Schubert K R, Jennings N T, Evans H J
Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon 97331.
Plant Physiol. 1978 Mar;61(3):398-401. doi: 10.1104/pp.61.3.398.
The interaction between the ATP-dependent evolution of H(2) catalyzed by nitrogenase and the oxidation of H(2) via a hydrogenase has been postulated to influence the efficiency of the N(2)-fixing process in nodulated legumes. A comparative study using soybean (Glycine max L. Merr.) cv. Anoka inoculated with either Rhizobium japonicum strain USDA 31 or USDA 110 and cowpea (Vigna unguiculata L. Walp.) cv. Whippoorwill inoculated with Rhizobium strain 176A27 or 176A28 cultured on a N-free medium was conducted to address this question. Nodules from the Anoka cultivar inoculated with USDA 31 evolved H(2) in air and the H(2) produced accounted for about 30% of the energy transferred to the nitrogenase system during the period of active N(2) fixation. In contrast the same soybean cultivar inoculated with USDA 110 produced nodules with an active hydrogenase and consequently did not evolve H(2) in air. A comparison of Anoka soybeans inoculated with the two different strains of R. japonicum showed that mean rates of C(2)H(2) reduction and O(2) consumption and mean mass of nodules taken at four times during vegetative growth were not significantly different.When compared to Anoka inoculated with USDA 31, the same cultivar inoculated with USDA 110 showed increases in total dry matter, per cent nitrogen, and total N(2) fixed of 24, 7, and 31%, respectively. Cowpeas in symbiosis with the hydrogenase-producing strain 176A28 in comparison with the same cultivar inoculated with the H(2)-evolving strain 176A27 produced increases in plant dry weight and total N(2) fixed of 11 and 15%, respectively. This apparent increase in the efficiency of N(2) fixation for nodulated legumes capable of reutilizing the H(2) evolved from nitrogenase is considered and it is concluded that provision of conclusive evidence of the role of the H(2)-recycling process in N(2)-fixing efficiency of legumes will require comparison of Rhizobium strains that are genetically identical with the exception of the presence of hydrogenase.
固氮酶催化的H₂的ATP依赖性进化与通过氢化酶的H₂氧化之间的相互作用被认为会影响根瘤豆科植物中N₂固定过程的效率。进行了一项比较研究，使用接种了日本根瘤菌菌株USDA 31或USDA 110的大豆（Glycine max L. Merr.）品种Anoka，以及接种了根瘤菌菌株176A27或176A28并在无氮培养基上培养的豇豆（Vigna unguiculata L. Walp.）品种Whippoorwill来解决这个问题。接种USDA 31的Anoka品种的根瘤在空气中会释放H₂，在活跃的N₂固定期间，产生的H₂约占转移到固氮酶系统的能量的30%。相比之下，接种USDA 110的同一大豆品种产生的根瘤具有活跃的氢化酶，因此在空气中不会释放H₂。对接种两种不同日本根瘤菌菌株的Anoka大豆进行比较，结果表明在营养生长期间四个时间点采集的根瘤的C₂H₂还原率、O₂消耗率和平均质量没有显著差异。与接种USDA 31的Anoka相比，接种USDA 110的同一品种的总干物质、氮百分比和固定的总N₂分别增加了24%、7%和31%。与接种释放H₂的菌株176A27的同一豇豆品种相比，与产生氢化酶的菌株176A28共生的豇豆的植物干重和固定的总N₂分别增加了11%和15%。考虑到能够重新利用固氮酶释放的H₂的根瘤豆科植物在N₂固定效率上的这种明显提高，得出的结论是，要提供H₂循环过程在豆科植物N₂固定效率中作用的确凿证据，需要比较除了存在氢化酶外基因相同的根瘤菌菌株。
