Characterization of TCHQ-induced genotoxicity and mutagenesis using the pSP189 shuttle vector in mammalian cells

Tetrachlorohydroquinone (TCHQ) is a major toxic metabolite of the widely used wood preservative, pentachlorophenol (PCP), and it has also been implicated in PCP genotoxicity. However, the underlying mechanisms of genotoxicity and mutagenesis induced by TCHQ remain unclear. In this study, we examined the genotoxicity of TCHQ by using comet assays to detect DNA breakage and formation of TCHQ-DNA adducts. Then, we further verified the levels of mutagenesis by using the pSP189 shuttle vector in A549 human lung carcinoma cells. We demonstrated that TCHQ causes significant genotoxicity by inducing DNA breakage and forming DNA adducts. Additionally, DNA sequence analysis of the TCHQ-induced mutations revealed that 85.36% were single base substitutions, 9.76% were single base insertions, and 4.88% were large fragment deletions. More than 80% of the base substitutions occurred at G:C base pairs, and the mutations were G:C to C:G, G:C to T:A or G:C to A:T transversions and transitions. The most common types of mutations in A549 cells were G:C to A:T (37.14%) and A:T to C:G transitions (14.29%) and G:C to C:G (34.29%) and G:C to T:A (11.43%) transversions. We identified hotspots at nucleotides 129, 141, and 155 in the supF gene of plasmid pSP189. These mutation hotspots accounted for 63% of all single base substitutions. We conclude that TCHQ induces sequence-specific DNA mutations at high frequencies. Therefore, the safety of using this product would be carefully examined.     

Genetic components and major QTL confer resistance to bean pyralid (Lamprosema indicata Fabricius) under multiple environments in four RIL populations of soybean

Bean pyralid (BP; Lamprosema indicata Fabricius) is one of the major leaf-feeding insects that affect soybean crops in central and southern China. Four recombinant inbred line populations (KY, WT, XG and SX) were tested during 2004-2006 in Nanjing, China, to identify quantitative trait loci (QTL) for resistance to BP on the basis of data for rolled leaflet percentage under field infestation conditions. The mapping was performed using QTL Network V2.0 and checked with Windows QTL Cartographer V2.5 and IciMapping V2.2. The results showed that 81-92?% of the phenotypic variation was accounted for by additive QTL (27-43?%), epistatic QTL pairs (5-13?%), and collective unmapped minor QTL (38-58?%). In total, 17 QTL were detected on 11 linkage groups, of which two had additive effects, six had both additive and epistatic effects, and nine had only epistatic effects. Eight epistatic QTL pairs were observed, of which three pairs involved two QTL with additive effects, one involved one QTL with additive effect, and four involved no QTL with additive effects. Different genetic structures for BP resistance were found among the populations. Eight QTL (five additive and three epistatic pairs) were detected in KY, ten QTL (four additive and five epistatic pairs) were detected in WT, and only one additive QTL was detected in both the XG and the SX populations. BP12-1 and BP1-1 are major QTL, with the former accounting for 15, 31, and 50?% of the total genetic variation (including epistasis) in KY, WT, and XG, respectively, and the latter accounting for 13 and 32?% of the total genetic variation in KY and SX, respectively. The additive?×?year and epistasis?×?year interaction effects were negligible, indicating that the QTL were stable over the years. Because 41-68?% of the total genetic variation could not be accounted for by these QTL, the use of both identified QTL and unmapped minor QTL in breeding for BP resistance should be considered.     

ADAM23 knockdown promotes neuronal differentiation of P19 embryonal carcinoma cells by up‐regulating P27KIP1 expression

ADAM23 (a disintegrin and metalloprotease 23), a member of brain MDC (macrophage‐derived chemokine) family, is important for the development of CNS (central nervous system). P19 mouse embryonal carcinoma cells can differentiate into neurons when cultured in aggregates and induced with RA (retinoic acid). We have found that under conditions without RA induction, knocking down ADAM23 with RNAi (RNA interference) promoted neuronal differentiation, and similarly recombinant GST (glutathione transferase)‐ADAM23‐DIS protein inhibited neuronal differentiation of P19/ADAM23KD (P19/ADAM23‐knockdown) cells. In P19/ADAM23KD, there were more cells arrested in G1 phase than normal P19 cells, due to the up‐regulation of P57^KIP2 and P27^KIP1 expression. P27^KIP1 was up‐regulated during the differentiation process of both P19/ADAM23KD cells without RA induction, and P19 cells with RA induction. Transient overexpression of P27^KIP1 in P19 cells also promoted neuronal differentiation of P19 cells. The findings indicate that ADAM23 suppresses neuronal differentiation through its disintegrin domain, and Adam23 KD up‐regulates P27^KIP1 in P19/ADAM23KD cells, one reason that P19/ADAM23KD cells can differentiate into neurons without RA induction.     

