POLYAMINE SYNTHESIS AND BIODISPONIBILY HAVE A MAYOR ROL IN THE PATHOGENESIS OF Pseudomonas syringae pv. tomato DC3000

SOLMI L; ROMERO FM; CORIGLIANO MG; ROSSI FR; GÁRRIZ A

Chapadmalal

Congreso; XVIII Congreso de la Sociedad Argentina de Microbiolgía General; 2023

Sociedad Argentina de Microbiolgía General

Pathogenicbacteria use multiple molecular mechanisms to achieve tissue colonization andevade host defense effectively. Activation or repression of these mechanisms aretightly coordinated. Polyamines (PAs) are cationic compounds that play acritical role in cell physiology and regulate virulence-associated cellularprocesses in human pathogenic bacteria. However, their role in phytopathogenicbacteria remains unexplored. In this study, we explore the function of PAs in Pseudomonassyringae pv. tomato DC3000 (Pto) - A. thaliana pathosystem. Westudy virulence capability of wild-type and mutant strains unable tosynthesized putrescine (∆speA∆speC) and spermidine (∆speE),the most abundant PAs found in bacteria. To entry into host tissue, Pto inhibitstomata closure by coronatine synthesis and secretion. ∆speE and ∆(speA-speC)show reduction in stomata aperture compared to the WT strain. We performed A.thaliana seedling flood-inoculation to analysed bacterial ability to enter.Measured cell growth in planta at different time revels that ∆speE onlyshowed reduction in colony counts at 24 hpi, but its recover at 48 hpi. In turn,population was significantly lower with ∆(speA-speC) mutant at bothtimes. We conduct syringe-infiltration to bypass entry process and evaluatebacteria proliferation inside the plant across time. ∆(speA-speC) hadsignificantly less cell number at all times points. In contrast, ∆speE exhibitedsame virulence as WT strain. Activation of type 3 secretion system (T3SS) andeffectors delivery are keys for successful pathogenesis. To test this system inmutant strains, we realized no-host assay using N. benthamiana in orderto visualized hypersensitive response (HR). Both mutant present a delay in HR-inductionindicating less activation of T3SS or effector delivery.  At last, apoplastic fluid extracted fromhealthy adult A. thaliana plants was used to supplement M9 minimal mediaand bacterial growth was measured by absorbance at 600nm. ∆speEresponded to media supplementation, indicating that the spermidine content inthe apoplast is sufficient to promote cell growth. Our results show thatputrescine (PUT) and spermidine (SPD) may regulate different mechanismassociated with virulence in Pto DC3000. Synthesis of PUT is essential for Ptofull-virulence. On the other hand, disruption of the SPD synthesis pathwayaffected some virulence mechanisms, but its bioavailability in plant enables bacterialcolonize host tissue correctly.