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Lombardi RL, Ramsey JS, Mahoney JE, MacCoss MJ, Heck ML, Slupsky CM. Longitudinal Transcriptomic, Proteomic, and Metabolomic Response of Citrus sinensis to Diaphorina citri Inoculation of Candidatus Liberibacter asiaticus. J Proteome Res 2024. [PMID: 38373055 DOI: 10.1021/acs.jproteome.3c00485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2024]
Abstract
Huanglongbing (HLB) is a fatal citrus disease that is currently threatening citrus varieties worldwide. One putative causative agent, Candidatus Liberibacter asiaticus (CLas), is vectored by Diaphorina citri, known as the Asian citrus psyllid (ACP). Understanding the details of CLas infection in HLB disease has been hindered by its Candidatus nature and the inability to confidently detect it in diseased trees during the asymptomatic stage. To identify early changes in citrus metabolism in response to inoculation of CLas using its natural psyllid vector, leaves from Madam Vinous sweet orange (Citrus sinensis (L.) Osbeck) trees were exposed to CLas-positive ACP or CLas-negative ACP and longitudinally analyzed using transcriptomics (RNA sequencing), proteomics (liquid chromatography-tandem mass spectrometry; data available in Dryad: 10.25338/B83H1Z), and metabolomics (proton nuclear magnetic resonance). At 4 weeks postexposure (wpe) to psyllids, the initial HLB plant response was primarily to the ACP and, to a lesser extent, the presence or absence of CLas. Additionally, analysis of 4, 8, 12, and 16 wpe identified 17 genes and one protein as consistently differentially expressed between leaves exposed to CLas-positive ACP versus CLas-negative ACP. This study informs identification of early detection molecular targets and contributes to a broader understanding of vector-transmitted plant pathogen interactions.
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Affiliation(s)
- Rachel L Lombardi
- Department of Food Science and Technology, University of California Davis, Davis, California 95616, United States
| | - John S Ramsey
- Agricultural Research Service, Emerging Pests and Pathogens Research Unit, Ithaca, New York 14853, United States
| | - Jaclyn E Mahoney
- Boyce Thompson Institute for Plant Research, Ithaca, New York 14853, United States
| | - Michael J MacCoss
- Department of Genome Sciences, University of Washington, Seattle, Washington 98195, United States
| | - Michelle L Heck
- Agricultural Research Service, Emerging Pests and Pathogens Research Unit, Ithaca, New York 14853, United States
- Plant Pathology and Plant Microbe Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, New York 14853, United States
| | - Carolyn M Slupsky
- Department of Food Science and Technology, University of California Davis, Davis, California 95616, United States
- Department of Nutrition, University of California Davis, Davis, California 95616, United States
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2
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Zuo S, Xu L, Zhang H, Jiang M, Wu S, Zhang LH, Zhou X, Wang J. FlgI Is a Sec-Dependent Effector of Candidatus Liberibacter asiaticus That Can Be Blocked by Small Molecules Identified Using a Yeast Screen. PLANTS (BASEL, SWITZERLAND) 2024; 13:318. [PMID: 38276775 PMCID: PMC10819201 DOI: 10.3390/plants13020318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 01/11/2024] [Accepted: 01/16/2024] [Indexed: 01/27/2024]
Abstract
Huanglongbing (HLB) is one of the most devastating diseases of citrus worldwide. The phloem-restricted bacterium Candidatus Liberibacter asiaticus (CLas) is considered to be the main pathogen responsible for HLB. There is currently no effective practical strategy for the control of HLB. Our understanding of how pathogens cause HLB is limited because CLas has not been artificially cultured. In this study, 15 potential virulence factors were predicted from the proteome of CLas through DeepVF and PHI-base searches. One among them, FlgI, was found to inhibit yeast growth when expressed in Saccharomyces cerevisiae. The expression of the signal peptide of FlgI fused with PhoA in Escherichia coli resulted in the discovery that FlgI was a novel Sec-dependent secretory protein. We further found that the carboxyl-terminal HA-tagged FlgI was secreted via outer membrane vesicles in Sinorhizobium meliloti. Fluoresence localization of transient expression FlgI-GFP in Nicotiana benthamiana revealed that FlgI is mainly localized in the cytoplasm, cell periphery, and nuclear periphery of tobacco cells. In addition, our experimental results suggest that FlgI has a strong ability to induce callose deposition and cell necrosis in N. benthamiana. Finally, by screening a large library of compounds in a high-throughput format, we found that cyclosporin A restored the growth of FlgI-expressing yeast. These results confirm that FlgI is a novel Sec-dependent effector, enriching our understanding of CLas pathogenicity and helping to develop new and more effective strategies to manage HLB.
