除草剂安全剂作用机制研究进展

除草剂安全剂在不影响除草剂对靶标杂草活性的前提下可选择性地保护作物免受除草剂的伤害。本文通过讨论安全剂对植物体内除草剂各种生理生化过程的影响,阐述了安全剂作用机制的研究。     

除草剂安全剂的生理生化作用机制研究进展

除草剂安全剂是一种化学物质,它可以通过生理或生化的途径降低除草剂对作物的毒性,而不降低除草剂的功效.安全剂影响作物的吸收和传导,诱导作物体内P450酶活性、谷胱甘肽调控及其靶标酶ALS的活性.其生理和生化机制研究,不仅有助于安全剂的开发和优化,同时也是了解和运用除草剂活性和抗性机制的途径.该文综述了近年来国内外安全剂生理生化作用机制的研究进展,并探讨其研究方向.     

除草剂安全剂作用机理研究进展

除草剂安全剂是一类可在不影响除草剂对靶标杂草活性的前提下,有选择性地保护作物免受除草剂伤害的特殊用途化合物,有关安全剂作用机理的研究对新安全剂的开发具有重要意义。目前关于除草剂安全剂的作用机理主要有4种观点:1）影响除草剂在作物体内的吸收和转运;2）与除草剂竞争靶标位点;3）影响靶标酶的活性;4）增强作物对除草剂的代谢。文章对近年来安全剂作用机理及安全剂对杂草的影响等研究进展进行了综述,并分析了当前存在的问题及未来的研究方向,旨在为深入研究安全剂的作用机理及新安全剂开发提供参考。     

Cytochrome P450‐mediated herbicide metabolism in plants: current understanding and prospects

Cytochrome P450s (P450s) have been at the center of herbicide metabolism research as a result of their ability to endow selectivity in crops and resistance in weeds. In the last 20 years, ≈30 P450s from diverse plant species have been revealed to possess herbicide‐metabolizing function, some of which were demonstrated to play a key role in plant herbicide sensitivity. Recent research even demonstrated that some P450s from crops and weeds metabolize numerous herbicides from various chemical backbones, which highlights the importance of P450s in the current agricultural systems. However, due to the enormous number of plant P450s and the complexity of their function, expression and regulation, it remains a challenge to fully explore the potential of P450‐mediated herbicide metabolism in crop improvement and herbicide resistance mitigation. Differences in the substrate specificity of each herbicide‐metabolizing P450 are now evident. Comparisons of the substrate specificity and protein structures of P450s will be beneficial for the discovery of selective herbicides and may lead to the development of crops with higher herbicide tolerance by transgenics or genome‐editing technologies. Furthermore, the knowledge will help design sound management strategies for weed resistance including the prediction of cross‐resistance patterns. Overcoming the ambiguity of P450 function in plant xenobiotic pathways will unlock the full potential of this enzyme family in advancing global agriculture and food security. © 2020 Society of Chemical Industry     

淡紫灰链霉菌株xjy活性产物的抑菌作用及对蔬菜病害的防治效果

拮抗性微生物是生物农药的重要来源之一,加强拮抗菌的应用基础研究对于发展生物农药具有促进作用.在植物病害生物防治中拮抗性微生物主要是链霉菌属及其相关类群[1].     

Chlorotoluron Metabolism in Leaves of Resistant and Susceptible Biotypes of the Grass Weed Alopecurus myosuroides

The metabolism of the herbicide chlorotoluron by susceptible and resistant biotypes of the grass weed, Alopecurus myosuroides, was examined. After administration of radiolabelled herbicide to leaves, metabolites were extracted and analysed. The metabolites identified consisted of mono-demethylated-, di-demethylated- and ring methyl-hydroxylated chlorotoluron. Metabolism was more extensive in the resistant biotype, yielding principally the non-phytotoxic ring methyl-hydroxylated metabolite. The metabolites observed are characteristic of the activity of cytochrome P450 mixed-function oxygenase action. The specific cytochrome P450 inhibitor, 1-aminobenzotriazole, reduced accumulation of the ring methyl-hydroxylated metabolite in the resistant biotype.     

