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Kan Y, Zhang Y, Lin W, Dong T. Differential plant cell responses to Acidovorax citrulli T3SS and T6SS reveal an effective strategy for controlling plant-associated pathogens. mBio 2023; 14:e0045923. [PMID: 37288971 PMCID: PMC10470598 DOI: 10.1128/mbio.00459-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 05/03/2023] [Indexed: 06/09/2023] Open
Abstract
Acidovorax citrulli is a gram-negative plant pathogen that employs the type Ⅲ secretion system (T3SS) to infect cucurbit crops and cause bacterial fruit blotch. This bacterium also possesses an active type Ⅵ secretion system (T6SS) with strong antibacterial and antifungal activities. However, how plant cells respond to these two secretion systems and whether there is any cross talk between T3SS and T6SS during infection remain unknown. Here, we employ transcriptomic analysis to compare cellular responses to the T3SS and the T6SS during in planta infection and report distinctive effects on multiple pathways. The T3SS-mediated differentially expressed genes were enriched in the pathways of phenylpropanoid biosynthesis, plant-pathogen interaction, MAPK signaling pathway, and glutathione metabolism, while the T6SS uniquely affected genes were related to photosynthesis. The T6SS does not contribute to the in planta virulence of A. citrulli but is critical for the survival of the bacterium when mixed with watermelon phyllosphere bacteria. In addition, T3SS-mediated virulence is independent of the T6SS, and the inactivation of the T3SS does not affect the T6SS-mediated competition against a diverse set of bacterial pathogens that commonly contaminate edible plants or directly infect plants. A T6SS-active T3SS-null mutant (Acav) could inhibit the growth of Xanthomonas oryzae pv. oryzae significantly both in vitro and in vivo and also reduce symptoms of rice bacterial blight. In conclusion, our data demonstrate the T6SS in A. citrulli is nonpathogenic to the plant host and can be harnessed as a pathogen killer against plant-associated bacteria. IMPORTANCE Chemical pesticides are widely used to protect crops from various pathogens. Still, their extensive use has led to severe consequences, including drug resistance and environmental contamination. Here, we show that an engineered T6SS-active, but avirulent mutant of Acidovorax citrulli has strong inhibition capabilities against several pathogenic bacteria, demonstrating an effective strategy that is an alternative to chemical pesticides for sustainable agricultural practices.
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Affiliation(s)
- Yumin Kan
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Yanjie Zhang
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Wenhui Lin
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Tao Dong
- Department of Immunology and Microbiology, School of Life Sciences, Southern University of Science and Technology, Shenzhen, Guangdong, China
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2
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Yang Y, Fei N, Ji W, Qiao P, Yang L, Liu D, Guan W, Zhao T. pilA Gene Contributes to Virulence, Motility, Biofilm Formation, and Interspecific Competition of Bacteria in Acidovorax citrulli. Microorganisms 2023; 11:1806. [PMID: 37512977 PMCID: PMC10385852 DOI: 10.3390/microorganisms11071806] [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: 05/30/2023] [Revised: 06/30/2023] [Accepted: 07/12/2023] [Indexed: 07/30/2023] Open
Abstract
Acidovorax citrulli, the causative agent of bacterial fruit blotch, can be divided into two main groups based on factors such as pathogenicity and host species preference. PilA is an important structural and functional component of type IV pili (T4P). Previous studies have found significant differences in pilA DNA sequences between group I and group II strains of A. citrulli. In this study, we characterized pilA in the group I strain pslb65 and the group II strain Aac5. pilA mutants, complementation strains, and cross-complementation strains were generated, and their biological phenotypes were analyzed to identify functional differences between pilA in the two groups. pilA deletion mutants (pslb65-ΔpilA and Aac5-ΔpilA) showed significantly reduced pathogenicity compared with the wild-type (WT) strains; pslb65-ΔpilA also completely lost twitching motility, whereas Aac5-ΔpilA only partially lost motility. In King's B medium, there were no significant differences in biofilm formation between pslb65-ΔpilA and WT pslb65, but Aac5-ΔpilA showed significantly reduced biofilm formation compared to WT Aac5. In M9 minimal medium, both mutants showed significantly lower biofilm formation compared to the corresponding WT strains, although biofilm formation was recovered in the complementation strains. The biofilm formation capacity was somewhat recovered in the cross-complementation strains but remained significantly lower than in the WT strains. The interspecies competitive abilities of pslb65-ΔpilA and Aac5-ΔpilA were significantly lower than in the WT strains; Aac5-ΔpilA was more strongly competitive than pslb65-ΔpilA, and the complementation strains recovered competitiveness to WT levels. Furthermore, the cross-complementation strains showed stronger competitive abilities than the corresponding WT strains. The relative expression levels of genes related to T4P and the type VI secretion system were then assessed in the pilA mutants via quantitative PCR. The results showed significant differences in the relative expression levels of multiple genes in pslb65-ΔpilA and Aac5-ΔpilA compared to the corresponding WT stains. This indicated the presence of specific differences in pilA function between the two A. citrulli groups, but the regulatory mechanisms involved require further study.
