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Zhang X, Wu N, Geng K, Yuan C, Wang B, Shi J, Qiu J, He J. Identification of a chlorosalicylic acid decarboxylase (CsaD) involved in decarboxylation of 3,6-DCSA from an anaerobic dicamba-degrading sludge. Appl Environ Microbiol 2024:e0131924. [PMID: 39248463 DOI: 10.1128/aem.01319-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2024] [Accepted: 08/22/2024] [Indexed: 09/10/2024] Open
Abstract
3,6-Dichlorosalicylic acid (3,6-DCSA) is the demethylation metabolite of herbicide 3,6-dichloro-2-methoxy benzoic acid (dicamba). Previous studies have shown that anaerobic sludge further transformed 3,6-DCSA through decarboxylation and dechlorination. However, the anaerobe, enzyme, and gene involved in the anaerobic degradation of 3,6-DCSA are still unknown. In this study, an anaerobic sludge that efficiently degraded dicamba was enriched, and a 3,6-DCSA decarboxylase, designated chlorosalicylic acid decarboxylase (CsaD), was partially purified and identified from the anaerobic sludge. Metagenomic analysis showed that the csaD gene was located in a gene cluster of metagenome-assembled genome 8 (MAG8). MAG8 belonged to an uncultured order, OPB41, in the class Coriobacteriia of the phylum Actinobacteria, and its abundance increased approximately once during the enrichment process. CsaD was a non-oxidative decarboxylase in the amidohydrolase 2 family catalyzing the decarboxylation of 3,6-DCSA and 6-chlorosalicylic acid (6-CSA). Its affinity and catalytic efficiency for 3,6-DCSA were significantly higher than those for 6-CSA. This study provides new insights into the anaerobic catabolism of herbicide dicamba.IMPORTANCEDicamba, an important hormone herbicide, easily migrates to anoxic habitats such as sediment, ground water, and deep soil. Thus, the anaerobic catabolism of dicamba is of importance. Anaerobic bacteria or sludge demethylated dicamba to 3,6-DCSA, and in a previous study, based on metabolite identification, it was proposed that 3,6-DCSA be further degraded via two pathways: decarboxylation to 2,5-dichlorophenol, then dechlorination to 3-chlorophenol (3-CP); or dechlorination to 6-CSA, then decarboxylation to 3-CP. However, there was no physiological and genetic validation for the pathway. In this study, CsaD catalyzed the decarboxylation of both 3,6-DCSA and 6-CSA, providing enzyme-level evidence for the anaerobic catabolism of 3,6-DCSA through the two pathways. CsaD was located in MAG8, which belonged to an uncultured anaerobic actinomycetes order, OPB41, indicating that anaerobic actinomycetes in OPB41 was involved in the decarboxylation of 3,6-DCSA. This study provides a basis for understanding the anaerobic catabolism of dicamba and the demethylation product, 3,6-DCSA.
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Affiliation(s)
- Xuan Zhang
- Department of Microbiology, College of Life Sciences, Nanjing Agricultural University, Key Laboratory of Agricultural and Environmental Microbiology, Ministry of Agriculture and Rural Affairs, Nanjing, China
| | - Ningning Wu
- Department of Microbiology, College of Life Sciences, Nanjing Agricultural University, Key Laboratory of Agricultural and Environmental Microbiology, Ministry of Agriculture and Rural Affairs, Nanjing, China
| | - Keke Geng
- College of Rural Revitalization, Jiangsu Open University, Nanjing, China
| | - Cansheng Yuan
- College of Rural Revitalization, Jiangsu Open University, Nanjing, China
| | - Baozhan Wang
- Department of Microbiology, College of Life Sciences, Nanjing Agricultural University, Key Laboratory of Agricultural and Environmental Microbiology, Ministry of Agriculture and Rural Affairs, Nanjing, China
| | - Junyu Shi
- Department of Microbiology, College of Life Sciences, Nanjing Agricultural University, Key Laboratory of Agricultural and Environmental Microbiology, Ministry of Agriculture and Rural Affairs, Nanjing, China
| | - Jiguo Qiu
- Department of Microbiology, College of Life Sciences, Nanjing Agricultural University, Key Laboratory of Agricultural and Environmental Microbiology, Ministry of Agriculture and Rural Affairs, Nanjing, China
| | - Jian He
- Department of Microbiology, College of Life Sciences, Nanjing Agricultural University, Key Laboratory of Agricultural and Environmental Microbiology, Ministry of Agriculture and Rural Affairs, Nanjing, China
- Agricultural Microbial Resources Protection and Germplasm Innovation and Utilization Center of Jiangsu Province, Nanjing, Jiangsu, China
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Zhang X, Wu N, Ke Z, Shi J, Wang L, Yuan C, He J. Anaerobic Degradation of Dicamba via a Novel Catabolic Pathway by a Consortium Enriched from Deep Paddy Soil. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2024; 72:1035-1043. [PMID: 38179682 DOI: 10.1021/acs.jafc.3c07903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2024]