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Affiliation(s)
| | | | | | | | | | | | - Xiaofan Zhou
- Integrative Microbiology Research Centre, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou 510642, China; (S.Z.); (L.X.); (H.Z.); (M.J.); (S.W.); (L.-H.Z.)
| | - Junxia Wang
- Integrative Microbiology Research Centre, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou 510642, China; (S.Z.); (L.X.); (H.Z.); (M.J.); (S.W.); (L.-H.Z.)
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3
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Pandey SS, Xu J, Achor DS, Li J, Wang N. Microscopic and Transcriptomic Analyses of Early Events Triggered by ' Candidatus Liberibacter asiaticus' in Young Flushes of Huanglongbing-Positive Citrus Trees. PHYTOPATHOLOGY 2023; 113:985-997. [PMID: 36449527 DOI: 10.1094/phyto-10-22-0360-r] [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: 06/17/2023]
Abstract
'Candidatus Liberibacter asiaticus' (CLas) is associated with the devastating citrus disease Huanglongbing (HLB). Young flushes are the center of the HLB pathosystem due to their roles in the psyllid life cycle and in the acquisition and transmission of CLas. However, the early events of CLas infection and how CLas modulates young flush physiology remain poorly understood. Here, transmission electron microscopy analysis showed that the mean diameter of the sieve pores decreased in young leaves of HLB-positive trees after CLas infection, consistent with CLas-triggered callose deposition. RNA-seq-based global expression analysis of young leaves of HLB-positive sweet orange with (CLas-Pos) and without (CLas-Neg) detectable CLas demonstrated a significant impact on gene expression in young leaves, including on the expression of genes involved in host immunity, stress response, and plant hormone biosynthesis and signaling. CLas-Pos and CLas-Neg expression data displayed distinct patterns. The number of upregulated genes was higher than that of the downregulated genes in CLas-Pos for plant-pathogen interactions, glutathione metabolism, peroxisome, and calcium signaling, which are commonly associated with pathogen infections, compared with the healthy control. On the contrary, the number of upregulated genes was lower than that of the downregulated genes in CLas-Neg for genes involved in plant-pathogen interactions and peroxisome biogenesis/metabolism. Additionally, a time-course quantitative reverse transcription-PCR-based expression analysis visualized the induced expression of companion cell-specific genes, phloem protein 2 genes, and sucrose transport genes in young flushes triggered by CLas. This study advances our understanding of early events during CLas infection of citrus young flushes.
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Affiliation(s)
- Sheo Shankar Pandey
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL 33850
| | - Jin Xu
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL 33850
| | - Diann S Achor
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL 33850
| | - Jinyun Li
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL 33850
| | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL 33850
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Gao Y, Xu J, Li Z, Zhang Y, Riera N, Xiong Z, Ouyang Z, Liu X, Lu Z, Seymour D, Zhong B, Wang N. Citrus genomic resources unravel putative genetic determinants of Huanglongbing pathogenicity. iScience 2023; 26:106024. [PMID: 36824272 PMCID: PMC9941208 DOI: 10.1016/j.isci.2023.106024] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Revised: 11/08/2022] [Accepted: 01/17/2023] [Indexed: 01/24/2023] Open
Abstract
Citrus HLB caused by Candidatus Liberibacter asiaticus is a pathogen-triggered immune disease. Here, we identified putative genetic determinants of HLB pathogenicity by integrating citrus genomic resources to characterize the pan-genome of accessions that differ in their response to HLB. Genome-wide association mapping and analysis of allele-specific expression between susceptible, tolerant, and resistant accessions further refined candidates underlying the response to HLB. We first developed a phased diploid assembly of Citrus sinensis 'Newhall' genome and produced resequencing data for 91 citrus accessions that differ in their response to HLB. These data were combined with previous resequencing data from 356 accessions for genome-wide association mapping of the HLB response. Genes determinants for HLB pathogenicity were associated with host immune response, ROS production, and antioxidants. Overall, this study has provided a significant resource of citrus genomic data and identified candidate genes to be further explored to understand the genetic determinants of HLB pathogenicity.
