Abscisic acid induces a decline in nitrogen fixation that involves leghaemoglobin, but is independent of sucrose synthase activity
Abscisic acid induces a decline in nitrogen fixation that involves leghaemoglobin, but is independent of sucrose synthase activity
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DOI：
10.1093/jexbot/52.355.285
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发表时间：
2001-02-01
影响因子：
6.9
通讯作者：
Arrese-Igor, C
中科院分区：
文献类型：
--
作者：
González, EM;Gálvez, L;Arrese-Igor, C
蔗糖合成酶(SS)活性被认为是根瘤代谢中的一个关键点，因为该酶在不同的胁迫下被下调，从而导致固氮率下降。在大豆中，SS转录本在干旱开始后的1d内急剧下降。如此快速的反应表明，信号转导分子起到了调节作用。脱落酸(ABA)是一个可能的候选分子，因为它在相当多的植物对环境限制的反应中起中介作用。通过研究外源ABA对豌豆根瘤代谢的影响，探讨了ABA控制根瘤代谢的假说。在本试验条件下，ABA对植物生物量、根瘤数和干重没有影响，但在5d内固氮率下降70%，9d后下降80%，从而导致植物有机氮含量下降。ABA处理对根瘤中的SS活性、谷氨酸氨基转移酶、碱性转氨酶、苹果酸脱氢酶、谷氨酸合成酶、尿苷二磷葡萄糖焦磷酸化酶、异柠檬酸脱氢酶和谷氨酰胺合成酶的活性均无影响。这些结果不支持ABA直接调节SS活性的假说。然而，他们确实表明，在环境约束下的根瘤中至少存在两种不同的控制途径，其中包括ABA参与LBL与氧有关的固氮控制。
Sucrose synthase (SS) activity has been suggested to be a key point of regulation in nodule metabolism since this enzyme is down-regulated in response to different stresses which lead to decreased nitrogen fixation. In soybean, a dramatic decline of SS transcripts has been observed within 1 d from the onset of drought. Such a quick response suggests mediation by a signal transduction molecule. Abscisic acid (ABA) is a likely candidate to act as such a molecule as it mediates in a significant number of plant responses to environmental constraints. The hypothesis of ABA controlling nodule metabolism was approached in this work by assessing nodule responses to exogenous ABA supply in pea. Under the experimental conditions, ABA did not affect plant biomass, nodule numbers or dry weight, However, nitrogen fixation rate was reduced by 70% within 5 d and by 80% after 9 d leading to a reduced plant organic nitrogen content. Leghaemoglobin (Lb) content declined in parallel with that of nitrogen fixation, SS activity, however, was not affected by ABA treatment, and neither were the activities of the enzymes aspartate amino transferase, alkaline invertase, malate dehydrogenase, glutamate synthase, uridine diphosphoglucose pyrophosphorylase, isocitrate dehydrogenase, and glutamine synthetase, Nodule bacteroid-soluble protein content was reduced in nodules only after 9 d of ABA treatment. These results do not support the hypothesis that ABA directly regulates SS activity. However, they do suggest the occurrence of at least two different control pathways in nodules under environmental constraints, which include ABA being involved in a Lbl oxygen-related control of nitrogen fixation.