Verma D P, Haugland R, Brisson N, Legocki R P, Lacroix L
Biochim Biophys Acta. 1981 Mar 26;653(1):98-107. doi: 10.1016/0005-2787(81)90108-8.
The expression of leghaemoglobin genes in effective and ineffective (unable to fix nitrogen) root nodules of soybean developed by Rhizobium japonicum strains 61A76, 61A24 and SM5 was measured by using a cDNA probe or a cloned leghaemoglobin sequence and in vitro translation of Lb-mRNA. Hybridization of the poly(A)-containing nodule polysomal RNA from 3-week-old nodules with a kinetically purified Lb-cDNA or with plasmid (pLbl) containing a leghaemoglobin sequence showed that Lb-mRNA is present in ineffective nodules formed by strains SM5 and 61A24 at reduced levels. Of the two major classes of electrophoretically distinguishable leghaemoglobins in soybean, LbS was not synthesized in 3-week-old strain 61A24-induced nodules while both sorts of leghaemoglobin were synthesized and accumulated in ineffective nodules formed by strain SM5 of Rhizobium. Ineffective nodules formed by strain 61A24 are green inside and do not appear to accumulate leghaemoglobin as measured by the haemochromogen assay, although low levels of apoleghaemoglobin were detected using leghaemoglobin antibodies. SM5-induced nodules were found to have about half as much as leghaemoglobin of the of effective (61A76-induced) nodules. This study demonstrates that while the appearance of leghaemoglobin is independent of nitrogenase activity in bacteroids, its synthesis is influenced to different degrees both by a mutation (SM5) and incompatibility (61A24) of Rhizobium. The primary regulation appears to be at the level of transcription or processing of mRNA since ineffective nodules contain Lb-mRNA approximately in proportion to the amount of apoleghaemoglobin present in these nodules.
利用cDNA探针或克隆的豆血红蛋白序列以及豆血红蛋白mRNA的体外翻译，测定了日本根瘤菌菌株61A76、61A24和SM5所形成的大豆有效根瘤和无效（不能固氮）根瘤中豆血红蛋白基因的表达。用动力学纯化的豆血红蛋白cDNA或含有豆血红蛋白序列的质粒（pLb1）与3周龄根瘤中含poly(A)的多聚核糖体RNA杂交，结果表明，在SM5和61A24菌株形成的无效根瘤中，豆血红蛋白mRNA的含量有所降低。在大豆中，两类主要的可通过电泳区分的豆血红蛋白中，在3周龄61A24菌株诱导的根瘤中不合成LbS，而在根瘤菌SM5菌株形成的无效根瘤中，两种豆血红蛋白都能合成并积累。61A24菌株形成的无效根瘤内部呈绿色，用血色原测定法测定似乎不积累豆血红蛋白，不过用豆血红蛋白抗体检测到了低水平的脱辅基豆血红蛋白。发现SM5诱导的根瘤中豆血红蛋白的含量约为有效（61A76诱导）根瘤的一半。这项研究表明，虽然类菌体中豆血红蛋白的出现与固氮酶活性无关，但其合成受到根瘤菌的突变（SM5）和不亲和性（61A24）不同程度的影响。主要调控似乎发生在mRNA转录或加工水平，因为无效根瘤中豆血红蛋白mRNA的含量与这些根瘤中脱辅基豆血红蛋白的含量大致成比例。
