title: Genetic and Biochemical Characterization of a Gene Operon fortrans-Aconitic Acid, a Novel Nematicide fromBacillus thuringiensis.
abstract: trans-Aconitic acid (TAA) is an isomer ofcis-aconitic acid (CAA), an intermediate of the tricarboxylic acid cycle that is synthesized by aconitase. Although TAA production has been detected in bacteria and plants for many years and is known to be a potent inhibitor of aconitase, its biosynthetic origins and the physiological relevance of its activity have remained unclear. We have serendipitously uncovered key information relevant to both of these questions. Specifically, in a search for novel nematicidal factors fromBacillus thuringiensis, a significant nematode pathogen harboring many protein virulence factors, we discovered a high yielding component that showed activity against the plant-parasitic nematodeMeloidogyne incognitaand surprisingly identified it as TAA. Comparison with CAA, which displayed a much weaker nematicidal effect, suggested that TAA is specifically synthesized byB. thuringiensisas a virulence factor. Analysis of mutants deficient in plasmids that were anticipated to encode virulence factors allowed us to isolate a TAA biosynthesis-related (tbr) operon consisting of two genes,tbrAandtbrBWe expressed the corresponding proteins, TbrA and TbrB, and characterized them as an aconitate isomerase and TAA transporter, respectively. Bioinformatics analysis of the TAA biosynthetic gene cluster revealed the association of the TAA genes with transposable elements relevant for horizontal gene transfer as well as a distribution acrossB. cereusbacteria and otherB. thuringiensisstrains, suggesting a general role for TAA in the interactions ofB. cereusgroup bacteria with nematode hosts in the soil environment. This study reveals new bioactivity for TAA and the TAA biosynthetic pathway, improving our understanding of virulence factors employed byB. thuringiensispathogenesis and providing potential implications for nematode management applications.
authors.affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Cuiying
authors.initials: C
authors.lastname: Du
authors.affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Shiyun
authors.initials: S
authors.lastname: Cao
authors.affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Xiangyu
authors.initials: X
authors.lastname: Shi
authors.affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Xiangtao
authors.initials: X
authors.lastname: Nie
authors.affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Jinshui
authors.initials: J
authors.lastname: Zheng
authors.affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Deng
authors.affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Lifang
authors.initials: L
authors.lastname: Ruan
authors.affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Donghai
authors.initials: D
authors.lastname: Peng
authors.affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China. Electronic address: m98sun@mail.hzau.edu.cn.
authors.forename: Ming
authors.initials: M
authors.lastname: Sun
mesh_terms: D000156:Aconitic Acid / Q000378:metabolism*; D000595:Amino Acid Sequence; D000969:Antinematodal Agents / Q000378:metabolism*; D001413:Bacillus thuringiensis / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D004251:DNA Transposable Elements; D005798:Genes, Bacterial; D007535:Isomerases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005810:Multigene Family; D009876:Operon; D016415:Sequence Alignment
chemical_list: D000969:Antinematodal Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004251:DNA Transposable Elements; D000156:Aconitic Acid; D007535:Isomerases
keywords: Bacillus thuringiensis; aconitate isomerase; bacterial genetics; bacterial toxin; biosynthesis; membrane transporter; nematicidal factor; small molecule; trans-aconitic acid; tricarboxylic acid cycle (TCA cycle) (Krebs cycle)