Abstract
Dicamba is widely used in the paddy field to control broadleaf weeds. Dicamba easily migrates to deep soil, which is anoxic; however, the anaerobic catabolism of dicamba in paddy soil is still unknown. In this study, an anaerobic dicamba-degrading consortium was enriched from deep paddy soil. The consortium completely degraded 0.83 mM dicamba within 7 days. Five metabolites were identified, one of which is a new metabolite, 2,5-dichlorophenol, and a novel anaerobic dicamba degradation pathway was proposed. 2.5 mM dicamba, 1.5-2.0% NaCl, and 20 mM electron acceptors Na2SO4, NaNO3, and FeCl3, and 0.5 mM or more of metabolites 3-CP and 2,5-DCP strongly inhibited the degradation efficiency. During enrichment, the microbial community of the consortium was significantly changed with OTU numbers, and diversity decreased. The study is valuable to elucidate the catabolism and ecotoxicology studies of dicamba in paddy soil and to facilitate the engineering application of anaerobic technology to treat dicamba-manufacturing wastewater.
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Affiliation(s)
- Xuan Zhang
- Department of Microbiology, College of Life Sciences, Key Laboratory of Agricultural and Environmental Microbiology, Ministry of Agriculture and Rural Affairs, Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China
| | - Ningning Wu
- Department of Microbiology, College of Life Sciences, Key Laboratory of Agricultural and Environmental Microbiology, Ministry of Agriculture and Rural Affairs, Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China
| | - Zhuang Ke
- College of Rural Revitalization, Jiangsu Open University, Nanjing, Jiangsu 210036, PR China
| | - Junyu Shi
- Department of Microbiology, College of Life Sciences, Key Laboratory of Agricultural and Environmental Microbiology, Ministry of Agriculture and Rural Affairs, Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China
| | - Lin Wang
- College of Rural Revitalization, Jiangsu Open University, Nanjing, Jiangsu 210036, PR China
| | - Cansheng Yuan
- College of Rural Revitalization, Jiangsu Open University, Nanjing, Jiangsu 210036, PR China
| | - Jian He
- Department of Microbiology, College of Life Sciences, Key Laboratory of Agricultural and Environmental Microbiology, Ministry of Agriculture and Rural Affairs, Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China
- Agricultural Microbial Resources Protection and Germplasm Innovation and Utilization Center of Jiangsu Province, Nanjing, Jiangsu 210095, PR China
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3
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Li N, Chen L, Chen E, Yuan C, Zhang H, He J. Cloning of a novel tetrahydrofolate-dependent dicamba demethylase gene from dicamba-degrading consortium and characterization of the gene product. Front Microbiol 2022; 13:978577. [PMID: 36033860 PMCID: PMC9404685 DOI: 10.3389/fmicb.2022.978577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2022] [Accepted: 07/14/2022] [Indexed: 11/13/2022] Open
Abstract
Dicamba, an important hormone-type systemic herbicide, is widely used to control more than 200 kinds of broadleaf weeds in agriculture. Due to its broad-spectrum, high efficiency and effectively killing glyphosate-resistant weeds, dicamba is considered as an excellent target herbicide for the engineering of herbicide-resistant crops. In this study, an efficient dicamba-degrading microbial consortium was enriched from soil collected from the outfall of a pesticide factory. The enriched consortium could almost completely degrade 500 mg/L of dicamba within 12 h of incubation. A novel tetrahydrofolate (THF)-dependent dicamba demethylase gene, named dmt06, was cloned from the total DNA of the enriched consortium. Dmt06 shared the highest identity (72.3%) with dicamba demethylase Dmt50 from Rhizorhabdus dicambivorans Ndbn-20. Dmt06 was expressed in Escherichia coli BL21 and purified to homogeneity using Co2+-charged nitrilotriacetic acid affinity chromatography. The purified Dmt06 catalyzed the transfer of methyl from dicamba to THF, generating the herbicidally inactive metabolite 3,6-dichlorosalicylate (3,6-DCSA) and 5-methyl-THF. The optimum pH and temperature for Dmt06 were detected to be 7.4 and 35°C, respectively. Under the optimal condition, the specific activity of Dmt06 reached 165 nmol/min/mg toward dicamba, which was much higher than that of Dmt and Dmt50. In conclusion, this study cloned a novel gene, dmt06, encoding an efficient THF-dependent dicamba demethylase, which was a good candidate for dicamba-resistant transgenic engineering.
