Hormonal signaling molecules triggered by plant growth-promoting bacteria

Abstract

One of the most widely used eco-friendly approaches to plant tolerance today is the "priming effect" of plant growth-promoting bacteria (PGPB). PGPBs and bioactive metabolites produced by these bacteria can effectively stimulate plant growth directly or indirectly. The direct mechanisms include facilitating resource acquisition and altering levels of plant hormones such as auxin, cytokinin, and gibberellin. Therefore, bacteria capable of forming symbiotic relationships with plants can improve plant health and growth by stabilizing atmospheric nitrogen, phosphate solubility, and siderophore production, increasing defense against various bacterial and fungal pathogens, or producing phytohormones, including ethylene, cytokines, auxins, and gibberellins. Many studies on PGPBs have revealed plants’ adaptation to stress conditions, especially by stimulating many signaling pathways of these bacteria. In this chapter, the hormonal signaling mechanisms, including auxin, jasmonates, salicylic acid, and abscisic acid that PGPBs and their metabolites produced in plants and the molecular responses that occur have been revealed. Transcription factors associated with hormonal signaling pathways affected by PGPBs and molecular responses involved in stress tolerance have been attempted to be revealed. Besides, the role of hormone-mediated induced systemic resistance (ISR) in the hormonal network due to the stimulation of PGPBs has been discussed in line with the latest updated data. © 2023 Elsevier Inc. All rights reserved.