Restricted capacity for PSI-dependent cyclic electron flow in ΔpetE mutant compromises the ability for acclimation to iron stress in Synechococcus sp PCC 7942 cells
Restricted capacity for PSI-dependent cyclic electron flow in ΔpetE mutant compromises the ability for acclimation to iron stress in Synechococcus sp PCC 7942 cells
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DOI：
10.1016/j.bbabio.2012.03.014
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发表时间：
2012-08-01
影响因子：
4.3
通讯作者：
Oquist, G.
中科院分区：
文献类型：
--
作者：
Ivanov, A. G.;Sane, P. V.;Oquist, G.
聚球藻野生型（WT）和质体蓝素编码petE基因缺陷突变体（Delta petE）暴露于低铁生长条件下，都伴随着类似的铁胁迫诱导的主要红叶绿素a吸收峰蓝移和Phc/Chl比值逐渐降低，尽管Delta petE突变体在暴露于缺铁条件下时更敏感。尽管铁应激诱导的表型变化相当，但与WT细胞相比，petE基因表达的失活伴随着生长速率的显著降低。为了检查体内光合电子通量，比较了在铁充足和铁缺乏条件下生长的WT和Delta petE突变体细胞在820 nm处的远红光诱导的P700氧化还原状态瞬变。用于定量估计光氧化P700（+）的吸光度变化程度（Delta A（820）/A（820））表明，在对照条件下，Delta petE中的P700（+）水平比WT细胞低2倍。这伴随着Δ petE中P700（+）的2倍慢的再还原速率，表明在缺乏质体蓝素的细胞中PSI周围的循环电子流的能力较低。热释光（TL）的测量没有发现显着差异，PSII光化学之间的控制WT和Delta petE细胞。然而，暴露于铁胁迫诱导WT细胞中P700（+）的水平降低4.5倍，P700（+）的再还原速率加快2倍，并且TL峰的温度偏移对应于S-2/S（3）Q（B）（-）电荷重组。相比之下，铁应激的Delta petE突变体仅表现出P700（+）降低40%，并且S-2/S（3）Q（B）（-）电荷重组没有显着的温度变化。讨论了移动的电子载体在调节光合电子通量和蓝藻对低铁环境的生理适应中的作用。这篇文章是特刊的一部分，题为：光合作用研究的可持续性：从自然到人工。(C)2012爱思唯尔有限公司版权所有。
Exposure of wild type (WT) and plastocyanin coding petE gene deficient mutant (Delta 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 Delta 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 Delta petE mutant cells grown under iron sufficient and iron deficient conditions were compared. The extent of the absorbance change (Delta A(820)/A(820)) used for quantitative estimation of photooxidizable P700(+) indicated a 2-fold lower level of P700(+) in Delta petE compared to WT cells under control conditions. This was accompanied by a 2-fold slower re-reduction rate of P700(+) in the Delta 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 Delta 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 S-2/S(3)Q(B)(-) charge recombination in WT cells. In contrast, the iron-stressed Delta petE mutant exhibited only a 40% decrease of P700(+) and no significant temperature shift in S-2/S(3)Q(B)(-) 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. (C) 2012 Elsevier B.V. All rights reserved.