防御素的生物学特性及其抗病基因工程

防御素是一种富含半胱氨酸的小分子多肽,对细菌等微生物具有广谱抗性,且作用机制特殊。迄今为止,国内外在防御素方面进行了大量的研究,已经从各类生物体中分离出不同种类的防御素,并在基因工程和医药领域呈现广泛的应用前景。文章对防御素的分类、生物学特性,包括哺乳动物α-、β-、θ-防御素、昆虫以及植物防御素的分子结构及抗菌活性进行了综述,阐述了防御素的膜作用及与细胞内复合物结合的作用机制。总结和归纳了防御素基因的分离、表达研究进展及动、植物防御素基因在抗病基因工程领域的应用,并对防御素在未来的生物制药和植物抗病基因工程方面的应用前景进行了展望。     

哺乳动物防御素的研究进展及其应用前景

防御素是生物界广泛存在的一类具微生物抗性的低分子短肽,其中哺乳动物防御素的抗性谱最为广泛,具有很高的应用潜力.概述了哺乳动物防御素的组成分布、立体结构、基因表达调控、抗菌谱等的国内外研究进展,并展望了其在医学和植物抗病基因工程中的应用前景.     

硫堇蛋白及细胞防御素在植物抗病性育种中的研究

硫堇蛋白及细胞防御素是一类广泛存在于植物细胞中并对细菌、真菌等病原微生物具有抑制或杀灭作用的小分子量多肽抗生素。二者在分子量、空间结构及某些化学性质具有相似性,近年来在植物抗病性育种中得以应用。对植物硫堇蛋白及细胞防御素的分类、结构、作用机制以及在植物抗性育种的应用实例进行综述。     

入侵植物乌桕防御策略的适应性进化研究

生长于不同昆虫群落胁迫下的植物地理种群可能进化出不同的防御策略。入侵植物在原产地同时受到专食性昆虫和广食性昆虫的取食危害, 而在入侵地“逃逸”了专食性昆虫的取食危害。入侵植物对不同类型昆虫防御策略的演化可能在其成功入侵的过程中起着至关重要的作用。该文主要以原产中国入侵北美的木本植物乌桕(Triadica sebifera)为例, 并结合其他入侵植物防御策略演化的研究, 从抗性和耐受性、直接抗性和间接抗性、组成抗性和诱导抗性三个方面系统分析不同昆虫选择压力下入侵植物防御策略的演化, 同时探讨入侵植物防御策略演化对生物防治效果的影响, 指出未来的重点研究方向。     

硅对植物抗虫性的影响及其机制

硅不是植物必需营养元素,但硅在提高植物对一系列非生物和生物胁迫的抗性方面都具有重要作用。综述了硅对植物抗虫性的影响及其机制。在多数植物中,增施硅肥可增强其抗虫性;所增强的抗性与硅肥种类和施用方式之间存在关系。植物组织中沉积的硅可增加其硬度和耐磨度,降低植物可消化性,从而增强植物组成性防御,包括延缓昆虫生长发育、降低繁殖力、减轻植物受害程度;植物体内的硅含量以及硅沉积的位点和排列方式影响组成性防御作用的强度。此外,硅可以调节植物诱导性防御,包括直接防御和间接防御,直接防御涉及增加有毒物质含量、产生局部过敏反应或系统获得抗性、产生有毒化合物和防御蛋白,从而延缓昆虫发育;间接防御主要通过释放挥发性化合物吸引植食性昆虫的捕食性和寄生性天敌而导致植食性昆虫种群下降。     

昆虫防御素基因( defensin) 的起源与分子进化

果蝇防御素基因位于它的第二条染色体右臂上,其编码产物具有抗菌肽活性,主要时革兰氏阳性菌有抗性。由于其有牢固的分子骨架、广泛的分布以及生物活性,对它的研究已成为当前国际研究热点。本文主要使用NCBI的资源分析黑腹果蝇防御素及其同源序列,并讨论了昆虫防御素的起源和分子进化。     

植物诱导性直接防御

众所周知,植物对植食性昆虫危害的反应表现在3个方面：直接防御,间接防御,和耐害性。直接防御是指植物自身所具有的能影响寄主植物感虫性的所有特性。植物对昆虫危害的直接防御包括：限制食物供给,降低营养价值,减少偏嗜程度,破坏组织结构和抑制害虫代谢途径。目前已知的防御化合物主要包括植物次生代谢物质、昆虫消化酶（蛋白）抑制剂、蛋白酶、凝集素、氨基酸脱氨酶和氧化酶。植物在防御某种昆虫为害时多个因素往往具有累加效应或协同作用,并且对一种昆虫起主导作用的因素在防御另一种昆虫时可能仅仅起次要作用甚至根本不起作用。因此,对寄主植物基因表达、蛋白水平和活性以及代谢物含量在不同时空条件下进行广泛的定量和定性的高通量分析,不仅可以促进对植物直接防御机制的全面理解,而且有助于在农业生产中加快对作物抗性的特定靶标的鉴定。     