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Affiliation(s)
- Na Li
- College of Life Science and Agricultural Engineering, Nanyang Normal University, Nanyang, China
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, China
| | - Le Chen
- Jiangsu Academy of Agricultural Sciences, Institute of Germplasm Resources and Biotechnology, Nanjing, China
| | - E. Chen
- The Environmental Monitoring Center of Gansu Province, Lanzhou, China
| | - Cansheng Yuan
- College of Rural Revitalization, Jiangsu Open University, Nanjing, China
- Cansheng Yuan,
| | - Hao Zhang
- College of Life Science and Agricultural Engineering, Nanyang Normal University, Nanyang, China
| | - Jian He
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, China
- College of Rural Revitalization, Jiangsu Open University, Nanjing, China
- *Correspondence: Jian He, ;
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Cai C, Xu Z, Zhou H, Chen S, Jin M. Valorization of lignin components into gallate by integrated biological hydroxylation, O-demethylation, and aryl side-chain oxidation. SCIENCE ADVANCES 2021; 7:eabg4585. [PMID: 34516898 PMCID: PMC8442903 DOI: 10.1126/sciadv.abg4585] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Converting lignin components into a single product is a promising way to upgrade lignin. Here, an efficient biocatalyst was developed to selectively produce gallate from lignin components by integrating three main reactions: hydroxylation, O-demethylation, and aryl side-chain oxidation. A rationally designed hydroxylase system was first introduced into a gallate biodegradation pathway–blocked Rhodococcus opacus mutant so that gallate accumulated from protocatechuate and compounds in its upper pathways. Native and heterologous O-demethylation systems were then used, leading to multiple lignin-derived methoxy aromatics being converted to gallate. Furthermore, an aryl side-chain oxidase was engaged to broaden the substrate spectrum. Consequently, the developed biocatalyst showed that gallate yields as high as 0.407 and 0.630 g of gallate per gram of lignin when alkaline-pretreated lignin and base-depolymerized ammonia fiber explosion lignin were applied as substrates, respectively. These results suggested that this rationally developed biocatalyst enabled the lignin valorization process to be simple and efficient.
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Affiliation(s)
- Chenggu Cai
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing 210094, China
| | - Zhaoxian Xu
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing 210094, China
| | - Huarong Zhou
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing 210094, China
| | - Sitong Chen
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing 210094, China
| | - Mingjie Jin
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing 210094, China
- Corresponding author.
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Li N, Peng Q, Yao L, He Q, Qiu J, Cao H, He J, Niu Q, Lu Y, Hui F. Roles of the Gentisate 1,2-Dioxygenases DsmD and GtdA in the Catabolism of the Herbicide Dicamba in Rhizorhabdus dicambivorans Ndbn-20. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2020; 68:9287-9298. [PMID: 32786824 DOI: 10.1021/acs.jafc.0c01523] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
3-Chlorogentisate is a key intermediate in the catabolism of the herbicide dicamba in R. dicambivorans Ndbn-20. In this study, we identified two gentisate 1,2-dioxygenases (GDOs), DsmD and GtdA, from Ndbn-20. The amino acid sequence similarity between DsmD and GtdA is 51%. Both of them are dimers and showed activities to gentisate and 3-chlorogentisate but not 3,6-dichlorogentisate (3,6-DCGA) or 6-chlorogentisate in vitro. The kcat/Km of DsmD for 3-chlorogentisate was 28.7 times higher than that of GtdA, whereas the kcat/Km of DsmD for gentisate was only one-fourth of that of GtdA. Transcription of dsmD was dramatically induced by 3-chlorogentisate but not gentisate, whereas gtdA was not induced. Disruption of dsmD resulted in a significant decline in the degradation rates of 3-chlorogentisate and dicamba but had no effect on the degradation of gentisate, whereas the result of disruption of gtdA was converse; the disruption of both dsmD and gtdA led to the inability to degrade 3-chlorogentisate and gentisate. This study revealed that 3-chlorogentisate but not gentisate or 3,6-DCGA is the ring-cleavage substrate in the dicamba degradation pathway in R. dicambivorans Ndbn-20; DsmD is specifically responsible for cleavage of 3-chlorogentisate, whereas GtdA is a general GDO involved in the catabolism of various natural aromatic compounds.
