Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Cells. 2022 Sep 5;11(17):2768. doi: 10.3390/cells11172768.
In photosynthetic organisms except angiosperms, an alternative electron sink that is mediated by flavodiiron proteins (FLVs) plays the major role in preventing PSI photoinhibition while cyclic electron flow (CEF) is also essential for normal growth under fluctuating light. However, the dynamic changes of FLVs and CEF has not yet been well clarified. In this study, we measured the P700 signal, chlorophyll fluorescence, and electrochromic shift spectra in the fern and the gymnosperm . We found that both species could not build up a sufficient proton gradient (∆pH) within the first 30 s after light abruptly increased. During this period, FLVs-dependent alternative electron flow was functional to avoid PSI over-reduction. This functional time of FLVs was much longer than previously thought. By comparison, CEF was highly activated within the first 10 s after transition from low to high light, which favored energy balancing rather than the regulation of a PSI redox state. When FLVs were inactivated during steady-state photosynthesis, CEF was re-activated to favor photoprotection and to sustain photosynthesis. These results provide new insight into how FLVs and CEF interact to regulate photosynthesis in non-angiosperms.
在除被子植物以外的光合生物中，由黄素蛋白（FLVs）介导的替代电子汇在防止 PSI 光抑制方面起着主要作用，而循环电子流（CEF）对于在波动光下的正常生长也是必不可少的。然而，FLVs 和 CEF 的动态变化尚未得到很好的阐明。在这项研究中，我们测量了蕨类植物和裸子植物中的 P700 信号、叶绿素荧光和电致变色位移光谱。我们发现，这两个物种在光突然增加后的最初 30 秒内都无法建立足够的质子梯度（∆pH）。在此期间，依赖于 FLVs 的替代电子流是有效的，可以避免 PSI 过度还原。FLVs 的这种功能时间比之前认为的要长得多。相比之下，在从低光到高光的过渡后的最初 10 秒内，CEF 就被高度激活，这有利于能量平衡而不是 PSI 氧化还原状态的调节。当 FLVs 在稳态光合作用期间失活时，CEF 被重新激活，以有利于光保护和维持光合作用。这些结果为 FLVs 和 CEF 如何相互作用来调节非被子植物中的光合作用提供了新的见解。
