Deg2蛋白酶在拟南芥光损伤D1降解及光保护中的作用

己有研究表明叶绿体内有200种蛋白酶，然而，多数蛋白酶的作用机制尚不清楚，尤其哪些蛋白酶参与了D1蛋白周转。其中Deg2蛋白酶体外实验证明，其参与了光损伤D1蛋白的的初步剪切。为了进一步研究Deg2蛋白酶在植物体内的作用机制，我们筛选了拟南芥De醇蛋白酶功能缺陷型突变体。在120μmol·m-2：·S^-1光照生长条件下，出萨突变体与野生型的生长曲线基本一致；在进一步的高光胁迫（1800μmol·m-2·S^-1）处理及相同的光胁迫处理条件下，无论林可霉素存在与否，突变体PSⅡ的最大光化学效率（Fv／Fm）都和野生型没有区别；利用蛋白免疫印迹实验同样证明了光损伤D1蛋白的降解速度在cfe霞突变体和野生型之间也没有明显区别。我们认为Deg2蛋白酶在光抑制情况下对于光损伤D1蛋白的降解以及PsⅡ的修复不是必需的。

Functional Analysis of Photodamaged D1 Protein Degradation and Photoprotection of Chloroplast Deg2 Protease in Arabidopsis

More than 200 proteases in chloroplasts have been reported. However, their possible mechanisms remained largely unknown, especially the proteases involved in the degradation of photodamaged D 1 protein. Deg2 protease has been proved that it performed the primary cleavage of the photodamaged D1 protein in vitro and located at the stromal side of the chloroplast thylakoid membrane. To further investigate the function of Deg2 in vivo, deg2 mutant of Arabidopsis was isolated, which was lacking the expression of Deg2 protease. Under normal il- lumination conditions （120 μmol·m-2：·S-1）, the phenotype of the deg2 mutant was similar to wild-type plants. During the high light treatment （1 800 μmol·m-2：·S-1）, either in the absence or presence of lincomycin, the maximum photochemical efficiency of PS Ⅱ （Fv/Fm） in deg2 mutant was also similar to that in wild-type. Further western blot analysis showed that the degradation rate of the photodamaged D1 protein in deg2 mutants was also equivalent to that of in wild-type. In conclusion, our results suggested that Deg2 protease was not necessary for D1 degradation and photoprotection ofphotosystem Ⅱfrom photoinhibition.