Drought tolerance: A molecular perspective

Plant growth and productivity is negatively affected by water stress and other environmental stresses, and genetic improvement of water stress tolerance is of special importance to agricultural plants. Early monitoring of molecular changes and tissue response to water stress can greatly aid the selection of drought-tolerant genotypes, and the elucidation of underlying control mechanisms. Water loss from plant tissues under drought conditions results in growth inhibition and in a number of other metabolic and physiological changes. These include accumulation of ABA, stomatal closure and reduced transpiration rates, a decrease in the water potential of plant tissues, decreased photosynthesis, and synthesis of new proteins and mRNAs. The majority of these transcripts encode polypeptides closely related to Lea and dehydrin-like proteins which are abundantly induced during embryo maturation in seeds of many higher plants, as well as in water-stressed seedlings. Some drought-induced proteins are highly hydrophilic and remain soluble after boiling. It has been suggested that these proteins (e.g. dehydrins) prevent cellular damage during desiccation, by binding to macromolecular structures. Since dehydrins appear during late embryogenesis, they have also been implicated in the acquisition of desiccation tolerance in seeds. In this mini-review we will summarize the basic know how in this field looking on the considerable progress, in identifying genes, that are important for stress tolerance.