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激光对增强的UV—B辐射蚕豆幼苗损伤的防护及修复作用
【作者】 齐智；
【导师】 王勋陵；
【作者基本信息】 西北大学 ， 植物学， 2001， 博士
【摘要】 增强的UV-B辐射（280-320nm）不仅使蚕豆丙二醛（MDA）和电解质渗透率（REL）升高，而且使植物DNA链上相邻的2个胸腺嘧啶之间形成胸腺嘧啶二聚体（CPD），因此增强的UV-B辐射可导致植物伤害。本文用激光来处理UV-B辐射导致伤害的植物，结果表明：激光对增强的UV-B辐射植物伤害有明显的防护和修复作用。 进一步研究发现，激光对植物的防护作用的机理是通过提高紫外吸收物的含量来加强植物第一条防线的屏蔽作用；激光辐射提高抗氧化酶SOD、CAT和APX的酶活性和抗氧化系统非酶类物质ASA和GSH的含量来增强植物防御UV-B辐射的第二条防线的防护能力；激光同时提高植物蛋白质的含量和促进某些“胁迫蛋白”的基因表达以防护增强的UV-B辐射对植物的伤害，本文认为这种防护方式叫植物第三条防线。 激光对植物的修复作用主要体现在植物DNA上。一方面，激光辐射可提高光修复酶的活性，从而加速植物DNA伤害的修复过程。另一方面，本文用T4核酸内切酶V（T4EndoV）为探针，通过琼脂糖凝胶电泳检测发现，增强的UV-B辐射导致植物DNA伤害，使DNA链上相邻的2个胸腺嘧啶形成大量的CPD；用激光处理这种植物DNA伤害时，CPD显著下降到对照水平（末受UV-B处理植物），但同样用红光（与He-Ne激光同波长，633nm）处理，CPD无任何变化。由此可见，激光对植物DNA的伤害有明显修复作用。探讨激光修复的机理发现了激光修复是一种新的修复方式：激光断键修复。激光辐射可以打断植物DNA链上的CPD之间的CC键（即二聚体单体化），从而使DNA恢复到正常水平，使DNA复制，转录等生理活动能够继续正常地进行。 激光对植物的防护效果非常明显，为今后激光在农业生产上的应用奠定了理论根据。同时，本文首次发现了DNA修复的一种新的方式——激光断键修复。这为人们今后探索DNA伤害修复开辟了一个新的领域和新的视角。
【Abstract】 An increase of the concentration of MDA and rate of electrolyte leakage of cellular membrane in broad bean (Vicia faba L.) plant was induced by exposure to enhanced UV-B irradiation. Moreover, UV-B irradiation caused DNA damage to yield CPD (dimer) between two adjacent thymines in plant DNA. As a result, the plants were damaged by increased UV-B radiation. However, laser was found to be capable to protect and repair plants from UV- B-induced damage. In research for laser role of protecting plants from UV-B irradiation, it was shown that primary response to UV-B radiation damage in plant was to increase the UV absorbing compounds. Laser irradiation increased the UV absorbing compounds in order to protect plants from UV-B radiation. Thus, an increase of content of UV absorbing compound by laser irradiation was strengthened primary response to UV-B radiation damage. The secondary responses to UV-B radiation in plant were participated in ASA, GSH and antioxidative enzymes SOD, CAT and APX. If UV-B treatment on plants following laser radiation, laser irradiation could build-up the content of ASA and GSH, and increase the activities of SOD, CAT and APX to protect plants from enhanced UV-B radiation. Meanwhile, laser irradiation improved the content of soluble protein and stimulated expression of some genes of 搕hreatening proteins? which was called “the third responses to increased UV-B radiation in plant employing laser treatment on UV-B-induced damage”in this paper. These proteins could help plants to strengthen protecting from UV-B irradiation. Laser repair role on UV-B-induced plant damage mainly appeared plant DNA repair role. On the one hand, laser irradiation was capable to increase the activity of photolyase and thus shortened the recovery time of DNA damage. On the other hand, this paper employed T4EndoV as a symbol to test the quantitation of CPD. The results were shown that increased UV-B radiation caused plant DNA damage and yielded a lot of CPD5. However, if using laser treatment on UV-B-induced plant damage, we found that the quantitation of CPDs quickly decreased the normal level (without UV-B irradiation plant). Meanwhile, red light radiation had no effect on decreasing CPDs level. Thus, laser had obviously repair effect on UV-B-induced-damage in plant DNA strains. In further research for laser repair mechanism, it was found that laser repair was a new pathway-laser repair of breaking bonds. Laser irradiation could break CC bonds in CPD and thus made CPD monomer. As a result, plant DNA damage was repair and plant DNA transcription and expression became normal. Laser protection of plant from UV-B radiation damage was obvious and would be employed in agriculture in future. Furthermore, this paper was found a new plant repair pathway-laser repair of breaking bonds in CPD, whichwould pioneer a new field of researching for DNA damage and repair.