An Antimetabolite Toxin (Mangotoxin) is Produced by Pseudomonas syringae pv. syringae Isolated from Mango

Abstract

In this study, we reported the production of an antimetabolite toxin (named mangotoxin), mainly by strains of Pseudomonas syringae pv. syringae pathogenic to mango. The target of mangotoxin is the enzymatic step where ornithine is produced from N-acetyl ornithine in the biosynthetic pathway of arginine. The inhibition of ornithine acetyltransferase [glutamate N-acetyltransferase] activity by mangotoxin was confirmed by exposing tomato leaf protein extracts to filtrates from cultures of P. syringae pv. syringae. Mutants impaired in the production of mangotoxin were constructed. Sequencing of Tn5 flanking regions of 9 non/low-producers mutants revealed that several genes codifying for putative acetyltransferase, non-ribosomal peptide synthetase and the global regulators proteins GacA and LemA could be involved in mangotoxin production. Mangotoxin also showed antimicrobial activity against some microorganisms, usually found on plant tissues as epiphytic or pathogenic microorganisms. To conclude, the possible role of the mangotoxin in pathogenesis is discussed.