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Affiliation(s)
- Yuwen Yang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
- National Nanfan Research Institute (Sanya), Chinese Academy of Agricultural Sciences, Sanya 572024, China
| | - Nuoya Fei
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
- College of Life Sciences, Jilin Normal University, Siping 136000, China
| | - Weiqin Ji
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Pei Qiao
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Linlin Yang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
- Department of Plant Pathology, Plant Protection College, Shenyang Agricultural University, Shenyang 110866, China
| | - Dehua Liu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
- College of Plant Protection, Jilin Agricultural University, Changchun 130118, China
| | - Wei Guan
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Tingchang Zhao
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
- National Nanfan Research Institute (Sanya), Chinese Academy of Agricultural Sciences, Sanya 572024, China
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3
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Qiao P, Zhao M, Guan W, Walcott R, Ye Y, Yang Y, Zhao T. A putative multi-sensor hybrid histidine kinase, BarA Ac , inhibits the expression of the type III secretion system regulator HrpG in Acidovorax citrulli. Front Microbiol 2022; 13:1064577. [PMID: 36532489 PMCID: PMC9748350 DOI: 10.3389/fmicb.2022.1064577] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2022] [Accepted: 11/14/2022] [Indexed: 07/30/2023] Open
Abstract
Bacterial fruit blotch (BFB), caused by Acidovorax citrulli, severely damages watermelon, melon, and other cucurbit crops worldwide. Although many virulence determinants have been identified in A. citrulli, including swimming motility, twitching motility, biofilm formation, and the type III secretion system (T3SS), research on their regulation is lacking. To study virulence regulation mechanisms, we found a putative histidine kinase BarA Ac that may be related to the T3SS regulator HrpG in A. citrulli. We deleted and characterized barAAc (Aave_2063) in A. citrulli Aac5 strain. Compared to the wild-type Aac5, virulence and early proliferation of barAAc mutant in host watermelon cotyledons were significantly increased, and induction of hypersensitive response in non-host tobacco was accelerated, while biofilm formation and swimming motility were significantly reduced. In addition, the transcriptomic analysis revealed that the expression of many T3SS-related genes was upregulated in the ΔbarAAc deletion mutant when cultured in KB medium. Meanwhile, the ΔbarAAc deletion mutant showed increased accumulation of the T3SS regulator HrpG in KB medium, which may account for the increased deployment of T3SS. This suggests that the putative histidine kinase BarA Ac is able to repress the T3SS expression by inhibiting HrpG in the KB medium, which appears to be important for rational energy allocation. In summary, our research provides further understanding of the regulatory network of A. citrulli virulence.
