海藻糖介导的信号转导与植物抗逆性

海藻糖是一种非还原性二糖,它广泛存在于细菌、真菌、酵母、昆虫、无脊椎动物和植物等生物体内。海藻糖不仅作为碳水化合物的储备,而且还是一个多功能分子。海藻糖作为一种信号分子,启动信号转导级联反应,改变基因表达和酶的活性,与激素也有一定的关系。采用基因工程和通过外源施加的方法增加海藻糖在植物体内的积累可以提高植物的抗逆性,这为提高农作物的抗逆性提供了新的策略。     

几种物理技术在提高植物抗逆性中的研究进展

提高植物自身对外界不良环境的抵抗能力一直是植物研究人员关注的热点,物理方法在这一领域中正得到日益广泛的应用。本文综合沦述了近年来电场、磁场、电离辐射、激光等物理技术处理植物的种子或幼苗在提高植物抗冻、旱以及病害等逆境的能力,促进农作物增产中的应用成果及其可能的生理生化机制,并对未来的发展方向作了展望。     

海藻糖及其在生物工程方面的应用

自海藻糖发现以来对其化学性质、生理功能、作用机理、代谢途径等已进行了较为深入的研究,其分子生物学的研究也渐渐兴起。研究表明海藻糖能提高生物体对干旱、低温、高温、pH、盐渍等逆境条件下的抗性。离体试验表明海藻糖能保护生物膜、蛋白质的结构并能保持逆境下的酶活性,同时,外源海藻糖同样对生物体有保护作用。由于海藻糖具有这些独特的生物学功能,它已在许多方面得以应用,可作为食品工业的一种添加剂和甜味剂,使干燥食品在得水后保持原有的色、香、味;也可作为医药工业的非特异性生物制品和生化药品保护剂,使其在常温下保存,从而降低运输与储存费用;另外,在农业研究中可利用现代分子生物技术培育表达海藻糖的转基因作物,提高农作物的抗旱、抗冻等抗逆性能。     

多倍体植物抗逆性研究进展

许多逆境能诱导多倍体植物发生,并可能作为筛选压力推动多倍体的形成。多倍体植物具有细胞、器官巨大化的特点,但株型不一定巨大化。在几种主要逆境条件下(如低温、高温、干旱、盐碱、病害等),多倍体植物抗逆性往往增强。多倍体植物主要通过调整细胞大小和结构、调节生物膜系统、提高渗透调节物质含量、增强抗氧化系统活性、增加基因表达和通过表观遗传变化来增强抗逆性,但也有研究显示多倍体植物的抗逆性降低。多倍体植物的抗逆性还需要更深入和细致研究,才能阐明抗逆机理。该文对近年来国内外有关多倍体植物的形成、特征、抗逆性表现及其调控机制等方面的研究进展进行综述。     

物理方法在提高植物抗逆性中的应用

介绍了物理因素处理,主要包括磁场、电场、热激、冷激与低温以及激光处理等提高植物抗逆性的研究进展.     

奇妙的双糖——海藻糖

奇妙的双糖──海藻糖黄平（益阳卫生学校,湖南益阳４１３０００）关键词　海藻糖,生物学功能某些生物（例如某些植物种子、酵母细胞、真菌孢子以及某些微小生物）当其细胞内的水分完全或几乎完全除去时,仍能以一种极低新陈代谢或停止生命活动的状态长期生存下来,若重...     

海藻糖的生物学功能简介

海藻糖（Ｔｒｅｈａｌｏｓｅ,α－Ｄ－ｇｌｕｃｏｐｙｒａｎｏｓｙｌ－α－Ｄ－ｇｌｕｃｏｐｙｒａｎｏｓｉｄｅ）是一种非还原性二糖,广泛存在于海藻、酵母、霉菌、食用菌、虾、昆虫、高等植物等生物体内,是一种贮藏性碳水化合物。它具有保护生物细胞和生物活动性物质...     

