Abstract
Synthetic pesticides have a positive impact on food production. However, there are concerns due to the outbreak of resistance along with negative side effects on human health and the environment. New active compounds and control strategies are needed for the management of phytopathogens. Antimicrobial peptides (AMPs) are evolutionarily conserved components of the innate immune response in almost all organisms that constitute an interesting source of potential molecules for use as pesticides. The naturally derived antimicrobial peptide Aq-AMP (Amaranthus quitensis-Antimicrobial Peptide), obtained from Amaranthus quitensis, is cysteine-rich with activity against several phytopathogens. In the present work, we report on the expression in Escherichia coli of functionally active Aq-AMP fused to thioredoxin (TrxAq-AMP). The in vitro antifungal activity of purified TrxAq-AMP was confirmed against Alternaria solani, Fusarium oxysporum f. sp. lycopersici, Pencillium digitatum and P. italicum, as well as the in vivo control of P. digitatum in oranges. We demonstrated the stability of TrxAq-AMP in a range of pH (from 3 to 11) and at temperatures from 0°C to 100°C. Furthermore, it maintained activity after digestion with various proteases and it displayed no haemolytic activity suggesting a highly stable and safe molecule. For topical application we present an AMP with gathering no hemolytic/phytotoxic activity that is effective, stable to a wide range of temperature and pH, pH-conditions and resistant to protease activity. Besides, this molecule is naturally stored in the seed, easily to extract and potentially produced through molecular farming. These findings encourage further biotechnological research on topical application of AMPs, especially those in relation related to molecule bioavailability.
Highlights
Synthetic pesticides have a significant impact on food production by reducing crop losses due to pests, disease and weeds
In order to obtain greater amounts of the recombinant protein Trx/ His/Aq-antimicrobial peptides (AMPs) we evaluated different expression conditions including two E. coli strains (BL21(D3) pLys and Shuffle) and two different induction temperatures (16°C ON and 37°C for 4 h)
The results showed better expression in the Shuffle strain with an induction temperature of 16°C ON
Summary
Synthetic pesticides have a significant impact on food production by reducing crop losses due to pests, disease and weeds. These positive benefits are being reconsidered in light of negative side effects. Searches are focused on new molecules with various properties including high specificity for target pathogens, effectiveness at low dosages and biodegradability, with a low risk for the development of resistance by the pathogen population. Most plant AMPs are small molecules with less than 50 amino acids, a molecular weight below 10 kDa, net positive charge, amphipathic and cysteine-rich with disulfide bonds that confer high stability [2,5]
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