Xie Zhi-Ping, Staehelin Christian, Broughton William J, Wiemken Andres, Boller Thomas, Müller Joachim
Botanisches Institut der Universität Basel, Hebelstrasse 1, CH-4056 Basel, Switzerland. Present address: Euchinus Ltd, Rheinschanze 8, CH-4056 Basel, Switzerland.
Botanisches Institut der Universität Basel, Hebelstrasse 1, CH-4056 Basel, Switzerland. Present address: Laboratoire de Biologie Moléculaire des Plantes Supérieures, Université de Genève, 1, Chemin de l'Impératrice, CH-1292 Chambésy / Genève, Switzerland.
Funct Plant Biol. 2003 Oct;30(9):965-971. doi: 10.1071/FP03002.
Roots of soybeans have the ability to form symbioses with nitrogen-fixing rhizobial bacteria to form nitrogen-fixing (Fix) nodules, thus allowing the plant to grow in the absence of mineral nitrogen. Several soybean cultivars from China nodulated normally with Bradyrhizobium japonicum USDA110 spc4, but developed only a few nodules with 61-A-101, another B. japonicum strain. When soybeans were infected with Rhizobium sp. NGR234, ineffective (Fix) nodules that do not fix nitrogen were formed. Plants infected with NGRΩnodD2, a mutant strain overproducing lipo-chitooligosaccharidic nodulation signals (Nod factors), showed significantly higher numbers of ineffective nodules. Nodules from the different plant-microsymbiont combinations were characterized with respect to their accumulation of soluble carbohydrates and their induction of trehalase and sucrose synthase. These two plant enzymes are known to be nodule-stimulated proteins. Pool sizes of soluble carbohydrates in nodules showed strain-specific alterations in sucrose and trehalose, whereas myo-inositol and pinitol were affected in a more cultivar-specific way. Immunoblots with nodulin-specific antiserum indicated that sucrose synthase is induced in Fix nodules, but undetectable in Fix nodules, indicating a strain-specific induction profile. Trehalase activity in nodules showed a similar strain-specific induction profile. High enzyme activity was measured for nodules harboring the Bradyrhizobium strains, whereas ineffective nodules containing NGR234 exhibited activities in the range of uninfected roots. Nodules induced by NGRΩnodD2 showed increased trehalase activity. A similar induction of trehalase was observed when uninfected roots were treated with Nod factors purified from NGR234. The data obtained are discussed in the context of carbohydrate allocation in nodules and the question of how rhizobial bacteria influence the carbohydrate metabolism of their host plant is addressed.
大豆根系能够与固氮根瘤菌形成共生关系，形成固氮（Fix）根瘤，从而使植物在无矿质氮的情况下生长。来自中国的几个大豆品种与慢生根瘤菌 USDA110 spc4 能正常结瘤，但与另一株慢生根瘤菌 61 - A - 101 结瘤很少。当大豆被根瘤菌 NGR234 感染时，会形成不固氮的无效（Fix）根瘤。被 NGRΩnodD2（一种过量产生脂壳寡糖结瘤信号（Nod 因子）的突变菌株）感染的植物，其无效根瘤数量显著增多。对不同植物 - 微共生体组合形成的根瘤，就其可溶性碳水化合物的积累以及海藻糖酶和蔗糖合酶的诱导情况进行了表征。已知这两种植物酶是受根瘤刺激的蛋白。根瘤中可溶性碳水化合物的库大小显示，蔗糖和海藻糖存在菌株特异性变化，而肌醇和松醇则以更具品种特异性的方式受到影响。用结瘤素特异性抗血清进行的免疫印迹表明，蔗糖合酶在固氮根瘤中被诱导，但在无效根瘤中检测不到，这表明存在菌株特异性的诱导模式。根瘤中海藻糖酶活性显示出类似的菌株特异性诱导模式。对含有慢生根瘤菌菌株的根瘤测定到较高的酶活性，而含有 NGR234 的无效根瘤的活性与未感染根的活性范围相当。由 NGRΩnodD2 诱导形成的根瘤显示出海藻糖酶活性增加。当用从 NGR234 纯化的 Nod 因子处理未感染根时，观察到海藻糖酶有类似的诱导情况。结合根瘤中碳水化合物分配的情况对所得数据进行了讨论，并探讨了根瘤菌如何影响其宿主植物碳水化合物代谢的问题。