海藻糖及其在微生物领域中的应用

海藻糖是生物体低湿休眠及微生物、生物大分子耐热抗干燥的稳定物质,８０年代以来受到国内外广泛关注并做了大量细致研究,本文详细介绍了这种独特双糖的理化及分子生物学特性、功能和作用机理以及它的制备和应用前景。     

茉莉酸在植物抗逆性中的研究进展

茉莉酸(jasmonic acid, JA)是一种植物内源合成的脂类激素,在植物响应胁迫的调控中发挥着重要作用。本文概括了JA的生物合成与代谢途径及其调控机制;总结了JA信号的传导通路;系统归纳了JA在植物响应生物和非生物胁迫应答中的作用机制和调控网络,重点关注了最新的研究进展。此外,本文梳理了JA与其他植物激素在植物抗逆性调节过程中的信号交流。最后讨论了JA信号通路介导的植物抗逆性研究中亟待解决的问题,并展望了新的分子生物学技术在调控JA信号通路增强作物抗性中的应用前景,以期为植物的抗逆性研究和改良提供参考。     

DNA甲基化与植物抗逆性研究进展

DNA甲基化是真核细胞基因组重要修饰方式之一.DNA甲基化通过与转录因子相互作用或通过改变染色质结构来影响基因的表达,从表观遗传水平对生物遗传信息进行调节,在生长发育过程中起着重要的作用,而且植物DNA甲基化还参与了环境胁迫下的基因表达调控过程.本文对植物DNA甲基化的产生机制、功能,以及DNA甲基化在植物应对逆境胁迫中的作用进行综述,以更好地理解植物DNA甲基化及其对环境胁迫的响应,为植物抗逆性研究及作物遗传改良提供理论参照.     

昆虫体色分化研究进展

昆虫体色分化现象在自然界中普遍存在,它给昆虫的分类等工作带来了不便。文章介绍了寄主专化论、环境因素控制论、基因控制论等有关昆虫体色分化机理的3个不同观点,着重从染色体和基因方面介绍了昆虫体色分化的研究,以及分子标记技术在其研究中的应用,并对昆虫体色分化的研究方向进行了展望。     

Oxylipins and plant abiotic stress resistance

Oxylipins are signaling molecules formed enzymatically or spontaneously from unsaturated fatty acids in all aerobic organisms. Oxylipins regulate growth, development, and responses to environmental stimuli of organisms. The oxylipin biosynthesis pathway in plants includes a few parallel branches named after first enzyme of the corresponding branch as allene oxide synthase, hydroperoxide lyase, divinyl ether synthase, peroxygenase, epoxy alcohol synthase, and others in which various biologically active metabolites are produced. Oxylipins can be formed non-enzymatically as a result of oxygenation of fatty acids by free radicals and reactive oxygen species. Spontaneously formed oxylipins are called phytoprostanes. The role of oxylipins in biotic stress responses has been described in many published works. The role of oxylipins in plant adaptation to abiotic stress conditions is less studied; there is also obvious lack of available data compilation and analysis in this area of research. In this work we analyze data on oxylipins functions in plant adaptation to abiotic stress conditions, such as wounding, suboptimal light and temperature, dehydration and osmotic stress, and effects of ozone and heavy metals. Modern research articles elucidating the molecular mechanisms of oxylipins action by the methods of biochemistry, molecular biology, and genetics are reviewed here. Data on the role of oxylipins in stress signal transduction, stress-inducible gene expression regulation, and interaction of these metabolites with other signal transduction pathways in cells are described. In this review the general oxylipin-mediated mechanisms that help plants to adjust to a broad spectrum of stress factors are considered, followed by analysis of more specific responses regulated by oxylipins only under certain stress conditions. New approaches to improvement of plant resistance to abiotic stresses based on the induction of oxylipin-mediated processes are discussed.     

A dual role for intracellular trehalose in the resistance of yeast cells to water stress.

It is well known that yeast cells survive environmental stresses such as desiccation and freezing and there is evidence that these phenomena may be related to the presence of trehalose in the cells. However, the molecular mechanism by which trehalose might exert an influence on cell functions remains unknown. In this report, thermogravimetry and differential thermal analysis were used to estimate the amount of bound water in yeast cells. It is shown that when the trehalose content is greater than 2-3% of the cell dry weight, the amount of bound water is drastically decreased and the viability of the dried cells is increased. This implies that a major portion of the bound water is replaced by trehalose. In addition, measurements of the NMR spin-lattice relaxation time of the intracellular water protons show that trehalose acts as a water-structuring agent in hydrated yeast cells. This dual role is essential for high resistance to water stress in yeast cells.     

Differential importance of trehalose in stress resistance in fermenting and nonfermenting Saccharomyces cerevisiae cells.

