Blue- and red-light action in photoorientation of chloroplasts in Adiantum protonemata

Abstract

An action spectrum for the low-fluencerate response of chloroplast movement in protonemata of the fern Adiantum capillus-veneris L. was determined using polarized light vibrating perpendicularly to the protonema axis. The spectrum had several peaks in the blue region around 450 nm and one in the red region at 680 nm, the blue peaks being higher than the red one. The red-light action was suppressed by nonpolarized far-red light given simultaneously or alternately, whereas the bluelight action was not. Chloroplast movement was also induced by a local irradiation with a narrow beam of monochromatic light. A beam of blue light at low energy fluence rates (7.3·10(-3)-1.0 W m(-2)) caused movement of the chloroplasts to the beam area (positive response), while one at high fluence rates (10 W m(-2) and higher) caused movement to outside of the beam area (negative response). A red beam caused a positive response at fluence rates up to 100 W m(-2), but a negative response at very high fluence rates (230 and 470 W m(-2)). When a far-red beam was combined with total background irradiation with red light at fluence rates causing a low-fluence-rate response in whole cells, chloroplasts moved out of the beam area. When blue light was used as background irradiation, however, a narrow far-red beam had no effect on chloroplast distribution. These results indicate that the light-oriented movement of Adiantum chloroplasts is caused by red and blue light, mediated by phytochrome and another, unidentified photoreceptor(s), respectively. This movement depends on a local gradient of the far-red-absorbing form of phytochrome or of a photoexcited blue-light photoreceptor, and it includes positive and negative responses for both red and blue light.

Chloroplast Photorelocation Movement: A Sophisticated Strategy for Chloroplasts to Perform Efficient Photosynthesis

“…Immediately after the light was turned off, the chloroplasts moved into the formerly irradiated area. Similar responses were also found in filamentous protonemal cells in A. capillus-veneris (Yatsuhashi et al, 1985) and P. patens (Kadota et al, 2000;Sato et al, 2001). These results suggested several characteristics of putative signals (reviewed by ): (i) Signals for both the accumulation and the avoidance responses are simultaneously generated by strong light.…”

Cellular and Subcellular Localization of Phototropin 1

“…Experiments with polarized blue light provided strong evidence for the fixed orientation of the photoreceptors for both chloroplast accumulation and avoidance movements in the protonemata of the fern Adiantum capillus-veneris, consistent with localization of the relevant photoreceptors to the plasma membrane (Yatsuhashi et al, 1985). In Arabidopsis, however, the fixed orientation of the photoreceptors involved in chloroplast movements has been demonstrated only for the avoidance response (Kagawa and Wada, 2000), which is known to be mediated exclusively by phot2 (Jarillo et al, 2001;Kagawa et al, 2001).…”

Phototropin Encoded by a Single-Copy Gene Mediates Chloroplast Photorelocation Movements in the LiverwortMarchantia polymorpha

“…In the fern A. capillus-veneris, chloroplast accumulation and avoidance responses are induced by both blue and red light (Yatsuhashi et al, 1985). This fern has three phototropin family proteins, two phototropins (Acphot1 and Acphot2; Kagawa et al, 2004), and one neochrome that possesses the chromophorebinding domain of phytochrome and complete phototropin domains (Nozue et al, 1998).…”