稻田萤蔺对苄嘧磺隆的抗药性

[目的]测定萤蔺对苄嘧磺隆抗性水平及抗性机制。[方法]采用整株剂量反应和离体ALS酶活性测定法。[结果]整株测定显示20个抗性萤蔺种群中R7、R17和R18达到高等抗性水平,抗性指数分别为95.22、96.15、90.08;离体ALS酶活性测定显示种群R7、R17和R18抗性指数分别为98.03、122.71、100.15,其抗性趋势与整株测定结果一致。[结论]20个萤蔺种群对苄嘧磺隆均产生不同水平的抗性,其体内ALS活性降低可能是产生抗性的原因之一。     

辽宁地区鸭跖草对莠去津抗性水平检测

[目的]明确辽宁地区鸭跖草对莠去津的抗药性水平,为其科学防除和抗性治理提供参考.[方法]采用整株生物测定法测定不同种群鸭跖草对莠去津的抗性水平.[结果]供试31个鸭跖草种群中,抗性种群占所有种群比例为93％,大部分产生了不同程度的抗药性.2个种群表现出中等抗性水平,抗性倍数在8.0～8.7之间,GR50为186.35～...     

野稷对烟嘧磺隆的抗性水平及抗性机制

[目的]明确辽宁省野稷对烟嘧磺隆的抗性水平及抗药性机制.[方法]采用整株生测法测定不同种群对烟嘧磺隆的抗药性水平及细胞色素P450s活性差异,并通过对野稷ALS序列片段进行扩增测序,研究ALS序列差异.[结果]采自辽宁省阜新市的种群R-3呈高等水平抗药性,GR50值为80.58 g a.i./hm2,抗性指数达22.2...     

辽宁省野慈姑对氯氟吡啶酯抗性风险评估

[目的]评估辽宁省野慈姑对氯氟吡啶酯产生抗药性的风险。[方法]采用整株生物测定法。[结果]35个敏感种群的球茎和种子繁殖野慈姑平均GR_(50)值分别为(3.72±1.406)、(2.44±0.776) g a.i./hm~2,2者敏感性频率分布近似正态分布;氯氟吡啶酯对20个抗苄嘧磺隆、吡嘧磺隆和乙氧磺隆及10个有激素类除草剂使用史的野慈姑种群的GR_(50)值相对敏感基线的抗性倍数均小于1。[结论]被测地区野慈姑种群对氯氟吡啶酯评估为低抗性风险。     

马唐对烟嘧磺隆抗药性水平及机制

[目的]明确辽宁、黑龙江、吉林、河北、河南5个省市马唐种群的抗药性水平及抗性机制。[方法]采用整株生物测定法测定不同种群对烟嘧磺隆抗药性水平，并通过ALS基因片段扩增研究抗敏种群ALS基因序列差异；同时，通过外源施用P450抑制剂马拉硫磷探究P450活性对抗性的影响。[结果]LN-11为敏感种群，其对烟嘧磺隆的GR₅₀值为17.19 g a.i./hm²，其余34个种群均有不同程度的抗药性产生，其抗性倍数在4.57～72.88之间；所有供试种群中均未检测到ALS基因突变；LN-1、LN-21、HLJ-1、HB-1、HN-1在叠加施用马拉硫磷后，对烟嘧磺隆的GR50值有明显下降。[结论]抗性种群对烟嘧磺隆产生抗药性的原因并非由ALS基因突变导致，可能是由细胞色素P450s活性增强参与导致的。     

东北地区稻稗对五氟磺草胺的抗药性机制

[目的]明确东北地区稻稗对五氟磺草胺的抗药性机制。[方法]采用整株生测法测定不同种群对五氟磺草胺的抗药性水平及P450s活性差异,并采用基因测序法,研究ALS序列差异。[结果]种群R-2呈高等水平抗药性,抗性指数达25.67,种群R-1和R-3分别呈低和中等水平抗药性;3个抗性种群均未检测到突变;在施用马拉硫磷后,抗性指数比分别为1.99、5.42和1.60。[结论]抗性种群对五氟磺草胺抗药性并非靶标基因突变导致的,可能是P450s活性增强导致的非靶标抗药性。     

