Expression and antimicrobial activity analysis of dermaseptin B1 recombinant peptides in tobacco transgenic plants

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.