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Title: Antibacterial and antifungal activity of a snakin-defensin hybrid protein expressed in tobacco and potato plants

item Zhao, Yan
item Hammond, Rosemarie

Submitted to: The Open Plant Science Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/4/2011
Publication Date: 8/17/2011
Citation: Kovalskaya, N., Zhao, Y., Hammond, R. 2011. Antibacterial and antifungal activity of a snakin-defensin hybrid protein expressed in tobacco and potato plants. The Open Plant Science Journal. 5:29-42.

Interpretive Summary: Phytopathogenic bacteria and fungi cause significant losses in important agricultural crops and are the primary cause of post harvest diseases of fruits and vegetables. While control of losses can be achieved by chemical and biological control methods, full realization of these strategies under commercial conditions can be hindered by environmental issues, the emergence of new virulent strains of pathogens, resistance to the current chemical and biological defenses, as well as practical difficulties, and warrant development of new and more effective plant protection techniques. Naturally occurring antimicrobial proteins can be used for crop protection applications; however, selection of appropriate proteins for target applications requires the production of large quantities of active proteins. We report the production of functionally active antimicrobial proteins using a bacterial expression system. These results will be of interest to scientists who are developing novel plant disease control strategies.

Technical Abstract: In this study, for the first time, functionally active recombinant cysteine-rich plant proteins snakin-1 (SN1) and defensin (PTH1) were successfully expressed and purified using a prokaryotic (bacterial) expression system. The overall level of antimicrobial activities of SN1 and PTH1 produced in Escherichia coli was commensurate with that of the same recombinant proteins previously obtained from plant tissues. Both proteins exhibited a strong antibacterial activity against the phytopathogenic bacteria Clavibacter michiganensis subsp. sepedonicus (50% inhibitory concentration (IC50) 1.5-8µM) and antifungal activity against phytopathogenic fungi Colletotrichum coccoides and Botrytis cinerea (IC50 5-14µM), while significantly weaker activity was observed against bacteria Pseudomonas syringae pv. syringae and Pseudomonas syringae pv. tabaci. A pronounced synergistic antimicrobial effect against P. syringae pv. syringae and P. syringae pv. tabaci occurred with combination of SN1 and PTH1 proteins. The ability of C. michiganensis subsp. sepedonicus bacterial cells to aggregate at all protein concentrations tested was observed with the combination of SN1 and PTH1 and with SN1 alone. The results obtained demonstrate the potential for utilization of the more advantageous and cost effective prokaryotic expression system for generation and in vitro characterization of plant cysteine-rich proteins with potential antimicrobial activities against a wide range of phytopathogenic microorganisms and subsequent selection of the most effective agents for future in vivo studies.