Sato Y, Wada M, Kadota A
Department of Biological Sciences in Graduate School of Science, Tokyo Metropolitan University, Minami-Osawa 1-1, Hachioji, Tokyo 192-0397, Japan.
J Cell Sci. 2001 Jan;114(Pt 2):269-79. doi: 10.1242/jcs.114.2.269.
Light induced chloroplast movement has been studied as a model system for photoreception and actin microfilament (MF)-based intracellular motilities in plants. Chloroplast photo-accumulation and -avoidance movement is mediated by phytochrome as well as blue light (BL) receptor in the moss Physcomitrella patens. Here we report the discovery of an involvement of a microtubule (MT)-based system in addition to an MF-based system in photorelocation of chloroplasts in this moss. In the dark, MTs provided tracks for rapid movement of chloroplasts in a longitudinal direction and MFs contributed the tracks for slow movement in any direction. We found that phytochrome responses utilized only the MT-based system, while BL responses had an alternative way of moving, either along MTs or MFs. MT-based systems were mediated by both photoreceptors, but chloroplasts showed movements with different velocity and pattern between them. No apparent difference in the behavior of chloroplast movement between the accumulation and avoidance movement was detected in phytochrome responses or BL responses, except for the direction of the movement. The results presented here demonstrate that chloroplasts use both MTs and MFs for motility and that phytochrome and a BL receptor control directional photo-movement of chloroplasts through the differential regulation of these motile systems.
光诱导的叶绿体运动已作为植物中光接收和基于肌动蛋白微丝（MF）的细胞内运动的模型系统进行了研究。在小立碗藓中，叶绿体的光聚集和避光运动由光敏色素以及蓝光（BL）受体介导。在此，我们报告发现在这种苔藓中，除了基于MF的系统外，基于微管（MT）的系统也参与叶绿体的重新定位。在黑暗中，MT为叶绿体在纵向的快速运动提供轨道，而MF为叶绿体在任何方向的缓慢运动提供轨道。我们发现光敏色素反应仅利用基于MT的系统，而BL反应有另一种运动方式，即沿着MT或MF运动。基于MT的系统由两种光感受器介导，但叶绿体在它们之间表现出不同速度和模式的运动。除了运动方向外，在光敏色素反应或BL反应中，未检测到叶绿体在聚集运动和避光运动之间的运动行为有明显差异。此处给出的结果表明，叶绿体利用MT和MF进行运动，并且光敏色素和BL受体通过对这些运动系统的差异调节来控制叶绿体的定向光运动。
