Distinct cyclin D genes show mitotic accumulation or constant levels of transcripts in tobacco bright yellow-2 cells.
The commitment of eukaryotic cells to division normally occurs during the G1 phase of the cell cycle. In mammals D-type cyclins regulate the progression of cells through G1 and therefore are important for both proliferative and developmental controls. Plant CycDs (D-type cyclin homologs) have been identified, but their precise function during the plant cell cycle is unknown. We have isolated three tobacco (Nicotiana tabacum) CycD cyclin cDNAs: two belong to the CycD3 class (Nicta;CycD3;1 and Nicta;CycD3;2) and the third to the CycD2 class (Nicta;CycD2;1). To uncouple their cell-cycle regulation from developmental control, we have used the highly synchronizable tobacco cultivar Bright Yellow-2 in a cell-suspension culture to characterize changes in CycD transcript levels during the cell cycle. In cells re-entering the cell cycle from stationary phase, CycD3;2 was induced in G1 but subsequently remained at a constant level in synchronous cells. This expression pattern is consistent with a role for CycD3;2, similar to mammalian D-type cyclins. In contrast, CycD2;1 and CycD3;1 transcripts accumulated during mitosis in synchronous cells, a pattern of expression not normally associated with D-type cyclins. This could suggest a novel role for plant D-type cyclins during mitosis.
Sorrell
D A
DA
Institute of Biotechnology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QT, United Kingdom.
Combettes
B
B
Chaubet-Gigot
N
N
Gigot
C
C
Murray
J A
JA
D000818:Animals; D056741:Cyclin D; D016213:Cyclins / Q000235:genetics* / Q000302:isolation & purification; D016193:G1 Phase / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008938:Mitosis / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics / Q000302:isolation & purification; D010947:Plants, Toxic; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D014026:Nicotiana / Q000166:cytology* / Q000235:genetics*
D056741:Cyclin D; D016213:Cyclins; D010940:Plant Proteins; D018749:RNA, Plant