Shaw Sidney L, Long Sharon R
Department of Biological Sciences, Stanford University, Stanford, California 94305-5020, USA.
Plant Physiol. 2003 Aug;132(4):2196-204. doi: 10.1104/pp.103.021113.
Hydrogen peroxide (H(2)O(2)) efflux was measured from Medicago truncatula root segments exposed to purified Nod factor and to poly-GalUA (PGA) heptamers. Nod factor, at concentrations > 100 pM, reduced H(2)O(2) efflux rates to 60% of baseline levels beginning 20 to 30 min after exposure, whereas the PGA elicitor, at > 75 nM, caused a rapid increase in H(2)O(2) efflux to >200% of baseline rates. Pretreatment of plants with Nod factor alters the effect of PGA by limiting the maximum H(2)O(2) efflux rate to 125% of that observed for untreated plants. Two Nod factor-related compounds showed no ability to modulate peroxide efflux, and tomato (Lycopersicon esculentum), a nonlegume, showed no response to 1 nM Nod factor. Seven M. truncatula mutants, lacking the ability to make nodules, were tested for Nod factor effects on H(2)O(2) efflux. The nfp mutant was blocked for suppression of peroxide efflux, whereas the dmi1 and dmi2 mutants, previously shown to be blocked for early Nod factor responses, showed a wild-type peroxide efflux modulation. These data demonstrate that exposure to Nod factor suppresses the activity of the reactive oxygen-generating system used for plant defense responses.
测定了经纯化的结瘤因子和聚半乳糖醛酸（PGA）七聚体处理的蒺藜苜蓿根段中的过氧化氢（H₂O₂）流出量。浓度大于100 pM的结瘤因子，在处理后20至30分钟开始将H₂O₂流出速率降低至基线水平的60%，而浓度大于75 nM的PGA激发子则导致H₂O₂流出量迅速增加至基线速率的200%以上。用结瘤因子预处理植物会改变PGA的作用，将最大H₂O₂流出速率限制在未处理植物所观察到的125%。两种与结瘤因子相关的化合物没有调节过氧化物流出的能力，非豆科植物番茄（Lycopersicon esculentum）对1 nM结瘤因子无反应。测试了七个缺乏结瘤能力的蒺藜苜蓿突变体对结瘤因子对H₂O₂流出的影响。nfp突变体在抑制过氧化物流出方面受阻，而先前已证明在早期结瘤因子反应方面受阻的dmi1和dmi2突变体则表现出野生型过氧化物流出调节。这些数据表明，暴露于结瘤因子会抑制用于植物防御反应的活性氧生成系统的活性。