养分影响入侵种喜旱莲子草对专食性天敌的防御

竞争力增强进化假说(Evolution of Increased Competitive Ability,EICA)认为入侵植物在入侵地由于天敌逃逸导致对天敌防御投入降低而增加生长和繁殖等投入。然而,EICA假说所预测防御能力的进化主要集中在防御的组成抗性方面,而从诱导抗性和耐受性的角度进行的验证还很有限,并且忽视了生境资源可利用性对植物防御策略的影响。本研究采用同质园实验比较了喜旱莲子草(Alternanthera philoxeroides)原产地(阿根廷)和入侵地(美国)各9个种群,在高、低养分和有、无专食性天敌取食处理下的防御相关功能性状(比茎长、根冠比)及其对天敌取食的诱导反应,以及它们与植物适合度相关指标的关系。结果表明:入侵地种群具有较高的总生物量(+14.7%)、较低的比茎长(防御钻茎化蛹天敌的重要指标,-27.5%),暗示其个体大小增加而防御投入降低,符合EICA假说的预测。入侵地种群耐受性与原产地种群没有显著差异。在高养分下,入侵地种群的比茎长对专食性天敌取食的诱导反应显著增加,且与总生物量呈显著正相关。这些结果表明,相比原产地种群,入侵地种群具有更高的生物量,对专食性天敌的组成抗性降低,且在高养分下对专食性天敌的诱导抗性增加,推测生境的养分富集可能会降低喜旱莲子草的生物防治效果。     

在转基因植物中利用植物凝集素防治害虫的研究

植物凝集素对包括同翅目在内的害虫具有有效抗性作用。本文就同翅目害虫的危害性、植物凝集素定义的不断深入认识、植物凝集素在植物体内的生理作用、对害虫的作用机理、并对人工饲喂害虫实验及转凝集素的抗虫基因工程研究进展、存在问题等方面作一阐述。     

增强UV-B辐射和SO2作用下植物光合响应及其相对抗性

 研究了20种野外生长的树种在增强UV-B、NaHSO3的作用下,它们的光合作用响应及其对这两种胁迫的抗性。研究结果表明,这些植物的抗性可分为抗性强、抗性中等和敏感3种类型。UV-B、NaHSO3以及UV-B+NaHSO3 3种处理与这些植物光合作用受抑制程度呈现良好的线性关系,说明这些植物在防御UV-B和NaHSO3伤害的能力方面有一致性,没有种的特异性。结果还表明,在这些植物中NaHSO3增强了UV-B对它们的抑制作用,敏感类型植物尤为明显。      

芽孢杆菌几种重要抗菌脂肽研究进展

多种芽孢杆菌为益生菌,能分泌多种天然抗菌活性物质,其中脂肽是重要的一类。目前已鉴定的脂肽约有90多种,多数为环脂肽。脂肽中表面活性素(surfactin)、伊枯草菌素(iturin)、芬原素(fengycin)、杆菌霉素(bacillomycin)、多粘菌素(polymyxins)等是研究最广泛的脂肽。其中surfactin、iturin、fengycin由于其具有表面活性剂特性及抗真菌、抗细菌、抗病毒、抗肿瘤、抗炎症等功能,应用潜力巨大。本文对surfactin、iturin及fengycin的结构、功能、合成调控及其分离纯化和生产等方面的研究进展进行了评述。合成生物学是提高脂肽产量的重要手段,未来脂肽可用于种植业、养殖业、食品、医药、石油工业和环保等领域,因此需要在新型脂肽的发现、高产活性脂肽的生产、脂肽低廉生产技术的研发及安全性的评估等方面加强研究。     

生物抗菌多肽

对微生物、动物、植物等产生的抗菌多肽的抗菌谱、作用机理进行了综述。     

抗菌整理织物的抗菌效力测试

本文对大连印染厂试产的X—Si—4有机硅等抗菌整理布进行了抗菌效力检测,显示对细菌具100％的抑菌率,而且有较强皮肤癣菌和污染性霉菌的效力,同时具耐紫外线照射,耐高温高压,耐洗涤等优良性能。试验均达预期效果,表明方法简易,重复性好,结果可信。本文并从菌种的选择,试验方法的配合使用,抗菌整理布的优良性能测试等诸方面进行了探讨。     

生物抗菌多肽

对微生物、动物、植物等产生的抗菌多肽的抗菌谱、作用机理进行了综述.     

