Scott-Craig J S, Casida J E, Poduje L, Walton J D
Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824, USA.
Plant Physiol. 1998 Mar;116(3):1083-9. doi: 10.1104/pp.116.3.1083.
Dichloroacetamide safeners protect maize (Zea mays L.) against injury from chloroacetanilide and thiocarbamate herbicides. Etiolated maize seedlings have a high-affinity cytosolic-binding site for the safener 3H-3-dichloroacetyl-2,2,5-trimethyl-1, 3-oxazol-idine ([3H]Saf), and this safener-binding activity (SafBA) is competitively inhibited by the herbicides. The safener-binding protein (SafBP), purified to homogeneity, has a relative molecular weight of 39,000, as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and an isoelectric point of 5.5. Antiserum raised against purified SafBP specifically recognizes a 39-kD protein in etiolated maize and sorghum (Sorghum bicolor L.), which have SafBA, but not in etiolated wheat (Triticum aestivum L.), oat (Avena sativa L.), barley (Hordeum vulgare L.), tobacco (Nicotiana tabacum L.), or Arabidopsis, which lack SafBA. SafBP is most abundant in the coleoptile and scarcest in the leaves, consistent with the distribution of SafBA. SBP1, a cDNA encoding SafBP, was cloned using polymerase chain reaction primers based on purified proteolytic peptides. Extracts of Escherichia coli cells expressing SBP1 have strong [3H]Saf binding, which, like binding to the native maize protein, is competitively inhibited by the safener dichlormid and the herbicides S-ethyl dipropylthiocarbamate, alachlor, and metolachlor. SBP1 is predicted to encode a phenolic O-methyltransferase, but SafBP does not O-methylate catechol or caffeic acid. The acquisition of its encoding gene opens experimental approaches for the evaluation of the role of SafBP in response to the relevant safeners and herbicides.
二氯乙酰胺安全剂可保护玉米（Zea mays L.）免受氯代乙酰苯胺类和硫代氨基甲酸酯类除草剂的伤害。黄化玉米幼苗对安全剂3H-3-二氯乙酰基-2,2,5-三甲基-1,3-恶唑烷（[3H]Saf）具有高亲和力的胞质结合位点，且这种安全剂结合活性（SafBA）受到除草剂的竞争性抑制。经纯化达到同质的安全剂结合蛋白（SafBP），通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳显示其相对分子质量为39000，等电点为5.5。针对纯化的SafBP产生的抗血清能特异性识别黄化玉米和高粱（Sorghum bicolor L.）中具有SafBA的一种39-kD蛋白，但不能识别黄化小麦（Triticum aestivum L.）、燕麦（Avena sativa L.）、大麦（Hordeum vulgare L.）、烟草（Nicotiana tabacum L.）或拟南芥中缺乏SafBA的该蛋白。SafBP在胚芽鞘中含量最高，在叶片中含量最少，这与SafBA的分布一致。基于纯化的蛋白水解肽，使用聚合酶链反应引物克隆了编码SafBP的cDNA SBP1。表达SBP1的大肠杆菌细胞提取物具有很强的[3H]Saf结合能力，与天然玉米蛋白的结合一样，该结合受到安全剂敌草胺和除草剂S-乙基二丙基硫代氨基甲酸酯、甲草胺和异丙甲草胺的竞争性抑制。预测SBP1编码一种酚类O-甲基转移酶，但SafBP不能使儿茶酚或咖啡酸发生O-甲基化。其编码基因的获得为评估SafBP在响应相关安全剂和除草剂中的作用开辟了实验途径。
