title: A functional 4-hydroxybenzoate degradation pathway in the phytopathogen Xanthomonas campestris is required for full pathogenicity.
abstract: Plants contain significant levels of natural phenolic compounds essential for reproduction and growth, as well as defense mechanisms against pathogens. Xanthomonas campestris pv. campestris (Xcc) is the causal agent of crucifers black rot. Here we showed that genes required for the synthesis, utilization, transportation, and degradation of 4-hydroxybenzoate (4-HBA) are present in Xcc. Xcc rapidly degrades 4-HBA, but has no effect on 2-hydroxybenzoate and 3-hydroxybenzoate when grown in XOLN medium. The genes for 4-HBA degradation are organized in a superoperonic cluster. Bioinformatics, biochemical, and genetic data showed that 4-HBA is hydroxylated by 4-HBA 3-hydroxylase (PobA), which is encoded by Xcc0356, to yield PCA. The resulting PCA is further metabolized via the PCA branches of the β-ketoadipate pathway, including Xcc0364, Xcc0365, and PcaFHGBDCR. Xcc0364 and Xcc0365 encode a new form of β-ketoadipate succinyl-coenzyme A transferase that is required for 4-HBA degradation. pobA expression was induced by 4-HBA via the transcriptional activator, PobR. Radish and cabbage hydrolysates contain 2-HBA, 3-HBA, 4-HBA, and other phenolic compounds. Addition of radish and cabbage hydrolysates to Xcc culture significantly induced the expression of pobA via PobR. The 4-HBA degradation pathway is required for full pathogenicity of Xcc in radish.
authors.affiliation: State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic &Developmental Sciences, School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Jia-Yuan
authors.initials: JY
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic &Developmental Sciences, School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Lian
authors.initials: L
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic &Developmental Sciences, School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic &Developmental Sciences, School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Shuang
authors.initials: S
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic &Developmental Sciences, School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic &Developmental Sciences, School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.affiliation: State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic &Developmental Sciences, School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Hongzhi
authors.initials: H
authors.lastname: Tang
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, and College of life science and technology, Guangxi University, Nanning 530004, China.
authors.forename: Bo-Le
authors.initials: BL
authors.lastname: Jiang
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, and College of life science and technology, Guangxi University, Nanning 530004, China.
authors.forename: Ji-Liang
authors.initials: JL
authors.lastname: Tang
authors.affiliation: State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic &Developmental Sciences, School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Ya-Wen
authors.initials: YW
authors.lastname: He
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001937:Brassica / Q000382:microbiology; D002853:Chromatography, Liquid; D023061:Gene Order; D005798:Genes, Bacterial / Q000235:genetics; D016680:Genome, Bacterial / Q000235:genetics; D013058:Mass Spectrometry; D053858:Metabolic Networks and Pathways / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family; D010226:Parabens / Q000378:metabolism*; D010636:Phenols / Q000378:metabolism; D010935:Plant Diseases / Q000382:microbiology*; D031224:Raphanus / Q000382:microbiology; D017386:Sequence Homology, Amino Acid; D014774:Virulence / Q000235:genetics; D016959:Xanthomonas campestris / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity
chemical_list: D001426:Bacterial Proteins; D010226:Parabens; D010636:Phenols; C038193:4-hydroxybenzoic acid