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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Cai L, Ma W, Zou L, Xu X, Xu Z, Deng C, Qian W, Chen X, Chen G. Xanthomonas oryzae Pv. oryzicola Response Regulator VemR Is Co-opted by the Sensor Kinase CheA for Phosphorylation of Multiple Pathogenicity-Related Targets. Front Microbiol 2022; 13:928551. [PMID: 35756024 PMCID: PMC9218911 DOI: 10.3389/fmicb.2022.928551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 05/11/2022] [Indexed: 11/13/2022] Open
Abstract
Two-component systems (TCSs) (cognate sensor histidine kinase/response regulator pair, HK/RR) play a crucial role in bacterial adaptation, survival, and productive colonization. An atypical orphan single-domain RR VemR was characterized by the non-vascular pathogen Xanthomonas oryzae pv. oryzicola (Xoc) is known to cause bacterial leaf streak (BLS) disease in rice. Xoc growth and pathogenicity in rice, motility, biosynthesis of extracellular polysaccharide (EPS), and the ability to trigger HR in non-host tobacco were severely compromised in the deletion mutant strain RΔvemR as compared to the wild-type strain RS105. Site-directed mutagenesis and phosphotransfer experiments revealed that the conserved aspartate (D56) residue within the stand-alone phosphoacceptor receiver (REC) domain is essential for phosphorelay and the regulatory activity of Xoc VemR. Yeast two-hybrid (Y2H) and co-immunoprecipitation (co-IP) data identified CheA as the HK co-opting the RR VemR for phosphorylation. Affinity proteomics identified several downstream VemR-interacting proteins, such as 2-oxoglutarate dehydrogenase (OGDH), DNA-binding RR SirA, flagellar basal body P-ring formation protein FlgA, Type 4a pilus retraction ATPase PilT, stress-inducible sensor HK BaeS, septum site-determining protein MinD, cytoskeletal protein CcmA, and Type III and VI secretion system proteins HrpG and Hcp, respectively. Y2H and deletion mutant analyses corroborated that VemR interacted with OGDH, SirA, FlgA, and HrpG; thus, implicating multi-layered control of diverse cellular processes including carbon metabolism, motility, and pathogenicity in the rice. Physical interaction between VemR and HrpG suggested cross-talk interaction between CheA/VemR- and HpaS/HrpG-mediated signal transduction events orchestrating the hrp gene expression.
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Affiliation(s)
- Lulu Cai
- State Key Laboratory of Microbial Metabolism, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, China
| | - Wenxiu Ma
- State Key Laboratory of Microbial Metabolism, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, China
| | - Lifang Zou
- State Key Laboratory of Microbial Metabolism, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, China
| | - Xiameng Xu
- State Key Laboratory of Microbial Metabolism, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, China
| | - Zhengyin Xu
- State Key Laboratory of Microbial Metabolism, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, China
| | - Chaoying Deng
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Wei Qian
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Xiaobin Chen
- State Key Laboratory of Microbial Metabolism, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, China
| | - Gongyou Chen
- State Key Laboratory of Microbial Metabolism, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, China
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Teper D, Pandey SS, Wang N. The HrpG/HrpX Regulon of Xanthomonads-An Insight to the Complexity of Regulation of Virulence Traits in Phytopathogenic Bacteria. Microorganisms 2021; 9:187. [PMID: 33467109 DOI: 10.3390/microorganisms9010187] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 01/11/2021] [Accepted: 01/13/2021] [Indexed: 12/05/2022] Open
Abstract
Bacteria of the genus Xanthomonas cause a wide variety of economically important diseases in most crops. The virulence of the majority of Xanthomonas spp. is dependent on secretion and translocation of effectors by the type 3 secretion system (T3SS) that is controlled by two master transcriptional regulators HrpG and HrpX. Since their discovery in the 1990s, the two regulators were the focal point of many studies aiming to decipher the regulatory network that controls pathogenicity in Xanthomonas bacteria. HrpG controls the expression of HrpX, which subsequently controls the expression of T3SS apparatus genes and effectors. The HrpG/HrpX regulon is activated in planta and subjected to tight metabolic and genetic regulation. In this review, we cover the advances made in understanding the regulatory networks that control and are controlled by the HrpG/HrpX regulon and their conservation between different Xanthomonas spp.
