Abstract
From the analyses on actin-visualized Arabidopsis line expressing GFP-talin, we previously reported short actin filaments on chloroplasts and their involvement in chloroplast movement. Under continuous blue excitation light for GFP, the chloroplast actin filaments (cp-actin) of wild type transiently disappear and then reappear on one side of chloroplast after which chloroplasts begin avoidance movement. In the present study, red light effects on cp-actin reorganization and cp-actin dynamics in phototropin mutants were analyzed by imaging cp-actin every 3 sec. Weak and strong red light promoted and inhibited, respectively, chloroplast avoidance movement by changing timing of cp-actin reappearance. In phot2 and phot1phot2 mutants, no cp-actin disappearance was detected. In phot1 mutant, both cp-actin disappearance and reappearance occurred earlier, resulting in earlier start of avoidance movement. These results indicate that cp-actin reorganization is regulated by multiple factors and that chloroplast avoidance movement occurs after these cp-actin reorganization steps
