Temperature-dependent signal transmission in chloroplast accumulation response
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Chloroplast photorelocation movement, well-characterized light-induced response found in various plant species from alga to higher plants, is an important phenomenon for plants to increase photosynthesis efficiency and avoid photodamage. The signal for chloroplast accumulation movement connecting the blue light receptor, phototropin, and chloroplasts remains to be identified, although the photoreceptors and the mechanism of movement via chloroplast actin filaments have now been revealed in land plants. The characteristics of the signal have been found; the speed of signal transfer is about 1 µm min−1 and that the signal for the accumulation response has a longer life and is transferred a longer distance than that of the avoidance response. Here, to collect the clues of the unknown signal substances, we studied the effect of temperature on the speed of signal transmission using the fern Adiantum capillus-veneris and found the possibility that the mechanism of signal transfer was not dependent on the simple diffusion of a substance; thus, some chemical reaction must also be involved. We also found new insights of signaling substances, such that microtubules are not involved in the signal transmission, and that the signal could even be transmitted through the narrow space between chloroplasts and the plasma membrane.
KeywordsBlue light Chloroplast movement Fern Phototropin Red light Signaling
This work was supported in part by the Japan Society of Promotion of Science [23120523, 25251033, 25120721, and 16K14758 to M.W. and 23870002, and 26840088 to Y.K.]. We would thank Dr. Akeo Kadota for his various support to this work, and Mr. Shun Kimura (Utsunomiya University) for his technical assistance.
Authors have made the following contributions to the manuscript: TH, YK, MW planned and designed the research. TH performed the experiments. SH, YH, YK designed and constructed a system for microbeam irradiation in a temperature-controlled microbeam irradiator.
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