Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, DUSYS, IBP, Universitätsstrasse 16, CHN H50.3, 8092 Zurich, Switzerland.
Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, USA.
Environ Sci Process Impacts. 2021 Apr 28;23(4):605-620. doi: 10.1039/d1em00010a.
Double-stranded ribonucleic acid (dsRNA) molecules are novel plant-incorporated protectants expressed in genetically modified RNA interference (RNAi) crops. Ecological risk assessment (ERA) of RNAi crops requires a heretofore-missing detailed understanding of dsRNA adsorption in soils, a key fate process. Herein, we systematically study the adsorption of a model dsRNA molecule and of two double-stranded deoxyribonucleic acid (DNA) molecules of varying lengths to three soil iron (oxyhydr-)oxides - goethite, lepidocrocite, and hematite - over a range of solution pH (4.5-10), ionic strength (I = 10-100 mM NaCl) and composition (0.5, 1, and 3 mM MgCl2) and in the absence and presence of phosphate (0.05-5 mM) as co-adsorbate. We hypothesized comparable adsorption characteristics of dsRNA and DNA based on their structural similarities. Consistently, the three nucleic acids (NAs) showed high adsorption affinities to the iron (oxyhydr-)oxides with decreasing adsorption in the order goethite, lepidocrocite, and hematite, likely reflecting a decrease in the hydroxyl group density and positive charges of the oxide surfaces in the same order. NA adsorption also decreased with increasing solution pH, consistent with weakening of NA electrostatic attraction to and inner-sphere complex formation with the iron (oxyhydr-)oxides surfaces as pH increased. Adsorbed NA concentrations increased with increasing I and in the presence of Mg2+, consistent with adsorbed NA molecules adopting more compact conformations. Strong NA-phosphate adsorption competition demonstrates that co-adsorbates need consideration in assessing dsRNA fate in soils. Comparable adsorption characteristics of dsRNA and DNA molecules to iron (oxyhydr-)oxides imply that information on DNA adsorption to soil particle surfaces can inform dsRNA ERA.
双链核糖核酸（dsRNA）分子是新型的植物整合保护剂，在经过基因改造的 RNA 干扰（RNAi）作物中表达。RNAi 作物的生态风险评估（ERA）需要对 dsRNA 在土壤中的吸附这一关键命运过程有一个前所未有的详细了解。在此，我们系统地研究了一种模型 dsRNA 分子和两种不同长度的双链脱氧核糖核酸（DNA）分子在一系列溶液 pH 值（4.5-10）、离子强度（I=10-100 mM NaCl）和组成（0.5、1 和 3 mM MgCl2）下，以及在无磷和有磷（0.05-5 mM）作为共吸附物的情况下，对三种土壤铁（氢氧）氧化物 - 针铁矿、纤铁矿和赤铁矿的吸附情况。我们基于它们的结构相似性假设 dsRNA 和 DNA 具有相似的吸附特征。一致地，这三种核酸（NAs）对铁（氢氧）氧化物表现出高吸附亲和力，吸附顺序为针铁矿、纤铁矿和赤铁矿，这可能反映了氧化物表面的羟基密度和正电荷随顺序减少。随着溶液 pH 值的增加，NA 的吸附减少，这与随着 pH 值的增加，NA 静电吸引和与铁（氢氧）氧化物表面的内球络合减弱一致。NA 吸附也随 I 的增加而增加，在有 Mg2+的情况下，这与吸附的 NA 分子采用更紧凑的构象一致。NA-磷酸盐的强烈吸附竞争表明，在评估 dsRNA 在土壤中的命运时需要考虑共吸附物。dsRNA 和 DNA 分子对铁（氢氧）氧化物的吸附特征相似，这意味着有关 DNA 吸附到土壤颗粒表面的信息可以为 dsRNA 的 ERA 提供信息。