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Affiliation(s)
- Yuxia Gao
- National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, Jiangxi, China
| | - Jin Xu
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA
| | - Zhilong Li
- National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, Jiangxi, China
| | - Yunzeng Zhang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA
| | - Nadia Riera
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA
| | - Zhiwei Xiong
- National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, Jiangxi, China
| | - Zhigang Ouyang
- National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, Jiangxi, China
| | - Xinjun Liu
- National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, Jiangxi, China
| | - Zhanjun Lu
- National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, Jiangxi, China
| | | | - Balian Zhong
- National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, Jiangxi, China
| | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA
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Peng T, Yuan Y, Huang A, He J, Fu S, Duan S, Yi L, Yuan C, Yuan H, Wang X, Zhou C. Interaction between the flagellum of Candidatus Liberibacter asiaticus and the vitellogenin-like protein of Diaphorina citri significantly influences CLas titer. Front Microbiol 2023; 14:1119619. [PMID: 37143541 PMCID: PMC10152367 DOI: 10.3389/fmicb.2023.1119619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 03/10/2023] [Indexed: 05/06/2023] Open
Abstract
Huanglongbing (HLB) is a global devastating citrus disease that is mainly caused by "Candidatus Liberibacter asiaticus" (CLas). It is mostly transmitted by the insect Asian citrus psyllid (ACP, Diaphorina citri) in a persistent and proliferative manner. CLas traverses multiple barriers to complete an infection cycle and is likely involved in multiple interactions with D. citri. However, the protein-protein interactions between CLas and D. citri are largely unknown. Here, we report on a vitellogenin-like protein (Vg_VWD) in D. citri that interacts with a CLas flagellum (flaA) protein. We found that Vg_VWD was upregulated in CLas-infected D. citri. Silencing of Vg_VWD in D. citri via RNAi silencing significantly increased the CLas titer, suggesting that Vg_VWD plays an important role in the CLas-D. citri interaction. Agrobacterium-mediated transient expression assays indicated that Vg_VWD inhibits BAX- and INF1-triggered necrosis and suppresses the callose deposition induced by flaA in Nicotiana benthamiana. These findings provide new insights into the molecular interaction between CLas and D. citri.
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Affiliation(s)
- Tao Peng
- National Citrus Engineering Research Center, Citrus Research Institute, Southwest University, Chongqing, China
| | - Yingzhe Yuan
- National Citrus Engineering Research Center, Citrus Research Institute, Southwest University, Chongqing, China
| | - Aijun Huang
- National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, China
| | - Jun He
- National Citrus Engineering Research Center, Citrus Research Institute, Southwest University, Chongqing, China
| | - Shimin Fu
- National Citrus Engineering Research Center, Citrus Research Institute, Southwest University, Chongqing, China
| | - Shuo Duan
- National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, China
| | - Long Yi
- National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, China
| | - Chenyang Yuan
- Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing, China
| | - Huizhu Yuan
- Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Ministry of Agriculture and Rural Affairs, Beijing, China
- *Correspondence: Huizhu Yuan, ; Xuefeng Wang, ; Changyong Zhou,
| | - Xuefeng Wang
- National Citrus Engineering Research Center, Citrus Research Institute, Southwest University, Chongqing, China
- *Correspondence: Huizhu Yuan, ; Xuefeng Wang, ; Changyong Zhou,
| | - Changyong Zhou
- National Citrus Engineering Research Center, Citrus Research Institute, Southwest University, Chongqing, China
- *Correspondence: Huizhu Yuan, ; Xuefeng Wang, ; Changyong Zhou,
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Garcia L, Molina MC, Padgett-Pagliai KA, Torres PS, