Oxytetracycline and Streptomycin Resistance Genes in Xanthomonas arboricola pv. pruni, the Causal Agent of Bacterial Spot in Peach

Xanthomonas arboricola pv. pruni (Xap) causes bacterial spot, a major worldwide disease of Prunus species. Very few chemical management options are available for this disease and frequent applications of oxytetracycline (OTC) in the United States peach orchards have raised concerns about resistance...

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Main Authors: Austin Herbert, C. Nathan Hancock, Brodie Cox, Guido Schnabel, Daniela Moreno, Renato Carvalho, Jeffrey Jones, Matthew Paret, Xueqing Geng, Hehe Wang
Format: Article
Language:English
Published: Frontiers Media S.A. 2022-02-01
Series:Frontiers in Microbiology
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Online Access:https://www.frontiersin.org/articles/10.3389/fmicb.2022.821808/full
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author Austin Herbert
C. Nathan Hancock
Brodie Cox
Guido Schnabel
Daniela Moreno
Renato Carvalho
Renato Carvalho
Jeffrey Jones
Matthew Paret
Matthew Paret
Xueqing Geng
Hehe Wang
author_facet Austin Herbert
C. Nathan Hancock
Brodie Cox
Guido Schnabel
Daniela Moreno
Renato Carvalho
Renato Carvalho
Jeffrey Jones
Matthew Paret
Matthew Paret
Xueqing Geng
Hehe Wang
author_sort Austin Herbert
collection DOAJ
description Xanthomonas arboricola pv. pruni (Xap) causes bacterial spot, a major worldwide disease of Prunus species. Very few chemical management options are available for this disease and frequent applications of oxytetracycline (OTC) in the United States peach orchards have raised concerns about resistance development. During 2017–2020, 430 Xap strains were collected from ten peach orchards in South Carolina. Seven OTC-resistant (OTCR) Xap strains were found in 2017 and 2020 from four orchards about 20–270 km apart. Interestingly, the seven strains were also resistant to streptomycin (STR). Six strains grew on media amended with ≤100 μg/mL OTC, while one strain, R1, grew on ≤250 μg/mL OTC. Genome sequence analysis of four representative OTCR strains revealed a 14–20 kb plasmid carrying tetC, tetR, and strAB in each strain. These three genes were transferable to Xanthomonas perforans via conjugation, and they were PCR confirmed in all seven OTCR Xap strains. When tetC and tetR were cloned and expressed together in a sensitive strain, the transconjugants showed resistance to ≤100 μg/mL OTC. When tetC was cloned and expressed alone in a sensitive strain, the transconjugants showed resistance to ≤250 μg/mL OTC. TetC and tetR expression was inducible by OTC in all six wild-type strains resistant to ≤100 μg/mL OTC. However, in the R1 strain resistant to ≤250 μg/mL OTC, tetR was not expressed, possibly due to the presence of Tn3 in the tetR gene, and in this case tetC was constitutively expressed. These data suggest that tetC confers OTC resistance in Xap strains, and tetR regulates the level of OTC resistance conferred by tetC. To our knowledge, this is the first report of OTC resistance in plant pathogenic xanthomonads.
