Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Synthetic Biology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China.
Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Synthetic Biology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China
Appl Environ Microbiol. 2018 Aug 31;84(18). doi: 10.1128/AEM.01222-18. Print 2018 Sep 15.
In response to a broad range of habitats and environmental stresses, cyanobacteria have evolved various effective acclimation strategies, which will be helpful for improving the stress tolerances of photosynthetic organisms, including higher plants. UTEX 2973 and PCC 7942 possess genomes that are 99.8% identical but exhibit significant differences in cell growth and stress tolerance. In this study, we found that a single amino acid substitution at FF ATP synthase subunit α (AtpA), C252Y, is the primary contributor to the improved stress tolerance of UTEX 2973. Site-saturation mutagenesis experiments showed that point mutations of cysteine 252 to any of the four conjugated amino acids could significantly improve the stress tolerance of PCC 7942. We further confirmed that the C252Y mutation increases AtpA protein levels, intracellular ATP synthase activity, intracellular ATP abundance, transcription of genes (especially ), photosystem II activity, and glycogen accumulation in PCC 7942. This work highlights the importance of AtpA in improving the stress tolerance of cyanobacteria and provides insight into how cyanobacteria evolve via point mutations in the face of environmental selection pressures. Two closely related strains showed significantly different tolerances to high light and high temperature but limited genomic differences, providing us opportunities to identify key genes responsible for stress acclimation by a gene complementation approach. In this study, we confirmed that a single point mutation in the α subunit of FF ATP synthase (AtpA) contributes mainly to the improved stress tolerance of UTEX 2973. The point mutation of AtpA, the important ATP-generating complex of photosynthesis, increases AtpA protein levels, intracellular ATP synthase activity, and ATP concentrations under heat stress, as well as photosystem II activity. This work proves the importance of ATP synthase in cyanobacterial stress acclimation and provides a good target for future improvement of cyanobacterial stress tolerance by metabolic engineering.
为了应对广泛的栖息地和环境压力，蓝藻进化出了各种有效的适应策略，这将有助于提高光合生物（包括高等植物）的胁迫耐受能力。UTEX 2973 和 PCC 7942 拥有 99.8%相同的基因组，但在细胞生长和胁迫耐受方面表现出显著差异。在这项研究中，我们发现 FF ATP 合酶亚基α（AtpA）中的一个单一氨基酸取代，C252Y，是 UTEX 2973 提高胁迫耐受能力的主要原因。定点饱和突变实验表明，将半胱氨酸 252 突变为任何四个共轭氨基酸都可以显著提高 PCC 7942 的胁迫耐受能力。我们进一步证实，C252Y 突变增加了 AtpA 蛋白水平、细胞内 ATP 合酶活性、细胞内 ATP 丰度、基因（特别是 ）转录、光系统 II 活性和糖原积累。这项工作强调了 AtpA 在提高蓝藻胁迫耐受能力方面的重要性，并为了解蓝藻如何通过点突变在面对环境选择压力时进化提供了思路。两个密切相关的 菌株对高光和高温的耐受能力有显著差异，但基因组差异有限，这为我们提供了通过基因互补方法识别负责应激适应的关键基因的机会。在这项研究中，我们证实了 FF ATP 合酶（AtpA）α亚基的一个单点突变主要导致 UTEX 2973 胁迫耐受能力的提高。光合作用中重要的 ATP 产生复合物 AtpA 的点突变增加了热胁迫下 AtpA 蛋白水平、细胞内 ATP 合酶活性和 ATP 浓度以及光系统 II 活性。这项工作证明了 ATP 合酶在蓝藻应激适应中的重要性，并为通过代谢工程提高蓝藻应激耐受能力提供了一个很好的目标。
