Yemelyanov V V, Prikaziuk E G, Lastochkin V V, Aresheva O M, Chirkova T V
Department of Genetics and Biotechnology, Faculty of Biology, Saint Petersburg State University, St. Petersburg, Russia Department of Plant Physiology and Biochemistry, Faculty of Biology, Saint Petersburg State University, St. Petersburg, Russia.
Department of Plant Physiology and Biochemistry, Faculty of Biology, Saint Petersburg State University, St. Petersburg, Russia Department of Water Resources, ITC Faculty of Geo-Information Science and Earth Observation, University of Twente, Enschede, the Netherlands.
Vavilovskii Zhurnal Genet Selektsii. 2024 Feb;28(1):44-54. doi: 10.18699/vjgb-24-06.
The most important part of the plant antioxidant system is the ascorbate-glutathione cycle (AGC), the activity of which is observed upon exposure to a range of stressors, including lack of O2, and oxidative stress occurring immediately after the restoration of oxygen access, hereafter termed reaeration or post-anoxia. The operation of the AGC (enzymes and low-molecular components) in wheat (Triticum aestivum, cv. Leningradka, non-resistant to hypoxia) and rice (Oryza sativa, cv. Liman, resistant) seedlings after 24 h anoxia and 1 h or 24 h reaeration was studied. Significant accumulation of oxidized forms of ascorbate and glutathione was revealed in the non-resistant plant (wheat) after 24 h of anoxia and reaeration, indicating the development of oxidative stress. In the resistant plant (rice), reduced forms of these antioxidants prevailed both in normoxia and under stress, which may indicate their intensive reduction. In wheat, the activities of ascorbate peroxidase and dehydroascorbate reductase in shoots, and monodehydroascorbate reductase and glutathione reductase in roots decreased under anoxia and reaeration. The activity of antioxidant enzymes was maintained in rice under lack of oxygen (ascorbate peroxidase, glutathione reductase) and increased during post-anoxia (AGC reductases). Anoxia stimulated accumulation of mRNA of the organellar ascorbate peroxidase genes OsAPX3, OsAPX5 in shoots, and OsAPX3-5 and OsAPX7 in roots. At post-anoxia, the contribution of the OsAPX1 and OsAPX2 genes encoding the cytosolic forms of the enzyme increased in the whole plant, and so did that of the OsAPX8 gene for the plastid form of the enzyme. The accumulation of mRNA of the genes OsMDAR2 and OsMDAR4 encoding peroxisomal and cytosolic monodehydroascorbate reductase as well as the OsGR2 and OsGR3 for cytosolic and organellar glutathione reductase was activated during reaeration in shoots and roots. In most cases, O2 deficiency activated the genes encoding the peroxisomal, plastid, and mitochondrial forms of the enzymes, and upon reaeration, an enhanced activity of the genes encoding the cytoplasmic forms was observed. Taken together, the inactivation of AGC enzymes was revealed in wheat seedlings during anoxia and subsequent reaeration, which disrupted the effective operation of the cycle and triggered the accumulation of oxidized forms of ascorbate and glutathione. In rice, anoxia led to the maintenance of the activity of AGC enzymes, and reaeration stimulated it, including at the level of gene expression, which ensured the effective operation of AGC.
植物抗氧化系统最重要的部分是抗坏血酸-谷胱甘肽循环（AGC），在暴露于一系列应激源时可观察到其活性，这些应激源包括缺氧，以及恢复氧气供应后立即出现的氧化应激，以下称为复氧或缺氧后阶段。研究了小麦（普通小麦，品种列宁格勒卡，对缺氧不抗性）和水稻（水稻，品种利曼，抗性）幼苗在缺氧24小时以及复氧1小时或24小时后AGC（酶和低分子成分）的运作情况。在缺氧24小时和复氧后，不抗性植物（小麦）中抗坏血酸和谷胱甘肽的氧化形式显著积累，表明氧化应激的发展。在抗性植物（水稻）中，这些抗氧化剂的还原形式在常氧和应激条件下均占主导，这可能表明它们的大量还原。在小麦中，缺氧和复氧后，地上部抗坏血酸过氧化物酶和脱氢抗坏血酸还原酶以及根部单脱氢抗坏血酸还原酶和谷胱甘肽还原酶的活性降低。在缺氧条件下，水稻中抗氧化酶的活性得以维持（抗坏血酸过氧化物酶、谷胱甘肽还原酶），并且在缺氧后阶段（AGC还原酶）活性增加。缺氧刺激了细胞器抗坏血酸过氧化物酶基因OsAPX3、OsAPX5在地上部以及OsAPX3 - 5和OsAPX7在根部的mRNA积累。在缺氧后阶段，编码该酶胞质形式的OsAPX1和OsAPX2基因在整个植株中的贡献增加，编码该酶质体形式的OsAPX8基因的贡献也增加。编码过氧化物酶体和胞质单脱氢抗坏血酸还原酶的OsMDAR2和OsMDAR4基因以及编码胞质和细胞器谷胱甘肽还原酶的OsGR2和OsGR3基因的mRNA积累在地上部和根部复氧过程中被激活。在大多数情况下，缺氧激活了编码该酶过氧化物酶体、质体和线粒体形式的基因，而复氧后，观察到编码细胞质形式的基因活性增强。综上所述，在缺氧和随后的复氧过程中，小麦幼苗中AGC酶失活，这破坏了循环的有效运作并引发了抗坏血酸和谷胱甘肽氧化形式的积累。在水稻中，缺氧导致AGC酶活性维持，而复氧刺激了其活性，包括在基因表达水平，这确保了AGC的有效运作。
