School of Life Sciences, and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, 430079, Hubei, People's Republic of China.
School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, 2006, Australia.
Planta. 2017 Nov;246(5):927-938. doi: 10.1007/s00425-017-2738-0. Epub 2017 Jul 14.
The sulfur-formation ( suf ) genes play important roles in both photosynthesis and respiration of cyanobacteria, but the organism prioritizes Fe-S clusters for respiration at the expense of photosynthesis. Iron-sulfur (Fe-S) clusters are important to all living organisms, but their assembly mechanism is poorly understood in photosynthetic organisms. Unlike non-photosynthetic bacteria that rely on the iron-sulfur cluster system, Synechocystis sp. PCC 6803 uses the Sulfur-Formation (SUF) system as its major Fe-S cluster assembly pathway. The co-expression of suf genes and the direct interactions among SUF subunits indicate that Fe-S assembly is a complex process in which no suf genes can be knocked out completely. In this study, we developed a condition-controlled SUF Knockdown mutant by inserting the petE promoter, which is regulated by Cu concentration, in front of the suf operon. Limited amount of the SUF system resulted in decreased chlorophyll contents and photosystem activities, and a lower PSI/PSII ratio. Unexpectedly, increased cyclic electron transport and a decreased dark respiration rate were only observed under photoautotrophic growth conditions. No visible effects on the phenotype of SUF Knockdown mutant were observed under heterotrophic culture conditions. The phylogenetic distribution of the SUF system indicates that it has a co-evolutionary relationship with photosynthetic energy storing pathways.
硫形成（suf）基因在蓝藻的光合作用和呼吸作用中都起着重要作用，但该生物优先将铁硫簇用于呼吸作用，而牺牲光合作用。铁硫（Fe-S）簇对所有生物体都很重要，但它们的组装机制在光合生物中还了解甚少。与依赖铁硫簇系统的非光合细菌不同，集胞藻 PCC 6803 使用硫形成（SUF）系统作为其主要的 Fe-S 簇组装途径。suf 基因的共表达和 SUF 亚基之间的直接相互作用表明，Fe-S 组装是一个复杂的过程，其中没有 suf 基因可以完全敲除。在这项研究中，我们通过在 suf 操纵子前面插入受铜浓度调节的 petE 启动子，开发了一种条件控制的 SUF 敲低突变体。SUF 系统的有限数量导致叶绿素含量和光系统活性降低，PSI/PSII 比值降低。出乎意料的是，仅在光自养生长条件下才观察到循环电子传递增加和暗呼吸速率降低。在异养培养条件下，SUF 敲低突变体的表型没有明显变化。SUF 系统的系统发育分布表明，它与光合作用储能途径具有共同进化关系。