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Affiliation(s)
- Na Li
- School of Life Science and Technology, Nanyang Normal University, Nanyang, Henan 473061, China
| | - Qian Peng
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China
| | - Li Yao
- School of Marine and Biological Engineering, Yancheng Teachers University, Yancheng, Jiangsu 224002, China
| | - Qin He
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China
| | - Jiguo Qiu
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China
| | - Hui Cao
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China
| | - Jian He
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China
| | - Qiuhong Niu
- School of Life Science and Technology, Nanyang Normal University, Nanyang, Henan 473061, China
| | - Yunfeng Lu
- School of Life Science and Technology, Nanyang Normal University, Nanyang, Henan 473061, China
- State Key Laboratory of Motor Vehicle Biofuel Technology, Nanyang, Henan 473000, China
| | - Fengli Hui
- School of Life Science and Technology, Nanyang Normal University, Nanyang, Henan 473061, China
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The Properties of 5-Methyltetrahydrofolate Dehydrogenase (MetF1) and Its Role in the Tetrahydrofolate-Dependent Dicamba Demethylation System in Rhizorhabdus dicambivorans Ndbn-20. J Bacteriol 2019; 201:JB.00096-19. [PMID: 31209079 DOI: 10.1128/jb.00096-19] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 06/13/2019] [Indexed: 11/20/2022] Open
Abstract
The herbicide dicamba is initially degraded via the tetrahydrofolate (THF)-dependent demethylation system in Rhizorhabdus dicambivorans Ndbn-20. Two THF-dependent dicamba methyltransferase gene clusters, scaffold 50 and scaffold 66, were found in the genome of strain Ndbn-20. Each cluster contains a dicamba methyltransferase gene and three THF metabolism-related genes, namely, metF (coding for 5,10-CH2-THF reductase), folD (coding for 5,10-CH2-THF dehydrogenase-5,10-methenyl-THF cyclohydrolase), and purU (coding for 10-formyl-THF deformylase). In this study, reverse transcription-PCR (RT-PCR) results showed that only genes in scaffold 66, not those in scaffold 50, were transcribed in dicamba-cultured cells. The metF gene of scaffold 66 (metF1) was expressed in Escherichia coli BL21(DE3), and the product was purified as a His6-tagged protein. Purified MetF1 was found to be a monomer and exhibited 5-CH3-THF dehydrogenase activity in vitro The k cat and Km for 5-CH3-THF were 0.23 s-1 and 16.48 μM, respectively. However, 5,10-CH2-THF reductase activity was not detected for MetF1 under the conditions tested. Gene disruption results showed that metF1 is essential for dicamba degradation, whereas folD1 is dispensable.IMPORTANCE There are several THF-dependent methyltransferase genes and THF-metabolic genes in the genome of R. dicambivorans Ndbn-20; however, which genes are involved in dicamba demethylation and the mechanism underlying THF regeneration remain unknown. This study revealed that scaffold 66 is responsible for dicamba demethylation and that MetF1 physiologically catalyzes the dehydrogenation of 5-CH3-THF to 5,10-CH2-THF in the THF-dependent dicamba demethylation system in R. dicambivorans Ndbn-20. Furthermore, the results showed that MetF1 differs from previously characterized MetF in phylogenesis, biochemical properties, and catalytic activity; e.g., MetF1 in vitro did not show 5,10-CH2-THF reductase activity, which is the physiological function of Escherichia coli MetF. This study provides new insights into the mechanism of the THF-dependent methyltransferase system.
