MOLECULAR ANALYSIS OF DESICCATION TOLERANCE IN BARLEY EMBRYOS AND IN THE RESURRECTION PLANT CRATEROSTIGMA-PLANTAGINEUM

Two experimental systems, developing barley embryos and the desiccatio n-tolerant plant Craterostigma plantagineum, have been used to isolate cDNA clones specifically expressed in dehydrated tissues. Sequence an alysis 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 prot eins expressed during late embryogenesis in many higher plants. The ex pression of these genes is induced by abscisic acid treatment in leave s and in undifferentiated callus tissue. Subcellular localization of t he corresponding proteins shows that most are cytoplasmic and that 3 d ehydration-induced proteins are localized in the chloroplast. In devel oping barley embryos, some of the cDNA clones are related to genes enc oding enzymes involved in sugar metabolism. One of these clones shows high homology to the animal aldose reductases involved in the synthesi s of the osmolyte sorbitol. The protein encoded by this clone has been over-expressed in Escherichia coli and the purified protein shows ald ose reductase activity.