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Affiliation(s)
- Pei Qiao
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Mei Zhao
- Department of Plant Pathology, College of Plant Protection, China Agricultural University, Beijing, China
- Department of Plant Pathology, University of Georgia, Athens, GA, United States
| | - Wei Guan
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Ron Walcott
- Department of Plant Pathology, University of Georgia, Athens, GA, United States
| | - Yunfeng Ye
- Horticultural Research Institute, Guangxi Academy of Agricultural Sciences, Nanning, China
| | - Yuwen Yang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Tingchang Zhao
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
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4
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Lee J, Lee J, Cho Y, Choi J, Han SW. A putative 2,3-bisphosphoglycerate-dependent phosphoglycerate mutase is involved in the virulence, carbohydrate metabolism, biofilm formation, twitching halo, and osmotic tolerance in Acidovorax citrulli. FRONTIERS IN PLANT SCIENCE 2022; 13:1039420. [PMID: 36438092 PMCID: PMC9681784 DOI: 10.3389/fpls.2022.1039420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 10/14/2022] [Indexed: 06/16/2023]
Abstract
Acidovorax citrulli (Ac) is a gram-negative bacterium that causes bacterial fruit blotch (BFB) disease in cucurbit crops including watermelon. However, despite the great economic losses caused by this disease worldwide, Ac-resistant watermelon cultivars have not been developed. Therefore, characterizing the virulence factors/mechanisms of Ac would enable the development of effective control strategies against BFB disease. The 2,3-bisphosphoglycerate-dependent phosphoglycerate mutase (BdpM) is known to participate in the glycolysis and gluconeogenesis pathways. However, the roles of the protein have not been characterized in Ac. To elucidate the functions of BdpmAc (Bdpm in Ac), comparative proteomic analysis and diverse phenotypic assays were conducted using a bdpmAc knockout mutant (bdpmAc:Tn) and a wild-type strain. The virulence of the mutant to watermelon was remarkably reduced in both germinated seed inoculation and leaf infiltration assays. Moreover, the mutant could not grow with fructose or pyruvate as a sole carbon source. However, the growth of the mutant was restored to levels similar to those of the wild-type strain in the presence of both fructose and pyruvate. Comparative proteomic analyses revealed that diverse proteins involved in motility and wall/membrane/envelop biogenesis were differentially abundant. Furthermore, the mutant exhibited decreased biofilm formation and twitching halo size. Interestingly, the mutant exhibited a higher tolerance against osmotic stress. Overall, our findings suggest that BdpmAc affects the virulence, glycolysis/gluconeogenesis, biofilm formation, twitching halo size, and osmotic tolerance of Ac, suggesting that this protein has pleiotropic properties. Collectively, our findings provide fundamental insights into the functions of a previously uncharacterized phosphoglycerate mutase in Ac.
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Rosenberg T, Jiménez-Guerrero I, Tamir-Ariel D, Yarnitzky T, Burdman S. The GDSL-Lipolytic Enzyme Lip1 Is Required for Full Virulence of the Cucurbit Pathogenic Bacterium Acidovorax citrulli. Microorganisms 2022; 10:microorganisms10051016. [PMID: 35630458 PMCID: PMC9147443 DOI: 10.3390/microorganisms10051016] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 05/04/2022] [Accepted: 05/09/2022] [Indexed: 02/01/2023] Open
Abstract
Bacterial fruit blotch caused by Acidovoraxcitrulli is a serious disease of cucurbit crops. Here we report characterization of a mutant strain of A. citrulli M6 defective in lip1, a gene encoding a lipolytic enzyme. The M6-lip1- mutant was detected in a mutant library screen aimed at identifying M6 mutants with altered levels of twitching motility. In this screen M6-lip1- was the only mutant that showed significantly larger twitching motility haloes around colonies than wild-type M6. Sequence analyses indicated that lip1 encodes a member of the GDSL family of secreted lipolytic enzymes. In line with this finding, lipolytic assays showed that the supernatants of M6-lip1- had lower lipolytic activity as compared with those of wild-type M6 and a lip1-complemented strain. The mutant was also affected in swimming motility and had compromised virulence on melon seedlings and on Nicotiana benthamiana leaves relative to wild-type and complemented strains. Lip1 contains a predicted N-terminal signal sequence for type II secretion. Evidence from our study confirms Lip1 is indeed secreted in a type II secretion-dependent manner, and this is required for full virulence of A. citrulli. To the best of our knowledge this is the first study reporting contribution of lipolytic activity to virulence of a plant-pathogenic Acidovorax species.
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Affiliation(s)
- Tally Rosenberg
- Department of Plant Pathology and Microbiology, Institute of Environmental Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 7610001, Israel; (T.R.); (I.J.-G.); (D.T.-A.); (T.Y.)
| | - Irene Jiménez-Guerrero
- Department of Plant Pathology and Microbiology, Institute of Environmental Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 7610001, Israel; (T.R.); (I.J.-G.); (D.T.-A.); (T.Y.)
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain
| | - Dafna Tamir-Ariel
- Department of Plant Pathology and Microbiology, Institute of Environmental Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 7610001, Israel; (T.R.); (I.J.-G.); (D.T.-A.); (T.Y.)
| | - Tali Yarnitzky
- Department of Plant Pathology and Microbiology, Institute of Environmental Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 7610001, Israel; (T.R.); (I.J.-G.); (D.T.-A.); (T.Y.)
| | - Saul Burdman
- Department of Plant Pathology and Microbiology, Institute of Environmental Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 7610001, Israel; (T.R.); (I.J.-G.); (D.T.-A.); (T.Y.)
