Chloroplast-encoded PsbT is required for efficient biogenesis of photosystem II complex in the green alga Chlamydomonas reinhardtii
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The small hydrophobic polypeptide PsbT is associated with the photosystem II (PSII) reaction center (D1/D2 heterodimer). Here, we report the effect of the deletion of PsbT on the biogenesis of PSII complex during light-induced greening of y-1 mutants of the green alga Chlamydomonas reinhardtii. The y-1 is unable to synthesize chlorophylls in the dark but do so in the light. The dark-grown y-1 cells accumulated no major PSII proteins but a small amount of PsbT. Upon illumination, PsbT was immediately synthesized while chlorophylls, major PSII proteins, and O2-evolving activity increased after a 1-h lag. The y-1 cells without PsbT accumulated chlorophylls and PSI protein at a similar rate, whereas the accumulation of PSII complex was specifically retarded during greening. The absence of PsbT did not affect the synthesis of PSII proteins. These results indicate that PsbT is required for the efficient biogenesis of PSII complex.
KeywordsPhotosynthesis Chlorophyll–protein complex Reaction center Greening Assembly y-1 mutant Pulse-labeling
Sodium dodecyl sulfate
Polyacrylamide gel electrophoresis
This work was supported by a Japan Society for the Promotion of Science Grant-in-aid for General Research for Creative Scientific Research (18GS0318) (to Y.T.).
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