Molecular characterization of XVT8, a stress-responsive gene from the resurrection plant Xerophyta viscosa Baker

Xerophyta viscosa (Baker) is a monocotyledonous resurrection plant that is capable of tolerating extremes of desiccation. Upon rewatering, it rehydrates completely, assuming its full physiological activities. Studies on changes in gene expression associated with dehydration stress tolerance were conducted. A cDNA library was constructed from mRNA isolated from dehydrated X. viscosa leaves [85%, 37% and 5% relative water content (RWC)]. XVT8 represents one of 30 randomly selected clones that were differentially expressed when X. viscosa was dehydrated. Sequence analysis of XVT8 revealed that XVT8 exhibited 45% and 43% identity to dehydrin proteins from Arabidopsis thaliana and Pisum sativum respectively, at the amino acid level. XVT8 encodes a glycine -rich protein (27 kDa) which is largely hydrophilic and contains a hydrophobic segment at the C-terminus. Southern blot analysis confirmed the presence of XVT8 in the X. viscosa genome. XVT8 transcripts accumulated in X. viscosa plants that were exposed to heat, low temperature and dehydration stresses, and to exogenous abscisic acid and ethylene. These results provide direct evidence for the heat, low temperature, dehydration, abscisic acid and ethylene -dependent regulation of the XVT8 gene in X. viscosa.