测定增效醚对酯酶封闭作用的新方法

害虫种群遗传变化导致的抗性可能会致使以前有用的农药不再有理想的防治效果。杀虫剂抗性水平和抗性发展速率与杀虫剂的化学特性、害虫的遗传和生物学因素有关。这些因素包括：杀虫剂的用量和使用频率;杀虫剂作用机理;单基因抗性还是多基因抗性;昆虫种群的内在遗传变异水平、生活史和生态学。例如,害虫世代周期短和能产生大量后代有利于抗药性的迅速发展和蔓延。     

斜纹夜蛾对茚虫威抗性风险分析及抗性生化机理

[目的]茚虫威是一种新型二嗪类杀虫剂,作用机制独特,探讨了斜纹夜蛾对茚虫威的抗性风险和抗性机理。[方法]采用饲料浸毒法对斜纹夜蛾敏感种群3龄幼虫经过13代11次抗性选育,测定斜纹夜蛾对茚虫威的抗性倍数及抗性机理。[结果]斜纹夜蛾对茚虫威的抗性倍数达到69.6倍。测定选育抗性种群3龄幼虫羧酸酯酶、谷胱甘肽S-转移酶和多功能氧化酶活性结果表明:选育种群羧酸酯酶活性和多功能氧化酶O-脱甲基活性分别是选育前的3.7倍和2.5倍,差异显著;谷胱甘肽S-转移酶为选育前的1.1倍,差异不显著。[结论]斜纹夜蛾对茚虫威的抗药性与羧酸酯酶和多功能氧化酶活性有关,与谷胱甘肽S-转移酶无关。     

磺酰脲类除草剂对抗、感性慈姑ALS活性的影响

2000—2002年,延边地区稻田发现了抗磺酰脲类除草剂苄嘧磺隆的生态型慈姑。与敏感型相比,苄嘧磺隆、吡嘧磺隆对抗药性慈姑乙酰乳酸合成酶活性的抑制效果很低,抗药性慈姑乙酰乳酸合成酶对苄嘧磺隆和吡嘧磺隆的抗性系数(RI50/SI50)值分别为57.3、20.0,并存在交互抗药性。确认抗药性生态型慈姑的抗药性是由其乙酰乳酸合成酶对苄嘧磺隆、吡嘧磺隆毒性反应钝化所致。     

柑橘木虱对4种新烟碱类杀虫剂的交互抗性

[目的]探明柑橘木虱在新烟碱类杀虫剂之间是否存在交互抗药性,为开发和应用这类杀虫剂提供依据。[方法]用药膜法测定了不同来源的柑橘木虱成虫对吡虫啉、噻虫嗪、呋虫胺的LC50、LC95和抗性指数。[结果]已对吡虫啉、啶虫脒产生抗药性的柑橘木虱种群,虽然从未施用过噻虫嗪、呋虫胺和其他新烟碱类杀虫剂,但对它们的抗性倍数也已达低抗至中等抗性水平。[结论]柑橘木虱在新烟碱类杀虫剂噻虫嗪、呋虫胺、吡虫啉、啶虫脒之间可能存在交互抗性。     

A Two-in-One Strategy: Target and Nontarget Site Mechanisms Both Play Important Role in IMI-Resistant Weedy Rice

The introduction of Clearfield technology allows the use of imidazolinone (IMI) herbicides to control weedy rice. Imidazolinone herbicides stop the acetolactate synthase (ALS) enzyme from synthesizing branched-chain amino acids, resulting in the death of the plant. Since the launch of Clearfield technology in Malaysia in 2010, many farmers have replaced traditional cultivars with Clearfield (CL) rice lines (MR220-CL1 and MR220-CL2). This technology was initially effective; however, in recent years, local farmers have reported the reduced efficacy of IMI herbicides in controlling the spread of weedy rice. Under IMI herbicide treatment, in previous weedy rice studies, the target-site resistance (TSR) mechanism of the ALS gene has been suggested as a key factor conferring herbicide resistance. In our study, a combination of ALS gene sequencing, enzyme colorimetric assay, and a genome-wide association study (GWAS) highlighted that a non-target-site resistance (NTSR) can be an alternative molecular mechanism in IMI-resistant weedy rice. This is supported by a series of evidence, including a weak correlation between single nucleotide polymorphisms (SNPs) within the ALS exonic region and ALS enzyme activity. Our findings suggest that the adaptability of weedy rice in Clearfield rice fields can be more complicated than previously found in other rice strains.     

