Amino Acid Metabolism and Transporters in Plant−Pathogen Interactions: Mechanisms and Implications

In the intricate landscape of plant-pathogen interactions, amino acids and their dedicated transporters emerge as pivotal players underpinning immune signalling and metabolic reprogramming. Amino acid metabolism serves as a linchpin in orchestrating systemic defence responses, with transporter-mediated amino acid homoeostasis intricately intertwined with immune pathways. This review synthesizes the dual roles of amino acids, including glutamate, proline, γ-aminobutyric acid, β-aminobutyric acid and pipecolic acid, as metabolic intermediates and signalling molecules that modulate defence responses. Complementing this metabolic framework, amino acid transporters, including LHT1 and members of the AAP and UMAMIT family, participate in plant defence against pathogens or provide nutrients to pathogens by regulating the transmembrane transport of amino acids. Their disease resistance or susceptibility functions are closely related to plant tissue-specificity and substrate-specificity. Additionally, this review explores the potential coordinated regulation between amino acid and sugar transporters in the context of plant-pathogen interactions. Looking ahead, future research should focus on resolving transporter mechanisms in resistance, dissecting regulatory hubs linking metabolism and transport, mapping nutrient fluxes at the host-pathogen interface and exploring the subcellular localization and transport direction of transporters to inform precision crop protection strategies.