Abstract Cyanobacterial type I NADH dehydrogenase (NDH-1) is involved in various bioenergetic reactions including respiration, cyclic electron transport (CET), and CO2 uptake. The role of NDH-1 is usually minor under normal growth conditions and becomes important under stress conditions. However, in our previous study, flux balance analysis (FBA) simulation predicted that the drive of NDH-1 as CET pathway with a photosystem (PS) I/PSII excitation ratio around 1.0 contributes to achieving an optimal specific growth rate. In this study, to experimentally elucidate the predicted functions of NDH-1, first, we measured the PSI/PSII excitation ratios of Synechocystis sp. PCC 6803 grown under four types of spectral light conditions. The specific growth rate was the highest and PSI/PSII excitation ratio was with 0.88 under the single-peak light at 630 nm (Red1). Considering this measured excitation ratios, FBA simulation predicted that NDH-1-dependent electron transport was the major pathway under Red1. Moreover, in actual culture, an NDH-1 deletion strain had slower growth rate than that of wild type only under Red1 light condition. Therefore, we experimentally demonstrated that NDH-1 plays an important role under optimal light conditions such as Red1 light, where Synechocystis exhibits the highest specific growth rate and PSI/PSII excitation ratio of around 1.0.

中文翻译：

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I型NADH脱氢酶在集胞藻中的作用。藻胆体激发红光下的PCC 6803

摘要 蓝藻 I 型 NADH 脱氢酶 (NDH-1) 参与各种生物能反应，包括呼吸、循环电子传递 (CET) 和 CO2 吸收。NDH-1 的作用在正常生长条件下通常是次要的，而在压力条件下变得重要。然而，在我们之前的研究中，通量平衡分析 (FBA) 模拟预测 NDH-1 作为 CET 途径的驱动，光系统 (PS) I/PSII 激发比约为 1.0，有助于实现最佳比生长速率。在这项研究中，为了通过实验阐明 NDH-1 的预测功能，首先，我们测量了集胞藻的 PSI/PSII 激发比。PCC 6803 在四种光谱光条件下生长。比生长率最高，PSI/PSII激发比为0。88 在 630 nm (Red1) 的单峰光下。考虑到这种测量的激发比，FBA 模拟预测 NDH-1 依赖性电子传输是 Red1 下的主要途径。此外，在实际培养中，仅在 Red1 光照条件下，NDH-1 缺失菌株的生长速度比野生型慢。因此，我们通过实验证明 NDH-1 在最佳光照条件下发挥重要作用，例如 Red1 光，其中集胞藻表现出最高的比生长速率和约 1.0 的 PSI/PSII 激发比。