Trehalose: a key player in plant growth regulation and tolerance to abiotic stresses

Plant abiotic stresses endanger crop production and food security to a growing degree under the present climate change scenario. This calls for effective measures to be deployed to increase the level of agricultural production to meet the needs of soaring world population. Application of osmo-protectants and soluble sugars were reported to counter abiotic stresses in many crop species. Trehalose (Tre) is one such non-reducing sugar found in bacteria and yeasts, where it serves as source of carbon, and in higher plants and animals, where it acts as osmo-protectant. Tre is involved in various physiological, biochemical and molecular mechanisms associated with plant growth, development and defense against drought, salinity, cold, heat, UV rays, nutrient deficiency and heavy metal stresses. It helps to maintain cellular integrity under stress by upgrading the antioxidant defense system. However, Tre amounts are lower than those needed to assure adequate plant stress tolerance. Interestingly, Tre supplementation up-regulates stress response genes and induces the accumulation of various osmolytes, including proline, glycine betaine and soluble sugars, which confer different kinds of stress tolerance. Alternatively, the development of transgenic plants with genes for Tre biosynthesis leads to appreciable tolerance against different stresses. However, some transgenic plants over-expressing Tre biosynthesis genes are adversely affected. This work aims to systematically review Tre's role as stress tolerance molecule and its crosstalk with other osmolytes under stress conditions, explaining mechanism of stress tolerance and pointing out areas for future research. It is evidenced that this compound owns a promising future as osmo-protectant in the coming years. The present review is intended as means to enrich the awareness on Tre potential benefits, in order to help the scientists as well as the practitioners to improve crop behavior and ultimate production under stress conditions.