除草剂安全剂对作物细胞色素P450及其他酶活性和水平的影响

综述了除草剂安全剂对作物中参与除草剂解毒作用的酶以及作为除草剂作用靶标位点酶水平与活性的影响。安全剂能增强细胞色素P450酶系统活性,诱导P450在除草剂降解中的作用;增加作物体内谷胱甘肽的含量,从而促进除草剂与谷胱甘肽的轭合而发挥解毒作用;降低由于除草剂对乙酰乳酸合成酶的抑制作用而引起的植物毒性等。     

靶标酶在除草剂研究与开发中的应用

大多数除草剂都是通过特殊酶的抑制而产生杀草作用的。因此,以靶标进行分子设计,鉴定化合物分子结构中的活性团,开发能有效杀死杂草、而不伤害作物并对动物及环境安全的除草剂品种有着重要意义。本文着重对各种不同类型靶标酶在除草剂的研究与开发过程中的应用加以阐述。     

几种除草剂靶酶及其抑制剂的研究进展

根据作用靶标对除草剂进行分类,对于新型除草剂的设计能够起到很大的帮助。迄今为止,人们已发现除草剂的不同作用位点近30种,涉及到50余种不同化学结构的化合物。文中介绍了谷氨酰胺合成酶(GS)、咪唑甘油磷酯脱水酶(IGPD)、乙酰辅酶A羧化酶(ACCace)、八氢番茄红素脱氢酶(PDS)及其各自抑制剂的研究进展。分别从酶的生理功能、酶学特征、抑制剂作用机理、抑制剂的研究、抗性等方面进行了不同程度的阐述。     

天然芸苔素内酯缓解胺苯磺隆对后茬水稻药害的作用机理初探

通过测定天然芸苔素内酯对水稻幼苗谷胱甘肽(GSH)含量、谷胱甘肽-S-转移酶(GST)活性以及在离体和活体条件下对水稻幼苗乙酰乳酸合成酶(ALS)活力的影响,研究天然芸苔素内酯减轻胺苯磺隆对水稻药害的作用机理。结果表明,其作用机理与水稻幼苗GSH含量、GST活性变化没有太大相关性,可能与其能间接激活水稻幼苗ALS活力有较大相关。     

细胞色素P450s酶系催化除草剂代谢的研究进展

综述了细胞色素P450s酶系催化的单加氧反应机理,细胞色素P450s酶系在酰胺类、三氮苯类、磺酰脲类、脲类、苯氧羧酸类等除草剂的活性或降解代谢中的催化反应。讨论了研究细胞色素P450s酶系代谢作用在除草剂选择性、抗药性机理,抗除草剂作物的培育以及除草剂安全剂的解毒机理等方面的意义。     

小麦田大穗看麦娘对精噁唑禾草灵的抗性

为明确小麦田大穗看麦娘对精噁唑禾草灵的抗性水平及产生抗性的机理,采用整株法测定了河南省小麦田大穗看麦娘种群对精噁唑禾草灵的抗性水平,以及细胞色素P450s抑制剂胡椒基丁醚(PBO)对精噁唑禾草灵的增效作用,并通过基因测序技术研究了其靶标ACCase基因的突变位点。结果显示:与敏感种群HN-06相比,抗性种群HN-05对精噁唑禾草灵的抗性倍数为52.2,其ACCase基因存在Ile-2041-Asn和Gly-2096-Ala位点突变;喷施PBO后,精噁唑禾草灵对大穗看麦娘的GR50值(有效成分)为5.4 g/hm^2,表现出明显的增效作用,与未喷施PBO处理的差异倍数为161.3。研究表明,抗性种群HN-05对精噁唑禾草灵已产生高水平抗性,该抗性的产生可能是由于其靶标基因突变和P450s介导的代谢增强同时导致的,即表现出了靶标抗性和非靶标抗性共存的现象。     

