Open AccessLight regulation of the cell cycle in Euglena gracilis bacillaris
Author(s) -
Yee MuhChing,
Bartholomew James C.
Publication year - 1988
Publication title -
cytometry
Language(s) - English
Resource type - Journals
eISSN - 1097-0320
pISSN - 0196-4763
DOI - 10.1002/cyto.990090417
Subject(s) - euglena gracilis , euglena , cell cycle , biology , cell division , microbiology and biotechnology , mitosis , darkness , phototroph , flow cytometry , biophysics , photosynthesis , cell , botany , chloroplast , biochemistry , gene
We have studied the light regulation of the cell division cycle in the photosynthetic alga Euglena gracilis bacillaris. Euglena grown under phototrophic conditions are easily synchronized to a 12 h light‐12 h dark regime. By inoculating stationary phase, nondividing cells into fresh media and exposing the diluted cells to either light or darkness, we have determined that initiation of DNA synthesis for the cell division cycle is light dependent. By varying the length of time in light to which synchronized cells are exposed, we have shown that commitment to the cell cycle requires exposure to more than 6 h of light. We propose that this is to allow the accumulation, through photosynthetic electron transport, of an initiating factor that will enable DNA synthesis to begin. Flow cytometry analysis also shows that once cells are committed to the cell cycle, they complete the cycle in the dark, so mitosis is a light‐independent step.