Thylakoid Terminal Oxidases Are Essential for the Cyanobacterium Synechocystis sp PCC 6803 to Survive Rapidly Changing Light Intensities1[C][W][OA]
Thylakoid Terminal Oxidases Are Essential for the Cyanobacterium Synechocystis sp PCC 6803 to Survive Rapidly Changing Light Intensities1[C][W][OA]
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DOI：
10.1104/pp.112.210260
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发表时间：
2013-05-01
期刊：
影响因子：
7.4
通讯作者：
Howe, Christopher J.
中科院分区：
文献类型：
--
作者：
Lea-Smith, David J.;Ross, Nic;Howe, Christopher J.
蓝藻在类囊体膜上进行光合作用和呼吸作用，这表明这两个过程是相互关联的。然而，在自然环境条件下的呼吸电子传递链的作用还没有建立。通过靶向基因破坏，集胞藻PCC 6803的突变体，产生缺乏组合的三个终端氧化酶：类囊体膜定位的细胞色素c氧化酶（考克斯）和醌醇氧化酶（Cyd）和细胞质膜定位的替代呼吸终端氧化酶。所有菌株表现出类似的增长下连续中度或高光或12小时中度光/暗方波周期。然而，在12小时的高光/暗方波周期，考克斯/Cyd突变体显示受损的增长和完全光漂白后约2天。相比之下，使用正弦光/暗周期来模拟自然昼夜条件导致光漂白很少，虽然增长较慢。在高光/暗方波周期下，与野生型相比，考克斯/Cyd突变体在黑暗期间光合效率显著降低，氧化应激水平更高，糖原降解减少。该突变体在脉冲光下对光抑制敏感，但在恒定光下对光抑制敏感。这些研究结果证实了类囊体定位的终端氧化酶在有效的暗呼吸，减少氧化应激，和突然的光变化的住宿的作用，表现出强大的选择性压力，以保持连接的光合作用和呼吸电子链内类囊体膜。据我们所知，这项研究是第一个报告终端氧化酶突变体和野生型细胞之间的生长表型差异，并强调需要在一系列条件下检查突变表型。
Cyanobacteria perform photosynthesis and respiration in the thylakoid membrane, suggesting that the two processes are interlinked. However, the role of the respiratory electron transfer chain under natural environmental conditions has not been established. Through targeted gene disruption, mutants of Synechocystis sp. PCC 6803 were generated that lacked combinations of the three terminal oxidases: the thylakoid membrane-localized cytochrome c oxidase (COX) and quinol oxidase (Cyd) and the cytoplasmic membrane-localized alternative respiratory terminal oxidase. All strains demonstrated similar growth under continuous moderate or high light or 12-h moderate-light/dark square-wave cycles. However, under 12-h high-light/dark square-wave cycles, the COX/Cyd mutant displayed impaired growth and was completely photobleached after approximately 2 d. In contrast, use of sinusoidal light/dark cycles to simulate natural diurnal conditions resulted in little photobleaching, although growth was slower. Under high-light/dark square-wave cycles, the COX/Cyd mutant suffered a significant loss of photosynthetic efficiency during dark periods, a greater level of oxidative stress, and reduced glycogen degradation compared with the wild type. The mutant was susceptible to photoinhibition under pulsing but not constant light. These findings confirm a role for thylakoid-localized terminal oxidases in efficient dark respiration, reduction of oxidative stress, and accommodation of sudden light changes, demonstrating the strong selective pressure to maintain linked photosynthetic and respiratory electron chains within the thylakoid membrane. To our knowledge, this study is the first to report a phenotypic difference in growth between terminal oxidase mutants and wild-type cells and highlights the need to examine mutant phenotypes under a range of conditions.