Transport of newly synthesized ribosome precedes initiation of S phase in root meristem cells in Helianthus annuus L.
According to earlier results, cold treatment blocks most of cells in G1 phase; after 3 h of postincubation at 20 degrees C these cells initiate S phase. Simultaneous cytophotometric (DNA stained with Methyl Green) and autoradiographic (3H-uridine, 3H-arginine) analyses of cold pretreated cells have shown that transport of 3H-RNA into cytoplasm is faster in G2 than in G1 cells: radioactivity of cytoplasm is faster in G2 cells becomes higher than that of nucleoli as early as between 2 h and 2.5 h postincubation, while in G1 cells--not until between 2.5. and 3.0 h. Simultaneous cytophotometric measurements of DNA (Feulgen) and protein (Naphthol Yellow S) contents demonstrate the considerable increase in cytoplasmic protein contents during the 2nd h of postincubation at 20 degrees C; therefore it precedes the export of more than 50% of 3H-RNA synthesized after cold treatment. The results of these experiments indicate two separate events in G1 cells: increase in cytoplasmic protein amounts (up to 2nd h of postincubation) and enhanced transport of newly-synthesized ribosome (2.5 h of postincubation), the later event immediately precede the entry of cells into S phase.
Olszewska
M J
MJ
Department of Plant Cytology and Cytochemistry, University of Lódź, Poland.
Marciniak
K
K
D001120:Arginine / Q000378:metabolism; D001692:Biological Transport; D003080:Cold Temperature / Q000379:methods; D003593:Cytoplasm / Q000032:analysis / Q000502:physiology; D006368:Helianthus / Q000166:cytology* / Q000378:metabolism / Q000502:physiology; D007399:Interphase; D009687:Nuclear Proteins / Q000032:analysis; D012335:RNA, Ribosomal / Q000032:analysis / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology; D012269:Ribosomal Proteins / Q000032:analysis; D012270:Ribosomes / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors; D014529:Uridine / Q000378:metabolism
D009687:Nuclear Proteins; D012335:RNA, Ribosomal; D012269:Ribosomal Proteins; D001120:Arginine; D014529:Uridine