Large-scale high-efficiency yeast transformation using the LiAc/SS carrier DNA/PEG method

Here, we describe a Library screen transformation protocol using the lithium acetate/single-stranded carrier DNA/PEG method of transformation for Saccharomyces cerevisiae. This method is suitable for screening complex plasmid libraries such as those used for yeast two-hybrid analysis. This procedure takes up to 2.5 h to complete once the yeast culture has been grown.     

农杆菌介导转化莱茵衣藻体系的优化

[目的]为建立根癌农杆菌介导的莱茵衣藻快速简便高效的遗传转化体系,本研究以模式生物莱茵衣藻为受体材料,从转化方法和转化子快速鉴定两个方面进行了优化.[方法]比较了固体培养基共培养转化方法和液体培养基共培养转化方法对根癌农杆菌LBA 4404介导的莱茵衣藻CC425转化效率的影响;研究并比较了(1)首先经过TE裂解再进行...     

微藻高效基因枪转化方法的建立

基因枪法是外源基因导入微藻细胞的重要手段。然而,发展至今,微藻细胞基因枪转化效率一直偏低（10~50个转化子/μg DNA）,高价低效的转化方法阻碍了基于高通量转化子的基因功能分析。为了提高基因枪的转化效率,本研究以三角褐指藻为材料,从抗生素选择培养基的改良,微载体的选择、制备、包埋、点膜和轰击参数的优化,以及受体细胞的处理等方面进行了系统研究。结果显示,采用50%海水盐度f/2培养基可以提高博来霉素的效价,f/2固体培养基中2216E营养物质的加入能缩短1/3的平板筛选时间。微载体制备应选择对金（钨）粉没有吸附作用的离心管,制备量/管应少于3.5 mg。微载体轰击量每次大约为0.75 mg,过量将会造成一个轰击死亡圈,过少将导致轰击成本上升。当轰击间距A为6.35 mm,间距B为11 mm,间距C为6 cm时,可以获得最多的转化细胞。109个受体细胞铺成较厚的多细胞层能显著提高转化效率。经过上述优化与改进,本研究将现有文献报道的转化效率提高了4.7~30倍,达到295 ± 60个转化子/μg DNA。该方法除适用于三角褐指藻外,也可广泛应用于其他微藻（杜氏盐藻、小球藻）的基因枪转化研究,可以为微藻基因工程研究提供快速,高效和可靠的操作技术。     

A sequential transformation method for validating soybean genome editing by CRISPR/Cas9 system

This study was performed to evaluate the sequential transformation for soybean genome editing using the CRISPR/Cas9 system as well as to show a strategy for examining the activity of CRISPR/Cas9 constructs, especially the designed guide RNAs (gRNAs). The gRNAs for targeted mutations of an exogenous gene and multiple endogenous genes were constructed and transferred into a stably-overexpressed-Cas9 soybean line using Agrobacterium rhizogenes-mediated hairy root induction system. The targeted mutations were identified and characterized by the poly-acrylamide gel electrophoresis (PAGE) heteroduplex method and by sequencing. Induced mutations of the exogenous gene (gus) were observed in 57% of tested transgenic hairy roots, while 100% of the transgenic root lines showed targeted mutations of the endogenous (SACPD-C) gene. Multiple gRNAs targeting two endogenous genes (SACPD-C and SMT) induced mutation rates of 75% and 67%, respectively. Various indels including small and large deletions as well as insertions were found in target sites of the tested genes. This sequential transformation method could present the targeting efficacy of different gRNAs of each tested gene. Additionally, in this study differences in gRNA ratings were found between bioinformatics predictions and actual experimental results. This is the first successful application of the sequential transformation method for genome editing in soybean using the hairy root system. This method could be potentially useful for validating CRISPR/Cas9 constructs, evaluating gRNA targeting efficiencies, and could be applied for other research directions.     

Quick and easy yeast transformation using the LiAc/SS carrier DNA/PEG method

Here, we describe a quick and easy version of the lithium acetate/single-stranded carrier DNA/PEG method of transformation for Saccharomyces cerevisiae. This method can be performed when only a few transformants are needed. The procedure can take less than an hour, depending on the duration of the heat shock. It can be used to transform yeast cells from various stages of growth and storage. Cells can be transformed from freshly grown cells as well as cells stored on a plate at room temperature or in a refrigerator.     