麦田不同杂草对苯磺隆敏感性差异的分子机制

为了探讨麦田常见杂草对苯磺隆敏感性差异的分子机制,测定了苯磺隆对4种杂草活性及对杂草体内靶标酶(ALS)和代谢酶(GSTs)的影响差异。结果表明,泽漆对苯磺隆的敏感性最低,IC50为123.16gai/hm2;猪殃殃和荠菜次之,分别为8.47、1.07gai/hm2;播娘蒿最敏感,为0.29gai/hm2。离体条件下,苯磺隆对播娘蒿、泽漆ALS的IC50值分别为6.40、54.90mgai/L。活体条件下,苯磺隆处理后,播娘蒿体内ALS活力低于对照,第9天降为对照的31.20%,而敏感性低的泽漆处理后1～2天ALS活力虽略有下降,但第3天明显提高,第4天达到峰值,为对照的2.90倍,此后逐渐恢复至对照水平。4种杂草本身所含GSTs活性存在较大差异,泽漆GSTs活性最高。经苯磺隆处理后,泽漆与猪殃殃GSTs活性明显提高,第4天时达到峰值,相对活性分别为1.23和1.25,并持续在较高水平;而荠菜、播娘蒿GSTs活性虽分别在第3、5天达到峰值,但多数时间相对活性低于1。结果表明,麦田不同杂草体内ALS的敏感性差异和GSTs的代谢差异是对苯磺隆敏感性不同的两个重要原因。     

除草剂靶酶—AHAS酶及基因突变体与除草剂设计(I). 野生型和突变型E. coli AHAS II 酶动力学性质的系统研究

针对除草剂敏感型乙酰羟基酸合成酶E. coli AHAS II的抗性域,引入W464A、W464F、W464L、W464Y点突变。采用Megaprimer PCR定点突变,测序鉴定,构建了4个E. coli AHAS IIW464位点的突变体。通过对E. coli AHAS II野生型及突变体动力学性质的测定,发现它们对于底物—丙酮酸及3种辅助因子(FAD、ThDP、Mg2+)有着不同的特征常数。这些部分抗性酶系的建立以及对动力学性质的系统研究,为探讨AHAS酶对农药分子抗性的作用机制、设计合成新除草剂及其筛选体系提供了基础。     

棉铃虫微粒体多功能氧化酶系组分含量及酶活性在不同生长发育阶段的变化规律研究

细胞色素 P4 50和细胞色素 b5在 KQR和 HDS种群棉铃虫的不同生长发育阶段含量不同 ,但变化规律大致相似 ,均是在 3龄期含量较低 ,从 3龄到 6龄含量上升并达到最高值 ,然后含量逐渐下降 ,直到蛹期达最低值。单加氧酶 MROD和 ECOD在 KQR种群棉铃虫不同生长发育阶段活性大小不同 ,而且变化规律明显不同。从 3龄到 6龄期间 ,MROD活性呈上升趋势 ,并在 6龄期达到最大 ,之后活性逐渐下降 ,在蛹和成虫阶段活性达最小 ;而 ECOD活性在不同生长发育阶段间的差异则不是很大 ,没有明显的阶段表达特异性     

靶标酶在研究杀虫活性构效关系中的应用

运用已建立的乙酰胆碱酯酶(AChE) 活力分析规范化筛选模型, 研究N-甲基取代苯基氨基甲酸酯类化合物和含硅氨基甲酸酯类新系列化合物与AChE 酶抑制中量( I50)构效关系的规律, 并以CA SAR 软件进行Q SAR 分析, 所得结果迅速反馈给化学合成, 为高效低毒新杀虫剂的创制提供有益的信息和科学依据。     

Biochemical and molecular mechanisms of diafenthiuron resistance in the whitefly,Bemisia tabaci

