Functional analysis of a biosynthetic cluster essential for production of 4-formylaminooxyvinylglycine, a germination-arrest factor from Pseudomonas fluorescens WH6

Abstract

Rhizosphere-associated Pseudomonas fluorescens WH6 produces the germination-arrest factor, 4-formylaminooxyvinylglycine (FVG). FVG has previously been shown to both arrest the germination of weedy grasses and to inhibit the growth of the bacterial plant pathogen Erwinia amylovora. Very little is known about the mechanism by which FVG is produced. Although a previous study identified a region of the genome that may be involved in FVG biosynthesis, it has not yet been determined which genes within that region are sufficient and necessary for FVG production. In the current study, we explored the role of each of the putative genes encoded in that region by constructing deletion mutations. Mutant strains were assayed for their ability to produce FVG with a combination of biological assays and thin-layer chromatographic analyses. This work defined the core FVG biosynthetic gene cluster and revealed several interesting characteristics of FVG production. We determined that FVG biosynthesis requires two small open reading frames of less than 150 nucleotides and that multiple transporters have overlapping but distinct functionality. In addition, two genes in the center of the biosynthetic gene cluster are not required for FVG production, suggesting that additional products may be produced from the cluster. Transcriptional analysis indicated that at least three active promoters play a role in the expression of genes within this cluster. The results of this study enrich our knowledge regarding the diversity of mechanisms by which bacteria produce non-proteinogenic amino acids like vinylglycines.