The Pseudomonas aeruginosa antimetabolite L‐2‐amino‐4‐methoxy‐trans‐3‐butenoic acid inhibits growth of Erwinia amylovora and acts as a seed germination‐arrest factor

Abstract

The Pseudomonas aeruginosa antimetabolite L-2-amino-4-methoxy-trans-3-butenoic acid (AMB) shares biological activities with 4-formylaminooxyvinylglycine, a related molecule produced by Pseudomonas fluorescens WH6. We found that culture filtrates of a P. aeruginosa strain overproducing AMB weakly interfered with seed germination of the grassy weed Poa annua and strongly inhibited growth of Erwinia amylovora, the causal agent of the devastating orchard crop disease known as fire blight. AMB was active against a 4-formylaminooxyvinylglycine-resistant isolate of E. amylovora, suggesting that the molecular targets of the two oxyvinylglycines in Erwinia do not, or not entirely, overlap. The AMB biosynthesis and transport genes were shown to be organized in two separate transcriptional units, ambA and ambBCDE, which were successfully expressed from IPTG-inducible tac promoters in the heterologous host P. fluorescens CHA0. Engineered AMB production enabled this model biocontrol strain to become inhibitory against E. amylovora and to weakly interfere with the germination of several graminaceous seeds. We conclude that AMB production requires no additional genes besides ambABCDE and we speculate that their expression in marketed fire blight biocontrol strains could potentially contribute to disease control.

Indole-3-acetic acid (IAA) producing Pseudomonas isolates inhibit seed germination and α-amylase activity in durum wheat (Triticum turgidum L.)

“…For example, some of the bacteria in this group are known to be pathogenic (Hirano & Upper, 2000), while others are known to be involved in disease suppression (Halgren et al, 2011). In addition, some members of this group of bacteria appear to increase seed germination (Selvakumar et al, 2009), while others exert inhibitory effects on seed germination (McPhail et al, 2010;Lee et al, 2013). Germination arrest factors (GAFs) have been the subject of increased research in recent years.…”

“…The 2 of seed germination in a wide range of graminaceous species (Banowetz et al, 2008). For example, the compounds 4-formylaminooxyvinylglycine (FVG) (McPhail et al, 2010) and L-2-amino-4-methoxy-trans-3-butenoic acid (AMB) (Lee et al, 2013) are two GAFs produced by Pseudomonas species. However, there is a gap in knowledge regarding the impact of GAFs on wheat seed germination, in general, and on durum wheat (Triticum turgidum L.) seed, in particular.…”

The periplasmic binding protein NrtT affects xantham gum production and pathogenesis in Xanthomonas citri

“…1B). In P. aeruginosa putative orthologues of NrtT belong to distinct loci: the first one (consisting of genes PA2305 up to PA2310) conserves part of the genome organization found in X. citri and also a gene encoding a taurine dehydrogenase (PA2310), which is implicated in l ‐2‐amino‐4‐methoxy‐ trans ‐3‐butenoic acid production 32. The second operon (genes PA3512 to PA3514) encodes a putative ABC transporter and belongs to an extensive locus that represents a set of hypothetical proteins involved with metabolism of aldehydes, adenyl succinate and acetolactate and with cell division.…”

The Pseudomonas aeruginosa antimetabolite L -2-amino-4-methoxy-trans-3-butenoic acid (AMB) is made from glutamate and two alanine residues via a thiotemplate-linked tripeptide precursor

“…Although AMB was found to inhibit growth and to induce cyst formation, the effective concentrations were rather high, making a strong contribution of AMB to the virulence of P. aeruginosa unlikely. AMB may be more important during interactions of P. aeruginosa with other microbes and it is interesting to note in this respect that AMB can inhibit the growth of important plant and animal pathogens such as Erwinia amylovora (Lee et al, 2013a) and Staphylococcus aureus (our unpublished observation).…”

“…Transposon mutagenesis and reverse genetics have previously led to the identification of the P. aeruginosa ambABCDE gene cluster which comprises two transcriptional units (Lee et al, 2010, 2013a; Figure 1 ). Transfer of this cluster to strains devoid of amb genes, such as P. aeruginosa PA7, or P. fluorescens CHA0, rendered them capable of synthesizing AMB (Lee et al, 2010, 2013a), demonstrating that these genes are both essential and sufficient for AMB production.…”