Biosynthesis of the yellow xanthomonadin pigments involves an ATP‐dependent 3‐hydroxybenzoic acid: acyl carrier protein ligase and an unusual type II polyketide synthase pathway

Abstract

Xanthomonadins are yellow pigments that are produced by the phytopathogen Xanthomonas campestris pv. campestris (Xcc). A pig cluster is responsible for xanthomonadin biosynthesis. Previously, Xcc4014 of the cluster was characterized as a bifunctional chorismatase that produces 3-hydroxybenzoic acid (3-HBA) and 4-HBA. In this study, genetic analysis identified 11 genes within the pig cluster to be essential for xanthomonadin biosynthesis. Biochemical and bioinformatics analysis suggest that xanthomonadins are synthesized via an unusual type II polyketide synthase pathway. Heterologous expression of the pig cluster in non-xanthomonadin-producing Pseudomonas aeruginosa strain resulted in the synthesis of chlorinated xanthomonadin-like pigments. Further analysis showed that xanC encodes an acyl carrier protein (ACP) while xanA2 encodes a ATP-dependent 3-HBA:ACP ligase. Both of them act together to catalyse the formation of 3-HBA-S-ACP from 3-HBA to initiate xanthomonadin biosynthesis. Finally, we showed that xanH encodes a FabG-like enzyme and xanK encodes a novel glycosyltransferase. Both xanH and xanK are not only required for xanthomonadin biosynthesis, but also required for the balanced biosynthesis of extracellular polysaccharides and DSF-family quorum sensing signals. These findings provide us with a better understanding of xanthomonadin biosynthetic mechanisms and directly demonstrate the presence of extensive cross-talk among xanthomonadin biosynthetic pathways and other metabolic pathways.

Biosynthesis of depsipeptides with a 3-hydroxybenzoate moiety and selective anticancer activities involves a chorismatase

“…The promising anticancer activities and the obscure biosynthetic origin of unantimycins prompted us to investigate further the biosynthetic pathway. Documentedly, 3-HBA generated by chorismatase from chorismate can be recruited as starting precursor in the biosynthesis of polyketides BC325, cuevaene, and xanthomonadin (14)(15)(16)(17) or as donor group in the late modification stage of terpenoid brasilicardin biosynthesis (18) (Fig. 2).…”

A novel 3‐oxoacyl‐ACP reductase (FabG3) is involved in the xanthomonadin biosynthesis of Xanthomonas campestris pv. campestris

“…In our study, Xcc fabG3 deletion abolished xanthomonadin production, which indicated that FabG3 plays a vital role in xanthomonadin synthesis. Cao et al (2018) identified 11 genes (named xanA2 to xanM, respectively) within the pig cluster as being essential for xanthomonadin synthesis, in which the ketoreductase-coding gene xanH corresponds to fabG3 in this study.…”

“…Xcc utilizes 3-hydroxybenzoic acid (3-HBA), a diffusible factor with regulatory function, as the precursor for xanthomonadin synthesis, and 3-HBA is synthesized by a unique bifunctional chorismatase XanB2 (He et al, 2011;Wang et al, 2015;Zhou et al, 2013a, b). Recently, Cao et al (2018) reported only 11 genes are responsible for xanthomonadin biosynthesis, and xanC encodes an acyl carrier protein (ACP) while xanA2 encodes the 3-HBA:ACP ligase to initiate xanthomonadin biosynthesis. However, further studies are required to define the detailed mechanisms of xanthomonadin synthesis.…”

The Plant Defense Signal Salicylic Acid Activates the RpfB-Dependent Quorum Sensing Signal Turnover via Altering the Culture and Cytoplasmic pH in the Phytopathogen Xanthomonas campestris

“…3A ). pchAB is responsible for the production of SA, a precursor for pyochelin, in Pseudomonas aeruginosa ( 37 ). When the Δ rpfC and Δ rpfC :: pchAB strains were grown in XYS medium, SA levels in Δ rpfC :: pchAB cultures were 55.1 μM at 12 hpi, 95.5 μM at 24 hpi, and 124.6 μM at 36 hpi, while SA was not detected in Δ rpfC cultures ( Fig.…”