Regulation of Protochlorophyll(ide) Levels in Dark-Grown Non-DividingEuglena3. Proplastid Structure during Loss and Regeneration of Protochlorophyll(ide)1

摘要

Cells ofEuglena gracilisKlebs var.bacillarisCori growing in darkness on a complete medium have small undifferentiated proplastids. On transfer to an incomplete (resting) medium in darkness, the cells cease division within 72 h. During this time the proplastid expands and several prothylakoids and prolamellar bodies develop even though phototransformable protochlorophyll(ide) PT-Pchl(ide) is decreasing. As PT-Pchl(ide) decreases further and reaches a stable plateau after 4–5 more days in darkness, the proplastid structure becomes highly reduced. Forty minutes of light plus a one h dark period, or addition of glutamate or malate for 7 h does not change the proplastid structure significantly even though PT-Pchl(ide) returns to the level found in growing cells. Upon prolonged incubation in darkness after light treatment (72 h) an expanded proplastid containing prothylakoids, prolamellar bodies and membrane whorls with mitochondria in close association is seen; most of the cellular paramylum is lost during this period leaving cavities in the cytoplasm. Without light, prolonged incubation in darkness (72 h) with malate leads to accumulation of cellular paramylum but no change in proplastid structure while prolonged treatment with glutamate (72 h) allows the formation of a few prothylakoids but no prolamellar bodie