Auger S, Baulcombe D, Verma D P
Biochim Biophys Acta. 1979 Jul 26;563(2):496-507. doi: 10.1016/0005-2787(79)90068-6.
In order to determine the number of structural genes expressed specifically in root nodules, the total complexities of poly(A) + polysomal RNA populations from uninfected roots and mature nodules were compared. Hybridization kinetics of nodule poly(A) + RNA (NRNA) to its cDNA (NcDNA) revealed a very abundant component comprising 18--20% of the NRNA. This component was shown to be leghaemoglobin (Lb) by the similarity of its kinetics of hybridization to that of purified Lb-cDNA. The hybridization kinetics of uninfected root cDNA (RcDNA) to root poly(A) + RNA (RRNA) indicate that this abundant RNA fraction is absent in RRNA. The extent of sequence homologies between root and nodule tissue was determined by heterologous hybridizations of RcDNA to NRNA and vice versa. The data suggest that the mRNA populations of the two tissues are substantially homologous, though shifts in abundance of certain sequences are quite marked. The hybridization of purified Lb-cDNA to total polysomal RNA from developing nodules shows that the increase in concentration of Lb-mRNA sequences parallels the leghaemoglobin synthesis in this tissue. Lb sequences appear to increase between 8 and 13 days after infection with Rhizobium.
为了确定在根瘤中特异性表达的结构基因的数量，对未感染根和成熟根瘤的聚腺苷酸（poly(A)）+多聚核糖体RNA群体的总复杂度进行了比较。根瘤聚腺苷酸（poly(A)）+RNA（NRNA）与其互补DNA（NcDNA）的杂交动力学显示，有一个非常丰富的组分，占NRNA的18%-20%。通过其杂交动力学与纯化的豆血红蛋白（Lb）-cDNA的杂交动力学相似性，表明该组分是豆血红蛋白（Lb）。未感染根的互补DNA（RcDNA）与根聚腺苷酸（poly(A)）+RNA（RRNA）的杂交动力学表明，RRNA中不存在这种丰富的RNA组分。通过RcDNA与NRNA的异源杂交以及反之亦然，确定了根和根瘤组织之间的序列同源程度。数据表明，尽管某些序列丰度的变化相当明显，但两种组织的信使核糖核酸（mRNA）群体基本同源。纯化的Lb-cDNA与发育中根瘤的总多聚核糖体RNA的杂交表明，Lb-mRNA序列浓度的增加与该组织中豆血红蛋白的合成平行。Lb序列似乎在感染根瘤菌后8至13天之间增加。