应用噬菌体肽库筛选能封阻霍乱噬菌体VP1转染菌细胞的寡肽

噬菌体感染细菌首先要吸附于细菌表面受体 ,从目前报道的细菌与噬菌体相互作用的研究中发现 ,这些受体包括细菌细胞外膜上的蛋白、糖脂结构和鞭毛等。霍乱弧菌是霍乱的病原体 ,高守一等 (副霍乱资料汇编 ,1 984,2 37～ 2 4 5 .)从国内分离并选择出 5株噬菌体 (VP1～VP5 ) ,根据霍乱弧菌菌株对噬菌体的敏感性不同 ,将埃尔托型霍乱弧菌分为 32个噬菌体型。结合生物学分型方法 ,可区分埃尔托型霍乱弧菌的两类不同菌株 (流行株和非流行株 )和不同菌型。对各种来源的菌株进行分型 ,可作为一种追溯传染来源、传播途径和分析流行形式的流行病学研…     

Characterization of an ethylene receptor homolog gene from rice

Ethylene is a gaseous hormone and plays important roles in plant growth and development, including seed germination, root hair development, flowering, pollination, abscission, and fruit ripening[1]. It is also involved in plant responses to biotic stress such as pathogen attack, and abiotic stresses such as wounding, drought and freezing[1]. Mutational and genetic analysis of Arabidopsis has led to the identification of five ethylene receptor genes, i.e. ETR1, ERS1, ETR2, EIN4 and ERS2. …     

OsbHLH1基因过表达载体构建及转化水稻研究

OsbHLH1基因编码bHLH类转录因子,与水稻耐寒性相关.以pCAMBIA3300为母体,利用玉米泛素(Ubiquitin)启动子构建了能使OsbHLH1基因过表达且含有Bar基因的植物表达载体p3300-Ubi-Ω- OsbHLH1.利用基因枪法将其转化到粳稻品种东稻3号中,获得再生苗47株.选取其中9株进行PCR、Southern检测,结果表明目的基因已经整合到水稻基因组中;草铵膦叶片涂布试验结果表明,Bar基因在水稻植株中正常表达;低温处理后,除45号植株外,其余8株光合速率的变化率显著低于非转基因对照,初步证明OsbHLH1基因在水稻中过表达显著提高了水稻的耐低温能力.     

Comparative analysis of transgenic rice plants obtained by Agrobacterium-mediated transformation and particle bombardment

We compared rice transgenic plants obtained by Agrobacterium-mediated and particle bombardment transformation by carrying out molecular analyses of the T₀, T₁ and T₂ transgenic plants. Oryza sativa japonica rice (c.v. Taipei 309) was transformed with a construct (pWNHG) that carried genes coding for neomycin phosphotransferase (nptII), hygromycin phosphotransferase (Hyg^r), and -glucuronidase (GUS). Thirteen and fourteen transgenic lines produced via either method were selected and subjected to molecular analysis. Based on our data, we could draw the following conclusions. Average gene copy numbers of the three transgenes were 1.8 and 2.7 for transgenic plants obtained by Agrobacterium and by particle bombardment, respectively. The percentage of transgenic plants containing intact copies of foreign genes, especially non-selection genes, was higher for Agrobacterium-mediated transformation. GUS gene expression level in transgenic plants obtained from Agrobacterium-mediated transformation was more stable overall the transgenic plant lines obtained by particle bombardment. Most of the transgenic plants obtained from the two transformation systems gave a Mendelian segregation pattern of foreign genes in T₁ and T₂ generations. Co-segregation was observed for lines obtained from particle bombardment, however, that was not always the case for T₁ lines obtained from Agrobacterium-mediated transformation. Fertility of transgenic plants obtained from Agrobacterium-mediated transformation was better. In summary, the Agrobacterium-mediated transformation is a good system to obtain transgenic plants with lower copy number, intact foreign gene and stable gene expression, while particle bombardment is a high efficiency system to produce large number of transgenic plants with a wide range of gene expression.