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Activation of Latent Origins of DNA Replication in Forally Determined Shoot Meristems of Long-day and Short-day Plants: Silene coeli-rosa and Pharbitis nil

Herbert, Rob and Durdan, S.F. and Francis, D (1998) Activation of Latent Origins of DNA Replication in Forally Determined Shoot Meristems of Long-day and Short-day Plants: Silene coeli-rosa and Pharbitis nil. Planta, 207 (2). pp. 235-240. ISSN 0032-0935 (Print) 1432-2048 (Online)

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Abstract

Replicon spacing was measured during the S-phase of the cell cycle in shoot meristems of Silene coeli-rosa L., a long-day (LD) plant, and Pharbitis nil Chois, a short-day (SD) plant to examine the hypothesis that activation of latent origins of DNA replication is a feature of foral determination. Silene coeli-rosa was germinated and grown in SD for 28 d and then exposed to either a florally inductive combination of 7 LD + 2 SD, the last day of which coincides with determination of the sepal and stamen whorls, or was germinated and grown in 37 non-inductive SD. Pharbitis nil was germinated and grown in continuous light (CL)for 5 d and then given either 48 h of inductive darkness followed by 1 d of CL, the last day of which coincides with determination of the sepal, petal and stamen whorls, or given one of two independent non-inductive treatments: 48 h dark interrupted by red light (R) + 1 d of CL, or 8 d of CL. Following these treatments, each batch of plants was exposed to tritiated [methyl-3H]thy- midine for 30, 60, 90 or 120 min. Apical domes were dissected, nuclei lysed and prepared as fibre autoradio- graphs from which replicon size was recorded. In S. coeli-rosa, replicon size was in the range 10±15 um in SD (non-inductive) and 0±5 um in LD (inductive) while in P. nil it was 10±15 um in the 48 h dark interrupted by R, 5±10 um in CL (both non-inductive) but was reduced to 0±5 um in the 48 h dark treatment (inductive). Therefore, the recruitment of additional initiation points for DNA replication occurred in both a LD and a SD plant immediately before the appearance of floral organs. The data are consistent in showing that a shortening of S-phase, which is a characteristic feature of florally determined shoot meristems for both species, is brought about by the activation of latent origins of DNA replication.

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Uncontrolled Keywords: cell cycle, DNA replication, flowering, Pharbitis (flowering),replicon, silene (flowering)
Subjects: Q Science > QK Botany
Divisions: Academic Departments > Institute of Science and the Environment
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Depositing User: Rob Herbert
Date Deposited: 27 Nov 2009 11:34
Last Modified: 27 Nov 2009 11:34
URI: https://eprints.worc.ac.uk/id/eprint/722

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