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Rossmassler K, Kim S, Broeckling CD, Galloway S, Prenni J, De Long SK. Impact of primary carbon sources on microbiome shaping and biotransformation of pharmaceuticals and personal care products. Biodegradation 2019; 30:127-145. [PMID: 30820709 DOI: 10.1007/s10532-019-09871-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Accepted: 02/14/2019] [Indexed: 12/26/2022]
Abstract
Knowledge of the conditions that promote the growth and activity of pharmaceutical and personal care product (PPCP)-degrading microorganisms within mixed microbial systems are needed to shape microbiomes in biotreatment reactors and manage process performance. Available carbon sources influence microbial community structure, and specific carbon sources could potentially be added to end-of-treatment train biotreatment systems (e.g., soil aquifer treatment [SAT]) to select for the growth and activity of a range of microbial phylotypes that collectively degrade target PPCPs. Herein, the impacts of primary carbon sources on PPCP biodegradation and microbial community structure were explored to identify promising carbon sources for PPCP biotreatment application. Six types of primary carbon sources were investigated: casamino acids, two humic acid and peptone mixtures (high and low amounts of humic acid), molasses, an organic acids mixture, and phenol. Biodegradation was tracked for five PPCPs (diclofenac, 5-fluorouracil, gemfibrozil, ibuprofen, and triclosan). Primary carbon sources were found to differentially impact microbial community structures and rates and efficiencies of PPCP biotransformation. Of the primary carbon sources tested, casamino acids, organic acids, and phenol showed the fastest biotransformation; however, on a biomass-normalized basis, both humic acid-peptone mixtures showed comparable or superior biotransformation. By comparing microbial communities for the different primary carbon sources, abundances of unclassified Beijerinckiaceae, Beijerinckia, Sphingomonas, unclassified Sphingomonadaceae, Flavobacterium, unclassified Rhizobiales, and Nevskia were statistically linked with biotransformation of specific PPCPs.
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Affiliation(s)
- Karen Rossmassler
- Department of Civil and Environmental Engineering, Colorado State University, 1301 Campus Delivery, Fort Collins, CO, 80523, USA
- Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, 80045, USA
| | - Sunah Kim
- Department of Civil and Environmental Engineering, Colorado State University, 1301 Campus Delivery, Fort Collins, CO, 80523, USA
- Department of Civil and Environmental Engineering, Pusan National University, Busan, 46241, Republic of Korea
| | - Corey D Broeckling
- Proteomics and Metabolomics Facility, Colorado State University, Fort Collins, CO, USA
| | - Sarah Galloway
- Proteomics and Metabolomics Facility, Colorado State University, Fort Collins, CO, USA
| | - Jessica Prenni
- Proteomics and Metabolomics Facility, Colorado State University, Fort Collins, CO, USA
| | - Susan K De Long
- Department of Civil and Environmental Engineering, Colorado State University, 1301 Campus Delivery, Fort Collins, CO, 80523, USA.
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Chen L, Yao S, Chen T, Tao Q, Xie X, Xiao X, Ding D, He Q, He J. Coexpression of Methyltransferase Gene dmt50 and Methylene Tetrahydrofolate Reductase Gene Increases Arabidopsis thaliana Dicamba Resistance. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2019; 67:1443-1452. [PMID: 30653319 DOI: 10.1021/acs.jafc.8b04944] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Dicamba, a broad-spectrum and highly efficient herbicide, is an excellent target herbicide for the engineering of herbicide-resistant crops. In this study, a new tetrahydrofolate (THF)-dependent dicamba methyltransferase gene, dmt50, was cloned from the dicamba-degrading strain Rhizorhabdus dicambivorans Ndbn-20. Dmt50 catalyzed the methyl transfer from dicamba to THF, generating the herbicidally inactive product 3,6-dichlorosalicylic acid (3,6-DCSA) and 5-methyl-THF. A dmt50 transgenic Arabidopsis thaliana clearly showed dicamba resistance (560 g/ha, the normal field application rate). However, Dmt50 demethylation activity was inhibited by the product 5-methyl-THF. Mthfr66, encoded by the 5,10-methylene-THF reductase gene mthfr66 could relieve the inhibition by removing 5-methyl-THF in vitro. Compared with expression of dmt50 alone, simultaneous expression of dmt50 and mthfr66 further improved the dicamba resistance (1120 g/ha) of transgenic A. thaliana. This study provides new genes for dicamba detoxification and a strategy for the engineering of dicamba-resistant crops.
