Key Lab of Crop Heterosis and Utilization of Ministry of Education, Beijing Key Lab of Crop Genetic Improvement, China Agricultural University, Beijing 100193, PR China.
Plant Sci. 2012 Nov;196:143-51. doi: 10.1016/j.plantsci.2012.08.003. Epub 2012 Aug 10.
Myo-inositol oxygenase (MIOX), a unique monooxygenase, catalyzes the oxidation of myo-inositol to d-glucuronic acid. However, the protective role of MIOX in plants against oxidative stress or drought stress remains unknown. In this study, the functional characterization of MIOX obtained from the cDNA library of upland rice (Oryza sativa L. cv. IRAT109), was performed. OsMIOX was expressed predominantly in the roots and induced by drought, H₂O₂, salt, cold and abscisic acid. The transgenic rice lines overexpressing OsMIOX showed obviously improved growth performance in the medium containing 200 mM mannitol. Further, the survival rate of leaves from the transgenic rice lines was significantly higher than that of the wild type plants under polyethylene glycol treatment. It was discovered that the activity of ROS-scavenging enzymes and proline content, as well as the transcript levels of many ROS scavenging genes were significantly increased in transgenic plants compared to the wild type plants under drought stress conditions. Together, these data suggest that OsMIOX has a specific function in drought stress tolerance by decreasing oxidative damage.
肌醇氧化酶（MIOX）是一种独特的单加氧酶，催化肌醇氧化为 D-葡萄糖醛酸。然而，MIOX 在植物中对氧化应激或干旱胁迫的保护作用尚不清楚。本研究从旱稻 cDNA 文库中克隆得到肌醇氧化酶基因（Oryza sativa L. cv. IRAT109），并对其功能进行了鉴定。OsMIOX 主要在根中表达，并受干旱、H₂O₂、盐、冷和脱落酸诱导。过表达 OsMIOX 的转基因水稻品系在含有 200mM 甘露醇的培养基中表现出明显改善的生长性能。此外，在聚乙二醇处理下，转基因水稻叶片的存活率明显高于野生型植物。研究发现，在干旱胁迫条件下，与野生型植物相比，转基因植物中 ROS 清除酶的活性、脯氨酸含量以及许多 ROS 清除基因的转录水平均显著升高。综上所述，这些数据表明 OsMIOX 通过降低氧化损伤在干旱胁迫耐受中具有特定功能。
