Fortin M G, Morrison N A, Verma D P
Nucleic Acids Res. 1987 Jan 26;15(2):813-24. doi: 10.1093/nar/15.2.813.
The peribacteroid membrane (pbm) of root nodules is derived from the plant cell plasma membrane but contains in addition several nodule-specific host proteins (nodulins). Antibodies raised against purified pbm of soybean were used to immunoprecipitate polysomes to isolate an RNA fraction that served as a template for the synthesis of a cDNA probe for screening a nodule-specific cDNA library. Clone p1B1 was found to encode a 26.5 kDa polypeptide (nodulin-26) which is immunoprecipitable specifically with the anti-pbm serum. Nodulin-26 has features of a transmembrane protein and its structure differs from that of nodulin-24 which appears to be a surface protein of pbm. The expression of these two pbm nodulins was examined in nodules induced by Bradyrhizobium japonicum Tn5 mutants that arrest nodule development at different stages of pbm biosynthesis. Nodules that do not show release of bacteria from the infection thread express nodulin-24 at a very low level. In contrast, the expression of nodulin-26 occurs fully in nodules that form infection threads only and is not affected by the release of bacteria from the threads.
根瘤的类菌体周膜（pbm）源自植物细胞质膜，但还含有几种结节特异性宿主蛋白（结节蛋白）。用针对大豆纯化pbm产生的抗体免疫沉淀多核糖体，以分离出一个RNA组分，该组分用作合成cDNA探针的模板，用于筛选结节特异性cDNA文库。发现克隆p1B1编码一种26.5 kDa的多肽（结节蛋白-26），它可以被抗pbm血清特异性免疫沉淀。结节蛋白-26具有跨膜蛋白的特征，其结构与似乎是pbm表面蛋白的结节蛋白-24不同。在由日本慢生根瘤菌Tn5突变体诱导的根瘤中检测了这两种pbm结节蛋白的表达，这些突变体在pbm生物合成的不同阶段使根瘤发育停滞。未显示细菌从感染丝中释放的根瘤中，结节蛋白-24的表达水平非常低。相反，结节蛋白-26的表达仅在形成感染丝的根瘤中完全发生，并且不受细菌从丝中释放的影响。
