title: A nonribosomal peptide synthase containing a stand-alone condensation domain is essential for phytotoxin zeamine biosynthesis.
abstract: Dickeya zeae is the causal agent of rice foot rot and maize stalk rot diseases, which could cause severe economic losses. The pathogen is known to produce two phytotoxins known as zeamine and zeamine II which are also potent antibiotics against both gram-positive and gram-negative bacteria pathogens. Zeamine II is a long-chain aminated polyketide and zeamine shares the same polyketide structure as zeamine II, with an extra valine derivative moiety conjugated to the primary amino group of zeamine II. In this study, we have identified a gene designated as zmsK encoding a putative nonribosomal peptide synthase (NRPS) by screening of the transposon mutants defective in zeamine production. Different from most known NRPS enzymes, which are commonly multidomain proteins, ZmsK contains only a condensation domain. High-performance liquid chromatography and mass spectrometry analyses showed that the ZmsK deletion mutant produced only zeamine II but not zeamine, suggesting that ZmsK catalyzes the amide bond formation by using zeamine II as a substrate to generate zeamine. We also present evidence that a partially conserved catalytic motif within the condensation domain is critical for zeamine production. Furthermore, we show that deletion of zmsK substantially decreased the total antimicrobial activity and virulence of D. zeae. Our findings provide a new insight into the biosynthesis pathway of zeamines and the virulence mechanisms of the bacterial pathogen D. zeae.
authors.forename: Yingying
authors.initials: Y
authors.lastname: Cheng
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Liu
authors.forename: Shuwen
authors.initials: S
authors.lastname: An
authors.forename: Changqing
authors.initials: C
authors.lastname: Chang
authors.forename: Yuanqiang
authors.initials: Y
authors.lastname: Zou
authors.forename: Luhao
authors.initials: L
authors.lastname: Huang
authors.forename: Jin
authors.initials: J
authors.lastname: Zhong
authors.forename: Qiongguang
authors.initials: Q
authors.lastname: Liu
authors.forename: Zide
authors.initials: Z
authors.lastname: Jiang
authors.forename: Jianuan
authors.initials: J
authors.lastname: Zhou
authors.forename: Lian-Hui
authors.initials: LH
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D000890:Anti-Infective Agents / Q000737:chemistry / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004755:Enterobacteriaceae / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity; D018525:Germination; D018942:Macrolides / Q000737:chemistry / Q000378:metabolism*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D012275:Oryza / Q000382:microbiology* / Q000502:physiology; D010453:Peptide Synthases / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D010935:Plant Diseases / Q000382:microbiology; D018517:Plant Roots / Q000382:microbiology / Q000502:physiology; D018520:Plant Shoots / Q000382:microbiology / Q000502:physiology; D011073:Polyamines / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012639:Seeds / Q000382:microbiology / Q000502:physiology; D016415:Sequence Alignment; D017384:Sequence Deletion; D014774:Virulence
chemical_list: D000890:Anti-Infective Agents; D001426:Bacterial Proteins; D018942:Macrolides; D011073:Polyamines; C547236:zeamine; D010453:Peptide Synthases; C104385:non-ribosomal peptide synthase