B-biotype Bemisia tabaci has developed high levels of resistance to many insecticides. To investigate the risks and explore possible mechanisms of resistance to diafenthiuron in B. tabaci, a 32.8-fold diafenthiuron-resistant strain (R-DfWf) was established after selection for 36 generations compared with the susceptible strain (S-Lab). Biochemical assays showed that the activity of cytochrome P450 towards p-NA was significantly higher (4.37-fold higher) in the R-DfWf strain than in the S-Lab strain. Similarly, the carboxylesterase (COE) activity and glutathione S-transferase (GST) activity were also significantly higher (3.12- and 1.83-fold higher, respectively) in the R-DfWf strain than in the S-Lab strain. The expression of five of seven P450 genes was significantly higher (>3-fold) in the R-DfWf strain than in the S-Lab strain. The expression of COE2 was significantly higher (>2.5-fold) in the R-DfWf than in the S-Lab strain. The expression of GST and GST2 was significantly higher (>2.3-fold) in the R-DfWf than in the S-Lab. Thus, cytochrome P450, COE and GST may appear to be responsible for the resistance to diafenthiuron in B. tabaci. It is also valuable for usage of insecticides for resistance management and control of this species.     

芳氧苯氧基丙酸酯类除草剂的应用进展

芳氧苯氧基丙酸酯（简称APP）类除草剂是近二十年发展起来的活性很好的新型除草剂,用于防除一年或多年生禾本科杂草。本文主要综述了APP的发展历史、作用机理、主要品种以及应用研究进展。     

酰胺类除草剂的研究和应用进展

酰胺类除草剂是目前世界使用最广泛的除草剂之一,适用作物种类和施用面积均居各类除草剂前列,其具有高效、低毒、经济等优点,因此备受人们的关注,本文系统的综述了此类除草剂的种类,作用机理及应用情况。     

Phase 1 and 2 Metabolism in Freshly Isolated Hepatocytes and Subcellular Fractions from Rat,Mouse, Chicken and Ox Livers

In toxicological studies hepatocytes offer an excellent alternative to whole-animal experiments, provided their metabolic competence has been established. We have compared Phase 1 and 2 metabolism in rat, mouse, chicken and ox liver microsomes and cytosol with freshly isolated hepatocytes. The relative amounts of total cytochrome P450 in microsomes and hepatocytes were equivalent. Rat liver had the highest P450 content while chicken liver had the lowest content (148·2(±75·7) and 20·6(±11·5) pmol mg^-1 hepatocellular protein, respectively). The metabolism of testosterone was assessed to determine selective cytochrome P450 isoenzyme activities. Only two metabolite products were common to all four species, namely 6β-hydroxytestosterone (6β-OHT) and androstenedione (ASD), which co-eluted with 6-dehydrotestosterone (6DHT). 16α-OHT was present in all incubations except for ox microsomes. The rate of metabolism of testosterone was generally lower in microsomes than hepatocytes, with the exception of the ox, but the pattern and quantity of metabolite formation was similar. The quantity of total products formed was 15- to 27-fold higher in rat and mouse livers than in chicken or ox. The major product formed in freshly isolated hepatocytes from mice and chickens was ASD/6DHT which accounted for 60% and 76% of the total metabolites, respectively. ASD/6DHT formation accounted for only 33% and 17% of the total metabolites formed by rat and ox hepatocytes, respectively. 2α-OHT production occurred in rat and mouse hepatocytes (14% of the total metabolites in rat and 7% in mouse hepatocytes) but was lacking in chicken or ox cells. The stability of P450 isoforms in culture was species-dependent. Rat and mouse hepatocyte cultures lost 54% and 31% of their initial P450 content after 72 h, while there was no loss in chicken hepatocytes over the same period. There was a good correlation between the relative glutathione S-transferase (GST) activities in cytosol and freshly isolated hepatocytes. Mouse liver exhibited highest GST activity (664·2(±203·5)) compared with rat, chicken or ox (320·4(±64·0), 341·5(±13·9) and 256·3(±109·9) nmol min^-1 mg^-1 cytosolic protein, respectively). © 1997 SCI.     

杂草对乙酰乳酸合成酶抑制剂类除草剂抗药性的研究进展

本文针对杂草对乙酰乳酸合成酶(ALS)抑制剂类除草剂抗药性的产生历史与发展现状、抗药性机理以及抗性基因的利用进行了综述,并讨论了该类除草剂在我国应用过程中应该注意的问题以及今后的发展方向。