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Affiliation(s)
- Le Chen
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences , Nanjing Agricultural University , Nanjing 210095 , Jiangsu , P. R. China
| | - Shigang Yao
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences , Nanjing Agricultural University , Nanjing 210095 , Jiangsu , P. R. China
| | - Tao Chen
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences , Nanjing Agricultural University , Nanjing 210095 , Jiangsu , P. R. China
| | - Qin Tao
- Beijing DBN Biotech Company, Limited , Beijing 100080 , P. R. China
| | - Xiangting Xie
- Beijing DBN Biotech Company, Limited , Beijing 100080 , P. R. China
| | - Xiang Xiao
- Beijing DBN Biotech Company, Limited , Beijing 100080 , P. R. China
| | - Derong Ding
- Beijing DBN Biotech Company, Limited , Beijing 100080 , P. R. China
| | - Qin He
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences , Nanjing Agricultural University , Nanjing 210095 , Jiangsu , P. R. China
| | - Jian He
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences , Nanjing Agricultural University , Nanjing 210095 , Jiangsu , P. R. China
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Roles of Two Glutathione-Dependent 3,6-Dichlorogentisate Dehalogenases in Rhizorhabdus dicambivorans Ndbn-20 in the Catabolism of the Herbicide Dicamba. Appl Environ Microbiol 2018; 84:AEM.00623-18. [PMID: 29934333 DOI: 10.1128/aem.00623-18] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 06/18/2018] [Indexed: 11/20/2022] Open
Abstract
The herbicide dicamba is initially demethylated to 3,6-dichlorosalicylate (3,6-DCSA) in Rhizorhabdus dicambivorans Ndbn-20 and is subsequently 5-hydroxylated to 3,6-dichlorogentisate (3,6-DCGA). In the present study, two glutathione-dependent 3,6-DCGA dehalogenases, DsmH1 and DsmH2, were identified in strain Ndbn-20. DsmH2 shared a low identity (only 31%) with the tetrachlorohydroquinone (TCHQ) dehalogenase PcpC from Sphingobium chlorophenolicum ATCC 39723, while DsmH1 shared a high identity (79%) with PcpC. In the phylogenetic tree of related glutathione S-transferases (GSTs), DsmH1 and DsmH2, together with PcpC and the 2,5-dichlorohydroquinone dehalogenase LinD, formed a separate clade. DsmH1 and DsmH2 were synthesized in Escherichia coli BL21 and purified as His-tagged enzymes. Both enzymes required glutathione (GSH) as a cofactor and could 6-dechlorinate 3,6-DCGA to 3-chlorogentisate in vitro DsmH2 had a significantly higher catalytic efficiency toward 3,6-DCGA than DsmH1. Transcription and disruption analysis revealed that DsmH2 but not DsmH1 was responsible for the 6-dechlorination of 3,6-DCGA in strain Ndbn-20 in vivo Furthermore, we propose a novel eta class of GSTs to accommodate the four bacterial dehalogenases PcpC, LinD, DsmH1, and DsmH2.IMPORTANCE Dicamba is an important herbicide, and its use and leakage into the environment have dramatically increased since the large-scale planting of genetically modified (GM) dicamba-resistant crops in 2015. However, the complete catabolic pathway of dicamba has remained unknown, which limits ecotoxicological studies of this herbicide. Our previous study revealed that 3,6-DCGA was an intermediate of dicamba degradation in strain Ndbn-20. In this study, we identified two glutathione-dependent 3,6-DCGA dehalogenases, DsmH1 and DsmH2, and demonstrated that DsmH2 is physiologically responsible for the 6-dechlorination of 3,6-DCGA in strain Ndbn-20. GSTs play an important role in the detoxification and degradation of a variety of endogenous and exogenous toxic compounds. On the basis of their sequence identities, phylogenetic status, and functions, the four bacterial GSH-dependent dehalogenases (PcpC, LinD, DsmH1, and DsmH2) were reclassified as a new eta class of GSTs. This study helps us to elucidate the microbial catabolism of dicamba and enhances our understanding of the diversity and functions of GSTs.
