The speed of intracellular signal transfer for chloroplast movement

Abstract

The photoreceptors for chloroplast photorelocation movement have been known, but the signal(s) raised by photoreceptors remains unknown. To know the properties of the signal(s) for chloroplast accumulation movement, we examined the speed of signal transferred from light-irradiated area to chloroplasts in gametophytes of Adiantum capillus-veneris. When dark-adapted gametophyte cells were irradiated with a microbeam of various light intensities of red or blue light for 1min or continuously, the chloroplasts started to move towards the irradiated area. The speed of signal transfer was calculated from the relationship between the timing of start moving and the distance of chloroplasts from the microbeam and was found to be constant at any light conditions. In prothallial cells, the speed was about 1.0 μm min-1 and in protonemal cells about 0.7 μm min-1 towards base and about 2.3 μm min-1 towards the apex. We confirmed the speed of signal transfer in Arabidopsis thaliana mesophyll cells under continuous irradiation of blue light, as was about 0.8 μm min-1. Possible candidates of the signal are discussed depending on the speed of signal transfer.

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Acknowledgements

This work was partly supported by the Japanese Ministry of Education, Sports, Science, and Technology (MEXT 13139203, 17084006 to M.W.), the Japan Society of Promotion of Science (JSPS 13304061, 16107002, 20227001 to M.W.), and a Research Fellowship for Young Scientists (to H.T.).

Figures and Tables

Figure 1 How to calculate the speed of signal transfer in the basal cell of two-celled protonema of Adiantum capillus-veneris. The relationship between the distance of chloroplast position from the edge of the microbeam to the center of each chloroplast as shown in left side of figure and the timing of chloroplast movement initiated shown as the black dots was obtained. Inclination of the approximate lines connecting dots indicates the speeds of the signal transfer.

Table 1 The speed of signal transfer in chloroplast accumulation response

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