Department of Agricultural Biochemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68583-0718.
Plant Physiol. 1983 Apr;71(4):797-802. doi: 10.1104/pp.71.4.797.
Root nodules were harvested from chamber-grown soybean (Glycine max L. Merrill cv Woodworth) plants throughout development. Apparent nitrogenase activity (acetylene reduction) peaked before seeds began to develop, but a significant amount of activity remained as the seeds matured. Nodule senescence was defined as the period in which residual nitrogenase activity was lost. During this time, soluble protein and leghemoglobin levels in the host cell cytosol decreased, and proteolytic activity against azocasein increased. Degradative changes were not detected in bacteroids during nodule senescence. Total soluble bacteroid protein per gram of nodule remained constant, and an increase in proteolytic activity in bacteroid extracts was not observed. These results are consistent with the view that soybean nodule bacteroids are capable of redifferentiation into free-living bacteria upon deterioration of the legume-rhizobia symbiosis.
根瘤在整个发育过程中从室培养的大豆（Glycine max L. Merrill cv Woodworth）植物中收获。固氮酶活性（乙炔还原）在种子开始发育前达到峰值，但随着种子成熟，仍有大量的活性存在。根瘤衰老被定义为残余固氮酶活性丧失的时期。在此期间，宿主细胞胞质溶胶中的可溶性蛋白和豆血红蛋白水平下降，对偶氮酪蛋白的蛋白酶活性增加。在根瘤衰老过程中，未检测到类菌体的降解变化。每克根瘤的总可溶性类菌体蛋白保持不变，类菌体提取物中的蛋白酶活性也没有增加。这些结果与大豆根瘤类菌体在豆科-根瘤菌共生关系恶化时能够重新分化为自由生活细菌的观点一致。
