Estimation of the Productivity by DNA Damage and Repair of Rice

利用碱性琼脂糖凝胶电泳及其图像分析系统研究了UV-B辐射对5个水稻品种DNA的损伤及其修复能力。对UV-B辐射敏感的5个水稻品种（Oryza sativa L.var.）Sasashigure和Norin 1）和抗性（Oryza sativa L.var. Hatsunishiki、Koshihikari和Sasanishiki）对紫外线的光复活能力不同。抗紫外线菌株具有较高的光复活能力，而紫外线敏感菌株的修复能力较弱。光复活系统对CPD的形成反应迅速，而切除修复系统反应缓慢。这些结果表明，水稻抗紫外线的能力来源于其较高的修复能力，水稻的修复能力可作为衡量水稻生产力的指标之一，水稻1-2叶、3-4叶、结果表明，水稻1-2叶期和3-4叶期的抗病能力非常相似，而5-6叶期水稻的DNA损伤及其修复能力降低了20%左右。其原因被认为是UV-B到达细胞核减少，因为在这个阶段的水稻含有许多叶绿体，变得厚而硬。因此，有必要对日本栽培的水稻的抗UV-B能力进行研究。

DNA damage in five strains of rice by irradiation of UV-B and its ability of repair were searched by alkaline agarose gel electrophoresis and its image analysis system. Compare of CPD(cyclobutyl pyrimidine dimmer) in DNA formed by UV-B irradiation was very similar in the five strains, which were sensitive(Oryza sativa L.var. Sasashigure and Norin1) and resistant (Oryza sativa L.var. Hatsunishiki, Koshihikari, and Sasanishiki) against UV.However, their abilities of photoreactivation were different. UV-resistant strain showed high abilities of photoreactivation, although UV-sensitive one was comparatively weak ability of repair system. While the photoreactivation quickly responded to formation of the CPD, the excision repair system was very slow response. Those results showed that UV-resistance of rice was originated high ability of repair systems and the ability of repair in rice is useful as one of the estimation of productivity.DNA damage, abilities of photoreactivation and excision repair at the 1-2 leaves, 3-4 leaves, and 5-6 leaves stage of rice were searches with measurement of their CPD.Their results showed that stages of 1-2 and 3-4 leaves stage of the rice were very similar ability, although DNA damage and their abilities of repair in rice of 5-6 leaves stage was diminish of about 20%. The reason was thought that UV-B reaching to nucleus in the cell was reduced, as rice at this stage contained many chloroplasts and became to be thick and rigid. It is necessary to search the ability against UV-B in rices cultivated in Japan.