does not play an essential role in the protective response against oxidative stress. They also suggest that a diminished Ntc1p activity might favour the growth of C. albicans cells subjected to a strong oxidative exposure.     

耐热芽孢杆菌高温中性蛋白酶制备工艺研究

为使耐热芽孢杆菌(Thermophilic Bacillus)XJT9503高温中性蛋白酶产业化并在生产中应用,对XJT9503高温中性蛋白酶的制备工艺进行了研究.结果表明,可采用加热真空薄膜浓缩,在40℃,-0.094～-0.096MPa真空度下,经过45～55min浓缩,可使发酵处理液浓缩2～3倍,其酶活力仅损失10%左右.确定了采用喷雾干燥法生产固体酶制剂的最优工艺条件进口温度170℃、出口温度75℃、流量30kg*h-1.在此条件下,酶得率为68%.对固体酶与液体酶保存期稳定性的测定结果表明,固体酶的保存效果远比液体酶好,当保存210d时,固体酶制剂的酶活损失仅为2～8%.     

Relationship between sucrose accumulation and activities of sucrose-phosphatase, sucrose synthase, neutral invertase and soluble acid invertase in micropropagated sugarcane plants

The activities of sucrose-phosphate synthase (SPS), sucrose synthase (SUSY), neutral invertase (NI) and soluble acid invertase (SAI) regulates sucrose activity in sugarcane were studied. Micropropagated sugarcane plants were obtained from callus cultures of four Mexican commercially available sugarcane varieties characterized by differences in sugar production, and activities of SPS, SUSY, NI, SAI and concentrations of sucrose were monitored in the sugarcane stem. The results indicated that sucrose accumulation was positively and significantly related to an increase in activity of SPS and SUSY and negatively to a reduction in activity of SAI and NI (P<0.05). SPS explained most of the variations found for sucrose accumulation and least for NI. The relationship between activity of SPS, SUSY, NI and SAI in sugarcane stem was similar in each variety.     

植物群落物种共存机制的研究进展

物种共存是由进化、历史及生态尺度上的过程决定的.现存的理论从不同的尺度探讨了植物群落物种共存的可能机制,本文阐述了其中几种重要的理论.种库理论在进化和历史尺度上解释了植物物种共存的形成原因.在生态尺度上,虽然传统的生态位理论受到质疑,但是更新生态位理论和资源比率/异质性假说越来越受到重视;竞争共存理论认为具有相似竞争能力或能够避免竞争排斥的植物物种可以共存.在非平衡条件下,生物和非生物因素对植物物种共存也有显著影响,它们一方面作用于竞争优势种,使竞争优势向稀有种转移,另一方面可以创造生境时空异质性,为生态位分化提供机会.生态漂变学说认为群落中物种的组成不断变化,物种的共存和分布由随机因素决定.这些植物群落物种共存理论各有所长,互相补充.应用现代科学技术进行研究,结果必将促进人们对植物物种共存问题的深刻理解.