Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, Yunnan, China.
Department of Biochemistry, Molecular Plant Biology, University of Turku, 20014, Turku, Finland.
Photosynth Res. 2018 Jul;137(1):129-140. doi: 10.1007/s11120-018-0484-1. Epub 2018 Jan 22.
We studied how high light causes photoinhibition of photosystem I (PSI) in the shade-demanding fern Nephrolepis falciformis, in an attempt to understand the mechanism of PSI photoinhibition under natural field conditions. Intact leaves were treated with constant high light and fluctuating light. Detached leaves were treated with constant high light in the presence and absence of methyl viologen (MV). Chlorophyll fluorescence and P700 signal were determined to estimate photoinhibition. PSI was highly oxidized under high light before treatments. N. falciformis showed significantly stronger photoinhibition of PSI and PSII under constant high light than fluctuating light. These results suggest that high levels of P700 oxidation ratio cannot prevent PSI photoinhibition under high light in N. falciformis. Furthermore, photoinhibition of PSI in N. falciformis was largely accelerated in the presence of MV that promotes the production of superoxide anion radicals in the chloroplast stroma by accepting electrons from PSI. From these results, we propose that photoinhibition of PSI in N. falciformis is mainly caused by superoxide radicals generated in the chloroplast stroma, which is different from the mechanism of PSI photoinhibition in Arabidopsis thaliana and spinach. Here, we provide some new insights into the PSI photoinhibition under natural field conditions.
我们研究了高光如何导致阴生蕨类植物肾蕨 PSI 的光抑制，试图了解在自然田间条件下 PSI 光抑制的机制。我们用恒定高光和波动光处理完整叶片，用恒定高光在有和没有甲紫精（MV）的情况下处理离体叶片。通过测定叶绿素荧光和 P700 信号来估计光抑制。在处理前，PSI 在高光下高度氧化。与波动光相比，肾蕨在恒定高光下 PSI 和 PSII 的光抑制明显更强。这些结果表明，在高光下，高水平的 P700 氧化还原比不能防止 PSI 光抑制。此外，MV 的存在大大加速了 PSI 在肾蕨中的光抑制，MV 通过接受来自 PSI 的电子，促进叶绿体基质中超氧阴离子自由基的产生。根据这些结果，我们提出 PSI 在肾蕨中的光抑制主要是由叶绿体基质中产生的超氧自由基引起的，这与拟南芥和菠菜中 PSI 光抑制的机制不同。在这里，我们为自然田间条件下的 PSI 光抑制提供了一些新的见解。