湖泊微拟球藻高含油突变株的构建及筛选

研究旨在建立湖泊微拟球藻(Nannochloropsis)的遗传转化体系, 然后根据外源基因随机插入的特性, 挑取抗性转化子构建突变体库, 并从突变体库中筛选高含油突变株。以湖泊微拟球藻自身β-tublin基因启动子和三角褐指藻fcpA终止子驱动和终止来源于细菌的sh ble抗性选择基因, 构建了一个转化载体pPha-T1-TUB。将线性化后的质粒以电穿孔的方法转化湖泊微拟球藻, 通过1 μg/mL zeocin的抗性平板筛选, 并经液体培养基连续传代后, 得到了可以稳定遗传的转化子。我们从这些转化子中筛选得到了数株油含量高于野生型, 且生长也优于野生型的突变株。其中, 2个突变株K26和G5的总脂中多不饱和脂肪酸含量更低, 其脂肪酸组成更符合作为生物柴油原料的标准。研究通过随机插入构建突变体库的方法为快速获取优良目的性状的高产油突变株提供了一个有效手段。     

The ets protein PEA3 suppresses HER-2/neu overexpression and inhibits tumorigenesis

Because HER-2/neu overexpression is important in cancer development, we looked for a method of suppressing the cell transformation mediated by HER-2/neu overexpression. We have identified that the DNA-binding protein PEA3, which is encoded by a previously isolated gene of the ets family, specifically targeted a DNA sequence on the HER-2/neu promoter and downregulated the promoter activity. Expression of PEA3 resulted in preferential inhibition of cell growth and tumor development of HER-2/neu-overexpressing cancer cells. This is a new approach to targeting HER-2/neu overexpression and also provides a rationale to the design for repressors of diseases caused by overexpression of pathogenic genes.     

根癌农杆菌介导真菌遗传转化的研究及应用

根癌农杆菌介导转化法（Agrobacterium tumefaciens-mediated transformation,ATMT）具有转化效率高、遗传稳定、适用范围广等诸多优点,已成为真菌遗传转化研究中的强有力手段,在真菌基因资源开发、真菌性疾病研究和外源蛋白表达研究中发挥巨大作用。本文概述了根癌农杆菌转化法在真菌转化中的研究进展、技术优缺点、转化机制、实验方法和应用现状,着重介绍影响其转化效率的因素并对优化方法进行探讨,展望了该技术在真菌基因资源发掘、基因编辑等方面的应用前景,为今后真菌的遗传转化研究提供参考。     

CCNB2/SASP/Cathepsin B & PGE2 Axis Induce Cell Senescence Mediated Malignant Transformation

Glioma is the most frequent and aggressive adult brain tumor with maximum mortality. However, the gene alteration and mechanism underlying malignant transformation of glioma remain largely unknown. We aimed to find key factors regulating tumor progression and malignant transformation of glioma. Here we compared the gene expression profiles of 693 glioma patients by HGG vs. LGG model, and identified a key factor CCNB2 for malignant transformation in glioma. CCNB2 induced a senescence-associated secretory phenotype (SASP) of glioma cells, and the malignant progression, such as invasion and excessive proliferation was mediated by secreting SASP cytokines, Cathepsin B and PGE2. These findings demonstrated a previously undiscovered link between senescence, CCNB2/SASP/Cathepsin B & PGE2 axis and malignant transformation in glioma. This might provide novel insights on developing new therapeutic regimens for abrogating aggressiveness of glioma.     

Photo catalogue for the classification of foci in the BALB/c 3T3 cell transformation assay

This catalogue is a display of focus photos representative of the BALB/c 3T3 cell transformation assay (CTA). It is intended as a visual aid for the identification and the scoring of foci in the conduct of the assay. A proper training from experienced personnel together with the protocol reported in this issue and the present photo catalogue will support method transfer and consistency in the assay results.     

