POLYKETIDE PRODUCTION BY PLANT-ASSOCIATED PSEUDOMONADS

Abstract

Polyketides constitute a huge family of structurally diverse natural products including antibiotics, chemotherapeutic compounds, and antiparasitics. Most of the research on polyketide synthesis in bacteria has focused on compounds synthesized by Streptomyces or other actinomycetes; however, plant-associated pseudomonads also produce a variety of compounds via the polyketide pathway including the phytotoxin coronatine, the antibiotic mupirocin, and the antifungal compounds pyoluteorin and 2,4-diacetylphloroglucinol. This review focuses on the mode of action, regulation, biosynthesis, and genetics of these four compounds and the potential use of Pseudomonas-derived polyketide synthases in the generation of novel compounds with unique activities.

2,5-Dialkylresorcinol Biosynthesis in Pseudomonas aurantiaca : Novel Head-to-Head Condensation of Two Fatty Acid-Derived Precursors

“…Shortly thereafter, Achenbach et al. reported identical 13 C-labeling patterns in the flexirubin DAR moiety (3); however, they also presented further evidence obtained from in vivo competitive labeling studies that is consistent with the hypothesis that orsellinic acid is a direct precursor of the DAR moiety. In addition, orsellinic acid was detected in culture extracts by isotope dilution techniques, further strengthening arguments that it is involved as a pathway precursor.…”

“…Because secondary metabolism significantly contributes to the molecular ecology of various Pseudomonas species and has also provided lead compounds for crop protection applications, several gene clusters that encode secondary metabolic pathways in this genus have been sequenced and characterized. Despite the structural simplicity of many Pseudomonas secondary metabolites, both the gene clusters and the metabolic pathways for the biosynthesis of these compounds often reveal surprising sophistication and divergence compared to the model systems studied in the gram-positive actinomycetes (13). For example, some Pseudomonas biosynthetic pathways have functionally combined modular, dissociated, or chalcone synthase-like polyketide synthases with adenylating enzymes (pyoluteorin, mupirocin, coronatine) or with components of fatty acid synthases (2,4-diacetylphloroglucinol) (13).…”

“…Despite the structural simplicity of many Pseudomonas secondary metabolites, both the gene clusters and the metabolic pathways for the biosynthesis of these compounds often reveal surprising sophistication and divergence compared to the model systems studied in the gram-positive actinomycetes (13). For example, some Pseudomonas biosynthetic pathways have functionally combined modular, dissociated, or chalcone synthase-like polyketide synthases with adenylating enzymes (pyoluteorin, mupirocin, coronatine) or with components of fatty acid synthases (2,4-diacetylphloroglucinol) (13). Other Pseudomonas pathways are composed of enzymes that rearrange and modify primary metabolic products to produce secondary metabolites (pyrrolnitrin, phenazine 1-carboxylic acid).…”

“…Achenbach et al initially described incorporation of radiolabeled acetate into the DAR moiety and speculated about the possibility that orsellinic acid is a DAR precursor (2). Sankawa et al subsequently demonstrated incorporation of [1,[2][3][4][5][6][7][8][9][10][11][12][13] C 2 ]acetate into HPR and, based on the observed labeling pattern, proposed that HPR arises by an unusual head-to-head condensation of two polyketide chains (45). Shortly thereafter, Achenbach et al.…”

A Prominent Role of the Flagellin Receptor FLAGELLIN-SENSING2 in Mediating Stomatal Response to Pseudomonas syringae pv tomato DC3000 in Arabidopsis

“…However, after 3 to 4 h, stomata reopen (Melotto et al, 2006). The ability of Pst DC3000 to reopen stomata is dependent on the polyketide toxin coronatine (COR), a virulence factor that had previously been shown to be important for bacterial multiplication within the mesophyll space, disease symptom development, and induction of systemic susceptibility of infected plants (Mittal and Davis, 1995;Bender et al, 1999;Budde and Ullrich, 2000;Brooks et al, 2004;Cui et al, 2005;Melotto et al, 2008b). Stomatal reopening by Pst DC3000 was also shown to be dependent on the RPM1-INTERACTING PROTEIN4 in Arabidopsis (Liu et al, 2009).…”