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Li N, Yao L, He Q, Qiu J, Cheng D, Ding D, Tao Q, He J, Jiang J. 3,6-Dichlorosalicylate Catabolism Is Initiated by the DsmABC Cytochrome P450 Monooxygenase System in Rhizorhabdus dicambivorans Ndbn-20. Appl Environ Microbiol 2018; 84:e02133-17. [PMID: 29196293 PMCID: PMC5795090 DOI: 10.1128/aem.02133-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 11/28/2017] [Indexed: 11/20/2022] Open
Abstract
The degradation of the herbicide dicamba is initiated by demethylation to form 3,6-dichlorosalicylate (3,6-DCSA) in Rhizorhabdusdicambivorans Ndbn-20. In the present study, a 3,6-DCSA degradation-deficient mutant, Ndbn-20m, was screened. A cluster, dsmR1DABCEFGR2, was lost in this mutant. The cluster consisted of nine genes, all of which were apparently induced by 3,6-DCSA. DsmA shared 30 to 36% identity with the monooxygenase components of reported three-component cytochrome P450 systems and formed a monophyletic branch in the phylogenetic tree. DsmB and DsmC were most closely related to the reported [2Fe-2S] ferredoxin and ferredoxin reductase, respectively. The disruption of dsmA in strain Ndbn-20 resulted in inactive 3,6-DCSA degradation. When dsmABC, but not dsmA alone, was introduced into mutant Ndbn-20m and Sphingobium quisquiliarum DC-2 (which is unable to degrade salicylate and its derivatives), they acquired the ability to hydroxylate 3,6-DCSA. Single-crystal X-ray diffraction demonstrated that the DsmABC-catalyzed hydroxylation occurred at the C-5 position of 3,6-DCSA, generating 3,6-dichlorogentisate (3,6-DCGA). In addition, DsmD shared 51% identity with GtdA (a gentisate and 3,6-DCGA 1,2-dioxygenase) from Sphingomonas sp. strain RW5. However, unlike GtdA, the purified DsmD catalyzed the cleavage of gentisate and 3-chlorogentisate but not 6-chlorogentisate or 3,6-DCGA in vitro Based on the bioinformatic analysis and gene function studies, a possible catabolic pathway of dicamba in R. dicambivorans Ndbn-20 was proposed.IMPORTANCE Dicamba is widely used to control a variety of broadleaf weeds and is a promising target herbicide for the engineering of herbicide-resistant crops. The catabolism of dicamba has thus received increasing attention. Bacteria mineralize dicamba initially via demethylation, generating 3,6-dichlorosalicylate. However, the catabolism of 3,6-dichlorosalicylate remains unknown. In this study, we cloned a gene cluster, dsmR1DABCEFGR2, involved in 3,6-dichlorosalicylate degradation from R. dicambivorans Ndbn-20, demonstrated that the cytochrome P450 monooxygenase system DsmABC was responsible for the 5-hydroxylation of 3,6-dichlorosalicylate, and proposed a dicamba catabolic pathway. This study provides a basis to elucidate the catabolism of dicamba and has benefits for the ecotoxicological study of dicamba. Furthermore, the hydroxylation of salicylate has been previously reported to be catalyzed by single-component flavoprotein or three-component Rieske non-heme iron oxygenase, whereas DsmABC was the only cytochrome P450 monooxygenase system hydroxylating salicylate and its methyl- or chloro-substituted derivatives.
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Affiliation(s)
- Na Li
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Li Yao
- School of Marine and Biological Engineering, Yancheng Teachers University, Yancheng, Jiangsu, China
| | - Qin He
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Jiguo Qiu
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Dan Cheng
- Laboratory Centre of Life Science, College of Life Science, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Derong Ding
- Beijing DBN Biotech Co., Ltd., Beijing, China
| | - Qing Tao
- Beijing DBN Biotech Co., Ltd., Beijing, China
| | - Jian He
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
- Laboratory Centre of Life Science, College of Life Science, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Jiandong Jiang
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
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A Novel Aerobic Degradation Pathway for Thiobencarb Is Initiated by the TmoAB Two-Component Flavin Mononucleotide-Dependent Monooxygenase System in Acidovorax sp. Strain T1. Appl Environ Microbiol 2017; 83:AEM.01490-17. [PMID: 28939603 DOI: 10.1128/aem.01490-17] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 09/13/2017] [Indexed: 11/20/2022] Open
Abstract
Thiobencarb is a thiocarbamate herbicide used in rice paddies worldwide. Microbial degradation plays a crucial role in the dissipation of thiobencarb in the environment. However, the physiological and genetic mechanisms underlying thiobencarb degradation remain unknown. In this study, a novel thiobencarb degradation pathway was proposed in Acidovorax sp. strain T1. Thiobencarb was oxidized and cleaved at the C-S bond, generating diethylcarbamothioic S-acid and 4-chlorobenzaldehyde (4CDA). 