Phytochrome- and blue-light-absorbing pigment-mediated directional movement of chloroplasts in dark-adapted prothallial cells of fernAdiantum as analyzed by microbeam irradiation |
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Authors: | Takatoshi Kagawa Masarnitsu Wada |
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Affiliation: | (1) Laboratory of Photoperception and Signal Transduction, Frontier Research System, RIKEN Institute, Hirosawa 2-1, 351-01 Wako, Saitama, Japan;(2) Department of Biology, Faculty of Science, Tokyo Metropolitan University, Minami Ohsawa 1-1, 192-03 Hachicji, Tokyo, Japan |
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Abstract: | When prothalli ofAdiantum capillus-veneris L. were kept for 2 d in the dark, chloroplasts gathered along the anticlinal walls (Kagawa and Wada, 1994, J Plant Res 107: 389–398). In these dark-adapted prothallial cells, irradiation with a microbeam (10 gm in diameter) of red (R) or blue light (B) for 60 s moved the chloroplasts towards the irradiated locus during a subsequent dark period. Chloroplasts located less than 20 gm from the center of the R microbeam (18 J·m–2) moved towards the irradiated locus. The higher the fluence of the light, the greater the distance from which chloroplasts could be attracted. The B microbeam was less effective than the R microbeam. Chloroplasts started to move anytime up to 20 min after the R stimulus, but with the B microbeam the effect of the stimulus was usually apparent within 10 min after irradiation. The velocity of chloroplast migration was independent of light-fluence in both R and B and was about - 0.3 m·min–1 between 15 min and 30 min after irradiation. Whole-cell irradiation with far-red light immediately after R- and B-microbeam irradiations demonstrated that these responses were mediated by phytochrome and a blue-light-absorbing pigment, respectively. Sequential treatment with R and B microbeams, whose fluence rates were less than the threshold values when applied separately, resulted in an additive effect and induced chloroplast movement, strongly suggesting that signals from phytochrome and the blue-light-absorbing pigment could interact at some point before the induction of chloroplast movement.Abbreviations B blue light - FR far-red light - IR infrared light - R red light |
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Keywords: | Adiantum (prothallial cell) Blue-lightabsorbing pigment Chloroplast movement (directional) Microbeam irradiation Phytochrome Signal-transduction chain |
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