Pedroso Rafael M, Al-Khatib Kassim, Hanson Bradley D, Fischer Albert J
Department of Plant Sciences, University of California at Davis, Davis, CA 95616, United States.
Department of Plant Sciences, University of California at Davis, Davis, CA 95616, United States.
Pestic Biochem Physiol. 2017 Jan;135:78-81. doi: 10.1016/j.pestbp.2016.06.001. Epub 2016 Jun 3.
Cyperus difformis L. (CYPDI) and Schoenoplectus mucronatus (L.) Palla (SCHMU) are major weeds of California (CA) rice, where resistance to acetolactate synthase (ALS)-inhibitors was identified in several CYPDI and SCHMU populations that have also evolved resistance to photosystem II (PSII)-inhibiting herbicides. The mechanism of ALS resistance in these populations remains to be clarified but this information is crucial in a weed management program, especially in a scenario where resistance to multiple herbicides has been identified. ALS activity assays are commonly used to diagnose resistance to ALS-inhibitors, but protocols currently available are burdensome for the study of CYPDI and SCHMU, as they require large amounts of plant material from young seedlings and have low yields. Our objective was to investigate the ALS resistance mechanism in suspected ALS-resistant (R) CYPDI and SCHMU biotypes using a modified ALS activity assay that requires less plant material. ALS enzymes from suspected R biotypes were at least 10,000-fold less sensitive to bensulfuron-methyl than susceptible (S) cohorts, indicating ALS resistance that is likely due to an altered target-site. Protein concentration (mgg tissue) did not differ between R and S biotypes within each species, suggesting that R biotypes do not over produce ALS enzymes. CYPDI biotypes had up to 4-fold more protein per mg of tissue than SCHMU biotypes, but up to 7-fold more acetoin per mg protein was quantified in SCHMU, suggesting greater ALS catalytic ability in SCHMU biotypes, regardless of their herbicide resistance status. Our optimized protocol to measure ALS activity allowed for up to a 3-fold increase in the number of assays performed per g of leaf tissue. The modified assay may be useful for measuring ALS activity in other weed species that also produce small amount of foliage in early growth stages when protein in tissue is most abundant.
异型莎草（Cyperus difformis L.，CYPDI）和具芒碎米莎草（Schoenoplectus mucronatus (L.) Palla，SCHMU）是加利福尼亚州水稻田的主要杂草，在多个CYPDI和SCHMU种群中发现了对乙酰乳酸合成酶（ALS）抑制剂的抗性，这些种群还对光系统II（PSII）抑制性除草剂产生了抗性。这些种群中ALS抗性的机制仍有待阐明，但这些信息在杂草管理计划中至关重要，尤其是在已鉴定出对多种除草剂具有抗性的情况下。ALS活性测定通常用于诊断对ALS抑制剂的抗性，但目前可用的方案对于CYPDI和SCHMU的研究来说负担较重，因为它们需要大量来自幼苗的植物材料且产量较低。我们的目标是使用一种改良的ALS活性测定方法来研究疑似抗ALS（R）的CYPDI和SCHMU生物型中的ALS抗性机制，该方法所需的植物材料较少。疑似R生物型的ALS酶对苄嘧磺隆的敏感性比对敏感（S）群体至少低10000倍，表明ALS抗性可能是由于靶标位点改变所致。每个物种内R和S生物型之间的蛋白质浓度（mg/g组织）没有差异，这表明R生物型不会过量产生ALS酶。CYPDI生物型每毫克组织中的蛋白质比SCHMU生物型多4倍，但每毫克蛋白质中检测到的乙偶姻在SCHMU中多达7倍，这表明无论其除草剂抗性状态如何，SCHMU生物型中的ALS催化能力更强。我们优化的测量ALS活性的方案使每克叶片组织进行的测定数量最多可增加3倍。这种改良的测定方法可能有助于测量其他杂草物种在早期生长阶段叶片组织中蛋白质最丰富时产生少量叶片的ALS活性。
