Antimicrobial peptides (AMPs) play a major role in almost all living organisms innate immune defenses. AMPs are small proteins with ~10 to 50 amino acids that forms unique 3D structures and mode of action. Acquiring resistance against AMPs for pathogens is difficult because AMPs apply diverse range of activity. The expression of AMPs in plants to resist plant pathogens as well as to produce novel AMPs for pharmaceutical applications has recently received much consideration. Defensins are one of the most important cationic peptide families in plants.
Plant defensins are small, low molecular weight, highly stable, amphipathic and cysteine-rich that play a major role plants’ innate immune system. Defensins show a broad-spectrum antibacterial and antifungal activities against Gram-positive and Gram-negative bacteria, fungi and etc. Alfalfa seeds express a strong defensing, alfAFP, showing antimicrobial activity in vitro. Chitin-binding domains are conserved domain present in some families of animals, plant and fungi proteins, showing high affinity towards chitin as substrate. Fusion of AMPs to different partners may enhance the activity of new recombinant peptides towards host pathogens. To this end. in an attempt to show whether defensins show activity when present as fusion partners, bioinformatics and in vitro assays were used. Hairy root systems (HR) are used to produce and study recombinant proteins in plants as a model. Ease of induction and compatibility to different transformation protocols as well as short regeneration period, have made HRs excellent genetics model for production of recombinant proteins in plants