A review of antimicrobial peptides: defensins and related cationic peptides

Cationic antimicrobial peptides are present throughout the plant and animal kingdoms and bear striking structural and functional similarities across species lines. They provide primitive, nonspecific means of combating a variety of bacteria, fungi, enveloped viruses, and protozoa. Some are also cytotoxic against host cells, including neoplastic cells. Cationic antimicrobial peptides may play various roles in inflammation and tissue repair. Antimicrobial peptides are found in epithelial tissues regularly exposed to microbial attack as well as in cells whose primary function is defense against potential pathogens. They constitute an important part of the nonoxidative antimicrobial arsenal of leukocytes. They are preformed and/or readily synthesized when the cells are stimulated by exposure to pathogens. They exert their effects directly by inserting into membranes of target cells and forming ion channels which increase membrane permeability; however, antimicrobial peptides can also act as opsonins to facilitate phagocytosis. Resistance to defensins is a virulence factor for organisms such as Salmonella sp. The study of cationic antimicrobial peptides is increasing our understanding of innate immunity, inflammation, and the pathogenesis of genetic diseases such as specific granule disease in humans. Therapeutic applications of antimicrobial peptides are currently under investigation.     

GST-MtDef4融合蛋白的原核表达及体外抑菌活性的检测

为研究苜蓿(Medicago truncatula)防卫素基因MtDef4的抑菌功能,以含有该基因片段的质粒pAND-MtDef4为模板,扩增出相应的目的基因,测序正确后将MtDef4基因片段连接到带有GST标签的原核表达载体pGEX6P-1中,转化大肠杆菌TransB(DE3),经IPTG诱导,Glutathione Sepharose 4B亲和纯化,通过SDS-PAGE电泳及Western blot确定融合蛋白的表达。体外抑菌试验表明,MtDef4能够抑制病原真菌Corynespora cassiicola而非Collectotrichum gloeosporioides的生长。本研究结果可为进一步培育转基因橡胶抗病品种奠定基础。     

抗菌肽的结构与功能研究

抗菌肽是一种具有抗菌、抗病毒的天然活性物质。在基础理论研究领域,抗菌肽是研究生物大分子结构的重要材料。同时,其独特的生物抗菌活性又在医药工业具有广阔的应用前景。抗菌肽的结构组成与其生物活性密切相关。以3类典型抗菌肽为例,阐述多肽结构对于生理功能的重要性,以展示抗菌肽重要的理论及应用价值。     

植物防御素D1基因种子特异表达载体构建及在玉米中的转化

以绿豆基因组DNA为模板,通过PCR技术扩增了绿豆防御素D1基因序列,与GenBank中绿豆防御素基因的相应片段有99.08%同源性,克隆片段长为355bp。将种子特异启动子sbeIIb和D1基因插入到带有耐盐基因的表达载体pCAMBIA1301-BADH中,构建了无抗生素选择标记的种子特异表达载体pSBEIIb-D-B,该载体是利用耐盐基因BADH替代抗生素基因作为筛选标记,消除了对环境及肠道微生物的潜在威胁。将该载体利用超声波辅助农杆菌介导法转化了2个玉米自交系丹598、988的愈伤组织,经分化诱导出苗后进行PCR检测,证明得到转基因阳性植株,相对转化率最高达到7.8%。     

Drugs from bugs: the use of insects as a valuable source of transgenes with potential in modern plant protection strategies

Transgenic expression of antimicrobial peptides in crops has become a novel approach among the strategies to combat phytopathogens in modern plant protection measures. The first antimicrobial transgenes of insect origin, modified cecropins, have been demonstrated to confer resistance of several transgenic cultivars against both bacterial and fungal phytopathogens. Insects represent a promising reservoir for antimicrobial peptides to engineer disease resistant crops. The increasing knowledge about the potent insect innate immunity may help to develop a novel strategy in sustainable agriculture. Several approaches are presently under investigation to prevent evolution of phytopathogens that can overcome disease resistance in transgenic crops expressing an insect antimicrobial peptide. Pathogen-induced expression of insect antimicrobial peptides in crops and combined multiple expression of different antimicrobial peptides along with proteinase inhibitors from insects may prevent selection of resistant phytopathogens. The potential of insect antimicrobial peptides as transgenes to render disease resistant crops has just started to be explored and may provide tools to be ahead of the evolutionary adaptability of phytopathogens.     

