DNA and desiccation tolerance

Abstract

AbstractThis article reviews mechanisms by which specialized cells of different life forms have overcome the lethal effects of dehydration and considers how the maintenance of genetic information is central to survival. As a dynamic and hydrated moleculein vivo, DNA can assume different conformational structures depending upon the water activity, the base sequence and the presence of specific binding proteins. The attainment of stable secondary structures that are resistant to degradationin vivoat low water potentials is proposed as a likely accompaniment to desiccation tolerance. In addition, chemical modification of bases in DNA, the extent of methylation and conformational changes could determine the expression of different gene sequences as cells pass from desiccation-tolerant to desiccation-intolerant states. We monitored the integrity of extracted DNA in embryos of seeds and in wind-dispersed pollen during transition from their desiccation tolerance to desiccation intolerance on hydration and germination. We present evidence to show that the DNA of these two stages is different and that it is the DNA from desiccation-tolerant cells only that retains integrity when the cells are subjected to desiccation regimes. We discuss these findings in relation to certain hydration-sensitive DNA structures and to other relevant biological systems.