水稻突变体对除草剂苯达松敏感致死的机理研究

水稻苯达松敏感致死突变体在杂交水稻生产中具有广阔的应用前景。分析了两个水稻突变体农林8m和8077S对除草剂苯达松敏感致死的生理和遗传规律，综述了其对苯达松敏感致死的分子机理。普通水稻品种具有对苯达松抗性是由于苯达松在普通水稻品种细胞中被羟基化，并最终被代谢为对植物无毒性的6-OH-葡萄糖苷苯达松和8-OH-葡萄糖苷苯达松。普通水稻品种具有的苯达松抗性基因可能是编码与苯达松羟基化相关的某种P450酶，或者编码某种参于解毒的受体蛋白，而苯达松本身对P450酶和受体蛋白有诱导和激活作用；此外，苯达松抗性基因也可能是一种催化羟基化苯达松与葡萄糖缀合、同淀粉合成酶相似的缀合酶基因，而水稻苯达松敏感致死突变体表现出对苯达松敏感致死是由于γ-射线导致上述与苯达松解毒相关的酶活性丧失所致。     

In Vitro Selection and Characterization of HIV-1 Variants with Increased Resistance to LP-40, Enfuvirtide-Based Lipopeptide Inhibitor

In our previous work, we replaced the TRM (tryptophan-rich motif) of T20 (Enfuvirtide) with fatty acid (C16) to obtain the novel lipopeptide LP-40, and LP-40 displayed enhanced antiviral activity. In this study, we investigated whether the C16 modification could enhance the high-resistance barrier of the inhibitor LP-40. To address this question, we performed an in vitro simultaneous screening of HIV-1_NL4-3 resistance to T20 and LP-40. The mechanism of drug resistance for HIV-1 Env was further studied using the expression and processing of the Env glycoprotein, the effect of the Env mutation on the entry and fusion ability of the virus, and an analysis of changes to the gp41 core structure. The results indicate that the LP-40 activity is enhanced and that it has a high resistance barrier. In a detailed analysis of the resistance sites, we found that mutations in L33S conferred a stronger resistance, except for the well-recognized mutations in amino acids 36–45 of gp41 NHR, which reduced the inhibitory activity of the CHR-derived peptides. The compensatory mutation of eight amino acids in the CHR region (NDQEEDYN) plays an important role in drug resistance. LP-40 and T20 have similar resistance mutation sites, and we speculate that the same resistance profile may arise if LP-40 is used in a clinical setting.     

Functional Identification of Serine Hydroxymethyltransferase as a Key Gene Involved in Lysostaphin Resistance and Virulence Potential of Staphylococcus aureus Strains

Gaining an insight into the mechanism underlying antimicrobial-resistance development in Staphylococcus aureus is crucial for identifying effective antimicrobials. We isolated S. aureus sequence type 72 from a patient in whom the S. aureus infection was highly resistant to various antibiotics and lysostaphin, but no known resistance mechanisms could explain the mechanism of lysostaphin resistance. Genome-sequencing followed by subtractive and functional genomics revealed that serine hydroxymethyltransferase (glyA or shmT gene) plays a key role in lysostaphin resistance. Serine hydroxymethyltransferase (SHMT) is indispensable for the one-carbon metabolism of serine/glycine interconversion and is linked to folate metabolism. Functional studies revealed the involvement of SHMT in lysostaphin resistance, as ΔshmT was susceptible to the lysostaphin, while complementation of the knockout expressing shmT restored resistance against lysostaphin. In addition, the ΔshmT showed reduced virulence under in vitro (mammalian cell lines infection) and in vivo (wax-worm infection) models. The SHMT inhibitor, serine hydroxymethyltransferase inhibitor 1 (SHIN1), protected the 50% of the wax-worm infected with wild type S. aureus. These results suggest SHMT is relevant to the extreme susceptibility to lysostaphin and the host immune system. Thus, the current study established that SHMT plays a key role in lysostaphin resistance development and in determining the virulence potential of multiple drug-resistant S. aureus.     

