Chlorophyll fluorescence lifetime studies of greening in yellow mutants of Chlamydomonas reinhardtii: assembly of the Photosystem I core complex
نویسنده
چکیده
Changes in the functional organization of chlorophyll occur during light-dependent chlorophyll accumulation in yellow mutants of Chlamydomonas reinhardti£ These changes were studied using single-photon counting techniques to determine the chlorophyll fluorescence decay kinetics at various times after transfer of de-greened cultures to the light. Several different yellow mutants were analyzed: y-l, a photoautotrophic strain; LM18-al2b, a Photosystem-II (PS II) -deficient deriVative of y-l; and C2, a strain deficient in both Photosystem I (PS I) and PS II. The results demonstrate that the residual chlorophyll present in de-greened cultures has a similar organization, independent of the chlorophyllprotein composition of the fully greened strains. Relative to the composition in light-grown cultures, the chlorophyll present in de-greened ceils is enriched in chlorophyll b and has fluorescence decay kineti~ similar to monomeric chlorophyll in solution. The reaction-center core complexes accumulate preferentially during the first 2 h of greening, and the light-harvesting complexes begin to accumulate more rapidly thereafter. After 5 -6 h, during the stage of maximal chlorophyll accumulation rate, reaction centers and antenna complexes accumulate in constant proportions. The PS I reaction-center core complex has a constant apparent size of about 130 Chl/P-700 at all stages of greening under the conditions we examined.
منابع مشابه
Antenna structure and excitation dynamics in photosystem I. II. Studies with mutants of Chlamydomonas reinhardtii lacking photosystem II.
Using time-resolved single photon counting, fluorescence decay in photosystem I (PS I) was analyzed in mutant strains of Chlamydomonas reinhardtii that lack photosystem II. Two strains are compared: one with a wild-type PS I core antenna (120 chlorophyll a/P700) and a second showing an apparent reduction in core antenna size (60 chlorophyll a/P700). These data were calculated from the lifetimes...
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