Snake cathelicidin from Bungarus fasciatus is a potent peptide antibiotics

Background

Cathelicidins are a family of antimicrobial peptides acting as multifunctional effector molecules of innate immunity, which are firstly found in mammalians. Recently, several cathelicidins have also been found from chickens and fishes. No cathelicidins from other non-mammalian vertebrates have been reported.

Principal Findings

In this work, a cathelicidin-like antimicrobial peptide named cathelicidin-BF has been purified from the snake venoms of Bungarus fasciatus and its cDNA sequence was cloned from the cDNA library, which confirm the presence of cathelicidin in reptiles. As other cathelicidins, the precursor of cathelicidin-BF has cathelin-like domain at the N terminus and carry the mature cathelicidin-BF at the C terminus, but it has an atypical acidic fragment insertion between the cathelin-like domain and the C-terminus. The acidic fragment is similar to acidic domains of amphibian antimicrobial precursors. Phylogenetic analysis revealed that the snake cathelicidin had the nearest evolution relationship with platypus cathelicidin. The secondary structure of cathelicidin-BF investigated by CD and NMR spectroscopy in the presence of the helicogenic solvent TFE is an amphipathic α-helical conformation as many other cathelicidins. The antimicrobial activities of cathelicidin BF against forty strains of microorganisms were tested. Cathelicidin-BF efficiently killed bacteria and some fungal species including clinically isolated drug-resistance microorganisms. It was especially active against Gram-negative bacteria. Furthermore, it could exert antimicrobial activity against some saprophytic fungus. No hemolytic and cytotoxic activity was observed at the dose of up to 400 µg/ml. Cathelicidin-BF could exist stably in the mice plasma for at least 2.5 hours.

Conclusion

Discovery of snake cathelicidin with atypical structural and functional characterization offers new insights on the evolution of cathelicidins. Potent, broad spectrum, salt-independent antimicrobial activities make cathelicidin-BF an excellent candidate for clinical or agricultural antibiotics.     

提高PCR产物的几种有效方法

结合作者的工作实际 ,着重介绍了有效提高PCR产物的几种方法 :如怎样高效快速地设计PCR引物 ,怎样尽快确定PCR反应的最适退火温度 ,如何提高GC富集区的扩增效率等 ,为分子生物学工作者提供一些可以借鉴的方法及经验。     

Mn-SOD基因导入黄瓜的遗传转化体系

黄瓜是我国栽培面积最大的喜温蔬菜之一。在生产上,高温干旱等环境胁、迫因子严重危害黄瓜的产量和品质,甚至导致绝收。任安芝等综述了SOD与水分、盐分、低温和大气污染等逆境胁迫之间的关系,认为:各种逆境胁迫引起的活性氧代谢平衡失调、生物膜结构破坏是导致植物遭受逆境伤害的机理之一。通过基因工程提高植物体内抗氧化酶活性及增加抗氧化代谢的水平是增强植物抗逆性的有效     

“探索生长素类似物促进插条生根的最适浓度”的教学组织

“探索生长素类似物促进插条生根的最适浓度”的实验探究活动．是引导学生将生物学知识运用于生产实践的好素材,从实验教学内容、学情、教学目标、教学过程的组织和教学建议等几个方面进行了分析和研究,希望通过有效的教学组织提高课堂的高效性,同时用生活化的内容充实课堂教学．为课程改革增添新的活力。     

