Molecular analysis of desiccation tolerance in barley embryo and in the resurrection plant Craterostigma plantagineum.

Two experimental systems, developing barley embryos and the desiccation-tolerant plant Craterostigma plantagineum, have been used to isolate cDNA clones specifically expressed in dehydrated tissues. Sequence analysis revealed that most of the isolated cDNA clones show homologies to previously reported genes. Most of the desiccation-induced genes in Craterostigma encode polypeptides with substantial homologies to proteins expressed during late embryogenesis in many higher plants. The expression of these genes is induced by abscisic acid treatment in leaves and in undifferentiated callus tissue. Subcellular localization of the corresponding proteins shows that most are cytoplasmic and that 3 dehydration-induced proteins are localized in the chloroplast. In developing barley embryos, some of the cDNA clones are related to genes encoding enzymes involved in sugar metabolism. One of these clones shows high homology to the animal aldose reductases involved in the synthesis of the osmolyte sorbitol. The protein encoded by this clone has been over-expressed in Escherichia coli and the purified protein shows aldose reductase activity.