Ontogenetic change of the PSI- and PSII-distribution in the thylakoid system of Euglena gracilis
1989
Brandt, P. | Keiz, A.
The thylakoid membranes of isolated Euglena chloroplasts were separated into two fractions by aqueous two-phase-partitioning (mixture of dextran 500 and poly(ethylene glycol) 4000) following press disruption. These two fractions differ in many respects during most of the cell cycle of this alga in comparison with the thylakoid characteristics of higher plants or green algae. The amount of thylakoid membranes with separation characteristics comparable with inside-out-vesicles of higher plant chloroplasts changes depending on the cell cycle stage of Euglena gracilis. Photosystems II and I are not restricted to one fraction. Both thylakoid membrane fractions evolve oxygen photosynthetically. When chloroplast differentiation in Euglena gracilis is complete (i.e. at the end of the light-time) the composition and the photosynthetic efficiency of the two thylakoid fractions are generally equal. Photosystem I-related LHCI is present in both fractions. Photosystem II-related CP29, however, was only detected in unfractionated thylakoid membranes. The implications for thylakoid organization in Euglena chloroplasts are discussed.
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