Osmolyte accumulation and implications in plant abiotic stress tolerance

Abstract

Plants being sessile are challenged by biotic and abiotic stresses. Osmotic adjustment has been shown to be an effective component of stress tolerance, and accumulation of osmoprotectants (proline, glycine betaine, gamma-aminobutyric acid and sugars) is a common response observed in different plant systems. Information on the metabolic pathways of these compatible solutes for their regulation, enzymes involved and compartmentalisation are well characterised in most important plant species. Such information has prompted researchers to devise strategies for improvement of plant tolerance through the accumulation of osmolytes in plants by expression of core biosynthetic enzymes or their derivatives and expression of related transporters. Pathway engineering for overproduction of compatible solutes is being attempted through stress-inducible and/or tissue-specific regulation in order to avoid primary metabolic costs and minimise the pleiotropic effects. Understanding the mechanisms by which plants perceive environmental signals and transmit them to cellular machinery to activate adaptive responses is crucial for the development of crop improvement strategies to impart stress tolerance.