Abstract
Plants respond to abiotic stresses by activating a specific genetic program that supports survival by developing robust adaptive mechanisms. This leads to accelerated senescence and reduced growth, resulting in negative agro-economic impacts on crop productivity. Cytokinins (CKs) customarily regulate various biological processes in plants, including growth and development. In recent years, cytokinins have been implicated in adaptations to osmotic stresses with improved plant growth and yield. Endogenous CK content under osmotic stresses can be enhanced either by transforming plants with a bacterial isopentenyl transferase (IPT) gene under the control of a stress inducible promoter or by exogenous application of synthetic CKs. CKs counteract osmotic stress-induced premature senescence by redistributing soluble sugars and inhibiting the expression of senescence-associated genes. Elevated CK contents under osmotic stress antagonize abscisic acid (ABA) signaling and ABA mediated responses, delay leaf senescence, reduce reactive oxygen species (ROS) damage and lipid peroxidation, improve plant growth, and ameliorate osmotic stress adaptability in plants.
Highlights
Osmotic stresses in plants are caused by drought, salinity and high temperature
Contrasting observations revealed that CK-deficient plants display a strong stress-tolerant phenotype with increased cell membrane integrity and abscisic acid (ABA) hypersensitivity [26] but at the cost of growth and yield [97]
High CKs in plants facilitate acclimation to osmotic stresses with satisfactory growth and yield by relapsing the conventional transcriptional program activated under abiotic stress [7,58,94,99]
Summary
Drought is a major global problem that impacts 1–3% of all land. This number is predicted to increase to 30% by. Osmotic stress tolerance is a complex process involving a myriad of signaling pathways and results in either upregulation or downregulation of innumerable genes. These genes may either be regulatory (i.e., transcription factors that may further induce some other genes) or functional (i.e., directly involved in the process of stress tolerance). Strategies used to create osmotic stress tolerant transgenic plants involve overexpression of such regulatory or functional genes. This review assesses functions of enhanced CK contents in improving osmotic stress adaptability of plants without compromising yield
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