Phloem glutamine and the regulation of O-2 diffusion in legume nodules
Phloem glutamine and the regulation of O-2 diffusion in legume nodules
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DOI：
10.1104/pp.113.1.259
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发表时间：
1997-01-01
期刊：
影响因子：
7.4
通讯作者：
Layzell, DB
中科院分区：
文献类型：
--
作者：
Neo, HH;Layzell, DB
本研究的目的是测试的假设，即N含量或组成的韧皮部汁液，供应crumulated根可能发挥作用，通过增加根瘤抗O-2扩散的反馈调节固氮酶活性。对羽扇豆（Lupinus albus cv马尼托巴）或大豆（Glycine mar L.）Merr. cv Maple Arrow）的韧皮部汁液中的总氮含量增加了1.3倍（羽扇豆）和2.6倍（大豆），而不改变其C含量。韧皮部N的增加主要是由于谷氨酰胺N浓度增加了4.8倍（羽扇豆）和10.5倍（大豆）。此外，有下降的表观固氮酶活性和总固氮酶活性，在4小时内开始，并达到约54%的初始活性在6小时内开始的NH3处理。然而，潜在的固氮酶活性值在处理的植物没有显着不同的对照植物。这些结果提供的证据表明，在韧皮部汁液的N组成的变化，特别是谷氨酰胺含量，可能会增加根瘤抵抗O-2扩散，从而下调根瘤代谢和固氮酶活性通过控制供应O-2的细菌感染的细胞。
The aim of the present study was to test the hypothesis that the N content or the composition of the phloem sap that supplies nodulated roots may play a role in the feedback regulation of nitrogenase activity by increasing nodule resistance to O-2 diffusion. Treating shoots of lupin (Lupinus albus cv Manitoba) or soybean (Glycine mar L. Merr. cv Maple Arrow) with 100 mu L L(-1) NH3 caused a 1.3-fold (lupin) and 2.6-fold (soybean) increase in the total N content of phloem sap without altering its C content. The increase in phloem N was due primarily to a 4.8-fold (lupin) and 10.5-told (soybean) increase in the concentration of glutamine N. In addition, there was a decline in both the apparent nitrogenase activity and total nitrogenase activity that began within 4 h and reached about 54% of its initial activity within 6 h of the start of the NH3 treatment. However, the potential nitrogenase activity values in the treated plants were not significantly different from those of the control plants. These results provide evidence that changes in the N composition of the phloem sap, particularly the glutamine content, may increase nodule resistance to O-2 diffusion and, thereby, down-regulate nodule metabolism and nitrogenase activity by controlling the supply of O-2 to the bacteria-infected cells.