HPLC测定水稻田土壤中苄嘧磺隆的残留量

建立了利用高效液相色谱法测定稻田土壤中苄嘧磺隆残留量的方法。样品以乙腈提取,用配有紫外检测器的液相色谱仪测定。苄嘧磺隆的最低检测量为0.5×10-9g。当添加浓度在0.02～2mg/kg时,添加回收率在85.6%～102.7%,变异系数在4.78%～10.8%,符合测定要求。     

Cholesterol metabolism in the liver and intestine of the chick: Effect of dietary cholesterol,taurocholic acid and cholestyramine

The effect of feeding cholesterol, taurocholic acid, or cholestyramine to chicks on cholesterolgenesis from [1-¹⁴C] acetate in liver and intestine was determined in vitro using tissue slices, and in vivo by i.v. injection of [¹⁴C] acetate. The conversion of cholesterol to bile acids in liver in vivo was measured in the same treatments after i.v. injection of [³H] cholesterol. Hepatic cholesterogenesis in vitro and in vivo was depressed by dietary cholesterol and taurocholate and enhanced by cholestyramine. Intestinal cholesterogenesis in vivo was depressed only by taurocholate whereas ileal cholesterogenesis in vitro was reduced by dietary cholesterol. Conversion of cholesterol to bile acids was enhanced by dietary cholesterol and cholestyramine and depressed by taurocholate. Hepatic cholesterol metabolism in the chick appears to be regulated by mechanisms similar to those reported for other species.     

Hairpin RNA Targeting Multiple Viral Genes Confers Strong Resistance to Rice Black-Streaked Dwarf Virus

Rice black-streaked dwarf virus (RBSDV) belongs to the genus Fijivirus in the family of Reoviridae and causes severe yield loss in rice-producing areas in Asia. RNA silencing, as a natural defence mechanism against plant viruses, has been successfully exploited for engineering virus resistance in plants, including rice. In this study, we generated transgenic rice lines harbouring a hairpin RNA (hpRNA) construct targeting four RBSDV genes, S1, S2, S6 and S10, encoding the RNA-dependent RNA polymerase, the putative core protein, the RNA silencing suppressor and the outer capsid protein, respectively. Both field nursery and artificial inoculation assays of three generations of the transgenic lines showed that they had strong resistance to RBSDV infection. The RBSDV resistance in the segregating transgenic populations correlated perfectly with the presence of the hpRNA transgene. Furthermore, the hpRNA transgene was expressed in the highly resistant transgenic lines, giving rise to abundant levels of 21–24 nt small interfering RNA (siRNA). By small RNA deep sequencing, the RBSDV-resistant transgenic lines detected siRNAs from all four viral gene sequences in the hpRNA transgene, indicating that the whole chimeric fusion sequence can be efficiently processed by Dicer into siRNAs. Taken together, our results suggest that long hpRNA targeting multiple viral genes can be used to generate stable and durable virus resistance in rice, as well as other plant species.     

The Acquisition of Colistin Resistance Is Associated to the Amplification of a Large Chromosomal Region in Klebsiella pneumoniae kp52145

The appearance of carbapenem-resistant Klebsiella pneumoniae has increased the use of colistin as a last-resort antibiotic for treating infections by this pathogen. A consequence of its use has been the spread of colistin-resistant strains, in several cases carrying colistin resistance genes. In addition, when susceptible strains are confronted with colistin during treatment, mutation is a major cause of the acquisition of resistance. To analyze the mechanisms of resistance that might be selected during colistin treatment, an experimental evolution assay for 30 days using as a model the clinical K. pneumoniae kp52145 isolate in the presence of increasing amounts of colistin was performed. All evolved populations presented a decreased susceptibility to colistin, without showing cross-resistance to antibiotics belonging to other structural families. We did not find any common mutation in the evolved mutants, neither in already known genes, previously known to be associated with the resistance phenotype, nor in new ones. The only common genetic change observed in the strains that evolved in the presence of colistin was the amplification of a 34 Kb sequence, homologous to a prophage (Enterobacteria phage Fels-2). Our data support that gene amplification can be a driving force in the acquisition of colistin resistance by K. pneumoniae.