Fuente: PubMed "Tomato process" Phytopathology. 2025 Dec 9. doi: 10.1094/PHYTO-05-25-0192-R. Online ahead of print.ABSTRACTThe LuxI/LuxR system, that produces and perceives N-acyl homoserine lactones, plays a significant role in regulating pathogenesis and communication in gram-negative bacteria. A homologous system exists in Pseudomonas syringae pv. tomato DC3000, which is encoded by the single copy genes psyI/psyR. We created a double knockout mutant of the AHL synthase (psyI) and the AHL receptor (psyR) genes in Pst DC3000 and a corresponding complemented strain to gain insights into their role in plant-pathogen interactions and the metabolic processes associated with this system in vitro. The mutant strain psyI-R- overcomes stomatal immunity as the parental strain Pst DC3000. However, the psyI-R- apoplastic population is significantly smaller than that of Pst DC3000 at three days post inoculation. Furthermore, PsyI/PsyR are required for necrosis but not chlorosis in infected tomato leaves, evidenced by the observed pharmacological and genetic complementation of the psyI-R- strain. By comparison, the coronatine deficient mutant DB29 is unable to cause neither necrosis nor chlorosis on leaves. The reduced virulence of psyI-R- is associated with an intermediate induction level of the tomato PR2b marker gene for salicylic acid signaling and reduced expression of bacterial virulence genes in infected leaf tissue. Transcriptomic analysis of psyI-R- and DB29 mutants showed misregulation of genes related to bacterial secretion system, chemotaxis, flagellar motility, ABC transporters, and iron transporters and a partial overlap between metabolic processes regulated by PsyI/PsyR and coronatine. Altogether, these findings indicate that the PsyI/PsyR is required for full bacterium virulence at the later stages of infection in tomato leaves.PMID:41364743 | DOI:10.1094/PHYTO-05-25-0192-R