Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, Nada, Kobe 657-8501, Japan.
Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, Nada, Kobe 657-8501, Japan
Plant Physiol. 2019 Apr;179(4):1479-1485. doi: 10.1104/pp.18.01493. Epub 2019 Jan 22.
PSI has the potential to generate reactive oxygen species and be oxidatively inactivated by the reactive oxygen species. The photo-oxidative damage of PSI (also called PSI photoinhibition) causes the inhibition of the plant growth and is a lethal event for plants. It has been reported that PSI photoinhibition does not occur as long as the reaction-center chlorophyll (P700) remains oxidized, even in excess light conditions. This process is termed P700 oxidation and is supported by various regulatory mechanisms and likely also by the stoichiometric quantities of photosynthetic apparatus. In this study, we assessed how decreased photochemically active PSI in Arabidopsis () affected a variety of photosynthetic parameters, including P700 oxidation. Inactivation of PSI was rapidly and selectively induced by repetitive short-pulse illumination. PSI photoinhibition correlated linearly with decreases in effective quantum yield of PSII and nonphotochemical quenching; however, the photosynthetic CO assimilation rate was less affected, as exemplified by ∼50% of the normal CO assimilation rate maintained with an 80% loss in PSI photochemical activity. In contrast, effective quantum yield of PSI was enhanced following PSI photoinhibition, mainly owing to a decrease in the electron donor-side limitation of PSI. Based on these results, we propose that the stoichiometric quantity of PSI is optimized to induce P700 oxidation for dissipating excess light energy in PSI, thus avoiding inhibition of photosynthetic CO assimilation caused by PSI photoinhibition.
PSI 有可能产生活性氧物质，并被活性氧物质氧化失活。PSI 的光氧化损伤（也称为 PSI 光抑制）会抑制植物生长，对植物来说是致命的。据报道，只要反应中心叶绿素（P700）保持氧化状态，PSI 就不会发生光抑制，即使在强光条件下也是如此。这一过程被称为 P700 氧化，它由各种调节机制支持，可能还由光合作用装置的化学计量数量支持。在这项研究中，我们评估了拟南芥中减少的光化学活性 PSI 如何影响各种光合作用参数，包括 P700 氧化。PSI 光抑制是通过重复短脉冲照射快速和选择性诱导的。PSI 光抑制与 PSII 的有效量子产率和非光化学猝灭的降低呈线性相关；然而，光合作用 CO 同化率受影响较小，例如，PSI 光化学活性损失 80%时，仍保持约 50%的正常 CO 同化率。相比之下，PSI 光抑制后 PSI 的有效量子产率增加，主要是由于 PSI 电子供体侧限制的降低。基于这些结果，我们提出 PSI 的化学计量数量被优化为诱导 P700 氧化，以耗散 PSI 中的过量光能，从而避免 PSI 光抑制引起的光合作用 CO 同化抑制。
