Identification of chromosomal type II toxin-antitoxin system from plant pathogenic Pseudomonas cichorii JBC 1

Abstract

Backgrounds: Almost all bacteria harbor toxin？antitoxin (TA) systems on their chromosomes, which are associated with diverse biological roles such as stress response, cell physiology, biofilm formation, and programmed cell death. Pseudomonas cichorii JBC1 has a diverse host range and can cause disease in a wide range of plant species. Under favorable environmental conditions, the bacterium can cause severe disease in nearly all of the crops that have been described. However, TA systems have not been determined. Objective: This study aimed to identify the TA system of P. cichorii JBC1 genome based on the cell toxicity of Escherichia coli regulated by TA systems and to evaluate the mRNA expression levels under various stressful growth conditions. Results: Among 11 putative TA pairs predicted from the P. cichorii JBC1 genome by in silico analysis, two toxins, PCH70-01,410 and ？ 16,540, caused cell growth arrest and cell death in E. coli, and the toxicity of PCH70-01,410 and ？ 16,540 was neutralized by its cognate antitoxin candidates, PCH70-01,400 and ？ 16,550 in PCH70-01,400/01410 and PCH70-16,550/16540 TA complexes, respectively. Moreover, mRNA expression levels of PCH70-01,400/01410 and PCH70-16,550/16540 differed under various stresses (i.e., oxidative, acidic, and heat shocks). Conclusion: Two TA systems, PCH70-01,400/01410 and PCH70-16,550/16540, were identified in P. cichorii JBC 1. These TA systems show different toxin and antitoxin mRNA expression levels according to stressful growth conditions, including oxidative, acidic, and heat shocks in E. coli.