农杆菌介导海洋草酸青霉转化体系及聚酮合酶Pks生物学功能*

为研究南海柳珊瑚共附生草酸青霉SCSGAF0023的聚酮合酶(PKS)生物学功能,采用农杆菌介导法构建草酸青霉SCSGAF0023的Pks敲除株ΔPks,比较野生菌株及ΔPks的生长发育及环境适应性差异。以草酸青霉SCSGAF0023分生孢子为受体,p0380-hygB为双元载体,成功实现草酸青霉SCSGAF0023的遗传转化。结果表明:农杆菌浓度为OD₆₀₀=0.5,在200μmol/L 乙酰丁香酮(AS)诱导下与10⁷个/ml草酸青霉SCSGAF0023孢子于25℃共孵育时转化效率最高。基于上述转化体系,成功获得Pks敲除株ΔPks,并首次证实Pks正向调控草酸青霉SCSGAF0023产孢,但不影响其对环境的适应性。这为进一步系统研究真菌PKSs及聚酮化合物对真菌生长发育与环境适应性的影响提供素材。     

Preparation of highly efficient electrocompetent Escherichia coli using glycerol/mannitol density step centrifugation

Traditional protocols for preparing Escherichia coli for electroporation are laborious and often deliver highly variable transformation efficiencies. Many laboratories resort to purchasing expensive commercially prepared cells. This article describes a simple method for producing electrocompetent E. coli by centrifuging bacteria through a glycerol/mannitol density cushion. The method is rapid and replaces tedious multistep procedures with two 15-min centrifugations. Standard cloning strains consistently produce more than 8 × 10⁹ transformants/μg pUC18, whereas the strains TG1 and LE392 display efficiencies of more than 3 × 10¹⁰/μg DNA.     

LC-ESI-MS/MS determination of phenylurea and triazine herbicides and their dealkylated degradation products in oysters

A method was developed for the determination of several phenylurea and triazine herbicides and their transformation products in oysters at the low microg/kg level. Pressurised liquid extraction (PLE) of lyophilisated samples had required successive SPE combined with a liquid/liquid extraction to provide relatively clean extracts for the determination in LC-MS/MS. This procedure was validated according to the 2002/657/EC analytical decision. Efficiency of the analytical method led to confirmatory CCalpha values ranging from 0.1 to 14 microg/kg with an R.S.D. value ranging from 14% to 66% and a recovery yield ranging from 32% to 46% for phenylureas and from 29% to 75% for triazines.     

Transformation of Zymomonas mobilis by a hybrid plasmid

The transformation of Zymomonas mobilis by plasmid DNA was achieved using a modification of the CaCl₂ method for Escherichia coli. The highest frequency of transformation obtained was 5 × 10³ transformants/μg DNA. The success of the method depended upon the use of a plasmid which is a cointegrate between a Z. mobilis cryptic plasmid and an E. coli plasmid carrying two selectable drug resistance markers.     

A new shuttle vector for gene expression in biopolymer-producing Ralstonia eutropha

Ralstonia eutropha (formerly Alcaligenes eutrophus) is a fascinating microorganism with a great scientific importance and an immense commercial potential. A new genetic transformation system for the organism would greatly facilitate the biological study and molecular engineering of this organism. We report here a versatile gene expression method for the genetic engineering of R. eutropha. This method, based on a simplified electroporation protocol, uses a recombinant plasmid, pBS29-P2, containing a Pseudomonas syringae promoter (P2) and two antibiotic-resistance markers (i.e., genes coding for kanamycin (Km)- and tetracycline (Tc)-resistance). Using this method, we successfully achieved transformation of wild-type R. eutropha and its poly(hydroxyalkanoate)-negative mutant, R. eutropha PHB⁻4, with various pBS29-P2-based recombinants. A transformation frequency as high as 4 × 10³ Km-resistance colonies/μg DNA was obtained per electroporation experiment. We further demonstrated the successful expression of a heterologous gene coding for green-fluorescent-protein by fluorescence measurement. In addition, our results indicated the expression of a truncated but active Streptomyces coelicolor α-galactosidase in R. eutropha.     

