【作者】 陈华；

【导师】 张承烈； 张立新；

【作者基本信息】 兰州大学 ， 植物学， 2006， 博士

【摘要】 光系统Ⅱ复合体是一个镶嵌在叶绿体类囊体膜中的多亚基的色素-蛋白膜脂复合物，其特殊之处在于能够催化水的裂解并释放氧气，从而维持整个地球大气层中的氧气含量的稳定。PSⅡ复合物包含25个以上不同亚基，结合大约250个左右的色素分子，其中约有至少18个是小分子量蛋白亚基。这类小分子量蛋白多数只含有一个跨膜α-螺旋，并且序列保守性较高。自1986年由Ljungberg等首次从PSⅡ中分离出小分子量蛋白PsbTn(5kDa)，这类分子在PSⅡ复合物中的定位和功能立即引起了广泛的关注。由于这些分子很难分离和分辨，对这类小分子蛋白功能的研究多都得益于对其相应缺失突变体的研究。综合目前研究结果推测，这类小分子蛋白对于PSⅡ复合体的生物发生、结构和的功能调节等具有重要作用。 Psb27是一个新近发现的与PSⅡ结合的类囊体囊腔蛋白。为了深入了解Psb27的功能，我们分离出一个T-DNA插入诱变的psb27基因功能缺失的Arabidopsis突变体。我们的研究结果表明，在正常生长条件下，突变体psb27中类囊体膜上光合作用相关的几种复合体的组装和累积都与野生型相似，尤其是突变体中PSⅡ复合体的结构和数量与野生型的差异不大。Northern blotting结果表明psb27基因对于叶绿体基因编码的光合基因的转录也无影响。而在室温叶绿素测定中发现突变体psb27的PSⅡ的原初光化学效率低于野生型，并且77K荧光测定表明突变体中两个光系统之间的能量分配发生了变化。进一步的快速叶绿素荧光诱导和衰减动力学分析结果显示，突变体psb27中电子传递链保持正常。PEA曲线测定发现，突变体psb27中PSⅡ异质性(PSⅡα和PSⅡβ)比例同野生型相比发生了改变。为了深入了解Psb27在PSⅡ复合体中的功能，我们对突变体psb27进行强光处理，发现突变体中PSⅡ的活性下降和PSⅡ反应中心D1蛋白的降解的速率都显著的快于野生型。但当用叶绿体蛋白合成抑制剂(林可霉素)处理后，突变体叶片中PSⅡ失活及D1蛋白降解的速率呈现出同野生型相似的趋势。其后，我们对经光抑制处理的叶片进行光恢复测定，发现突变体叶片中PSⅡ活性恢复速率明显慢于野生型叶片，这些研究表明Psb27在光破坏PSⅡ修复过程起着重要的作用。 综合所有的实验结果，我们推测Arabidopsis中Psb27对PSⅡ复合体的生物发生和电子传递链没有影响，但在高光条件下，它参与了PSⅡ修复循环过程。更多还原

【Abstract】 The photosystem II (PSII) complex is located in the thylakoid membrane of higher plants, algae and cyanobacteria and drives the water oxidation process of photosynthesis, which splits water into reducing equivalents and molecular oxygen by solar energy. The by-product of photosynthesis, oxygen, has enabled life to move from the oceans to land. The PSII supracomplex consists of more than 25 different protein subunits, binding about 250 Chl, however, among which there are at least 18 low molecular mass (<10 kDa)subunits. The location and function in higher plants within PSII, still remains to be resolved.Psb27 is a newly identified lumen protein associated with PSII. Predictions of the secondary structure of the Psb27 show that the mature protein does not have any transmembrane helix. To gain insight into the function of Psb27, we isolated a mutant Arabidopsis plant with a loss of psb27 function. The quantity of PSII complexes and electron transfer within PSII remain largely unaffected in the psb27 mutant. Our results also showed that under high light illumination,PSII activity and the contents of the PSII reaction center Dl protein decreased more significantly in the psb27 mutant than in wild-type(WT)plant. Treatment of leaves with a chloroplast protein synthesis inhibitor resulted in similar light-induced PSII inactivation levels and Dl protein degradation rates in the WT and psb27 knockout plants. Recovery of PSII activity after photoinhibition was delayed in the psb27 mutant, suggesting that Psb27 is required for efficient recovery of the photodamaged PSII complex.Overall, these results demonstrated that the Psb27 protein in Arabidopsis is not essential for oxygenic photosynthesis and PSII formation. Instead, our results provide evidence for the involvement of this lumen protein in the recovery process of PSII.更多还原