防御素基因的化学合成及克隆

将防御素基因分成４个寡聚核苷酸片段，采用固相亚磷酰胺法在ＤＮＡ合成仪上化学合成。片段２和４分别用Ｔ＿４多聚核苷酸激酶将５′端磷酸化，４个片段等量混合，用Ｔ＿４ＤＮＡ连接酶连成一个１０９ｂｐ的双股ＤＮＡ片段，其两侧为ＢａｍＨＩ和ＳａｌⅠ粘性末端。把它与经上述双酶切的质粒ｐＵＣ１９连接，转化大肠杆菌ＤＨＳα。转化株经含Ｘｇａｌ青霉素平板初筛，质粒酶切分析以及ＰＣＲ专一性扩增，证实已获得完整的防御素基因克隆。为进一步表达防御素提供了材料．     

兔防御素NP—l基因在小麦抗病育种中应用的初步研究

兔防御素NP—1是抗性谱最广的防御素之一。为了得到转NP—1基因的小麦柱株，采用电激法、基因枪法和花粉管通道法将兔防御素NP—1基因导入普通小麦品种G9501和G8901中，经过抗生素和除草剂初步筛选得到8抹G9501和4株G8901的转化植株。田间抗病虫鉴定结果表明，这些植株对于白粉病、叶锈和条锈病的抗性有较大的提高，但对于蚜虫的抗性没有提高，初步认为兔防御素NP—1基因已经导入小麦，并已经在小麦中得到了表达。转基因植株的进一步检测工作正在进行中。     

花粉管通道法介导小麦抗病相关基因的转化和抗锈性鉴定

为了筛选小麦的新抗病基因,进而培育抗病种质材料,以小麦品种小偃22、小偃6和西农1376为受体,利用花粉管通道法将防御素基因alfAFP、脂质转运蛋白基因LTP和抗菌肽基因spCEMA转入栽培品种中,并对转基因植株进行了目的基因和bar基因的PCR鉴定,获得了转化alfAFP基因和LTP基因的转基因后代,总体转化率为0.135％.对转基因后代进行的条锈病抗性鉴定,发现alfAFP基因对小麦抗病性提高有一定的作用.     

小肠潘氏细胞防御素

防御素(Defensins)是主要存在于哺乳动物和人的多形核中性粒细胞(Polymorphonuclear neutrophils,PMN)、巨嗜细胞(Macrophage)、小肠潘氏细胞(Paneth Cell)及多种组织上皮细胞中的一组同源性很高的低分子短肽。小肠潘氏细胞防御素是存在于哺乳动物小肠肠腺底部的潘氏细胞颗粒内的一类抗微生物肽,在肠道天然免疫中起重要作用。本文概述了小肠潘氏细胞防御素的一般特征、基因结构和抗微生物活性的国内外研究进展。     

A spruce defensin showing strong antifungal activity and increased transcript accumulation after wounding and jasmonate treatments

In this work, a cDNA encoding a defensin from Picea glauca, named PgD1, was isolated. The corresponding PgD1 cDNA encodes a putative protein of 83 amino acids with a calculated molecular mass of 8.9 kDa. The mature protein of 50 amino acids is characterized by the presence of specific highly conserved residues common to all plant defensins. PgD1 is developmentally expressed during seed germination and is also up-regulated by wounding and by jasmonic acid treatment, suggesting a role in both the constitutive and induced defense mechanisms. The recombinant protein was found to cause extensive growth inhibition of three fungal pathogens (Cylindrocladium floridanum, Fusarium oxysporum and Nectria galligena) at 2.5 μM.