Plastic deformation behaviours of CuZr amorphous/crystalline nanolaminate: a molecular dynamics study

Abstract

The plastic deformation behaviours of Cu₅₀Zr₅₀/B2 CuZr amorphous/crystalline nanolaminate were studied at the atomic scale using molecular dynamics simulations. For pure metallic glass, the highly localised shear banding leads to the overall shear failure. And the plastic deformation of B2 CuZr crystal is mainly determined by the martensitic phase transformation. The composite material, nanolaminate, achieves great improvement of plastic deformation compared with the pure metallic glass and the pure crystal. This plasticity enhancement is attributed to two mechanisms: the suppression effect of the nucleation and propagation of the shear band and the regulating effect of the distribution of the shear transformation zones and phase transformation zones. The shear transformation zones can be induced by the interaction between phase transformation zones and interface. The immature shear band or shear transformations zones and phase transformation zones form a network to transmit the strain jointly within the entire sample. Amorphous/crystalline interface connects different layers and transmits the strain within the nanolaminate. Interfaces also plays the roles of source and sink of the shear transformation zones, shear band and phase transformation zones. On the basis of this plastic deformation mechanism, the present study provides a route for controlling the plasticity properties of amorphous/crystalline nanolaminate.     

Proteomic identification of ZO-1/2 as a novel scaffold for Src/Csk regulatory circuit

To elucidate the regulatory mechanism of cell transformation induced by c-Src tyrosine kinase, we performed a proteomic analysis of tyrosine phosphorylated proteins that interact with c-Src and/or its negative regulator Csk. The c-Src interacting proteins were affinity-purified from Src transformed cells using the Src SH2 domain as a ligand. LC-MS/MS analysis of the purified proteins identified general Src substrates, such as focal adhesion kinase and paxillin, and ZO-1/2 as a transformation-dependent Src target. The Csk binding proteins were analyzed by a tandem affinity purification method. In addition to the previously identified Csk binding proteins, including Cbp/PAG, paxillin, and caveolin-1, we found that ZO-1/2 could also serve as a major Csk binding protein. ZO-2 was phosphorylated concurrently with Src transformation and specifically bound to Csk in a Csk SH2 dependent manner. These results suggest novel roles for ZO proteins as Src/Csk scaffolds potentially involved in the regulation of Src transformation.     

Recommended protocols based on a survey of current practice in genotoxicity testing laboratories: III. Cell transformation in C3H/10T1/2 mouse embryo cell, BALB/c 3T3 mouse fibroblast and Syrian hamster embryo cell cultures

A standardized protocol and guidelines for the performance of cell transformation testing in mouse embryo (C3H/10T1/2), mouse fibroblast (BALB/c 3T3) and Syrian hamster embryo (SHE) cells have been developed. The protocol is based primarily on current laboratory practices as determined by responses to a detailed questionnaire completed by North American and European governmental, university and contract laboratories involved with cell transformation experimentation. This report identifies those modifications to previously described methodologies which are being used on a regular basis and also serves to clarify confusing or inconsistent practices.     

Obtaining transgenic plants using the bio-active beads method

Several methods of transformation are currently available for delivering exogenous DNA into animal and plant cells. In this study, a novel and efficient transformation system for DNA delivery/expression with a capacity to transport DNA of high molecular weight was developed. This system can overcome the shortcomings of traditional transformation methods such as Agrobacterium-mediated transformation, particle bombardment, and the electroporation method. The method developed in this study uses calcium alginate micro beads to immobilize DNA molecules in combination with polyethylene glycol treatment. In addition, it is simple and low-cost, and requires limited equipment. Using this method, we have successfully transformed tobacco plants, screening by kanamycin resistance. The transformed genes in the transformants were confirmed by PCR and Southern hybridization.     

冻融法转化苜蓿中华根瘤菌

对于苜蓿中华根瘤菌转化方法的研究仅限于三亲杂交法和电激转化,本实验首次将冻融法用于转化苜蓿中华根瘤菌。将携带CUS片段并且含有壮观霉素抗性的质粒用冻融法转移至野生型苜蓿中华根瘤菌菌株,得到的抗性克隆用GUS引物进行PCR扩增鉴定。经过计算,冻融法的转化率为2．2×10^5／μg。与传统方法比较,冻融法操作简单,转化过程快速,转化率较高,所需时间较短,转化成本低,是适合用于苜蓿中华根瘤菌的转化方法。