Neutralization of Bacterial YoeB(Spn) Toxicity and Enhanced Plant Growth in Arabidopsis thaliana via Co-Expression of the Toxin-Antitoxin Genes

Bacterial toxin-antitoxin (TA) systems have various cellular functions, including as part of the general stress response. The genome of the Gram-positive human pathogen Streptococcus pneumoniae harbors several putative TA systems, including yefM-yoeB(Spn), which is one of four systems that had been demonstrated to be biologically functional. Overexpression of the yoeB(Spn) toxin gene resulted in cell stasis and eventually cell death in its native host, as well as in Escherichia coli. Our previous work showed that induced expression of a yoeB(Spn) toxin-Green Fluorescent Protein (GFP) fusion gene apparently triggered apoptosis and was lethal in the model plant, Arabidopsis thaliana. In this study, we investigated the effects of co-expression of the yefM(Spn) antitoxin and yoeB(Spn) toxin-GFP fusion in transgenic A. thaliana. When co-expressed in Arabidopsis, the YefM(Spn) antitoxin was found to neutralize the toxicity of YoeB(Spn)-GFP. Interestingly, the inducible expression of both yefM(Spn) antitoxin and yoeB(Spn) toxin-GFP fusion in transgenic hybrid Arabidopsis resulted in larger rosette leaves and taller plants with a higher number of inflorescence stems and increased silique production. To our knowledge, this is the first demonstration of a prokaryotic antitoxin neutralizing its cognate toxin in plant cells.