A strong nucleotypic effect on the cell cycle regardless of ploidy level

Background and Aims: In published studies, positive relationships between nucleotypeand the duration of the mitotic cell cycle in angiosperms havebeen reported but the highest number of species analyzed wasapprox. 60. Here an analysis is presented of DNA C-values andcell cycle times in root apical meristems of angiosperms comprising110 measurements, including monocots and eudicots within a settemperature range, and encompassing an approx. 290-fold variationin DNA C-values. Methods: Data for 110 published cell cycle times of seedlings grown attemperatures between 20–25 °C were compared with DNAC-values (58 values for monocots and 52 for eudicots). Regressionanalyses were undertaken for all species, and separately formonocots and eudicots, diploids and polyploids, and annualsand perennials. Cell cycle times were plotted against the nuclearDNA C-values. Key Results: A positive relationship was observed between DNA C-value andcell cycle time for all species and for eudicots and monocotsseparately, regardless of the presence or absence of polyploidvalues. In this sample, among 52 eudicots the maximum cell cyclelength was 18 h, whereas the 58 monocot values ranged from 8–120h. There was a striking additional increase in cell cycle durationin perennial monocots with C-values greater than 25 pg. Indeed,the most powerful relationship between DNA C-value and cellcycle time and the widest range of cell cycle times was in perennialsregardless of ploidy level. Conclusions: DNA replication is identified as a rate limiting step in thecell cycle, the flexibility of DNA replication is explored,and we speculate on how the licensing of initiation points ofDNA replication may be a responsive component of the positivenucleotypic effect of C-value on the duration of the mitoticcell cycle.