- Correspondence: ; Tel.: +972-8-9489369
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6
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Wang Y, Zhao Y, Xia L, Chen L, Liao Y, Chen B, Liu Y, Gong W, Tian Y, Hu B. yggS Encoding Pyridoxal 5'-Phosphate Binding Protein Is Required for Acidovorax citrulli Virulence. Front Microbiol 2022; 12:783862. [PMID: 35087487 PMCID: PMC8787154 DOI: 10.3389/fmicb.2021.783862] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 12/06/2021] [Indexed: 11/26/2022] Open
Abstract
Bacterial fruit blotch, caused by seed-borne pathogen Acidovorax citrulli, poses a serious threat to the production of cucurbits globally. Although the disease can cause substantial economic losses, limited information is available about the molecular mechanisms of virulence. This study identified that, a random transposon insertion mutant impaired in the ability to elicit a hypersensitive response on tobacco. The disrupted gene in this mutant was determined to be Aave_0638, which is predicted to encode a YggS family pyridoxal phosphate-dependent enzyme. YggS is a highly conserved protein among multiple organisms, and is responsible for maintaining the homeostasis of pyridoxal 5′-phosphate and amino acids in cells. yggS deletion mutant of A. citrulli strain XjL12 displayed attenuated virulence, delayed hypersensitive response, less tolerance to H2O2 and pyridoxine, increased sensitivity to antibiotic β-chloro-D-alanine, and reduced swimming. In addition, RNA-Seq analysis demonstrated that yggS was involved in regulating the expression of certain pathogenicity-associated genes related to secretion, motility, quorum sensing and oxidative stress response. Importantly, YggS significantly affected type III secretion system and its effectors in vitro. Collectively, our results suggest that YggS is indispensable for A.citrulli virulence and expands the role of YggS in the biological processes.
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Affiliation(s)
- Yuanjie Wang
- College of Plant Protection and Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing, China
| | - Yuqiang Zhao
- Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-sen), Nanjing, China
| | - Liming Xia
- College of Plant Protection and Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing, China
| | - Lin Chen
- College of Plant Protection and Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing, China
| | - Yajie Liao
- College of Plant Protection and Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing, China
| | - Baohui Chen
- College of Plant Protection and Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing, China
| | - Yiyang Liu
- College of Plant Protection and Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing, China
| | - Weirong Gong
- Plant Protection and Quarantine Station of Province, Nanjing, China
| | - Yanli Tian
- College of Plant Protection and Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing, China
| | - Baishi Hu
- College of Plant Protection and Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing, China
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Guan W, Wang T, Huang Q, Tian E, Liu B, Yang Y, Zhao T. A LuxR-type regulator, AcrR, regulates flagellar assembly and contributes to virulence, motility, biofilm formation, and growth ability of Acidovorax citrulli. MOLECULAR PLANT PATHOLOGY 2020; 21:489-501. [PMID: 31943660 PMCID: PMC7060138 DOI: 10.1111/mpp.12910] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 12/05/2019] [Accepted: 12/20/2019] [Indexed: 05/26/2023]
Abstract
LuxR-type regulators regulate many bacterial processes and play important roles in bacterial motility and virulence. Acidovorax citrulli is a seedborne bacterial pathogen responsible for bacterial fruit blotch, which causes great losses in melon and watermelon worldwide. We identified a LuxR-type, nonquorum sensing-related regulator, AcrR, in the group II strain Aac-5 of A. citrulli. We found that the acrR mutant lost twitching and swimming motilities, and flagellar formation. It also showed reduced virulence, but increased biofilm formation and growth ability. Transcriptomic analysis revealed that 394 genes were differentially expressed in the acrR mutant of A. citrulli, including 33 genes involved in flagellar assembly. Our results suggest that AcrR may act as a global regulator affecting multiple important biological functions of A. citrulli.
