PARTICIPATION OF Ralstonia solanacearum CATALASES IN PLANT-PATHOGEN INTERACTION

VANDECAVEYE, A.; TONDO, M.L.; DE PEDRO-JOVÉ, R.; CORRAL, J.; VALLS, M.; ORELLANO, E.G.

Montevideo

Simposio; 7th International Bacterial Wilt Symposium; 2023

Ralstonia solanacearum (Rso) is a saprophytic soil bacterium that causes the disease known as bacterial wilt in more than 200 plant species worldwide. The accumulation of reactive oxygen species (ROS) constitutes one of the first plant defense responses against infection by pathogens. To overcome this barrier, microorganisms have various detoxification enzymes capable of eliminating these ROS, and among these enzymes, catalases are central components of detoxification pathways. Rso GMI1000 genome revealed the presence of genes encoding putative catalase enzymes such as the monofunctional catalase KatE, and the catalase-peroxidase enzymes KatG encoded by RSc0775/RSc0776. The present work aims to study and characterize the physiological role of the KatG enzyme. The Rso katG and the katEkatG double mutant strains were generated and were physiologically characterized. The analysis of Rso soluble protein extracts in native polyacrylamide gels revealed for catalase activity allowed the band identification corresponding to the KatG enzyme. In addition, the detection of peroxidase activity in non-denaturing gels allowed us to corroborate its catalase-peroxidase bifunctional enzymatic nature. The katG mutant strain did not show differences in catalase activity levels compared to the wild type strain, however, exhibiting higher inhibition halos in assays against H2O2. On the other hand, the double mutant strain did not present detectable levels of catalase activity and exhibited considerably higher inhibition halos on BG-Agar Soft plates. Furthermore, the protein expression levels of Rso catalases were analyzed when exposed to methyl viologen, and it was observed that the KatG enzyme increases its activity when faced with this oxidizing agent. These results suggest that Rso catalases do not play an essential role in the early oxidative response triggered by plants against infection.