Unité Mixte de Recherche INRA 1088/CNRS 5184/Université de Bourgogne, Plante-Microbe-Environnement, 17 rue Sully, BP 86510, 21065 Dijon cedex, France.
Mol Plant. 2008 Mar;1(2):218-28. doi: 10.1093/mp/ssm016. Epub 2007 Oct 31.
Nitric oxide (NO) is a diatomic gas that performs crucial functions in a wide array of physiological processes in animals. The past several years have revealed much about its roles in plants. It is well established that NO is synthesized from nitrite by nitrate reductase (NR) and via chemical pathways. There is increasing evidence for the occurrence of an alternative pathway in which NO production is catalysed from L-arginine by a so far non-identified enzyme. Contradictory results have been reported regarding the respective involvement of these enzymes in specific physiological conditions. Although much remains to be proved, we assume that these inconsistencies can be accounted for by the limited specificity of the pharmacological agents used to suppress NO synthesis but also by the reduced content of L-arginine as well as the inactivity of nitrate-permeable anion channels in nitrate reductase- and/or nitrate/nitrite-deficient plants. Another unresolved issue concerns the molecular mechanisms underlying NO effects in plants. Here, we provide evidence that the second messenger Ca2+, as well as protein kinases including MAPK and SnRK2, are very plausible mediators of the NO signals. These findings open new perspectives about NO-based signaling in plants.
一氧化氮（NO）是一种双原子气体，在动物的广泛生理过程中发挥着至关重要的作用。过去几年的研究揭示了许多关于它在植物中的作用。已经证实，NO 可以由硝酸盐还原酶（NR）通过亚硝酸盐和化学途径合成。越来越多的证据表明存在一种替代途径，其中由尚未鉴定的酶从 L-精氨酸催化产生 NO。关于这些酶在特定生理条件下的各自参与，报告了相互矛盾的结果。尽管还有很多需要证明，但我们假设这些不一致可以归因于用于抑制 NO 合成的药理学试剂的有限特异性，以及 L-精氨酸含量的降低以及硝酸盐通透阴离子通道在硝酸盐还原酶和/或硝酸盐/亚硝酸盐缺乏植物中的失活。另一个未解决的问题涉及植物中 NO 作用的分子机制。在这里，我们提供的证据表明，第二信使 Ca2+以及包括 MAPK 和 SnRK2 在内的蛋白激酶是 NO 信号的非常合理的介质。这些发现为植物中基于 NO 的信号提供了新的视角。