On the mechanism of action and selectivity of the corn herbicide topramezone: a new inhibitor of 4-hydroxyphenylpyruvate dioxygenase

Topramezone is a new, highly selective herbicide of pyrazole structure for the post-emergence control of broadleaf and grass weeds in corn. The biokinetic properties and mode of action of topramezone were investigated in plants of Setaria faberi Herrm, Sorghum bicolor (L.) Moench, Solanum nigrum L. and the crop species corn (Zea mays L.). Within 2-5 days after treatment, topramezone caused strong photobleaching effects on the shoot, followed by plant death of sensitive weeds. The selectivity of topramezone between corn and the weed species has been quantified as above 1000-fold. By virtue of the plant symptoms and the reversal of the effects in Lemna paucicostata L. by adding homogentisate, it was hypothesized that topramezone blocks the formation of homogentisate, possibly through inhibition of 4-hydroxyphenylpyruvate dioxygenase (4-HPPD). Indeed, topramezone strongly inhibited 4-HPPD activity in vitro, with I(50) values of 15 and 23 nM for the enzyme isolated from S. faberi and recombinant enzyme of Arabidopsis thaliana L. respectively. The enzyme activity from corn was approximately 10 times less sensitive. After root and foliar application of [(14)C]topramezone, equivalent to field rates of 75 g ha(-1), the herbicide was rapidly absorbed and systemically translocated in the plant. Only marginal differences between leaf uptake and translocation of topramezone by the weeds and corn were found. Metabolism of foliar-applied [(14)C]topramezone was far more rapid in corn than in the weeds. A more rapid metabolism combined with a lower sensitivity of the 4-HPPD target enzyme contributes to the tolerance of corn to topramezone.     

The use of cytochrome P450 genes to introduce herbicide tolerance in crops: a review

Mechanisms of herbicide resistance include (1) modified target site, (2) enhanced detoxification or delayed activation, and (3) alterations in the uptake, translocation, or compartmentalization of a herbicide. The first two mechanisms have mainly been identified in plants. Herbicide resistance genes were isolated for several herbicides of different modes of action. Genes that coded for herbicide target or detoxification enzymes were transferred into crop plants. The transgenic plants expressing these genes were tolerant of the active ingredients of herbicides. Before commercialization, the transgenic plants were tested in the field for risk assessment. In the case of crops with herbicide detoxification enzymes, including cytochrome-P450-species-metabolizing xenobiotics, the substrate specificity of the enzymes as well as the toxicological properties of the herbicide metabolites and the pattern of secondary metabolites in plants must be evaluated. © 1999 Society of Chemical Industry     

On the mechanism of selectivity of the corn herbicide BAS 662H: a combination of the novel auxin transport inhibitor diflufenzopyr and the auxin herbicide dicamba

BAS 662H, a 1:2.5 combination of the semicarbazone-type auxin transport inhibitor diflufenzopyr and the auxin herbicide dicamba, is used as a post-emergence herbicide in corn. The combination has been observed to provide more effective broadleaf weed control and improved tolerance in corn than typical rates of dicamba used alone. In order to analyze this phenomenon, the uptake, translocation, metabolism and action of both compounds, applied alone and in combination, were investigated in Amaranthus retroflexus L, Galium aparine L and corn (Zea mays L). When plants at the third-leaf stage were foliarly treated with diflufenzopyr and dicamba equivalent to field rates of 100 and 250 gha-1, respectively, diflufenzopyr synergistically increased dicamba-induced 1-aminocyclopropane-1-carboxylic acid (ACC) synthase activity and ethylene formation in G aparine and even more in A retroflexus, followed by accumulations of (+)-abscisic acid (ABA) in the shoot tissue within 20 h. This correlated with subsequent growth inhibition, hydrogen peroxide overproduction and progressive tissue damage. Diflufenzopyr also enhanced the activity of other auxin herbicides, such as quinclorac and picloram, and of the synthetic auxin, 1-naphthaleneacetic acid. After foliar and root application of [14C]diflufenzopyr, alone or as BAS 662H, considerably lower tissue concentrations and systemic translocation of radioactivity beyond treated plant parts were found in corn, compared to G aparine and particularly A retroflexus. Furthermore, diflufenzopyr decreased foliar uptake of [14C]dicamba by c 50% selectively in corn, compared to the treatment alone. Metabolism of [14C]diflufenzopyr was more rapid in corn than in the weed species. In combination, the two compounds had no mutual effect on their metabolic degradation. In BAS 662H, diflufenzopyr synergizes the herbicidal activity of dicamba in sensitive weed species. In corn this effect is prevented by a more rapid metabolism of diflufenzopyr, coupled with lower uptake and translocation. Selectivity of BAS 662H is additionally favoured by a higher crop tolerance to dicamba because of reduced foliar uptake of this herbicide in corn under the influence of diflufenzopyr.     

