Examination of chlorophyll fluorescence in sulfur-deprived cells of Chlamydomonas reinhardtii

• Published in: Biophysics (Oxford) 2006-04, Vol.51 (2), p.251-257
• Main Authors: Antal, T K, Volgusheva, A A, Kukarskikh, G P, Krendeleva, TE, Tusov, V B, Rubin, AB
• Format: Article
• Language: English
• Subjects: Chlamydomonas reinhardtii; Chlorophyll; Photosynthesis
• ISSN: 0006-3509; 1555-6654
• DOI: 10.1134/S0006350906020151

Pulse amplitude modulation fluorimetry was used to assess chlorophyll fluorescence parameters in Chlamydomonas reinhardtii cells during sulfur deprivation. A significant (fourfold) increase in the chlorophyll fluorescence yield (parameters F sub(0) and F sub(m)) normalized to the chlorophyll concentration was shown for deprived cells. The chlorophyll content did not change during the deprivation experiments. An analysis of nonphotochemical quenching of chlorophyll fluorescence indicated a considerable modification of the energy deactivation pathways in photosystem II (PSII) of sulfur-deprived cells. For example, starved cells exhibited a less pronounced pH-dependent quenching of excited states and a higher thermal dissipation of excess light energy in the reaction centers of PSII. It was also shown that the photosynthetic apparatus of starved cells is primarily in state 2 and that back transition to state 1 is suppressed. However, these changes cannot cause the discovered elevation of chlorophyll fluorescence intensity (F sub(0) and F sub(m)) in the cells under sulfur limitation. The observed increase in the chlorophyll fluorescence intensity under sulfur deprivation may be due to partial dissociation of peripheral light-harvesting complexes from the reaction centers of PSII or a malfunction of the dissipative cycle in PSII, involving cytochrome b sub(559).