Recently, new molecular breeding and genetic engineering approaches have emerged to overcome the
limitations of conventional breeding methods in generating disease-resistance transgenic plants. The
use of antimicrobial peptides (AMPs) to produce transgenic plants resistant to a wide range of plant
pathogens has achieved great success. Among huge number of AMPs, Dermaseptin B1 (DrsB1), an
antimicrobial cationic 31 amino acids peptide, exhibits significant antimicrobial activities towards a
wide range of pathogens. In order to increase the antimicrobial efficacy of DrsB1, the DrsB1 encoding
DNA sequence was either fused to the N- or C-terminus of the sequence encoding chitin-binding
domain (CBD) of Avr4 gene from Cladosporium fulvum and constructs (CBD-DrsB1 and DrsB1-
CBD) were used for tobacco leaf disk Agrobacterium-mediated transformation. Polymerase chain
reaction (PCR), semi-quantitative RT-PCR and SDS-PAGE analysis indicated the integration of
transgenes in tobacco genome and expression of the recombinant genes in transgenic plants,
respectively. The antimicrobial activity of extracted recombinant peptides were assessed against a
number of plant and human pathogens. Both recombinant peptides had statistically significant
(P<0.01) inhibitory effects on the growth and development of fungi pathogens. Also, CFU test result
showed that extracted recombinant peptides from transgenic plants, had a relatively high inhibitory
effect on plant pathogens. The CBD-DrsB1 recombinant peptide demonstrated a higher antibacterial
activity, whereas the DrsB1-CBD recombinant peptide performed a greater antifungal activity. In
addition, the expression of DrsB1-CBD recombinant peptide significantly inhibited R.solani fungal
infection in comparison with Pythium sp. interestingly, fungi with a higher amount of cell wall chitin
were more vulnerable to recombinant peptides, suggesting recombinant peptides present a higher
affinity for cell wall chitin. Owing to the high antimicrobial activity and novelty of recombinant
peptides, this strategy for the first time, could be used to generate transgenic crop plants resistant to
devastating plant pathogens.