Abstract
Antimicrobial peptides have been long known to confer resistance to plant pathogens. In this study, new recombinant peptides constructed from a dermaseptin B1 (DrsB1) peptide fused to a chitin-binding domain (CBD) from Avr4 protein, were used for Agrobacterium tumefaciens-mediated transformation of tobacco plants. Polymerase chain reaction (PCR), semi‐quantitative RT‐PCR, and western blotting analysis demonstrated the incorporation and expression of transgenes in tobacco genome and transgenic plants, respectively. In vitro experiments with recombinant peptides extracted from transgenic plants demonstrated a significant (P<0.01) inhibitory effect on the growth and development of plant pathogens. The DrsB1-CBD recombinant peptide had the highest antifungal activity against fungal pathogens. The expression of the recombinant peptides greatly protected transgenic plants from Alternaria alternata, Alternaria solani, Fusarium oxysporum, and Fusarium solani fungi, in comparison to Pythium sp. and Pythium aphanidermatum. Expression of new recombinant peptides resulted in a delay in the colonization of fungi and appearance of fungal disease symptoms from 6 days to more than 7 weeks. Scanning electron microscopy images revealed that the structure of the fungal mycelia appeared segmented, cling together, and crushed following the antimicrobial activity of the recombinant peptides. Greenhouse bioassay analysis showed that transgenic plants were more resistant to Fusarium and Pythium infections as compared with the control plants. Due to the high antimicrobial activity of the recombinant peptides against plant pathogens and novelty of recombinant peptides, this report shows the feasibility of this approach to generate disease resistance transgenic plants.
Highlights
Global food security is continuously threatened by many growing risk factors, including rapid world population growth, and devastating plant parasites
Polymerase chain reaction (PCR) analysis resulted in amplification of the expected fragments with the right size providing evidences that the transfer DNAs (T-DNAs) encoding the recombinant peptides had been incorporated into the transgenic lines genome
Selected transgenic tobacco lines were classified as low (L), medium (M), and high (H) expression based on the transcription level of transgenes relative to that of the elf1a as the housekeeping reference gene (Figure 2A)
Summary
Global food security is continuously threatened by many growing risk factors, including rapid world population growth, and devastating plant parasites. Biotic stress management has played a pivotal role in increasing food production in the last 50 years, plant. A long-chain polymer of N-acetylglucosamine, plays a crucial structural role in fungal cell walls and it is not produced by plant cells (Wan et al, 2008). Plant cells perceive chitin and chitooligosaccharides released from fungal invaders and trigger signaling via MAMP cascade initiating defense signaling through plasma membrane receptors (Kaku et al, 2006; Wan et al, 2008). Cladosporium fulvum Avr effector proteins bind to chitin molecules, preventing host chitinases from degradation activity (Van den Burg et al, 2006), suggesting that MAMPtriggered immunity is a critical barrier to overcome plant pathogens damage to plants
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