Arbuscular mycorrhizal symbiosis and alleviation of osmotic stress. New perspectives for molecular studies.

Water deficit is considered one of the most important abiotic factors limiting plant growth and yield in many areas on earth. Several eco-physiological studies have demonstrated that the arbuscular mycorrhizal (AM) symbiosis often results in altered rates of water movement into, through and out of the host plants, with consequent effects on tissue hydration and plant physiology. It is now accepted that the contribution of AM symbiosis to plant drought tolerance is the result of accumulative physical, nutritional, physiological and cellular effects. This review considers several aspects that should be investigated at a molecular level in order to gain a whole understanding of the different mechanisms by which the AM symbiosis protects the host plants against the detrimental effects of water deficit.