Submitted to: The Open Plant Science Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2011
Publication Date: 8/17/2011
Citation: Kovalskaya, N., Zhao, Y., Hammond, R. 2011. Antimicrobial activity of snakin-defensin hybrid protein in tobacco and potato plants. The Open Plant Science Journal. 5:29-42.
Interpretive Summary: 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 caused by these diseases can be achieved by chemical and biological methods, these methods can be hindered by the emergence of new variants of the bacteria and fungi that are resistant to the current chemical and biological controls. We report the production of a functionally active novel protein in plants that inhibits the growth of certain bacteria and fungi that cause plant disease. These results will be of interest to scientists who are developing novel plant disease control strategies.
Technical Abstract: To augment plant protection against phytopathogens, we constructed a fusion gene for the simultaneous expression of snakin-1 (SN1) and defensin-1 (PTH1) antimicrobial proteins as a hybrid protein (SAP) in plant cells. Prior to in vivo evaluation of SAP phytoprotective activity, the hybrid protein expressed in and purified from Escherichia coli was tested against on a variety of phytopathogenic microorganisms in vitro. SAP exhibited the highest antimicrobial activity against bacterium Clavibacter michiganensis subsp. sepedonicus, cause of potato ring rot disease, and the anthracnose-causing fungus Colletotrichum coccoides by complete inhibition of cell growth or spore germination, respectively, at a concentration of 6 micromolar. Notably, the hybrid protein showed higher inhibitory activities against Pseudomonas syringae pv. syringae, P. syringae pv. tabaci and Colletotrichum coccoides, than individual SN1 and PTH1 proteins, whereas its effect on C. michiganensis subsp. sepedonicus in vitro was comparable to that of PTH1 alone. To evaluate antimicrobial properties of SAP in vivo, the hybrid protein was transiently expressed in plants from the Potato virus X (PVX)-based vectors (pP2C2S and pGR107). Antimicrobial activity of SAP against C. coccoides and C. michiganensis subsp. sepedonicus was assessed on Nicotiana benthamiana and Solanum tuberosum, respectively. Both SAP-expressing plants were significantly more resistant to infection than control plants. Our results demonstrate that in vivo co-expression of recombinant SN1 and PTH1 in the form of hybrid is a promising strategy for antimicrobial plant defense applications.