Symbiotic Bradyrhizobium japonicum Reduces N2O Surrounding the Soybean Root System via Nitrous Oxide Reductase
Symbiotic Bradyrhizobium japonicum Reduces N2O Surrounding the Soybean Root System via Nitrous Oxide Reductase
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DOI：
10.1128/aem.72.4.2526-2532.2006
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发表时间：
2006-04
影响因子：
4.4
通讯作者：
Reiko Sameshima-Saito;K. Chiba;Junta Hirayama;Manabu Itakura;H. Mitsui;S. Eda;K. Minamisawa
中科院分区：
文献类型：
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作者：
Reiko Sameshima-Saito;K. Chiba;Junta Hirayama;Manabu Itakura;H. Mitsui;S. Eda;K. Minamisawa
摘要通过对N2O的吸收和15N-N2O向15N-N2的转化，对缓生根瘤菌形成的大豆根瘤中N2O还原酶活性进行了评价。USDA110的自由活细胞显示N2O还原酶活性，而nosZ突变体则没有。将nosZ突变体与含有日本稻USDA110 nosRZDFYLX基因的两个子体互补，恢复了N2O还原酶的活性。用USDA110形成的离体大豆根瘤，用15N-N2O处理后，根瘤外迅速排放15N-N2，吸收量为15N-N2O的98.5%，而接种了nosZ突变体的根瘤则没有。令人惊讶的是，即使在含有低浓度N2O （0.34 ppm）的环境空气中，也可以观察到USDA110结瘤的大豆根系对N2O的吸收。这些结果表明，N2O转化为N2完全取决于呼吸N2O还原酶，携带nos基因的日本芽孢杆菌结瘤的大豆根系能够去除极低浓度的N2O。
ABSTRACT N2O reductase activity in soybean nodules formed with Bradyrhizobium japonicum was evaluated from N2O uptake and conversion of 15N-N2O into 15N-N2. Free-living cells of USDA110 showed N2O reductase activity, whereas a nosZ mutant did not. Complementation of the nosZ mutant with two cosmids containing the nosRZDFYLX genes of B. japonicum USDA110 restored the N2O reductase activity. When detached soybean nodules formed with USDA110 were fed with 15N-N2O, they rapidly emitted 15N-N2 outside the nodules at a ratio of 98.5% of 15N-N2O uptake, but nodules inoculated with the nosZ mutant did not. Surprisingly, N2O uptake by soybean roots nodulated with USDA110 was observed even in ambient air containing a low concentration of N2O (0.34 ppm). These results indicate that the conversion of N2O to N2 depends exclusively on the respiratory N2O reductase and that soybean roots nodulated with B. japonicum carrying the nos genes are able to remove very low concentrations of N2O.