Role of plant endophytes in conferring abiotic stress tolerance

Abstract

Plants, being stationary, are continuously challenged to extreme environmental conditions like drought, salinity, heat, cold, etc. that limit crop productivity by about 50-70%. The response of plants to these abiotic stresses is complex and involves a plethora of physiological, biochemical, and gene expression changes. A number of approaches like plant breeding, genetic engineering, mutagenesis, and omics-based approaches have been used to understand and impart tolerance against various types of stresses in economically important plant species. This chapter would, however, focus on the application of endophytes (a group of beneficial microorganisms present within the plant tissues) in conferring selective advantage to host plants with which they are associated in harsh environmental conditions. Numerous reports have proposed that endophytes impart stress tolerance to plants either by activation of host stress response system or by biosynthesis of anti-stress metabolites like plant growth regulators, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, volatiles, bioactive compounds, etc. Depending on the types of abiotic stress, different types of endophytes adopt different signaling mechanisms which may include synthesis and accumulation of compatible solutes, adjustment in ion transport, expression of stress-responsive genes, generation of ROS scavenger molecules, etc. In particular, the role of endophyte-mediated stress tolerance against drought, salinity, and heavy metal conditions has been discussed in detail.