Plant and Cell Physiology, 2002, Vol. 43, No. 6 587-594
© 2002 Oxford University Press
Unique Fluorescence Properties of a Cyanobacterium Gloeobacter violaceus PCC 7421: Reasons for Absence of the Long-Wavelength PSI Chl a Fluorescence at –196°C
1 Department of Physics, Biology and Informatics, Faculty of Science, Yamaguchi University, Yoshida, Yamaguchi, 753-8512 Japan
2 Department of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo, 060-8628 Japan
3 Faculty of Engineering, Tokyo Agriculture and Technology University, Koganei, Tokyo, 184-8588 Japan
We investigated the reason for the absence of the long-wavelength PSI Chl a fluorescence at –196°C in the cyanobacterium Gloeobacter violaceus using two methods: p-nitrothiophenol (p-NTP) treatment and time-resolved fluorescence spectra. The p-NTP treatment showed that PSII Chl a fluorescence was specifically affected in a manner similar to that for Synechocystis sp. PCC 6803 and spinach chloroplasts, although there were no components modified by the p-NTP treatment, indicating an absence of the long-wavelength PSI Chl a fluorescence. The time-resolved fluorescence spectra with a time resolution of 1.3 ps and spectral resolution of 1.0 nm gave no indication of the presence of the long-wavelength PSI fluorescence in the wavelength region between 700 nm and 760 nm, indicating that a very fast energy transfer among Chl a molecules could not account for the absence of the long-wavelength PSI fluorescence. From these data, it seems that the absence of the long-wavelength PSI fluorescence is due to a lack of the formation of a component responsible for the fluorescence at –196°C, which may originate from a difference in the amino acid sequence. We discuss the significance of this phenomenon and interpret our findings in terms of the evolution of cyanobacteria.
4 Present address: Department of Technology and Ecology, Hall of Global Environmental Studies, Kyoto University, Sakyo-ku, Kyoto, 606-8501 Japan
5 Corresponding author: E-mail, mamo_mi@bio.h.kyoto-u.ac.jp; Fax, +81-75-753-6855.