Class I defensins (BraDef) from broccoli ( Brassica oleracea var. italica ) seeds and their antimicrobial activity

The objective of this study was to determine whether seeds ofBrassica oleraceavar. italica (i.e. broccoli, an edible plant) produce defensins that inhibit phytopathogenic fungi and pathogenic bacteria of clinical significance. Crude extracts obtained from broccoli seeds were fractioned by molecular exclusion techniques and analyzed by liquid chromatography-high-resolution mass spectrometry. Two peptides were identified, BraDef1 (10.68  kDa) and BraDef2 (9.9 kDa), which were categorized as Class I defensins based on (a) their primary structure, (b) the presence of four putative cysteine disulfide bridges, and (c) molecular modeling predictions. BraDef1 and BraDef2 show identities of, respectively, 98 and 71%, and 67 and 85%, wit h defensins fromBrassica napus andArabidopsis thaliana. BraDef (BraDef1  + BraDef2) disrupted membranes ofColletotrichum gloeosporioides andAlternaria alternata and also reduced hyphal growth ofC. gloeosporioides by  ~ 56% after 120 h of incubation. Pathogenic bacteria (Bacilluscereus 183,Listeria monocytogenes,Salmonella typhimurium,Pseudomonas aeruginosa, andVibrio parahaemolitycus) were susceptible to BraDef, but probiotic bacteria such asBifidobacterium animalis,Lactobacillus acidophilus, andLactobacillus casei were not inhibited. To our knowledge, this is the first report of defensins present in seeds ofB. oleracea var.italica (i.e. edible broccoli). Our findings suggest an applied value for BraDef1/BraDef2 in controlling phytopathogeni...
Source: World Journal of Microbiology and Biotechnology - Category: Microbiology Source Type: research