Harmonizing plant defenses: exploring phytohormones, and their interplay in biotic stress responses

Abstract

In their natural habitat, plants confront a diverse array of pathogens including bacteria, viruses, nematodes, and fungi, collectively referred to as biotic stress, Distinguished multilayered response mechanisms are part of the intricate defense system in plants that evolved through time. The initial line of defense is Pattern-triggered immunity (PTI), which involves the recognition of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRRs), followed by effector-triggered immunity (ETI) mediated by resistance (R) proteins. At the heart of these defense mechanisms, phytohormones such as salicylic acid (SA), jasmonic acid (JA), ethylene (ET), and abscisic acid (ABA) orchestrate intricate regulatory networks. Additionally, phytohormones commonly known for plant growth, such as auxin (AUX), cytokinin (CK), gibberellic acid (GA), and brassinosteroids (BR) have emerged as key players in immune responses. As the plant deploys various defense strategies, pathogens employ clever molecular tactics to disrupt hormone biogenesis and signaling pathways, thereby creating a constant interplay in the struggle for dominance. Therefore, understanding these regulatory mechanisms is essential for deciphering the plant defense network and developing strategies to enhance crop resilience against pathogens. This review explores the roles of defense hormones and pathogen-mediated disruptions in shaping plant responses to biotic stress.