ABSTRACT
Being sessile organisms, plants face several environmental perturbations throughout their life cycle and have therefore developed an array of responses and adaptive mechanisms to various abiotic stress conditions for survival and growth. One of the vital adaptive mechanisms is stimulated synthesis and accumulation of small organic molecules, known as compatible solutes/osmolytes for maintaining the cellular integrity and help cells to function normally under stressed conditions. These multifunctional biochemical entities most commonly include the betaines (b-alanine betaine, glycine betaine, proline betaine), sugars (glucose, fructose, fructan, raffinose, trehalose), sulfonium compounds (choline sulfate, dimethyl sulfonium propionate), polyols (mannitol, glycerol, sorbitol, initol), polyamines (spermine, spermidine, putrescine) and amino acids (proline, glutamine). Owing to their significance in maintaining normal cellular functions under harsh conditions, they have emerged as potent targets for genetic manipulations for engineering abiotic stress tolerance in major crop plants. This chapter is an attempt to provide an update on different classes of compatible solutes, their differential accumulation and roles under abiotic stress conditions and transgenic technologies implemented to improve abiotic stress tolerance in plants through engineering compatible solutes biosynthetic pathways.
