Ortega J L, Sánchez F, Soberón M, Flores M L
Centro de Investigación sobre Ingenieria Genética y Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 2-246, Cuernavaca, Mor. México.
Plant Physiol. 1992 Feb;98(2):584-7. doi: 10.1104/pp.98.2.584.
Nodulated bean (Phaseolus vulgaris) plants were grown for 17 days after infection in normal (0.02%) CO(2) and from day 8 to 17 in high (0.1%) CO(2) in order to increase nitrogen fixation and define how nodule glutamine synthetase (GS) isoforms are regulated by the ammonia derived from the bacteroid. Nitrogenase activity was detected by day 10, and by day 17 activity was over twofold higher in 0.1% of CO(2) compared with plants grown in 0.02% CO(2) and inoculated with Rhizobium wild-type strain CE3. Likewise, plant fresh weight increased in response to increased CO(2), particularly in plants inoculated with the Rhizobium phaseoli mutant strain CFN037. Glutamine synthetase specific activity increased 2.5- to 6.5-fold from day 11 to 17. However, increased CO(2) did not appear to have an effect on GS specific activity. Analysis of the nodule GS polypeptide composition revealed that the gamma polypeptide was significantly reduced in response to high CO(2), whereas the beta polypeptide was not affected. The significance of this result in relation to the regulation of GS isoforms and their role in the assimilation of ammonia in the nodule is discussed in this paper.
在正常（0.02%）二氧化碳浓度下感染后，将结瘤菜豆（菜豆）植株培养17天，并从第8天至第17天置于高（0.1%）二氧化碳浓度环境中，以提高固氮作用，并确定根瘤谷氨酰胺合成酶（GS）同工型如何受类菌体衍生氨的调节。到第10天检测到固氮酶活性，与在0.02%二氧化碳浓度下生长并接种根瘤菌野生型菌株CE3的植株相比，在0.1%二氧化碳浓度下，到第17天活性高出两倍多。同样，植株鲜重随着二氧化碳浓度升高而增加，特别是接种菜豆根瘤菌突变菌株CFN037的植株。从第11天至第17天，谷氨酰胺合成酶比活性增加了2.5至6.5倍。然而，二氧化碳浓度升高似乎对GS比活性没有影响。对根瘤GS多肽组成的分析表明，γ多肽因高二氧化碳浓度而显著减少，而β多肽不受影响。本文讨论了该结果与GS同工型调节及其在根瘤氨同化中的作用的相关性。
