Igamberdiev Abir U, Bykova Natalia V
Department of Biology, Memorial University of Newfoundland, St. John's, NL, Canada.
Morden Research and Development Centre, Agriculture and Agri-Food Canada, Morden, MB, Canada.
J Exp Bot. 2025 Jan 22. doi: 10.1093/jxb/eraf021.
Alternative oxidase (AOX) regulates the level of reactive oxygen species and nitric oxide (NO) in plants. While under normoxic conditions it alleviates NO formation, there are several indications that in the conditions of low oxygen such as during seed germination before radicle protrusion, in meristematic stem cells, and in flooded roots AOX can be involved in the production of NO from nitrite. Whereas the first reports considered this role as indirect, more evidence is accumulated that AOX can act as a nitrite: NO reductase. Such activity of the structurally similar di-iron proteins in bacteria has been demonstrated. We review the literature on this topic and show that AOX can be induced under hypoxic conditions and participate in NO turnover via the phytoglobin-NO cycle. This results in the facilitation of glycolytic reactions by reoxidation of the glycolytically formed NADH and diverting the glycolytic carbon toward the formation of alanine and other amino acids. Pyruvate formed in glycolysis can activate AOX and facilitate its operation under these conditions. It is concluded that AOX is an important player in the hypoxic response in plants that regulates the redox level by participating in NO turnover as a nitrite: NO reductase in cooperation with nitrate reductase and phytoglobin.
交替氧化酶（AOX）调节植物中活性氧和一氧化氮（NO）的水平。在常氧条件下，它可减轻NO的形成，但有多种迹象表明，在低氧条件下，如种子在胚根突出前萌发期间、在分生组织干细胞中以及在水淹根系中，AOX可能参与亚硝酸盐产生NO的过程。尽管最初的报道认为这一作用是间接的，但越来越多的证据表明AOX可作为亚硝酸盐：NO还原酶发挥作用。细菌中结构相似的双铁蛋白的这种活性已得到证实。我们综述了关于该主题的文献，并表明AOX可在缺氧条件下被诱导，并通过植物血红蛋白 - NO循环参与NO的周转。这通过糖酵解形成的NADH的再氧化促进糖酵解反应，并使糖酵解碳转向丙氨酸和其他氨基酸的形成。糖酵解中形成的丙酮酸可激活AOX并促进其在这些条件下的运作。得出的结论是，AOX是植物缺氧反应中的一个重要参与者，它作为亚硝酸盐：NO还原酶与硝酸还原酶和植物血红蛋白协同作用，通过参与NO周转来调节氧化还原水平。