生态袋护坡技术在三峡水库消落带植被恢复中应用的可行性研究

通过对三峡水库重庆市巫山县双龙镇和巫峡镇段消落带开展生态袋护坡复绿试验7年后,生态袋上（内）、生态袋堆叠处上方和左侧消落带狗牙根（Cynodon dactylon）的种群密度、表型生长性状、地上和地下生物质量,以及土壤理化性质的测定,探讨以狗牙根为生态袋上的种植植物,将生态袋护坡技术用于三峡水库消落带植被恢复的可行性。结果表明：（1）各试验地生态袋上与其堆叠处上方和左侧消落带的狗牙根种群密度和地上生物质量差异不显著。（2）狗牙根的表型生长性状和根系生物质量因地和在生态袋堆叠处的方位不同而异。在双龙镇试验地,生态袋上比其堆叠处上方消落带上狗牙根的植株长度和节间长度低23.9%和22.6%（P<0.05）,除此之外的各项指标差异均不显著;生态袋内0-5 cm土层的根系生物质量比其堆叠处上方消落带增加了75.7%（P<0.05）,比其堆叠处左侧消落带降低了11.8%,在5-15 cm各土层降低了91.6%-96.9%（P<0.05）,15-20 cm土层的差异不显著。在巫峡镇试验地,生态袋上与其堆叠处上方和左侧消落带的各表型生长性状的差异均不显著;生态袋内各土层的根系生物质量均比其堆叠处上方和左侧消落带增加了20.0%-138.7%。（3）各试验地生态袋内与其堆叠处上方和左侧消落带土壤容重的差异不显著,土壤化学性质因地和在生态袋堆叠处的方位不同而异。在双龙镇试验地,生态袋内的土壤全氮和速效氮含量比其堆叠处上方消落带分别降低了13.6%和40.9%（P<0.05）,比其堆叠处左侧消落带分别降低了11.9%和33.0%（P<0.05）;速效钾含量比其堆叠处上方和左侧消落带分别增加了18.3%和34.1%（P<0.05）;除此之外各指标的差异均不显著。在巫峡镇试验地,生态袋内的土壤pH值和全氮含量比其堆叠处上方消落带分别降低了1.4%和27.9%（P<0.05）,全钾含量增加了6.1%（P<0.05）;土壤全钾和速效钾含量比生态袋堆叠处左侧消落带分别降低了8.1%和24.9%（P<0.05）;除此之外各指标的差异也不显著。（4）狗牙根种群密度、大多数生长指标和生物质量与土壤理化指标相关不紧密。总体上,生态袋上（内）与其堆叠处上方和左侧消落带的大多数表型生长指标,地上和地下生物质量,以及土壤理化指标的差异不显著。狗牙根耐淹、抗旱、耐贫瘠,根系发达,且穿透力强,能够在生态袋上正常生长;生态袋透水不透土,且具有一定的保肥能力。因此,以狗牙根为生态袋上的种植植物,将生态袋护坡技术用于三峡水库消落带植被恢复具有一定的可行性。     

Accumulated Expression Level of Cytosolic Glutamine Synthetase 1 Gene (OsGS1;1 or OsGS1;2) Alter Plant Development and the Carbon-Nitrogen Metabolic Status in Rice

Maintaining an appropriate balance of carbon to nitrogen metabolism is essential for rice growth and yield. Glutamine synthetase is a key enzyme for ammonium assimilation. In this study, we systematically analyzed the growth phenotype, carbon-nitrogen metabolic status and gene expression profiles in GS1;1-, GS1;2-overexpressing rice and wildtype plants. Our results revealed that the GS1;1-, GS1;2-overexpressing plants exhibited a poor plant growth phenotype and yield and decreased carbon/nitrogen ratio in the stem caused by the accumulation of nitrogen in the stem. In addition, the leaf SPAD value and photosynthetic parameters, soluble proteins and carbohydrates varied greatly in the GS1;1-, GS1;2-overexpressing plants. Furthermore, metabolite profile and gene expression analysis demonstrated significant changes in individual sugars, organic acids and free amino acids, and gene expression patterns in GS1;1-, GS1;2-overexpressing plants, which also indicated the distinct roles that these two GS1 genes played in rice nitrogen metabolism, particularly when sufficient nitrogen was applied in the environment. Thus, the unbalanced carbon-nitrogen metabolic status and poor ability of nitrogen transportation from stem to leaf in GS1;1-, GS1;2-overexpressing plants may explain the poor growth and yield.     

Molecular characterization and phylogenetic analysis of a novel glutenin gene (Dy10.1t) from Aegilops tauschii.

A novel y-type high molecular mass glutenin subunit (HMM-GS) possessing a mobility that is slightly slower than that of the subunit Dy10 obtained by SDS-PAGE, named Dy10.1t, in the wild wheat Aegilops tauschii was identified by 1- and 2-dimensional gel electrophoresis, capillary electrophoresis, and matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS). The gene encoding the HMM subunit Dy10.1t was amplified with allele-specific PCR primers, and the amplified products were cloned and sequenced. The coding domain of the Dy10.1t subunit gene consisted of 1980 bp encoding a protein of 658 residues with an M rs of 68 611 Da, which was similar to the M rs determined by MALDI-TOF-MS. The deduced amino acid sequence indicated that Dy10.1t subunit displayed a greater similarity to the Dy12 subunit, differing by only 8 amino acid substitutions. Six coding region single-nucleotide polymorphisms were discovered in the Dy10.1t gene by multiple alignments (1 per 330 bp), 1 in the N-terminal domain and the others in the central repeats. Five of them resulted in residue substitutions, whereas 3 created enzyme site changes. The homology and neighbour-joining trees constructed from code domain sequences of 20 x- and y-type glutenin genes from different Triticum species separated into 2 halves, which corresponded to the x-type and y-type HMM glutenin alleles. Phylogenetic analysis revealed that the Glu-1 gene duplication event probably occurred at about 16.83 million years ago, whereas the divergence times of A, B, and D genomes within x-type and y-type halves were before 7.047 and 10.54 million years ago, respectively.