Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2001
Publication Date: 6/1/2001
Citation: RAJASEKARAN, K., STROMBERG, K.D., CARY, J.W., CLEVELAND, T.E. BROAD SPECTRUM ANTIMICROBIAL ACTIVITY IN VITRO OF THE SYNTHETIC PEPTIDE D4E1. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY. 2001. V. 49(6). P. 2799-2803. Interpretive Summary: Fungal and bacterial diseases of cultivated crop plants cause huge losses in agricultural productivity. Certain fungi adversely affect human and livestock health by producing toxins in the affected grain and feed crops. In collaboration with the agricultural biotechnology industry, we studied the antimicrobial effects of a small protein called a peptide. We demonstrated that the synthetic peptide, D4E1, possesses a broadspectrum antimicrobial effect against several fungal and bacterial pathogens that affect crop productivity, and causes food and feed safety-related concerns due to mycotoxins. Previous research has shown that the D4E1 gene, when introduced into plants, provides built-in resistance to fungal diseases. Taken together, genetic modification of crop plants with this peptide has great utility in protecting plants against devastating microbial pathogens without using chemical fungicides.
Technical Abstract: Broadspectrum antimicrobial activity of a synthetic peptide, D4E1, has been documented in this report. D4E1 inhibited the growth of several fungal phytopathogens belonging to four classes - Ascomycetes, Basidiomycetes, Deuteromycetes and Oomycetes, and two bacterial pathogens, Pseudomonas syringae pv. tabaci and Xanthomonas campestris pv. malvacearum race 18. The minimum inhibitory concentration (MIC) of D4E1 required to completely inhibit the growth of all fungi studied ranged from 4.67 to slightly more than 25 uM. Fungal pathogens highly sensitive to D4E1 include Thielaviopsis basicola, Verticillium dahliae, Fusarium moniliforme, Phytophthora cinnamomi, and Phytophthora parasitica. Comparatively, the least sensitive fungal pathogens were Alternaria alternata, Colletotrichum destructivum, and Rhizoctonia solani. The two bacterial pathogens, P. syringae pv. tabaci and X. campestris pv. malvacearum race 18 were most sensitive to D4E1 with the MIC values 2.25 and 1.25 uM, respectively. Microscopic analysis of D4E1 effects on fungal morphology revealed abnormal hyphal growth, discontinuous cytoplasm and reduced spore germination. The suitability of the peptide D4E1 to enhance disease resistance in transgenic crop plants is presented in this report.