Changes in cell cycle status and expression of p34cdc2 kinase during potato tuber meristem dormancy.
Campbell, M. A.; Suttle, J. C.; Sell, T. W.;
Physiologia Plantarum Year: 1996 Vol: 98 Issue: 4 Pages: 743-752 Ref: 41 ref.
1996
บทคัดย่อ
Potato tubers undergo a period of endodormancy that is characterized by cell division arrest. In a study with potatoes cv. Russet Burbank, the tubers at the time of harvest, were completely endodormant (i.e. 0% sprouting). After 120 days of storage at 3 deg C, tubers transferred to 20 deg had begun to exit endodormancy and exhibited about 50% sprouting. After 223 days of 3 deg storage, tubers transferred to 20 deg were completely nondormant and exhibited 100% sprouting. Based on flow cytometry, about 70% of nuclei isolated from endodormant meristems were arrested in the G1/G0 phase of the cell cycle. Storage of tubers at 3 deg did not alter the cell cycle position nor did transfer of tubers from 3 to 20 deg for 7 days prior to analysis unless tubers had been stored for at least 223 days. After 223 days of cold (3 deg ) storage, tubers transferred to 20 deg for 7 days showed sprout growth in excess of 5 mm and an increase in the percentage of nuclei in the G2 phase of the cell cycle. Uptake and i
ncorporation of 3H-thymidine into DNA was low in all tubers up until 120 days postharvest. After that time, only tubers incubated at 20 deg for 7 days prior to analysis exhibited an increase in 3H-thymidine incorporation. This increase coincided with visible sprout growth, demonstrating that cell cycle shifts in tuber meristems relate directly to sprout growth and not the breakage of the endodormancy per se. Using degenerate primers, a portion of a p34cdc2 homologue was amplified from RNA isolated from log-phase potato suspension culture cells by polymerase chain reaction. Northern analysis with this probe demonstrated that mRNA levels for two p34cdc2 homologues were present throughout the endodormant period. Immunoblot analysis demonstrated that levels of at least four proteins containing a PSTAIRE (i.e. cdc2-like) epitope were present at reduced levels in endodormant meristems and increased in reactivated tuber meristems that showed a shift in cell cycle kinetics based on flow cytometry and increased 3H-th
ymidine incorporation. These results indicate that the temporal shift in competence for cell division in potato meristems induced by dormancy is not accompanied by alterations in the level of mRNA for p34cdc2 homologues but is correlated with a change in the level of PSTAIRE-containing proteins. This suggests that during endodormancy cell division in potato tuber meristems is regulated indirectly by post-transcriptional regulation of genes controlling the cell cycle.