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Zou J, Zhang Z, Yu S, Kang Q, Shi Y, Wang J, Zhu R, Ma C, Chen L, Wang J, Li J, Li Q, Liu X, Zhu J, Wu X, Hu Z, Qi Z, Liu C, Chen Q, Xin D. Responses of Soybean Genes in the Substituted Segments of Segment Substitution Lines Following a Xanthomonas Infection. Front Plant Sci 2020; 11:972. [PMID: 32719700 PMCID: PMC7351525 DOI: 10.3389/fpls.2020.00972] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 06/15/2020] [Indexed: 06/11/2023]
Abstract
Bacterial blight, which is one of the most common soybean diseases, is responsible for considerable yield losses. In this study, a novel Xanthomonas vasicola strain was isolated from the leaves of soybean plants infected with bacterial blight under field conditions. Sequencing the X. vasicola genome revealed type-III effector-coding genes. Moreover, the hrpG deletion mutant was constructed. To identify the soybean genes responsive to HrpG, two chromosome segment substitution lines (CSSLs) carrying the wild soybean genome, but with opposite phenotypes following Xanthomonas inoculations, were used to analyze gene expression networks based on RNA sequencing at three time points after inoculations with wild-type Xanthomonas or the hrpG deletion mutant. To further identify the hub genes underlying soybean responses to HrpG, the genes located on the substituted chromosome segments were examined. Finally, a combined analysis with the QTLs for resistance to Xanthomonas identified 35 hub genes in the substituted chromosomal segments that may help regulate soybean responses to Xanthomonas and HrpG. Furthermore, two candidate genes in the CSSLs might play pivotal roles in response to Xanthomonas.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - Zhaoming Qi
- *Correspondence: Zhaoming Qi, ; Chunyan Liu, ; Qingshan Chen, ; Dawei Xin,
| | - Chunyan Liu
- *Correspondence: Zhaoming Qi, ; Chunyan Liu, ; Qingshan Chen, ; Dawei Xin,
| | - Qingshan Chen
- *Correspondence: Zhaoming Qi, ; Chunyan Liu, ; Qingshan Chen, ; Dawei Xin,
| | - Dawei Xin
- *Correspondence: Zhaoming Qi, ; Chunyan Liu, ; Qingshan Chen, ; Dawei Xin,
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Zhang H, Wei J, Qian W, Deng C. Analysis of HrpG regulons and HrpG-interacting proteins by ChIP-seq and affinity proteomics in Xanthomonas campestris. Mol Plant Pathol 2020; 21:388-400. [PMID: 31916392 PMCID: PMC7036363 DOI: 10.1111/mpp.12903] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 11/06/2019] [Accepted: 11/27/2019] [Indexed: 06/02/2023]
Abstract
Gamma-proteobacteria Xanthomonas spp. cause at least 350 different plant diseases among important agricultural crops, which result in serious yield losses. Xanthomonas spp. rely mainly on the type III secretion system (T3SS) to infect their hosts and induce a hypersensitive response in nonhosts. HrpG, the master regulator of the T3SS, plays the dominant role in bacterial virulence. In this study, we used chromatin immunoprecipitation followed by sequencing (ChIP-seq) and tandem affinity purification (TAP) to systematically characterize the HrpG regulon and HrpG interacting proteins in vivo. We obtained 186 candidate HrpG downstream genes from the ChIP-seq analysis, which represented the genomic-wide regulon spectrum. A consensus HrpG-binding motif was obtained and three T3SS genes, hpa2, hrcU, and hrpE, were confirmed to be directly transcriptionally activated by HrpG in the inducing medium. A total of 273 putative HrpG interacting proteins were identified from the TAP data and the DNA-binding histone-like HU protein of Xanthomonas campestris pv. campestris (HUxcc ) was proved to be involved in bacterial virulence by increasing the complexity and intelligence of the bacterial signalling pathways in the T3SS.
