Plant and Cell Physiology Advance Access published online on July 24, 2007
Plant and Cell Physiology, doi:10.1093/pcp/pcm095
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Blue-light-dependent nuclear positioning in Arabidopsis thaliana leaf cells
1 Department of Biological Sciences, Graduate School of Science, Osaka University, Machikaneyama-cho 1-1, Toyonaka, Osaka, 560-0043 Japan
2 RIKEN Plant Science Center, Suehiro-cho 1-7-22, Tsurumi, Yokohama, Kanagawa, 230-0045 Japan
3 To whom correspondence should be addressed. IWABUCHI, Kosei, Machikaneyama-cho 1-1, Toyonaka, Osaka, 560-0043 JAPAN, Tel.: +81-6-6850-6776 (ext. 6776), E-mail: iwabuchi{at}bio.sci.osaka-u.ac.jp
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Abstract |
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The plant nucleus changes its intracellular position not only upon cell division and cell growth but also in response to environmental stimuli such as light. We found that the nucleus takes different intracellular positions depending on blue light in Arabidopsis thaliana leaf cells. Under dark condition, nuclei in mesophyll cells were positioned at the center of the bottom of cells (dark position). Under blue light at 100 µmol m-2 s-1, in contrast, nuclei were located along the anticlinal walls (light position). The nuclear positioning from the dark position to the light position was fully induced within a few hours of blue-light illumination, and it was a reversible response. The response was also observed in epidermal cells, which have no chloroplasts, suggesting that the nucleus has a potential to actively change its position without chloroplasts. Light-dependent nuclear positioning was induced specifically by blue light at over 50 µmol m-2 s-1. Furthermore, the response to blue light was induced in phot1 but not in phot2 and phot1phot2 mutants. Unexpectedly, we also found that nuclei as well as chloroplasts in phot2 and phot1phot2 mutants took unusual intracellular positions under both dark and light conditions. The lack of the response and the unusual positioning of nuclei and chloroplasts in phot2 mutant were recovered by externally introducing PHOT2 gene into the mutant. These results indicate that phot2 mediates the blue-light-dependent nuclear positioning and the proper positioning of nuclei and chloroplasts. This is the first characterization of light-dependent nuclear positioning in the spermatophytes.
Keywords: Arabidopsis thaliana - blue light - epidermal cell - mesophyll cell - nuclear positioning - phototropin
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