4CDA was then oxidized to 4-chlorobenzoic acid (4CBA) and hydrolytically dechlorinated to 4-hydroxybenzoic acid (4HBA). The identification of catabolic genes suggested further hydroxylation to protocatechuic acid (PCA) and finally degradation through the protocatechuate 4,5-dioxygenase pathway. A novel two-component monooxygenase system identified in the strain, TmoAB, was responsible for the initial catabolic reaction. TmoA shared 28 to 32% identity with the oxygenase components of pyrimidine monooxygenase from Agrobacterium fabrum, alkanesulfonate monooxygenase from Pseudomonas savastanoi, and dibenzothiophene monooxygenase from Rhodococcus sp. TmoB shared 25 to 37% identity with reported flavin reductases and oxidized NADH but not NADPH. TmoAB is a flavin mononucleotide (FMN)-dependent monooxygenase and catalyzed the C-S bond cleavage of thiobencarb. Introduction of tmoAB into cells of the thiobencarb degradation-deficient mutant T1m restored its ability to degrade and utilize thiobencarb. A dehydrogenase gene, tmoC, was located 7,129 bp downstream of tmoAB, and its transcription was clearly induced by thiobencarb. The purified TmoC catalyzed the dehydrogenation of 4CDA to 4CBA using NAD+ as a cofactor. A gene cluster responsible for the complete 4CBA metabolic pathway was also cloned, and its involvement in thiobencarb degradation was preliminarily verified by transcriptional analysis.IMPORTANCE Microbial degradation is the main factor in thiobencarb dissipation in soil. In previous studies, thiobencarb was degraded initially via N-deethylation, sulfoxidation, hydroxylation, and dechlorination. However, enzymes and genes involved in the microbial degradation of thiobencarb have not been studied. This study revealed a new thiobencarb degradation pathway in Acidovorax sp. strain T1 and identified a novel two-component FMN-dependent monooxygenase system, TmoAB. Under TmoAB-mediated catalysis, thiobencarb was cleaved at the C-S bond, producing diethylcarbamothioic S-acid and 4CDA. Furthermore, the downstream degradation pathway of thiobencarb was proposed. Our study provides the physiological, biochemical, and genetic foundation of thiobencarb degradation in this microorganism.
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Huang X, He J, Yan X, Hong Q, Chen K, He Q, Zhang L, Liu X, Chuang S, Li S, Jiang J. Microbial catabolism of chemical herbicides: Microbial resources, metabolic pathways and catabolic genes. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2017; 143:272-297. [PMID: 29183604 DOI: 10.1016/j.pestbp.2016.11.010] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2016] [Revised: 11/21/2016] [Accepted: 11/23/2016] [Indexed: 06/07/2023]
Abstract
Chemical herbicides are widely used to control weeds and are frequently detected as contaminants in the environment. Due to their toxicity, the environmental fate of herbicides is of great concern. Microbial catabolism is considered the major pathway for the dissipation of herbicides in the environment. In recent decades, there have been an increasing number of reports on the catabolism of various herbicides by microorganisms. This review presents an overview of the recent advances in the microbial catabolism of various herbicides, including phenoxyacetic acid, chlorinated benzoic acid, diphenyl ether, tetra-substituted benzene, sulfonamide, imidazolinone, aryloxyphenoxypropionate, phenylurea, dinitroaniline, s-triazine, chloroacetanilide, organophosphorus, thiocarbamate, trazinone, triketone, pyrimidinylthiobenzoate, benzonitrile, isoxazole and bipyridinium herbicides. This review highlights the microbial resources that are capable of catabolizing these herbicides and the mechanisms involved in the catabolism. Furthermore, the application of herbicide-degrading strains to clean up herbicide-contaminated sites and the construction of genetically modified herbicide-resistant crops are discussed.
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Affiliation(s)
- Xing Huang
- Department of Microbiology, Key Lab of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, 210095 Nanjing, People's Republic of China
| | - Jian He
- Department of Microbiology, Key Lab of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, 210095 Nanjing, People's Republic of China
| | - Xin Yan
- Department of Microbiology, Key Lab of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, 210095 Nanjing, People's Republic of China
| | - Qing Hong
- Department of Microbiology, Key Lab of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, 210095 Nanjing, People's Republic of China
| | - Kai Chen
- Department of Microbiology, Key Lab of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, 210095 Nanjing, People's Republic of China
| | - Qin He
- Department of Microbiology, Key Lab of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, 210095 Nanjing, People's Republic of China
| | - Long Zhang
- Department of Microbiology, Key Lab of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, 210095 Nanjing, People's Republic of China
| | - Xiaowei Liu
- Department of Microbiology, Key Lab of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, 210095 Nanjing, People's Republic of China
| | - Shaochuang Chuang
- Department of Microbiology, Key Lab of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, 210095 Nanjing, People's Republic of China
| | - Shunpeng Li
- Department of Microbiology, Key Lab of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, 210095 Nanjing, People's Republic of China
| | - Jiandong Jiang
- Department of Microbiology, Key Lab of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, 210095 Nanjing, People's Republic of China.
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