Restricted capacity for PSI-dependent cyclic electron flow in 螖petE mutant compromises the ability for acclimation to iron stress in Synechococcus sp. PCC 7942 cells

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• 作者：A.G. Ivanov^a ; ^b ; P.V. Sane^c ; I. Simidjiev^b ; Y.-I. Park^d ; N.P.A. Huner^a ; ^{nhuner@uwo.ca} ; G. Ö ; quist^b
• 关键词：AC ; actinic light ; Chl ; chlorophyll ; DCMU ; 3-(3 ; 4-dichlorophenyl)-1 ; 1-dimethylurea ; DBMIB ; 2 ; 5-dibromo-3-methyl-6-isopropyl-p-benzoquinone ; MOPS ; 3-(N-morpholino) propane sulfonic acid ; P700 ; reaction center pigment of PSI ; P700+ ; oxidized form of the rea
• 刊名：Biochimica et Biophysica Acta (BBA)/Bioenergetics
• 出版年：2012
• 期刊代码：13_00052728
• 类别：bio
• 出版时间：August, 2012
• 卷：1817
• 期：8
• 页码：1277-1284
• 文件大小：745 K

摘要

Exposure of wild type (WT) and plastocyanin coding petE gene deficient mutant (螖petE) of Synechococcus cells to low iron growth conditions was accompanied by similar iron-stress induced blue-shift of the main red Chl a absorption peak and a gradual decrease of the Phc/Chl ratio, although 螖petE mutant was more sensitive when exposed to iron deficient conditions. Despite comparable iron stress induced phenotypic changes, the inactivation of petE gene expression was accompanied with a significant reduction of the growth rates compared to WT cells. To examine the photosynthetic electron fluxes in vivo, far-red light induced P700 redox state transients at 820 nm of WT and 螖petE mutant cells grown under iron sufficient and iron deficient conditions were compared. The extent of the absorbance change (螖A₈₂₀/A₈₂₀) used for quantitative estimation of photooxidizable P700⁺ indicated a 2-fold lower level of P700⁺ in 螖petE compared to WT cells under control conditions. This was accompanied by a 2-fold slower re-reduction rate of P700⁺ in the 螖petE indicating a lower capacity for cyclic electron flow around PSI in the cells lacking plastocyanin. Thermoluminescence (TL) measurements did not reveal significant differences in PSII photochemistry between control WT and 螖petE cells. However, exposure to iron stress induced a 4.5 times lower level of P700⁺, 2-fold faster re-reduction rate of P700⁺ and a temperature shift of the TL peak corresponding to S₂/S₃Q_B^{鈭?/sup> charge recombination in WT cells. In contrast, the iron-stressed 螖petE mutant exhibited only a 40%decrease of P700+ and no significant temperature shift in S₂/S₃Q_B鈭?/sup> charge recombination. The role of mobile electron carriers in modulating the photosynthetic electron fluxes and physiological acclimation of cyanobacteria to low iron conditions is discussed. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.}