Synthesis of EF-Tu and distribution of its mRNA between stroma and thylakoids during the cell cycle of Chlamydomonas reinhardii.
In Chlamydomonas reinhardii the elongation factor EF-Tu is encoded in the chloroplast DNA. We identified EF-Tu in the electrophoretic product pattern of chloroplast-made proteins and showed that this protein is only synthesized in the first half of the light period in synchronized cells. The newly synthesized EF-Tu contributed little to the almost invariable content of EF-Tu in chloroplasts during the light period of the cell cycle. However, increasing cell volume and the lack of EF-Tu synthesis in the second half of the light period led to a decrease in the concentration of EF-Tu in chloroplasts. At different times in the vegetative cell cycle, the RNA was extracted from whole chloroplasts and from free and thylakoid-bound chloroplast polysomes. The content of mRNA of EF-Tu in chloroplasts and the distribution between stroma and thylakoids were determined. During the light period, the content of the mRNA for EF-Tu varied in parallel to the rate of EF-Tu synthesis. However, in the dark, some mRNA was present even in the absence of EF-Tu synthesis. Most of the mRNA was bound to thylakoids during the whole cell cycle. This suggests that synthesis of EF-Tu is associated with thylakoid membranes.
Breidenbach
E
E
Institut für Biochemie, Universität Bern, Switzerland.
Leu
S
S
Michaels
A
A
Boschetti
A
A
D001345:Autoradiography; D015152:Blotting, Northern; D002696:Chlamydomonas / Q000166:cytology / Q000235:genetics* / Q000254:growth & development; D002736:Chloroplasts / Q000378:metabolism*; D003001:Cloning, Molecular; D015342:DNA Probes; D007700:Kinetics; D009693:Nucleic Acid Hybridization; D015388:Organelles / Q000378:metabolism; D010444:Peptide Elongation Factor Tu / Q000096:biosynthesis / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics* / Q000302:isolation & purification; D013431:Sulfates / Q000378:metabolism; D013462:Sulfur Radioisotopes
D015342:DNA Probes; D012333:RNA, Messenger; D013431:Sulfates; D013462:Sulfur Radioisotopes; D010444:Peptide Elongation Factor Tu