▪ Abstract Plant responses to salinity stress are reviewed with emphasis on molecular mechanisms of signal transduction and on the physiological consequences of altered gene expression that affect biochemical reactions downstream of stress sensing. We make extensive use of comparisons with model organisms, halophytic plants, and yeast, which provide a paradigm for many responses to salinity exhibited by stress-sensitive plants. Among biochemical responses, we emphasize osmolyte biosynthesis and function, water flux control, and membrane transport of ions for maintenance and re-establishment of homeostasis. The advances in understanding the effectiveness of stress responses, and distinctions between pathology and adaptive advantage, are increasingly based on transgenic plant and mutant analyses, in particular the analysis of Arabidopsis mutants defective in elements of stress signal transduction pathways. We summarize evidence for plant stress signaling systems, some of which have components analogous to t...

Plant cellular and molecular responses to high salinity.

Roles of glycine betaine and proline in improving plant abiotic stress resistance

Striking convergent evolution is found in the properties of the organic osmotic solute (osmolyte) systems observed in bacteria, plants, and animals Polyhydric alcohols, free amino acids and their derivatives, and combinations of urea and methylamines are the three types of osmolyte systems found in all water-stressed organisms except the halobacteria The selective advantages of the organic osmolyte systems are, first, a compatibility with macromolecular structure and function at high or variable (or both) osmolyte concentrations, and, second, greatly reduced needs for modifying proteins to function in concentrated intracellular solutions Osmolyte compatibility is proposed to result from the absence of osmolyte interactions with substrates and cofactors, and the nonperturbing or favorable effects of osmolytes on macromolecular-solvent interactions

https://science.sciencemag.org/content/sci/217/4566/1214.full.pdf

Living with water stress: evolution of osmolyte systems

Salt tolerance and salinity effects on plants: a review.

Agricultural productivity worldwide is subject to increasing environmental constraints, particularly to drought and salinity due to their high magnitude of impact and wide distribution. Traditional breeding programs trying to improve abiotic stress tolerance have had some success, but are limited by the multigenic nature of the trait. Tolerant plants such as Craterostigma plantagenium, Mesembryanthemum crystallinum, Thellungiella halophila and other hardy plants could be valuable tools to dissect the extreme tolerance nature. In the last decade, Arabidopsis thaliana, a genetic model plant, has been extensively used for unravelling the molecular basis of stress tolerance. Arabidopsis also proved to be extremely important for assessing functions for individual stress-associated genes due to the availability of knock-out mutants and its amenability for genetic transformation. In this review, the responses of plants to salt and water stress are described, the regulatory circuits which allow plants to cope wit...

Drought and Salt Tolerance in Plants

The major nitrogenous osmolytes present in the cells of marine invertebrates, notably the free amino acids glycine, alanine and proline, and trimethylamine oxide and betaine, are highly compatible with proper enzyme function and structure. These nitrogenous osmolytes display either non-perturbing or, in some cases, favorable effects on enzyme-substrate and enzyme-cofactor complex formation, catalytic velocity and protein structural stability. In contrast, inorganic salts (KCl and NaCl) and certain of the free amino acids which play only a minor osmotic role, e.g., arginine and lysine, have strongly perturbing effects on one or more of these enzymic parameters. The compatible nitrogenous solutes therefore are suitable for use at high (several tenths molar) concentrations and at widely varying concentrations in osmo-conforming species. Certain nitrogenous solutes, especially trimethylamine oxide, betaine and glutamate, offset some of the perturbing effects of inorganic ions on enzyme function. The selective accumulation of osmolytes thus involves not only the concentration of non-perturbing solutes, but also a balanced accumulation of solutes with opposing effects on enzymes. The selection of end-products of anaerobic metabolism also appears to be based, in part, on considerations of solute compatibility with enzyme function. Octopine is a non-perturbing solute, whereas arginine, which is condensed with pyruvate to form octopine, is very strongly perturbing. Succinate has marked stabilizing effects on protein structure. We conclude that the composition of the intracellular fluids of marine invertebrates reflects selection for osmolytes and end-products whose net effects create a cellular microenvironment which is conducive to optimal enzyme function and structure. The accumulation of compatible solutes may preclude the necessity for widespread changes in protein structure in adapting to concentrated or highly variable osmotic environments.

Solute compatibility with enzyme function and structure: rationales for the selection of osmotic agents and end-products of anaerobic metabolism in marine invertebrates.

R D Bowlus

Papers

Living with water stress: evolution of osmolyte systems

Solute compatibility with enzyme function and structure: rationales for the selection of osmotic agents and end-products of anaerobic metabolism in marine invertebrates.