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

SOLMI LEANDRO; FERNANDO M. ROMERO; CORIGLIANO MARIANA; FRANCO R. ROSSI; GÁRRIZ ANDRES

Chapadmalal

Congreso; XVIII Congreso SAMIGE; 2023

Sociedad Argentina de Microbiología General

Pathogenic bacteria use multiple molecular mechanisms to achieve tissue colonizationand evade host defense effectively. Activation or repression of these mechanisms are tightlycoordinated. Polyamines (PAs) such as putrescine (PUT) and spermidine (SPD) arecationic compounds that play a critical role in cell physiology and regulate virulenceassociated cellular processes in human pathogenic bacteria. However, their role inphytopathogenic bacteria remains unknown. In this study, we explore the function of PAs inPseudomonas syringae pv. tomato DC3000 (Pto). We study virulence capability of wild-typeand mutant strains unable to synthesized putrescine (∆speA∆speC) and spermidine(∆speE), the most abundant PAs found in this species. To entry into host tissue, Pto inhibitsstomata closure through coronatine synthesis and secretion. ∆speE and ∆speA∆speCprovoke minor effects on stomata closure compared to the WT strain. We then performedArabidopsis thaliana seedling flood-inoculation to analyse the ability of bacteria to enterplant tissues. Measured cell growth in planta at different time revels that ∆speE only showed reduction in colony counts at 24 h pi, but these values recover at 48 h pi. In turn, populationwas significantly lower with the ∆speA∆speC mutant. We also conducted syringe-infiltrationto bypass the entry process and evaluated bacteria proliferation inside the plant.∆speA∆speC had significantly less cell number counts at all time points. In contrast, once∆speE was inside the plant, it exhibited similar virulence as the WT strain. Activation of type3 secretion system (T3SS) and effectors delivery are keys for successful pathogenesis. Totest the activation of this system in the mutant strains, we inoculated the non-host Nicotianabenthamiana in order to visualize hypersensitive response (HR). Both mutants show a delayin HR-induction indicating less activation of T3SS or effector delivery. At last, apoplasticfluid extracted from healthy adult A. thaliana plants was used to supplement M9 minimalmedia and bacterial growth was measured by absorbance at 600nm. ∆speE responded tomedia supplementation, indicating that the SPD content in the apoplast is sufficient topromote cell growth. Our results show that putrescine and spermidine are involved indifferent mechanism associated with virulence in Pto DC3000. Synthesis of PUT is essentialfor Pto full-virulence. On the other hand, disruption of the SPD synthesis pathway affectedsome virulence mechanisms, but its bioavailability in plants enables bacterial to colonizehost tissue correctly.