Beyond pathogenicity: the immunomodulatory role of the type III secretion system in beneficial plant-microbe interactions.

Abstract

The type III secretion system (T3SS) has traditionally been studied for its role in bacterial virulence. However, recent research emphasizes its dual role in beneficial interactions between bacteria and plants. This review examines the immunomodulatory functions of T3SS beyond pathogenicity and focuses on how T3SS effectors manipulate plant immune responses to promote symbioses. By comparing T3SS mechanisms in pathogenic and non-pathogenic bacteria, we aim to understand how this system enables beneficial microbes to colonize plants and improve plant growth and stress resilience. We also investigate the potential of T3SS to trigger induced systemic resistance in plants, a mechanism that could be utilized in agriculture to improve crop resistance to pathogens. The review concludes with an outlook on future research and emphasizes the need for comprehensive studies on T3SS effectors in non-pathogenic bacteria and their interactions with plant hosts.