Department of Agronomy, University of Illinois, 1102 S. Goodwin Avenue, Urbana, Illinois 61801.
Plant Physiol. 1991 Feb;95(2):435-42. doi: 10.1104/pp.95.2.435.
The isoflavones, daidzein and genistein, have been isolated and identified as the major inducers of nod genes of Bradyrhizobium japonicum. The common nod genes of rhizobia are in turn responsible for stimulating root hair curling and cortical root cell division, the earliest steps in the host response. This study evaluated whether there was a relationship between root isoflavonoid production and the hypernodulation phenotype of selected soybean (Glycine max [L.] Merr.) mutants. Three independently selected hypernodulating soybean mutants (NOD1-3, NOD2-4, and NOD3-7) and a nonnodulating mutant (NN5) were compared with the Williams parent for isoflavonoid concentrations. High performance liquid chromatographic analyses of soybean root extracts showed that all lines increased in daidzein, genistein, and coumestrol concentrations throughout the 12-day growth period after transplanting of both inoculated and noninoculated plants; transplanting and inoculation were done 6 days after planting. No significant differences were detected in the concentration of these compounds among the three noninoculated hypernodulating mutants and the Williams parent. In response to inoculation, the three hypernodulating mutants had higher isoflavonoid concentrations than did the Williams control at 9 to 12 days after inoculation when grown at 0 millimolar N level. However, the inoculated nonnodulating mutant also had higher isoflavonoid concentrations than did Williams. N application [urea, (NH(4))(2)SO(4) and NO(3) (-)] decreased the concentration of all three isoflavonoid compounds in all soybean lines. Application of NO(3) (-) was most inhibitory to isoflavonoid concentrations, and inhibition by NO(3) (-) was concentration dependent. These results are consistent with a conclusion that differential NO(3) (-) inhibition of nodulation may be partially due to changes in isoflavonoid levels, although the similar response of the nonnodulating mutant brings this conclusion into question. Alternatively, the nodulation control in the NN5 mutant may be due to factors totally unrelated to isoflavonoids, leaving open the possibility that isoflavonoids play a role in differential nodulation of lines genetically competent to nodulate.
染料木黄酮和大豆黄酮已被分离和鉴定为诱导根瘤菌 Bradyrhizobium japonicum nod 基因的主要诱导物。根瘤菌的常见 nod 基因反过来又负责刺激根毛卷曲和皮层根细胞分裂，这是宿主反应的最早步骤。本研究评估了大豆（Glycine max [L.] Merr.）突变体中根异黄酮的产生与超结瘤表型之间是否存在关系。三个独立选择的超结瘤大豆突变体（NOD1-3、NOD2-4 和 NOD3-7）和一个不结瘤突变体（NN5）与 Williams 亲本进行了异黄酮浓度比较。对大豆根提取物的高效液相色谱分析表明，在接种和未接种植物移栽后 12 天的整个生长期间，所有系的染料木黄酮、大豆黄酮和香豆雌酚浓度均增加；移栽和接种在种植后 6 天进行。在未接种的三个超结瘤突变体和 Williams 亲本之间，这些化合物的浓度没有差异。在 0 毫摩尔 N 水平下，接种后 9 至 12 天，与 Williams 对照相比，三个超结瘤突变体的异黄酮浓度更高。然而，接种的不结瘤突变体的异黄酮浓度也高于 Williams。氮素施用量[尿素、（NH 4 ）2 SO 4 和 NO 3 - ]降低了所有大豆品系中所有三种异黄酮化合物的浓度。所有大豆品系中，NO 3 - 的应用对异黄酮浓度的抑制作用最大，并且抑制作用与 NO 3 - 的浓度有关。这些结果表明，NO 3 - 对结瘤的差异抑制可能部分归因于异黄酮水平的变化，尽管不结瘤突变体的相似反应使这一结论受到质疑。或者，NN5 突变体中的结瘤控制可能是由于与异黄酮完全无关的因素，这使得异黄酮在具有结瘤能力的系的差异结瘤中发挥作用的可能性仍然存在。
