INSTITUTO TECNOLOGICO DE CHASCOMUS
Unidad Ejecutora - UE
congresos y reuniones científicas
AN INTEGRATIVE ANALYSIS OF THE POLYAMINE METABOLISM IN PSEUDOMONAS SYRINGAE: DECODING ITS ROLES IN BACTERIAL PHYSIOLOGY
SOLMI L.; POMBO M.; RUIZ O.A.; ROSLI H.G.; ROMERO M.; STALDER S.; ROSSI F.R.; GARRIZ, A.
Congreso; SAIB-SAMIGE 2020; 2020
Putrescine, and its aminopropylated derivative spermidine, are the main polyamines found in bacteria and play crucial roles in the physiology of human pathogens. However, their contribution to virulence and stress resistance of phytopathogenic bacteria has been poorly explored. With the purpose to unveil the potential functions played by polyamines during bacterial plant infection and in the response to oxidative stress, we first carried out a meta-analysis of publicly available transcriptomic data sets from experiments conducted on Pseudomonas syringae. We found that bacterial polyamine biosynthesis and transport is induced in planta, and gene expression correlation analysis showed that the cognate genes are associated to the induction of general biosynthetic processes. In addition, our analysis indicated that the elicitation of plant defense responses provokes minor effects on the expression of polyamine metabolism genes. Therefore, polyamine synthesis is seemingly important for plant colonization, and successful pathogens are able to preserve polyamine homeostasis from the negative impacts derived from the activation of plant defense (i.e.: oxidative stress). In this trend, our analysis of transcriptomic data sets also evidenced a contrasting behavior of polyamine synthesis in response to hydrogen peroxide in in vitro experiments, as under this situation the biosynthetic genes were generally repressed. We then analyzed the production of polyamines by P. syringae pv. tomato DC3000 exposed to sublethal concentrations of hydrogen peroxide, and found that large quantities of putrescine are secreted while the intracellular levels of spermidine are reduced in early growth stages. In turn, our experiments shown that pre-treatment of bacterial cells with spermidine (but not putrescine) enhanced stress susceptibility. These results agree with the hypothesis that high intracellular levels of spermidine may have a negative effect on stress tolerance. In order to corroborate this interpretation, we examined the phenotype of mutant strains unable to synthesize polyamines. This analysis showed that, whereas the simultaneous disruption of the putrescine biosynthetic genes speA and speC leads to high susceptibility to oxidative stress, deletion of the spermidine biosynthetic gene speE enhanced stress tolerance. Altogether, these results demonstrate that the metabolism of polyamines must be fine-tuned during plant infection to assure the normal development of important anabolic processes while counteract the oxidative environment that follows the elicitation of plant defense responses. In addition to that, this work is the first report describing contrasting roles played by putrescine and spermidine in the response to stress in bacterial species.