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Affiliation(s)
- Wei Guan
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant ProtectionChinese Academy of Agricultural SciencesBeijingChina
| | - Tielin Wang
- State Key Laboratory Breeding Base of Dao‐di HerbsNational Resource Center for Chinese Materia MedicaChina Academy of Chinese Medical SciencesBeijingChina
| | - Qi Huang
- Floral and Nursery Plants Research UnitU.S. Department of AgricultureAgricultural Research ServiceBeltsvilleMDUSA
| | - Eryuan Tian
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant ProtectionChinese Academy of Agricultural SciencesBeijingChina
| | - Bo Liu
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant ProtectionChinese Academy of Agricultural SciencesBeijingChina
| | - Yuwen Yang
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant ProtectionChinese Academy of Agricultural SciencesBeijingChina
| | - Tingchang Zhao
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant ProtectionChinese Academy of Agricultural SciencesBeijingChina
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8
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Abstract
Twitching and swimming are two bacterial movements governed by pili and flagella. The present work identifies for the first time in the Gram-negative plant pathogen Ralstonia solanacearum a pilus-mediated chemotaxis pathway analogous to that governing flagellum-mediated chemotaxis. We show that regulatory genes in this pathway control all of the phenotypes related to pili, including twitching motility, natural transformation, and biofilm formation, and are also directly implicated in virulence, mainly during the first steps of the plant infection. Our results show that pili have a higher impact than flagella on the interaction of R. solanacearum with tomato plants and reveal new types of cross-talk between the swimming and twitching motility phenotypes: enhanced swimming in bacteria lacking pili and a role for the flagellum in root attachment. Ralstonia solanacearum is a bacterial plant pathogen causing important economic losses worldwide. In addition to the polar flagella responsible for swimming motility, this pathogen produces type IV pili (TFP) that govern twitching motility, a flagellum-independent movement on solid surfaces. The implication of chemotaxis in plant colonization, through the control flagellar rotation by the proteins CheW and CheA, has been previously reported in R. solanacearum. In this work, we have identified in this bacterium homologues of the Pseudomonas aeruginosapilI and chpA genes, suggested to play roles in TFP-associated motility analogous to those played by the cheW and cheA genes, respectively. We demonstrate that R. solanacearum strains with a deletion of the pilI or the chpA coding region show normal swimming and chemotaxis but altered biofilm formation and reduced twitching motility, transformation efficiency, and root attachment. Furthermore, these mutants displayed wild-type growth in planta and impaired virulence on tomato plants after soil-drench inoculations but not when directly applied to the xylem. Comparison with deletion mutants for pilA and fliC—encoding the major pilin and flagellin subunits, respectively—showed that both twitching and swimming are required for plant colonization and full virulence. This work proves for the first time the functionality of a pilus-mediated pathway encoded by pil-chp genes in R. solanacearum, demonstrating that pilI and chpA genes are bona fide motility regulators controlling twitching motility and its three related phenotypes: virulence, natural transformation, and biofilm formation. IMPORTANCE Twitching and swimming are two bacterial movements governed by pili and flagella. The present work identifies for the first time in the Gram-negative plant pathogen Ralstonia solanacearum a pilus-mediated chemotaxis pathway analogous to that governing flagellum-mediated chemotaxis. We show that regulatory genes in this pathway control all of the phenotypes related to pili, including twitching motility, natural transformation, and biofilm formation, and are also directly implicated in virulence, mainly during the first steps of the plant infection. Our results show that pili have a higher impact than flagella on the interaction of R. solanacearum with tomato plants and reveal new types of cross-talk between the swimming and twitching motility phenotypes: enhanced swimming in bacteria lacking pili and a role for the flagellum in root attachment.
