Chloroplast Actin Filaments Involved in Chloroplast Photorelocation Movements
Plants have evolved sophisticated mechanisms to survive in various environmental changes. Chloroplast movement is an essential response to optimize photosynthesis and to avoid photodamage under fluctuating light conditions. Chloroplasts accumulate at periclinal walls to maximize light absorption under weak light while they move to anticlinal walls to minimize light exposure under strong light. The light strength is monitored by blue light receptor phototropins in general. In Arabidopsis thaliana, both phototropin1 (phot1) and phototropin2 (phot2) are involved in accumulation response, but phot2 is specifically involved in avoidance response. Such appropriate photorelocation movements of chloroplasts are mediated by a structure made of short actin filaments specialized for chloroplast movement. The short actin filaments are dynamically reorganized on the leading edges of moving chloroplasts, so that named chloroplast actin (cp-actin) filaments. In this chapter, we summarize recent knowledge about cp-actin filaments and next challenges to elucidate the underlying mechanisms.
The work was supported by the grants from the Japan Society for the Promotion of Science (JSPS) (No. 20227001, 23120523, 25120721, 25251033, and 16K14758) and from Ohsumi Frontier Science Foundation to M.W. and by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. 2016R1D1A3B03935947) and the Next-Generation BioGreen 21 Program grant funded by the Korea government Rural Development Administration (RDA) (No. PJ01366901) to S.-G. K.
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