Abstract
Syringomycin E (SRE) is a phytotoxin produced by Pseudomonas syringae pv syringae with high potential as a safe and effective therapy for the control of human fungal infections and as a preservative for the food industry. In this study, 27 strains of P. syringae pv syringae were isolated from plums, potatoes, apricots and peaches, of which P. syringae pv syringae 120 (PS120) showed the highest SRE production levels. Furthermore, random mutagenesis induced by ultraviolet (UV) radiation resulted in the generation of a P. syringae pv syringae mutant that produced 30% more SRE than the parental strain PS120. To elucidate molecular mechanism underlying the higher SRE production ability of the mutant strain, syrB1 and syrB2 genes, which are known to be involved in SRE production, were cloned and sequenced. The nucleotide and amino acid sequences analysis showed that UV radiation induced numerous mutations at the AMP binding site on adenylation domain of syrB1, while no mutation was detected in syrB2 gene. Real-time polymerase chain reaction (PCR) results showed that expression of syrB1 gene in mutant strain was six-fold higher than that of PS120 strain. Taken together, these results suggest that the mutations at AMP binding site and overexpression of syrB1 were responsible for increased biosynthesis of SRE in P. syringae pv syringae. Key words: Antifungal protein, syringomycin E, UV mutagenesis, Pseudomonas syringae pv syringae, syrB1.
Highlights
The widespread resistance to commonly used antimicrobials and an increasing public health concern about the presence of chemicals in the food-chain have stimulated search for novel, effective and safeAfr
Random mutagenesis induced by ultraviolet (UV) radiation resulted in the generation of a P. syringae pv syringae mutant that produced 30% more Syringomycin E (SRE) than the parental strain pv syringae 120 (PS120)
These results suggest that the mutations at AMP binding site and overexpression of syrB1 were responsible for increased biosynthesis of SRE in P. syringae pv syringae
Summary
The widespread resistance to commonly used antimicrobials and an increasing public health concern about the presence of chemicals in the food-chain have stimulated search for novel, effective and safeAfr. Syringomycin has emerged as a new class of peptide presenting strong antimicrobial activity. Numerous studies have demonstrated the effectiveness of syringomycin E (SRE) against multiple filamentous fungal and yeast pathogens (Mazu et al, 2016; Im et al, 2003; Bender et al, 1999; De Lucca and Walsh, 1999; Fukuchi et al, 1992). The SRE is more effective at killing germinated spores of Aspergillus and Fusarium species than other peptides such as cecropin A, cecropin B and dermaseptin (De Lucca and Walsh, 1999). Kawasaki et al (2016) showed that SRE inhibits 50 and 90% of P. ultimum oospore germination at 31.3 and 250 μg/ml, respectively
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