The trehalose content in laboratory and industrial baker's yeast is widely believed to be a major determinant of stress resistance. Fresh and dried baker's yeast is cultured to obtain a trehalose content of more than 10% of the dry weight. Initiation of fermentation, e.g., during dough preparation, is associated with a rapid loss of stress resistance and a rapid mobilization of trehalose. Using specific Saccharomyces cerevisiae mutants affected in trehalose metabolism, we confirm the correlation between trehalose content and stress resistance but only in the absence of fermentation. We demonstrate that both phenomena can be dissociated clearly once the cells initiate fermentation. This was accomplished both for cells with moderate trehalose levels grown under laboratory conditions and for cells with trehalose contents higher than 10% obtained under pilot-scale conditions. Retention of a high trehalose level during fermentation also does not prevent the loss of fermentation capacity during preparation of frozen doughs. Although higher trehalose levels are always correlated with higher stress resistance before the addition of fermentable sugar, our results show that the initiation of fermentation causes the disappearance of any other factor(s) required for the maintenance of stress resistance, even in the presence of a high trehalose content.     

脱落酸调节植物抵御水分胁迫的机制研究

干旱、盐渍、低温等均可导致植物可利用水分的亏缺,表现为水分胁迫。植物感受到水分胁迫,诱导脱落酸（abscisic acid,ABA）生物合成。ABA可通过促使气孔关闭或抑制气孔开放,使作物尽可能地降低蒸腾失水,以抵御水分胁迫。该文就植物激素ABA及其下游信号过氧化氢（hydrogenperoxide,H2O2）、一氧化氮（nitric oxide,NO）以及Ca2＋等在植物气孔运动调节方面的研究进展进行概述,以构建水分胁迫下ABA调节植物气孔运动的可能模式。     

铅胁迫下植物抗性机制的研究进展

综述了近10多年来国内外研究重金属铅对植物的伤害机理,以及植物对铅的耐性机制的研究进展.首先从细胞分裂、细胞膜透性、光合作用和抗氧化酶系统等生理生化方面讨论了铅对植物的伤害机理,其次分析了铅离子跨膜运输、根系分泌物、金属配位体、铅离子区域化分布与植物抗性的关系.     

The involvement of trehalose in yeast stress tolerance

Summary A total of 12 yeast strains from various genera were examined for their ability to produce ethanol in the presence of high concentrations of glucose. From these studies, the yeastsTorulaspora delbrueckii andZygosaccharomyces rouxii were observed to the most osmotolerant. These osmotolerant yeast strains were also observed to possess high concentrations of intracellular trehalose. Futhermore, these strains were found to be tolerant to long-term storage at –20°C and to storage at 4°C in beer containing 5% (v/v) ethanol. Cells containing high trehalose levels at the time of freezing or cold storage exhibited the highest cell viabilities. Trehalose concentration was observed to increase during growth on glucose, reaching a maximum after 24–48 h. Increasing the incubation temperature from 21 to 40°C also resulted in an increase in intracellular trehalose content. These results suggest that trehalose plays a role in enhancing yeast survival under environmentally stressful conditions.     

Effect of xylitol and trehalose on dry resistance of yeasts

The effects of dehydration/rehydration on two strains of Saccharomyces cerevisiae: S600, a metabolically engineered xylose-utilising strain, and H158, the non-xylose-utilising host strain; and on the naturally xylose-utilising yeast Pachysolen tannophilus CBS 4044, were compared after glucose and xylose utilisation respectively. The yeast strains differed in their ability to excrete and accumulate intracellular xylitol. A high intracellular xylitol content before and after dehydration coincided with a higher viability after a dehydration/rehydration cycle. The intracellular trehalose content increased during dehydration in all three yeast strains, but this did not correspond to enhanced cell viability after dehydration/rehydration. The results are discussed in relation to the ability of xylitol and trehalose to structure water. Received: 9 July 1996 / Received revision: 29 October 1996 / Accepted: 2 November 1996     

Effect of trehalose on a phospholipid membrane under mechanical stress

Explicit solvent molecular dynamics simulations were used to investigate at atomic resolution the effect of trehalose on a hydrated phospholipid bilayer under mechanical stress (stretching forces imposed in the form of negative lateral pressure). Simulations were performed in the absence or presence of trehalose at 325 K, and with different values for negative lateral pressure. In the concentration regime (2 molal) and range of lateral pressures (1 to −250 bar) investigated, trehalose was found to interact directly with the membrane, partially replacing water molecules in the formation of hydrogen bonds with the lipid headgroups. Similar to previous findings in the context of thermal stress, the number, degree of bridging, and reaching depth of these hydrogen bonds increased with the magnitude of perturbation. However, at the concentration considered, trehalose was not sufficient to preserve the integrity of the membrane structure and to prevent its extreme elongation (and possible disruption) under the effect of stretching forces.