Department of Biochemistry, Faculty of Science, Banaras Hindu University, Varanasi, 221005, India.
Protoplasma. 2013 Apr;250(2):585-600. doi: 10.1007/s00709-012-0444-0. Epub 2012 Aug 28.
Water deficit for rice is a worldwide concern, and to produce drought-tolerant varieties, it is essential to elucidate molecular mechanisms associated with water deficit tolerance. In the present study, we investigated the differential responses of nonenzymatic antioxidants ascorbate (AsA), glutathione (GSH), and their redox pool as well as activity levels of enzymes of ascorbate-glutathione cycle in seedlings of drought-sensitive rice (Oryza sativa L.) cv. Malviya-36 and drought-tolerant cv. Brown Gora subjected to water deficit treatment of -1.0 and -2.1 MPa for 24-72 h using PEG-6000 in sand cultures. Water deficit caused increased production of reactive oxygen species such as O2Symbol: see text, H2O2, and HO[Symbol: see text] in the tissues, and the level of production was higher in the sensitive than the tolerant cultivar. Water deficit caused reduction in AsA and GSH and decline in their redox ratios (AsA/DHA and GSH/GSSG) with lesser decline in tolerant than the sensitive seedlings. With progressive level of water deficit, the activities of monodehydroascorbate reductase, dehydroascorbate reductase, ascorbate peroxidase (APX), and glutathione transferase increased in the seedlings of both rice cultivars, but the increased activity levels were higher in the seedlings of drought-tolerant cv. Brown Gora compared to the sensitive cv. Malviya-36. Greater accumulation of proline was observed in stressed seedlings of tolerant than the sensitive cultivar. In-gel activity staining of APX revealed varying numbers of their isoforms and their differential expression in sensitive and tolerant seedlings under water deficit. Results suggest that an enhanced oxidative stress tolerance by a well-coordinated cellular redox state of ascorbate and glutathione in reduced forms and induction of antioxidant defense system by elevated activity levels of enzymes of ascorbate-glutathione cycle is associated with water deficit tolerance in rice.
水亏缺是一个全球性的问题，为了培育耐旱品种，阐明与耐旱性相关的分子机制至关重要。本研究以PEG-6000 模拟水分亏缺，通过砂培试验，研究了敏感品种 Malviya-36 和耐旱品种 Brown Gora 的幼苗在 -1.0 和 -2.1 MPa 水分亏缺处理 24-72 h 时非酶抗氧化剂抗坏血酸（AsA）、谷胱甘肽（GSH）及其氧化还原库以及抗坏血酸-谷胱甘肽循环酶活性的差异响应。水分亏缺导致组织中活性氧（如 O2Symbol: see text、H2O2 和 HO[Symbol: see text]）的产生增加，且在敏感品种中产生的水平高于耐旱品种。水分亏缺导致 AsA 和 GSH 的减少及其氧化还原比（AsA/DHA 和 GSH/GSSG）下降，而耐旱品种的下降幅度小于敏感品种。随着水分亏缺程度的增加，两品种幼苗的单脱氢抗坏血酸还原酶、脱氢抗坏血酸还原酶、抗坏血酸过氧化物酶（APX）和谷胱甘肽转移酶活性均增加，但耐旱品种 Brown Gora 幼苗的活性增加水平高于敏感品种 Malviya-36。耐旱品种胁迫幼苗中脯氨酸的积累量高于敏感品种。APX 的胶内活性染色显示，在水分亏缺下，其同工酶的数量及其在敏感和耐旱幼苗中的差异表达不同。结果表明，通过还原型抗坏血酸和谷胱甘肽的细胞氧化还原状态的良好协调以及通过提高抗坏血酸-谷胱甘肽循环酶的活性水平诱导抗氧化防御系统，增强了水稻对水分亏缺的胁迫耐受性。
