Effects of T3SS-positive Pseudomonas isolates on sugar beet growth stimulation and pathogen resistance

Abstract The intricate interplay between plants and microorganisms in agricultural ecosystems holds immense potential for increasing crop productivity and resilience in the face of climate change and increasing pathogen pressure. This study addresses the function of the type 3 secretion system (T3SS) in nonpathogenic Pseudomonas strains associated with sugar beet (Beta vulgaris L.). We identified T3SS-positive isolates and characterised their genetic diversity and T3SS expression profiles. Our results show that T3SS is widely distributed among sugar beet-associated Pseudomonas, with variations in T3SS gene sequences and expression patterns. Notably, T3SS functionality was demonstrated in one isolate, P. marginalis OL141. In planta experiments with this isolate showed a correlation between T3SS and the growth of sugar beet and resistance to Pseudomonas syringae infections. The T3SS-mediated interactions in P. marginalis OL141 point to a novel mechanism underlying plant-microbe symbiosis and offer promising opportunities for sustainable agriculture. Future research directions include elucidating the mechanistic basis of T3SS-mediated plant-microbe interactions and exploring their broader implications for sustainable agriculture and global food security.