Bioluminescence of outer membrane defective mutants of Photobacterium phosphoreum

Abstract Mutants of Photobacterium phosphoreum NCMB7 hypersensitive to several antimicrobiol agents were independently isolated and characterized. The hypersensitivity was probably due to changes in the outer membrane (OM) structure; the electrophoretic lipopolysaccharide profile of one mutant was altered. In addition, 2 mutants exhibited elevated cell surface hydrophobicity. With respect to bioluminescence, the mutants were dim or dark, and showed strongly reduced activities of the inducible enzymes luciferase and fatty acid reductase. Our results suggest that the outer membrane is involved in the regulation of bacterial bioluminescence.     

革兰阴性杆菌对头孢哌酮／舒巴坦耐药率的变迁

目的调查革兰阴性杆菌对头孢哌酮／舒巴坦的耐药率变化。方法收集2004年1月至2007年12月从我院住院患者各种临床标本中分离的革兰阴性杆菌,使用VITEK-60全自动微生物分析仪进行菌种的鉴定,采用K-B法对头孢哌酮／舒巴坦进行药敏试验,对结果进行回顾性凋查。结果肠杆菌科细菌对头孢哌酮／舒巴坦的耐药率较低,大肠埃希菌、肺炎克雷伯菌和阴沟肠杆菌对头孢哌酮／舒巴坦的耐药率分别为1．7％,7．7％和5．8％。嗜麦芽窄食假单胞菌、洋葱伯克霍尔德菌、脑膜脓毒性金黄杆菌、铜绿假单胞菌和鲍曼不动杆菌对头孢哌酮／舒巴坦的耐药率分别为27．6％、38．0％、2．3％、23．5％和4．8％。铜绿假单胞菌和鲍曼不动杆菌对头孢哌酮／舒巴坦的耐药率从2004年的35．1％和23．7％下降至2007年的12．4％和0．4％。结论头孢哌酮／舒巴坦对肠杆菌科细菌具有非常强的体外抗菌活性,铜绿假单胞菌和鲍曼不动杆菌对头孢哌酮／舒巴坦的耐药率呈下降趋势。     

Coumarins scaffolds as COX inhibitors

The discovery of COX enzymes has led to a better understanding of inflammation and its related biological pathways. Apart from being related to inflammation and pain, it has also been associated with cancer and neuropsychiatric diseases such as schizophrenia. Proverbially speaking, study of these enzymes has been crucial as they happen to “have fingers in many pies”. Non-steroidal anti-inflammatory drugs (NSAID) that act specifically as COX-2 inhibitors have been known for a while; however these are also associated with severe side effects such as cardiac problems. Several heterocylic molecules have been tested for their anti-inflammatory activity specifically as COX-inhibitors. Coumarins also known as benzopyrans are widely found in nature, and are routinely employed as herbal remedies since early days. Over 1300 coumarins have been identified, principally as secondary metabolites in green plants, fungi and bacteria. Recently the use of natural and synthetic coumarins has garnered a lot of attention for their anti-inflammatory activities. In this review we delve further into the study of natural and synthetic coumarins as COX-inhibitors. Although the study is still in its nascent stage, we believe there is scope for a lot of development.     

Maintenance management and eradication of established aquatic invaders

Although freshwater invasions have not been targeted for maintenance management or eradication as often as terrestrial invasions have, attempts to do so are frequent. Failures as well as successes abound, but several methods have been improved and new approaches are on the horizon. Many freshwater fish and plant invaders have been eliminated, especially by chemical and physical methods for fishes and herbicides for plants. Efforts to maintain invasive freshwater fishes at low levels have sometimes succeeded, although continuing the effort has proven challenging. By contrast, successful maintenance management of invasive freshwater plants is uncommon, although populations of several species have been managed by biological control. Invasive crayfish populations have rarely been controlled for long. Marine invasions have proven far less tractable than those in fresh water, with a few striking eradications of species detected before they had spread widely, and no marine invasions have been substantially managed for long at low levels. The rapid development of technologies based on genetics has engendered excitement about possibly eradicating or controlling terrestrial invaders, and such technologies may also prove useful for certain aquatic invaders. Methods of particular interest, alone or in various combinations, are gene-silencing, RNA-guided gene drives, and the use of transgenes.

     

Host defense mechanisms of cephalopods

Humoral and cellular mechanisms of defense have been described for cephalopods, a relatively advanced group of mollusks. Typical of other mollusks, cephalopod agglutinins are the most documented component of humoral immunity. Lectins, which have agglutinating properties, have been described and characterized from octopuses. Agglutinins from cephalopod hemolymph have also been shown to agglutinate a variety of vertebrate red blood cells, as well as potential bacterial pathogens. Hemocytes are the primary component of cellular immunity. Although the hemocyte role in phagocytosis has been extensively studied in other mollusks, the mechanisms of phagocytosis have not been described extensively for cephalopods. Cephalopod hemocytes have phagocytic capabilities and may function in encapsulation and neutralization of foreign substances; however, the effects of environmental factors and the full extent of phagocytic capabilities of cephalopod hemocytes have not been reported. Hemocytes from cephalopods have a role in wound healing and inflammation which have been reported in detail by several investigators.