Unveiling the dual role of Priestia megaterium VIT-2021 membrane vesicles as an antimicrobial and immunomodulator in supporting the growth ofOryza sativa ADT38.

To increase yield and productivity, plants are treated with chemicals; however, these interventions have inadvertently contributed to a decline in food security. To mitigate these challenges, plant growth-promoting rhizobacteria (PGPRs), which increase yield, have been widely used to modulate plant immunity. Some PGPRs have recently been reported to exhibit opportunistic pathogenicity in humans, raising safety concerns regarding their widespread application. Membrane vesicles (MVs) derived from PGPR may retain similar plant growth-promoting (PGP) traits and thus could aid in plant protection. This research tests the hypothesis that MVs derived from the PGPR Priestia megaterium VIT-2021 as an effective and sustainable alternative for combating bacterial infection. MVs were successfully isolated and characterized, and the results ensured that these MVs are efficient antimicrobial agents against Pseudomonas syringae. Proteomic analysis of the MVs revealed the presence of four antimicrobial peptides AMP underlying their antimicrobial effects. Furthermore, in vitro treatment with these MVs downregulated P. syringae virulence genes, including avrE, hrpS, and mgrA. In planta experiments conducted on Oryza sativa demonstrated that P. megaterium MVs effectively reduced P. syringae pathogenicity through immune modulation, as evidenced by the upregulation of WRKY13, IPA1, WKRY45, NPR1 and PR1, with fold increase of approximately 2.98, 3.55, 1.73, 2.44, and 5.51, respectively, at 4.2 × 10⁸ particle concentration. WRKY13 is involved in SA-mediated secondary cell wall synthesis, which resists pathogen ingress. Increased IPA1 promoted the upregulation of WRKY45, which could contribute to SA-mediated antimicrobial secondary metabolite synthesis. Increased expression of NPR1 and PR1 mediate cell wall rigidification and antimicrobial activity, ultimately contribute to robust immunity. Additionally, increased IPA1 is associated with multiple tiller outgrowths, panicle branching, and grain size development. Thus, P. megaterium MVs demonstrated dual functionality of immunomodulation and growth promotion in O. sativa. Therefore, the current research highlights a pioneering strategy for sustainable crop protection and yield enhancement.