Distinct Virulence Mechanisms of Burkholderia gladioli in Onion Foliar and Bulb Scale Tissues
Slippery skin of onion caused by Burkholderia gladioli pv. alliicola (Bga) is a common bacterial disease reported from onion-growing regions around the world. Despite the increasing attention in recent years, our understanding of the virulence mechanisms of this pathogen remains limited. In this stu...
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The American Phytopathological Society
2025-01-01
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| Series: | Molecular Plant-Microbe Interactions |
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| Online Access: | https://apsjournals.apsnet.org/doi/10.1094/MPMI-10-24-0129-R |
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| author | Sujan Paudel Yaritza Franco Mei Zhao Bhabesh Dutta Brian H. Kvitko |
| author_facet | Sujan Paudel Yaritza Franco Mei Zhao Bhabesh Dutta Brian H. Kvitko |
| author_sort | Sujan Paudel |
| collection | DOAJ |
| description | Slippery skin of onion caused by Burkholderia gladioli pv. alliicola (Bga) is a common bacterial disease reported from onion-growing regions around the world. Despite the increasing attention in recent years, our understanding of the virulence mechanisms of this pathogen remains limited. In this study, we characterized the predicted genetic determinants of virulence in Bga strain 20GA0385 using a reverse genetics approach. Using the closely related rice pathogen B. glumae as a reference, comparative genomics analysis was performed to identify Bga candidate virulence factors and regulators. Marked and unmarked deletion mutants were generated using allelic exchange, and the mutants were functionally validated using in vitro and in vivo assays. The role of mutants in pathogenic phenotypes was analyzed using onion foliar/seedling necrosis assays, the red scale necrosis assay, and in planta bacterial population counts. The phytotoxin toxoflavin was a major contributor to foliar necrosis and bacterial populations, whereas the type II and type III secretion systems (T2SS/T3SS) were dispensable for foliar symptoms. In onion scale tissue, the T2SS single mutant gspC and its double and triple mutant derivatives all contributed to scale lesion area. Neither the lipocyclopeptide icosalide, toxoflavin, nor T3SS was required for scale symptoms. Our results suggest that the quorum sensing tofIMR system in Bga regulates toxoflavin, T2SS, and T3SS, contributing to onion symptom production. We show that different virulence factors contribute to onion tissue-specific virulence patterns in Bga and that decreases in scale symptoms often do not result in decreased Bga populations in onion tissue. [Figure: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license. |
| format | Article |
| id | doaj-art-bd0d4b655872439692a8b41a0e89403a |
| institution | Kabale University |
| issn | 0894-0282 1943-7706 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | The American Phytopathological Society |
| record_format | Article |
| series | Molecular Plant-Microbe Interactions |
| spelling | doaj-art-bd0d4b655872439692a8b41a0e89403a2025-08-20T03:26:56ZengThe American Phytopathological SocietyMolecular Plant-Microbe Interactions0894-02821943-77062025-01-0138342743910.1094/MPMI-10-24-0129-RDistinct Virulence Mechanisms of Burkholderia gladioli in Onion Foliar and Bulb Scale TissuesSujan Paudel0Yaritza Franco1Mei Zhao2Bhabesh Dutta3Brian H. Kvitko4Department of Plant Pathology, University of Georgia, Athens, GA, U.S.A.Department of Microbiology, University of Georgia, Athens, GA, U.S.A.Department of Plant Pathology, University of Georgia, Tifton, GA, U.S.A.Department of Plant Pathology, University of Georgia, Tifton, GA, U.S.A.Department of Plant Pathology, University of Georgia, Athens, GA, U.S.A.Slippery skin of onion caused by Burkholderia gladioli pv. alliicola (Bga) is a common bacterial disease reported from onion-growing regions around the world. Despite the increasing attention in recent years, our understanding of the virulence mechanisms of this pathogen remains limited. In this study, we characterized the predicted genetic determinants of virulence in Bga strain 20GA0385 using a reverse genetics approach. Using the closely related rice pathogen B. glumae as a reference, comparative genomics analysis was performed to identify Bga candidate virulence factors and regulators. Marked and unmarked deletion mutants were generated using allelic exchange, and the mutants were functionally validated using in vitro and in vivo assays. The role of mutants in pathogenic phenotypes was analyzed using onion foliar/seedling necrosis assays, the red scale necrosis assay, and in planta bacterial population counts. The phytotoxin toxoflavin was a major contributor to foliar necrosis and bacterial populations, whereas the type II and type III secretion systems (T2SS/T3SS) were dispensable for foliar symptoms. In onion scale tissue, the T2SS single mutant gspC and its double and triple mutant derivatives all contributed to scale lesion area. Neither the lipocyclopeptide icosalide, toxoflavin, nor T3SS was required for scale symptoms. Our results suggest that the quorum sensing tofIMR system in Bga regulates toxoflavin, T2SS, and T3SS, contributing to onion symptom production. We show that different virulence factors contribute to onion tissue-specific virulence patterns in Bga and that decreases in scale symptoms often do not result in decreased Bga populations in onion tissue. [Figure: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.https://apsjournals.apsnet.org/doi/10.1094/MPMI-10-24-0129-RBurkholderia gladioli pv. alliicolageneticsregulatorsslippery skin of onionvirulence |
| spellingShingle | Sujan Paudel Yaritza Franco Mei Zhao Bhabesh Dutta Brian H. Kvitko Distinct Virulence Mechanisms of Burkholderia gladioli in Onion Foliar and Bulb Scale Tissues Molecular Plant-Microbe Interactions Burkholderia gladioli pv. alliicola genetics regulators slippery skin of onion virulence |
| title | Distinct Virulence Mechanisms of Burkholderia gladioli in Onion Foliar and Bulb Scale Tissues |
| title_full | Distinct Virulence Mechanisms of Burkholderia gladioli in Onion Foliar and Bulb Scale Tissues |
| title_fullStr | Distinct Virulence Mechanisms of Burkholderia gladioli in Onion Foliar and Bulb Scale Tissues |
| title_full_unstemmed | Distinct Virulence Mechanisms of Burkholderia gladioli in Onion Foliar and Bulb Scale Tissues |
| title_short | Distinct Virulence Mechanisms of Burkholderia gladioli in Onion Foliar and Bulb Scale Tissues |
| title_sort | distinct virulence mechanisms of burkholderia gladioli in onion foliar and bulb scale tissues |
| topic | Burkholderia gladioli pv. alliicola genetics regulators slippery skin of onion virulence |
| url | https://apsjournals.apsnet.org/doi/10.1094/MPMI-10-24-0129-R |
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