Baena-González Elena, Allahverdiyeva Yagut, Svab Zora, Maliga Pal, Josse Eve-Marie, Kuntz Marcel, Mäenpää Pirkko, Aro Eva-Mari
Department of Biology, Plant Physiology and Molecular Biology, University of Turku, FIN-20014 Turku, Finland.
Plant J. 2003 Sep;35(6):704-16. doi: 10.1046/j.1365-313x.2003.01842.x.
We have constructed a tobacco psbA gene deletion mutant that is devoid of photosystem II (PSII) complex. Analysis of thylakoid membranes revealed comparable amounts, on a chlorophyll basis, of photosystem I (PSI), the cytochrome b6f complex and the PSII light-harvesting complex (LHCII) antenna proteins in wild-type (WT) and DeltapsbA leaves. Lack of PSII in the mutant, however, resulted in over 10-fold higher relative amounts of the thylakoid-associated plastid terminal oxidase (PTOX) and the NAD(P)H dehydrogenase (NDH) complex. Increased amounts of Ndh polypeptides were accompanied with a more than fourfold enhancement of NDH activity in the mutant thylakoids, as revealed by in-gel NADH dehydrogenase measurements. NADH also had a specific stimulating effect on P700+ re-reduction in the DeltapsbA thylakoids. Altogether, our results suggest that enhancement of electron flow via the NDH complex and possibly other alternative electron transport routes partly compensates for the loss of PSII function in the DeltapsbA mutant. As mRNA levels were comparable in WT and DeltapsbA plants, upregulation of the alternative electron transport pathways (NDH complex and PTOX) occurs apparently by translational or post-translational mechanisms.
我们构建了一个缺乏光系统II（PSII）复合物的烟草psbA基因缺失突变体。类囊体膜分析显示，以叶绿素为基础，野生型（WT）和DeltapsbA叶片中的光系统I（PSI）、细胞色素b6f复合物和PSII捕光复合物（LHCII）天线蛋白含量相当。然而，突变体中PSII的缺失导致类囊体相关的质体末端氧化酶（PTOX）和NAD（P）H脱氢酶（NDH）复合物的相对含量高出10倍以上。如凝胶内NADH脱氢酶测量所示，突变体类囊体中Ndh多肽含量的增加伴随着NDH活性超过四倍的增强。NADH对DeltapsbA类囊体中P700 +的再还原也有特异性刺激作用。总之，我们的结果表明，通过NDH复合物和可能的其他替代电子传递途径增强电子流，部分补偿了DeltapsbA突变体中PSII功能的丧失。由于WT和DeltapsbA植物中的mRNA水平相当，替代电子传递途径（NDH复合物和PTOX）的上调显然是通过翻译或翻译后机制发生的。