1,8-萘二甲酸酐对高浓度单嘧磺隆协迫下玉米的解毒作用

为避免单嘧磺隆对后茬玉米的药害、评估单嘧磺隆原药中存在的主要杂质对玉米生长的影响,利用室内毒力测定、温室栽培试验和生理生化试验,对单嘧磺隆对玉米的毒力及其高浓度协迫下1,8-萘二甲酸酐(NA)对玉米的解毒作用进行了研究。试验结果表明,单嘧磺隆对玉米掖单13和农大 3138的IC50值分别为6.42和84.38 μg/kg,对玉米生长有抑制作用;而原药中的主要杂质对玉米生长的抑制作用很小,其IC50值均大于619 μg/kg。单嘧磺隆对玉米离体乙酰乳酸合成酶(ALS)的I50值在15.15~66.73 nmol/L之间,高浓度单嘧磺隆对玉米活体ALS的活性也有抑制作用。温室盆栽试验结果表明,1 000 μg/mL 的NA对171.44 μg/kg单嘧磺隆协迫下的玉米掖单13和农大3138有解毒作用;游离辅氨酸含量和叶绿素含量测定结果表明,NA对自身抗逆性较强的玉米品种农大3138的游离辅氨酸含量和叶绿素生物合成影响不显著,但能明显提高单嘧磺隆协迫下自身抗逆性较差的玉米品种掖单13的游离辅氨酸含量,并在一定程度上提高叶绿素的含量。因此,NA对单嘧磺隆协迫下玉米的解毒作用与NA提高了玉米的抗逆性有关。     

不同水分状况下秸秆覆盖量对玉米根、冠生长的影响

在遮雨棚控水条件下,采用盆栽的方式研究了不同秸秆覆盖量对玉米根、冠生长的影响.试验按对照(CK)和秸秆覆盖量0.3 kg/m2(SM0.3)、0.6 kg/m2(SM0.6)、0.9 kg/m2(SM0.9)、1.2 kg/m2.(SM1.2)共设5个处理,水分按高水(占田间持水量的90%)和低水(占田间持水量的60%)设两个水平.分别测定了玉米根、茎、叶、穗干重,根系垂直空间分布及叶片叶绿素相对含量等指标.结果表明:秸秆覆盖明显改变了玉米根系和地上部分的生长;高水条件下SM0.6处理玉米根系、茎秆、叶和穗干重均高于其它处理;低水条件下,地上部分干重SM1.2最大,SM0.6次之;根系的垂直空间分布与水分和覆盖条件都有密切的关系,覆盖措施主要影响下层根系的生长和发育.     

Expression of a wheat cytochrome P450 monooxygenase cDNA in yeast catalyzes the metabolism of sulfonylurea herbicides

A wheat cytochrome P450 cDNA (CYP71C6v1) was cloned by RT-PCR and heterologously expressed in yeast. The microsomal fractions derived from this strain could catalyze the metabolism of some sulfonylurea herbicides such as chlorsulfuron, triasulfuron, metsulfuron-metyl, bensulfuron-metyl, and tribenuron-metyl, but not sulfonylurea herbicides such as thifensulfuron and pyrazosulfuron. Kinetic parameters K_m for chlorsulfuron and triasulfuron were 57 (±15) μM and 38 (±16) μM in vitro, respectively. Analysis of the metabolites demonstrated that the CYP71C6v1 functioned as a 5-phenyl ring hydroxylase when chlorsulfuron and triasulfuron were the substrates.