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Desiccation and survival in the recalcitrant seeds of Avicennia marina: DNA replication, DNA repair and protein synthesis

Published online by Cambridge University Press:  22 February 2007

Ivan Boubriak
Affiliation:
Oxford Research Unit, Open University, Foxcombe Hall, Boars Hill, Oxford, OX1 5HR, UK Institute of Cell Biology and Genetic Engineering, 148 Zabolotnogo Street, Kiev, 252143, Ukraine
Mariuccia Dini
Affiliation:
Plant Cell Biology Research Unit, School of Life and Environmental Sciences, University of Natal, Durban, 4041, South Africa
Patricia Berjak
Affiliation:
Plant Cell Biology Research Unit, School of Life and Environmental Sciences, University of Natal, Durban, 4041, South Africa
Daphne J. Osborne*
Affiliation:
Oxford Research Unit, Open University, Foxcombe Hall, Boars Hill, Oxford, OX1 5HR, UK
*
*Correspondence Fax: +44-1865-326322 Email: d.j.osborne@open.ac.uk

Abstract

Abstract An autoradiographic study was made of leucine and thymidine incorporation into the meristematic root primordia and hypocotyl tips of seeds of the recalcitrant mangrove species, Avicennia marina. The investigations show that although there is a temporary reduction of protein synthesis at shedding, root primordia and surrounding hypocotyl cells of the axis never wholly cease incorporation of [3H]leucine and regain pre-shedding levels of activity within a day. Precursor studies using methyl-[3H]thymidine show that, at shedding, there is a temporary cessation of incorporation into root meristem nuclei that lasts no longer than 48 h and, within a day, pre-shedding levels are regained in the meristem nuclei. Analysis of DNA fragmentation patterns in root tips at the time of shedding, and their ability to repair radiation-induced DNA damage, indicate that DNA repair processes are markedly compromised in these cells if water loss reaches 22%. Protein synthesis and DNA replication are reduced by more than half by a water loss of 18% and 16%, respectively. DNA replication does not fully recover on rehydration after only 8% water loss. DNA fragmentation to nucleosomes indicates a programme of cell death at a water loss of 10%. We suggest that the feature of continuous protein synthesis activity with only a temporary interruption in active cell cycling in A. marina root primordia helps to explain both the rapidity in seedling establishment and the extreme vulnerability to desiccation.

Information

Type
Research Article
Copyright
Copyright © Cambridge University Press 2000

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