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Affiliation(s)
- Hong‐Yu Zhang
- State Key Laboratory of Plant GenomicsInstitute of MicrobiologyChinese Academy of SciencesBeijingChina
- College of Life SciencesUniversity of Chinese Academy of SciencesBeijingChina
| | - Jin‐Wei Wei
- State Key Laboratory of Plant GenomicsInstitute of MicrobiologyChinese Academy of SciencesBeijingChina
- College of Life SciencesUniversity of Chinese Academy of SciencesBeijingChina
| | - Wei Qian
- State Key Laboratory of Plant GenomicsInstitute of MicrobiologyChinese Academy of SciencesBeijingChina
| | - Chao‐Ying Deng
- State Key Laboratory of Plant GenomicsInstitute of MicrobiologyChinese Academy of SciencesBeijingChina
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Fan S, Tian F, Li J, Hutchins W, Chen H, Yang F, Yuan X, Cui Z, Yang C, He C. Identification of phenolic compounds that suppress the virulence of Xanthomonas oryzae on rice via the type III secretion system. Mol Plant Pathol 2017; 18:555-568. [PMID: 27084974 PMCID: PMC6638228 DOI: 10.1111/mpp.12415] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The targeting of bacterial type III secretion systems (T3SSs), which are critical virulence factors in most Gram-negative pathogens, is regarded as an alternative strategy for the development of novel anti-microbial drugs. Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc) are two of the most important bacterial pathogens on rice, which cause leaf blight and leaf streak diseases, respectively. To identify potential anti-virulence drugs against these two pathogens, we screened a library of plant phenolic compounds and derivatives for their effects on the Xoo T3SS. Ten of 56 compounds significantly inhibited the promoter activity of a harpin gene, hpa1. These inhibitors were further tested for their impact on the hypersensitive response (HR) caused by Xoo on non-host tobacco plants. The results showed that pretreatment of Xoo with TS006 (o-coumaric acid, OCA), TS010, TS015 and TS018 resulted in significantly attenuated HR without affecting bacterial growth or survival. In addition, Cya translocation assays demonstrated that the translocation of two T3 effectors was suppressed by the four inhibitors. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis showed that mRNA levels of representative genes in the hrp (hypersensitive response and pathogenicity) cluster, as well as the regulatory genes hrpG and hrpX, were reduced by treatment with the four inhibitors, suggesting that expression of the Xoo T3SS was suppressed. The expression of other virulence factors was not suppressed, which indicated possible T3SS-specific inhibition. Finally, we demonstrated that these inhibitors reduced the disease symptoms of Xoo and Xoc on the rice cultivar (Oryza sativa) IR24 to varying extents.
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Affiliation(s)
- Susu Fan
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant Protection, Chinese Academy of Agricultural SciencesBeijing100193China
| | - Fang Tian
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant Protection, Chinese Academy of Agricultural SciencesBeijing100193China
| | - Jianyu Li
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant Protection, Chinese Academy of Agricultural SciencesBeijing100193China
| | - William Hutchins
- Department of Biological SciencesUniversity of Wisconsin‐MilwaukeeMilwaukeeWI 53211USA
| | - Huamin Chen
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant Protection, Chinese Academy of Agricultural SciencesBeijing100193China
| | - Fenghuan Yang
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant Protection, Chinese Academy of Agricultural SciencesBeijing100193China
| | - Xiaochen Yuan
- Department of Biological SciencesUniversity of Wisconsin‐MilwaukeeMilwaukeeWI 53211USA
| | - Zining Cui
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Department of Plant PathologySouth China Agricultural UniversityGuangzhou510642China
| | - Ching‐Hong Yang
- Department of Biological SciencesUniversity of Wisconsin‐MilwaukeeMilwaukeeWI 53211USA
| | - Chenyang He
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant Protection, Chinese Academy of Agricultural SciencesBeijing100193China
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