Phototropin-dependent biased relocalization of cp-actin filaments can be induced even when chloroplast movement is inhibited.

Noboru Yamada, Noriyuki Suetsugu, Masamitsu Wada, Akeo Kadota

Department of Biological Sciences, Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo, Japan.

Plant signaling & behavior 2011 Nov

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In a recent publication using an actin-visualized line of Arabidopsis (Ichikawa et al. 2011, ref. 11), we reported a detailed analysis with higher time resolution on the dynamics of chloroplast actin filaments (cp-actin filaments) during chloroplast avoidance movement and demonstrated a good correlation between the biased configuration of cp-actin filaments and chloroplast movement. However, we could not conclusively determine whether the reorganization of cp-actin filaments into a biased configuration preceded actual chloroplast movement (and, thus, whether it could be a cause of the movement). In this report, we present clear evidence that the reorganization of cp-actin filaments into a biased distribution is induced even in the absence of the actual movement of chloroplasts. When the cells were treated with 2,3-butanedione monoxime (BDM), a potent inhibitor of myosin ATPase, chloroplast motility was completely suppressed. Nevertheless, the disappearance and biased relocalization of cp-actin filaments toward the side of the prospective movement direction were induced by irradiation with a strong blue light microbeam. The results definitively indicate that the reorganization of cp-actin filaments is not an effect of chloroplast movement; however, it is feasible that the biased localization of cp-actin filaments is an event leading to chloroplast movement.

Citation

Noboru Yamada, Noriyuki Suetsugu, Masamitsu Wada, Akeo Kadota. Phototropin-dependent biased relocalization of cp-actin filaments can be induced even when chloroplast movement is inhibited. Plant signaling & behavior. 2011 Nov;6(11):1651-3