Under blue light, plant chloroplasts relocate to different areas of the cell. The photoreceptor phototropin2 (phot2) mediates the chloroplast movement mechanism under excess blue light alongside the chloroplast unusual positioning1 (chup1) protein. Recently, it has been proposed that leaf transmittance changes associated with chloroplast relocation affect measurements of nonphotochemical quenching (NPQ), resulting in kinetic differences due to these movements (termed "qM"). We evaluated these claims using Arabidopsis (Arabidopsis thaliana) knock-out mutants lacking either phot2 or chup1 and analyzed the kinetics of both the onset and recovery of NPQ under equivalent intensities of both red and blue light. We also evaluated the photoprotective ability of chloroplast movements both during the early onset of photoinhibition and under sustained excess light. We monitored photoinhibition using the chlorophyll fluorescence parameter of photochemical quenching in the dark, which measures the redox state of Q_A within PSII without any of the complications of traditional F_v/F_m measurements. While there were noticeable differences between the responses under red and blue light, the chloroplast movement mechanism had no effect on the rate or amplitude of NPQ onset or recovery. Therefore, we were unable to replicate the "qM" component and its corresponding influence on the kinetics of NPQ in Arabidopsis grown under "shade" conditions. Furthermore, chloroplast relocation had no effect on the high-light tolerance of these plants. These data cast doubt upon the existence of a chloroplast movement-dependent component of NPQ. Therefore, the influence of chloroplast movements on photoprotection should be thoroughly reevaluated.

在蓝光下，植物叶绿体重新定位到细胞的不同区域。感光细胞phototropin2（phot2）在过量蓝光下与叶绿体异常定位1（chup1）蛋白一起介导叶绿体运动机制。最近，已经提出，与叶绿体重定位相关的叶片透射率变化影响非光化学猝灭（NPQ）的测量，由于这些运动而导致动力学差异（称为“ qM”）。我们使用缺乏phot2或chup1的拟南芥（Arabidopsis thaliana）敲除突变体评估了这些说法，并分析了NPQ发作和恢复的动力学在相同强度的红色和蓝色光下 我们还评估了在光抑制的早期发作期间和在持续的过量光照下叶绿体运动的光保护能力。我们在黑暗中使用光化学猝灭的叶绿素荧光参数监测了光抑制作用，该参数可测量PSII中Q _A的氧化还原状态，而没有传统F _v / F _m测量的任何复杂性。虽然红光和蓝光下的响应之间存在明显差异，但叶绿体移动机制对NPQ的速率或幅度没有影响发作或恢复。因此，我们无法在“阴影”条件下生长的拟南芥中复制“ qM”成分及其对NPQ动力学的相应影响。此外，叶绿体迁移对这些植物的高耐光性没有影响。这些数据使人怀疑NPQ是否存在依赖于叶绿体运动的成分。因此，应彻底重新评估叶绿体运动对光保护的影响。