Burns Erin E, Keith Barbara K, Refai Mohammed Y, Bothner Brian, Dyer William E
Department of Plant Sciences & Plant Pathology, PO Box 173150, Montana State University, Bozeman, MT 59717, United States.
Department of Chemistry & Biochemistry Research, PO Box 173400, Montana State University, Bozeman, MT 59717, United States.
Pestic Biochem Physiol. 2017 Aug;140:69-78. doi: 10.1016/j.pestbp.2017.06.007. Epub 2017 Jun 9.
Extensive herbicide usage has led to the evolution of resistant weed populations that cause substantial crop yield losses and increase production costs. The multiple herbicide resistant (MHR) Avena fatua L. populations utilized in this study are resistant to members of all selective herbicide families, across five modes of action, available for A. fatua control in U.S. small grain production, and thus pose significant agronomic and economic threats. Resistance to ALS and ACCase inhibitors is not conferred by target site mutations, indicating that non-target site resistance mechanisms are involved. To investigate the potential involvement of glutathione-related enzymes in the MHR phenotype, we used a combination of proteomic, biochemical, and immunological approaches to compare their constitutive activities in herbicide susceptible (HS1 and HS2) and MHR (MHR3 and MHR4) A. fatua plants. Proteomic analysis identified three tau and one phi glutathione S-transferases (GSTs) present at higher levels in MHR compared to HS plants, while immunoassays revealed elevated levels of lambda, phi, and tau GSTs. GST specific activity towards 1-chloro-2,4-dinitrobenzene was 1.2-fold higher in MHR4 than in HS1 plants and 1.3- and 1.2-fold higher in MHR3 than in HS1 and HS2 plants, respectively. However, GST specific activities towards fenoxaprop-P-ethyl and imazamethabenz-methyl were not different between untreated MHR and HS plants. Dehydroascorbate reductase specific activity was 1.4-fold higher in MHR than HS plants. Pretreatment with the GST inhibitor NBD-Cl did not affect MHR sensitivity to fenoxaprop-P-ethyl application, while the herbicide safener and GST inducer mefenpyr reduced the efficacy of low doses of fenoxaprop-P-ethyl on MHR4 but not MHR3 plants. Mefenpyr treatment also partially reduced the efficacy of thiencarbazone-methyl or mesosulfuron-methyl on MHR3 or MHR4 plants, respectively. Overall, the GSTs described here are not directly involved in enhanced rates of fenoxaprop-P-ethyl or imazamethabenz-methyl metabolism in MHR A. fatua. Instead, we propose that the constitutively elevated GST proteins and related enzymes in MHR plants are representative of a larger, more global suite of abiotic stress-related changes.
广泛使用除草剂导致了抗除草剂杂草种群的进化，这些杂草会造成大量作物产量损失并增加生产成本。本研究中使用的多重抗除草剂（MHR）野燕麦种群对美国小粒谷物生产中可用于防治野燕麦的所有选择性除草剂家族的成员均具有抗性，涉及五种作用模式，因此构成了重大的农艺和经济威胁。对ALS和ACCase抑制剂的抗性并非由靶标位点突变引起，这表明涉及非靶标位点抗性机制。为了研究谷胱甘肽相关酶在MHR表型中的潜在作用，我们结合蛋白质组学、生物化学和免疫学方法，比较了它们在除草剂敏感（HS1和HS2）和MHR（MHR3和MHR4）野燕麦植株中的组成活性。蛋白质组学分析确定，与HS植株相比，MHR植株中三种tau型和一种phi型谷胱甘肽S-转移酶（GSTs）的含量更高，而免疫分析显示lambda、phi和tau GSTs的水平升高。MHR4植株对1-氯-2,4-二硝基苯的GST比活性比HS1植株高1.2倍，MHR3植株对1-氯-2,4-二硝基苯的GST比活性分别比HS1和HS2植株高1.3倍和1.2倍。然而，未处理的MHR和HS植株对精恶唑禾草灵和咪草烟的GST比活性没有差异。脱氢抗坏血酸还原酶的比活性在MHR植株中比HS植株高1.4倍。用GST抑制剂NBD-Cl预处理不会影响MHR对精恶唑禾草灵施用的敏感性，而除草剂安全剂和GST诱导剂苯氧吡唑啉可降低低剂量精恶唑禾草灵对MHR4植株的药效，但对MHR3植株无效。苯氧吡唑啉处理还分别部分降低了甲基硫菌灵或甲基二磺隆对MHR3或MHR4植株的药效。总体而言，本文所述的GSTs并非直接参与MHR野燕麦中精恶唑禾草灵或咪草烟代谢速率的提高。相反，我们认为MHR植株中组成性升高的GST蛋白和相关酶代表了一组更大、更全面的与非生物胁迫相关的变化。