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iTRAQ-based proteomic analyses of the plant-pathogenic bacterium Acidovorax citrulli during entrance into and resuscitation from the viable but nonculturable state. J Proteomics 2020; 211:103547. [DOI: 10.1016/j.jprot.2019.103547] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 09/28/2019] [Accepted: 10/07/2019] [Indexed: 12/26/2022]
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10
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Tian Y, Zhao Y, Zhou J, Sun T, Luo X, Kurowski C, Gong W, Hu B, Walcott RR. Prevalence of Acidovorax citrulli in Commercial Cucurbit Seedlots During 2010-2018 in China. PLANT DISEASE 2020; 104:255-259. [PMID: 31613189 DOI: 10.1094/pdis-03-19-0666-re] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Acidovorax citrulli is the causal agent of bacterial fruit blotch (BFB), a serious threat to cucurbit fruit and seed production worldwide. In recent years, the BFB has spread to many areas of China, mainly via the inadvertent distribution of contaminated commercial seeds. To assess the prevalence of seedborne A. citrulli in commercial watermelon and other cucurbitaceous seedlots in China, a 9-year survey was conducted between 2010 and 2018. A total of 4,839 seedlots of watermelon and other cucurbitaceous species were collected from 13 major seed production areas of China and tested by a semiselective media-based colony PCR technique for A. citrulli. Overall, A. citrulli was detected in 18.00% (871/4,839) of all cucurbitaceous seedlots. The bacterium was detected in 21.59% (38/176), 19.19% (33/172), 23.44% (214/913), 40.76% (247/606), 13.28% (85/640), 15.40% (95/617), 13.25% (73/551), 8.03% (48/598), and 6.71% (38/566) of all commercial seedlots tested from the 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, and 2018 growing seasons, respectively. Additionally, the prevalence of A. citrulli in cucurbit seedlots was determined for different seed production areas. The prevalence of A. citrulli in cucurbitaceous seedlots produced in Xinjiang, Gansu, Ningxia, Inner Mongolia, and 9 other provinces was 18.76% (582/3103), 26.34% (103/391), 21.47% (82/382), 11.11% (14/126), and 10.75% (90/837), respectively. This is the first survey for A. citrulli in commercial cucurbit seeds in China, and the relatively high prevalence suggests that commercial seeds represent a substantial source of primary inoculum that can threaten cucurbit seed and fruit production in China.
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Affiliation(s)
- Yanli Tian
- College of Plant Protection and Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing 210095, China
| | - Yuqiang Zhao
- Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Nanjing 210014, China
| | - Jiaju Zhou
- College of Plant Protection and Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing 210095, China
| | - Ting Sun
- College of Plant Protection and Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing 210095, China
| | - Xue Luo
- College of Plant Protection and Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing 210095, China
| | | | - Weirong Gong
- Plant Protection and Quarantine Station of JiangSu Province, Nanjing, China
| | - Baishi Hu
- College of Plant Protection and Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing 210095, China
| | - Ron R Walcott
- Department of Plant Pathology, University of Georgia, Athens, GA 30602, U.S.A
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11
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Kim M, Lee J, Heo L, Han SW. Putative Bifunctional Chorismate Mutase/Prephenate Dehydratase Contributes to the Virulence of Acidovorax citrulli. FRONTIERS IN PLANT SCIENCE 2020; 11:569552. [PMID: 33101336 PMCID: PMC7546022 DOI: 10.3389/fpls.2020.569552] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Accepted: 09/09/2020] [Indexed: 05/21/2023]
Abstract
Acidovorax citrulli (Ac) is a plant pathogenic bacterium that causes bacterial fruit blotch (BFB) in cucurbit crops. Despite its importance in the cucurbit industry, resistant cultivars/lines against BFB have not yet been identified. Therefore, there is a need to characterize the virulence factors/mechanisms in Ac to control the disease. Chorismate mutase, a key enzyme in the shikimate pathway, produces aromatic amino acids. Here, we report the functions of putative bifunctional chorismate mutase/prephenate dehydratase in Ac (CmpAc) determined by proteomic analysis and phenotypic assays. Ac strain lacking CmpAc, AcΔcmpAc(EV), were significantly less virulent on watermelon in the germinated-seed inoculation and leaf infiltration assays. Sequence analysis revealed that CmpAc possesses two distinct domains: chorismate mutase and prephenate dehydratase, indicating that CmpAc is a bifunctional protein. Auxotrophic assays demonstrated that CmpAc is required for the biosynthesis of phenylalanine, but not tyrosine. The comparative proteomic analysis revealed that CmpAc is mostly involved in cell wall/membrane/envelop biogenesis. Furthermore, AcΔcmpAc(EV) showed reduced twitching halo production and enhanced biofilm formation. In addition, AcΔcmpAc(EV) was less tolerant to osmotic stress but more tolerant to antibiotics (polymyxin B). Thus, our study provides new insights into the functions of a putative bifunctional protein related to virulence in Ac.
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Affiliation(s)
- Minyoung Kim
- Department of Plant Science and Technology, Chung-Ang University, Anseong, South Korea
| | - Jongchan Lee
- Department of Plant Science and Technology, Chung-Ang University, Anseong, South Korea
| | - Lynn Heo
- Department of Plant Science and Technology, Chung-Ang University, Anseong, South Korea
| | - Sang-Wook Han
- Department of Plant Science and Technology, Chung-Ang University, Anseong, South Korea
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