Expression of the Streptococcus pneumoniae yoeB chromosomal toxin gene causes cell death in the model plant Arabidopsis thaliana.

Fauziah Abu Bakar,Chew Chieng Yeo,Jennifer Ann Harikrishna

doi:10.1186/s12896-015-0138-8

Fauziah Abu Bakar, Chew Chieng Yeo + Show 1 more

Open Access

https://doi.org/10.1186/s12896-015-0138-8

Copy DOI

Abstract

BackgroundBacterial toxin-antitoxin systems usually comprise of a pair of genes encoding a stable toxin and its cognate labile antitoxin and are located in the chromosome or in plasmids of several bacterial species. Chromosomally-encoded toxin-antitoxin systems are involved in bacterial stress responses and activation of the toxins usually leads to cell death or dormancy. Overexpression of the chromosomally-encoded YoeB toxin from the yefM-yoeB toxin-antitoxin locus of the Gram-positive bacterium Streptococcus pneumoniae has been shown to cause cell death in S. pneumoniae as well as E. coli.ResultsInduction of a YoeB-GFP fusion protein using a 17-β-estradiol-inducible plant expression system in Arabidopsis thaliana Col 0, was lethal in all T2 progeny. Examination of plants by fluorescent confocal microscopy showed GFP fluorescence in all parts of the leaves at 24 hours after 17-β-estradiol induction, continuing up to plant death. Quantitative RT-PCR analysis revealed that the expression of the yoeB toxin gene peaked at 3 days after induction with 17-β-estradiol, coinciding with the onset of visible effects on the plants. Moreover, we detected DNA laddering in the transgenic plants at 24 hours after yoeB induction, indicative of apoptosis.ConclusionsExpression of the YoeB toxin from Streptococcus pneumoniae is lethal in Arabidopsis. We believe this is the first report of a toxin from a bacterial toxin-antitoxin system functioning in plants. The results presented here mark an important milestone towards the development of a cell ablation based bio-containment strategy, which may be useful for functional studies and for the control of spread of transgenic plants.

Highlights

Bacterial toxin-antitoxin systems usually comprise of a pair of genes encoding a stable toxin and its cognate labile antitoxin and are located in the chromosome or in plasmids of several bacterial species
Out of 100 T2 YoeBSpn-Green fluorescent protein (GFP) transgenic plants that grew on the selection medium, 11 were randomly chosen for genomic DNA preparation and PCR amplification using GFP-specific primers (Figure 1B, lanes 1 – 11)
The presence of a 732 bp band indicated the presence of the yoeBSpn-GFP fusion transgene and, the successful integration of the transgene into the Arabidopsis plants

Summary

Introduction

Bacterial toxin-antitoxin systems usually comprise of a pair of genes encoding a stable toxin and its cognate labile antitoxin and are located in the chromosome or in plasmids of several bacterial species. Chromosomally-encoded toxin-antitoxin systems are involved in bacterial stress responses and activation of the toxins usually leads to cell death or dormancy. Most bacteria harbour toxin-antitoxin (TA) systems, usually comprising a pair of genes coding for a toxin and its cognate antitoxin [1]. Type II TA systems have been most widely studied [14] and encode a toxic protein and a relatively less stable cognate proteic antitoxin. Environmental stress conditions usually lead to the induction of endogenous proteases which results in the degradation of antitoxins, thereby releasing the toxins from the inert toxinantitoxin complex.

Methods

Results

Discussion

Conclusion