Transient expression and characterization of the antimicrobial peptide protegrin-1 in Nicotiana tabacum for control of bacterial and fungal mammalian pathogens

Mammalian infectious diseases are widespread, and some are becoming difficult to control due to inappropriate use of antibiotics. This has contributed to incidence of bacterial strains with resistance to commonly used antibiotics. Thus, effective alternative antibiotics are essential for treatment of infectious diseases. Antimicrobial peptides are viable alternatives to address this problem. Among those, protegrin-1 (PG-1) is a broad-spectrum antimicrobial peptide. In this study, a magnICON was used to express the PG-1 peptide in Nicotiana tabacum, using a transient expression system mediated by Agrobacterium tumefaciens transfection. Reverse-transcriptase polymerase chain reaction (RT-PCR) and Northern blot analyses of transformed N. tabacum were employed to detect viral replicons, 290 bp and 6.1 kb. SDS/PAGE revealed presence of a band corresponding to the molecular weight of PG-1 (2.1 kDa), which was absent in wild-type N. tabacum. Antimicrobial/antifungal assays of protein extracts from transiently transformed N. tabacum were performed, and these demonstrated that PG-1 peptide activity in these plant tissues was viable and contributed to inhibition of 53.2 % of Klebsiella pneumoniae, 70.2 %, of Staphylococcus aureus, 56.6 % of Escherichia coli, 72 % of Mycobacterium bovis BCG, and 70 % of Candida albicans cultures. No inhibition of any of these fungal and bacterial pathogens was detected when wild-type N. tabacum extracts were used. Therefore, PG-1 produced in plant cells of infiltrated tobacco was active and controlled growth of several bacterial and fungal human pathogens.