Bacterial elicitors of the plant immune system : an overview and the way forward

A wide variety of root-associated bacterial mutualist species sensitize plant defenses to counteract pathogen infections. These beneficial bacteria produce myriad molecules that induce systemic resistance (ISR) in plants. Here, we review pioneering and recent studies describing the role of different ISR elicitors, including quorum sensing molecules, lipids, oligosaccharides, proteins, iron-chelating molecules, and volatiles. The concepts and differences between ISR and other plant immune responses, such as Localized Acquired Resistance (LAR) and Systemic Acquired Resistance (SAR) are also explored. We also highlight the necessity of understanding plant responses to such a wide chemical diversity of molecules. Finally, we discuss the urgency of using such elicitors to develop more sustainable agriculture by helping plant crops defend themselves from invading pathogens.