Transgenic tobacco plants expressing a chimeric antimicrobial protein show disease resistance to plant diseases

Plant-pathogen interactions are universal in nature and jeopardise plant health and ultimately global food security. Plant innate immunity can be enhanced by expressing antimicrobial proteins that interfere with the life cycle of plant pathogens. To this end, a recombinant protein comprising a chitinase chitin-binding domain (CBD) from rice and the Phyllomedusa bicolor Dermaseptin B1 (DrsB1) antimicrobial peptide was designed to target fungal cell wall component, chitin. Agrobacterium-mediated transformation of tobacco plants led to the transgenic plants exhibiting significantly resistance to fungal and bacterial plant pathogens. Fungal colonization as well as appearance of fungal disease symptoms delayed for one-week, taking a crucial opportunity from pathogens to establish infections at appropriate time and opportune environmental condition. Furthermore, results of in vitro analysis showed that total protein from transgenic plants significantly hindered growth and development of selected plant pathogens. Predictably, the CBD-DrsB1 recombinant protein had a stronger antimicrobial effect against fungal than bacterial and oomycete pathogens, suggesting that the CBD interferes with fungal cell wall component, chitin oligomers. Scanning electron micrograph (SEM) revealed that CBD-DrsB1 indeed interferes with fungal pathogens by damaging the overall cell wall integrity. Inoculating in vitro transgenic lines with Fusarium oxysporum, Alternaria solani and Pythium sp showed that plants remained green and vigorous and survived up to 51, 56 and 16 days post inoculation (dpi), respectively, whereas non-transgenic plants collapsed completely a few days post inoculation. The results of this study demonstrate that CBD-DrsB1 over-expression limits fungal and bacterial infections, suggesting both in vivo antibacterial activity and possible biotechnological application to engineer crop plants resistant to destructive plant pathogens.