Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India.
J Photochem Photobiol B. 2013 Nov 5;128:27-34. doi: 10.1016/j.jphotobiol.2013.07.028. Epub 2013 Aug 8.
Photosynthetic organisms during acclimation to light, differences in the amount of energy absorbed by photosystems leads to an imbalance in the energy distribution between photosystem (PS) II and PSI. Here, we describe the changes in fast chlorophyll (Chl) a fluorescence transients (OJIP) in wild type and stn7 under state I and state II light conditions. Fluorescence quenching in the OJIP transients recorded from state II exposed wt leaves is due to mobilization of LHCII to PSI. Similar kind of quenching was not observed in stn7 plants exposed to state II light. OJIP transients can be used to study the changes in Chl a fluorescence upon state transitions in A. thaliana. Immunoblotting and 2 dimensional gel electrophoresis studies have shown that phosphorylated Lhcb2 under state II condition exhibited 4 isoforms, whereas dephosphorylated Lhcb2 exhibited 3 isoforms in state I. Phosphorylation and migration of LHCII to PSI resulted in changes in the pigment protein profile of the thylakoid membranes in state II from wt. The increase in circular dichroism (CD) signals at 663 nm and 679 nm was due to association of chirally active trimeric LHCII to PSI-LHCI supercomplex leading to macro-aggregation of pigment-pigment complexes in state II pre-illuminated conditions in wt A. thaliana.
在对光的适应过程中，光合生物吸收的能量差异导致光合作用系统 II（PSII）和 PSI 之间的能量分配不平衡。在这里，我们描述了野生型和 stn7 在 I 态和 II 态光条件下快速叶绿素（Chl）a 荧光瞬变（OJIP）的变化。从暴露在 II 态光下的 wt 叶片中记录的 OJIP 瞬变的荧光猝灭是由于 LHCII 向 PSI 的动员。在暴露在 II 态光下的 stn7 植物中没有观察到类似的猝灭。OJIP 瞬变可用于研究拟南芥在状态转变过程中 Chl a 荧光的变化。免疫印迹和二维凝胶电泳研究表明，在 II 态条件下磷酸化的 Lhcb2 表现出 4 种同工型，而在 I 态下去磷酸化的 Lhcb2 表现出 3 种同工型。LHCII 向 PSI 的磷酸化和迁移导致 wt 状态 II 下的类囊体膜中色素蛋白图谱发生变化。663nm 和 679nm 处圆二色性（CD）信号的增加是由于具有手性活性的三聚体 LHCII 与 PSI-LHCI 超复合物结合，导致色素-色素复合物在 wt 拟南芥的 II 态预照明条件下发生宏观聚集。