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spelling doaj-art-cf05d4e617824ebeafe2250e020bb0b82025-08-20T02:57:03ZengFrontiers Media S.A.Frontiers in Microbiology1664-302X2022-02-011310.3389/fmicb.2022.821808821808Oxytetracycline and Streptomycin Resistance Genes in Xanthomonas arboricola pv. pruni, the Causal Agent of Bacterial Spot in PeachAustin Herbert0C. Nathan Hancock1Brodie Cox2Guido Schnabel3Daniela Moreno4Renato Carvalho5Renato Carvalho6Jeffrey Jones7Matthew Paret8Matthew Paret9Xueqing Geng10Hehe Wang11Edisto Research and Education Center, Clemson University, Blackville, SC, United StatesDepartment of Biology and Geology, University of South Carolina Aiken, Aiken, SC, United StatesDepartment of Plant and Environmental Sciences, Clemson University, Clemson, SC, United StatesDepartment of Plant and Environmental Sciences, Clemson University, Clemson, SC, United StatesEdisto Research and Education Center, Clemson University, Blackville, SC, United StatesDepartment of Plant Pathology, University of Florida, Gainesville, FL, United StatesNorth Florida Research and Education Center, University of Florida, Quincy, FL, United StatesDepartment of Plant Pathology, University of Florida, Gainesville, FL, United StatesDepartment of Plant Pathology, University of Florida, Gainesville, FL, United StatesNorth Florida Research and Education Center, University of Florida, Quincy, FL, United StatesSchool of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, ChinaEdisto Research and Education Center, Clemson University, Blackville, SC, United StatesXanthomonas arboricola pv. pruni (Xap) causes bacterial spot, a major worldwide disease of Prunus species. Very few chemical management options are available for this disease and frequent applications of oxytetracycline (OTC) in the United States peach orchards have raised concerns about resistance development. During 2017–2020, 430 Xap strains were collected from ten peach orchards in South Carolina. Seven OTC-resistant (OTCR) Xap strains were found in 2017 and 2020 from four orchards about 20–270 km apart. Interestingly, the seven strains were also resistant to streptomycin (STR). Six strains grew on media amended with ≤100 μg/mL OTC, while one strain, R1, grew on ≤250 μg/mL OTC. Genome sequence analysis of four representative OTCR strains revealed a 14–20 kb plasmid carrying tetC, tetR, and strAB in each strain. These three genes were transferable to Xanthomonas perforans via conjugation, and they were PCR confirmed in all seven OTCR Xap strains. When tetC and tetR were cloned and expressed together in a sensitive strain, the transconjugants showed resistance to ≤100 μg/mL OTC. When tetC was cloned and expressed alone in a sensitive strain, the transconjugants showed resistance to ≤250 μg/mL OTC. TetC and tetR expression was inducible by OTC in all six wild-type strains resistant to ≤100 μg/mL OTC. However, in the R1 strain resistant to ≤250 μg/mL OTC, tetR was not expressed, possibly due to the presence of Tn3 in the tetR gene, and in this case tetC was constitutively expressed. These data suggest that tetC confers OTC resistance in Xap strains, and tetR regulates the level of OTC resistance conferred by tetC. To our knowledge, this is the first report of OTC resistance in plant pathogenic xanthomonads.https://www.frontiersin.org/articles/10.3389/fmicb.2022.821808/fullantibiotic resistanceplant diseasebacterial pathogenstone fruitshorizontal gene transfertransposon
spellingShingle Austin Herbert
C. Nathan Hancock
Brodie Cox
Guido Schnabel
Daniela Moreno
Renato Carvalho
Renato Carvalho
Jeffrey Jones
Matthew Paret
Matthew Paret
Xueqing Geng
Hehe Wang
Oxytetracycline and Streptomycin Resistance Genes in Xanthomonas arboricola pv. pruni, the Causal Agent of Bacterial Spot in Peach
Frontiers in Microbiology
antibiotic resistance
plant disease
bacterial pathogen
stone fruits
horizontal gene transfer
transposon
title Oxytetracycline and Streptomycin Resistance Genes in Xanthomonas arboricola pv. pruni, the Causal Agent of Bacterial Spot in Peach
title_full Oxytetracycline and Streptomycin Resistance Genes in Xanthomonas arboricola pv. pruni, the Causal Agent of Bacterial Spot in Peach
title_fullStr Oxytetracycline and Streptomycin Resistance Genes in Xanthomonas arboricola pv. pruni, the Causal Agent of Bacterial Spot in Peach
title_full_unstemmed Oxytetracycline and Streptomycin Resistance Genes in Xanthomonas arboricola pv. pruni, the Causal Agent of Bacterial Spot in Peach
title_short Oxytetracycline and Streptomycin Resistance Genes in Xanthomonas arboricola pv. pruni, the Causal Agent of Bacterial Spot in Peach
title_sort oxytetracycline and streptomycin resistance genes in xanthomonas arboricola pv pruni the causal agent of bacterial spot in peach
topic antibiotic resistance
plant disease
bacterial pathogen
stone fruits
horizontal gene transfer
transposon
url https://www.frontiersin.org/articles/10.3389/fmicb.2022.821808/full
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