Genetic engineering for osmolyte overproduction for abiotic stress tolerance in plants

Many plants accumulate organic osmolytes in response to the imposition of environmental stresses that cause cellular dehydration. Even though an adaptive involvement of these compounds in regulating osmotic adjustment and preventing subcellular structure from adverse conditions has vital role in stress physiology, the proof in favour of this proposition is largely correlative. Transgenic plants engineered to accumulate proline, mannitol, fructans, trehalose, glycine betaine or ononitol exhibit marginal enhancement in salt and/or drought tolerance. There is significant causative relationships which connects both osmolyte levels and stress tolerance, the complete osmolyte concentrations in these plants are improbable to mediate osmotic adjustment. Metabolic benefits of osmolyte accumulation may supplement the classically proved the roles of these compounds. In re-assessing the functional significance of compatible solute accumulation, it is suggested that proline and glycine betaine synthesis may buffer cellular redox potential. Instability in hexose sensing in transgenic plants which modify to produce trehalose, fructans or mannitol may be an important causative factor to the stress-tolerant phenotypes observed. Osmolyte transport between compartments of subcellular organs or different organs correspond to a bottleneck that confines stress tolerance at the whole-plant level is presently imprecise. None the less, if osmolyte metabolism interrupt on hexose or redox signalling, then it may be important in long-range signal transmission throughout the plant.