Department of Chemistry & Biochemistry, Mount Allison University, Sackville, New Brunswick E4L 3M7, Canada.
Department of Chemistry & Biochemistry, Mount Allison University, Sackville, New Brunswick E4L 3M7, Canada.
Biochim Biophys Acta Bioenerg. 2017 Jun;1858(6):459-474. doi: 10.1016/j.bbabio.2017.03.003. Epub 2017 Mar 14.
Fast Repetition and Relaxation chlorophyll fluorescence induction is used to estimate the effective absorption cross section of PSII (σ), to analyze phytoplankton acclimation and electron transport. The fitting coefficient ρ measures excitation transfer from closed PSII to remaining open PSII upon illumination, which could theoretically generate a progressive increase in σ for the remaining open PSII. To investigate how ρ responds to illumination we grew marine phytoplankters with diverse antenna structures (Prochlorococcus, Synechococcus, Ostreococcus and Thalassiosira pseudonana) under limiting or saturating growth light. Initial ρ varied with growth light in Synechococcus and Thalassiosira. With increasing actinic illumination PSII closed progressively and ρ decreased for all four taxa, in a pattern explicable as an exponential decay of ρ with increasing distance between remaining open PSII reaction centers. This light-dependent down-regulation of ρ allows the four phytoplankters to limit the effect of increasing light upon σ. The four structurally distinct taxa showed, however, distinct rates of response of ρ to PSII closure, likely reflecting differences in the spacing or orientation among their PSII centers. Following saturating illumination recovery of ρ in darkness coincided directly with PSII re-opening in Prochlorococcus. Even after PSII had re-opened in Synechococcus a transition to State II slowed dark recovery of ρ. In Ostreococcus sustained NPQ slowed dark recovery of ρ. In Thalassiosira dark recovery of ρ was slowed, possibly by a light-induced change in PSII spacing. These patterns of ρ versus PSII closure are thus a convenient probe of comparative PSII spacings.
快速重复和弛豫叶绿素荧光诱导用于估计 PSII 的有效吸收截面（σ），以分析浮游植物的适应和电子传递。拟合系数 ρ 测量在光照下从关闭的 PSII 到剩余的开放 PSII 的激发转移，这在理论上可以为剩余的开放 PSII 产生 σ 的逐渐增加。为了研究 ρ 如何响应光照，我们在限制或饱和生长光下培养具有不同天线结构的海洋浮游植物（聚球藻、蓝藻、卵形藻和拟南芥）。在蓝藻和拟南芥中，初始 ρ 随生长光而变化。随着光强的增加，PSII 逐渐关闭，所有四个分类群的 ρ 都降低，这种模式可以解释为 ρ 随剩余开放 PSII 反应中心之间距离的增加呈指数衰减。这种光依赖性的 ρ 下调允许四个浮游植物限制光对 σ 的影响。然而，这四个结构不同的分类群显示出 ρ 对 PSII 关闭的反应具有不同的速率，这可能反映了它们的 PSII 中心之间的间隔或取向的差异。在饱和光照后，黑暗中 ρ 的恢复与聚球藻中 PSII 的重新开放直接吻合。即使在 PSII 已经在蓝藻中重新开放后，向状态 II 的转变也会减缓 ρ 在黑暗中的恢复。在卵形藻中，持续的 NPQ 会减缓 ρ 在黑暗中的恢复。在拟南芥中，ρ 的黑暗恢复速度较慢，可能是由于 PSII 间隔的光诱导变化。因此，ρ 与 PSII 关闭的这种关系模式是比较 PSII 间隔的一种方便探针。
