Abstract
We have been analyzing the role of actin filaments on chloroplast surface in the chloroplast photorelocation movement, using Marchantia polymorpha thallus cells expressing tdTomato-talin. In the previous experiments using cytoskeletal inhibitors, actin filaments were shown to play a crucial role in the chloroplast movement. On the chloroplast surface, short actin filaments (cp-actin filaments) were seen and they showed continuous change in their organization. When reorganization of cp-actin filaments during accumulation and avoidance responses induced by microbeam irradiation with low and high fluence-rate was examined, biased relocalization of cp-actin filaments on the leading half of chloroplast was revealed both in avoidance and accumulation movement. The speed of chloroplast movement correlated with the degree of biased localization of cp-actin filaments. Blue light irradiation on whole cells also induced reorganization of cp-actin filaments similar to that under microbeam irradiation. The evidences indicate the significance of biased configuration of cp-actin filaments in the mechanism of chloroplast relocation.
