AOBPreview originally published online on May 11, 2007
Annals of Botany 2008 101(2):277-283; doi:10.1093/aob/mcm089
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Possible Role of Pectin-containing Mucilage and Dew in Repairing Embryo DNA of Seeds Adapted to Desert Conditions
1 Laboratory of Quantitative Vegetation Ecology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, P.R. China
2 Institute of Cell Biology and Genetic Engineering UAS, Kiev, 03143, Ukraine
3 Department of Biochemistry, Oxford University, South Parks Road, Oxford OX1 3QU, UK
4 Oxford Research Unit, The Open University, Foxcombe Hall, Boars Hill, Oxford OX1 5HR, UK
5 Jacob Blaustein Institute for Desert Research and Department of Life Sciences, Ben-Gurion University of the Negev, Sede Boker Campus, 84990, Israel
* For correspondence. E-mail gutterma{at}bgu.ac.il
Received: 31 January 2007 Returned for revision: 22 February 2007 Accepted: 9 March 2007 Published electronically: 11 May 2007
Background and Aims: Repair of damage to DNA of seed embryos sustained during long periods of quiescence under dry desert conditions is important for subsequent germination. The possibility that repair of embryo DNA can be facilitated by small amounts of water derived from dew temporarily captured at night by pectinaceous surface pellicles was tested. These pellicles are secreted during early seed development and form mucilage when hydrated.
Methods: Seeds of Artemisia sphaerocephala and Artemisia ordosica were collected from a sandy desert. Their embryos were damaged by gamma radiation to induce a standard level of DNA damage. The treated seeds were then exposed to nocturnal dew deposition on the surface of soil in the Negev desert highlands. The pellicles were removed from some seeds and left intact on others to test the ability of mucilage to support repair of the damaged DNA when night-time humidity and temperature favoured dew formation. Repair was assessed from fragmentation patterns of extracted DNA on agarose gels.
Key Results: For A. sphaerocephala, which has thick seed pellicles, DNA repair occurred in seeds with intact pellicles after 50 min of cumulative night dew formation, but not in seeds from which the pellicles had been removed. For A. ordosica, which has thin seed pellicles, DNA repair took at least 510 min of cumulative night dewing to achieve partial recovery of DNA integrity. The mucilage has the ability to rehydrate after daytime dehydration.
Conclusions: The ability of seeds to develop a mucilaginous layer when wetted by night-time dew, and to repair their DNA under these conditions, appear to be mechanisms that help maintain seed viability under harsh desert conditions.
Key words: Adaptation strategy, Artemisia, desert dew, DNA repair, pectin, pellicle, seed survival
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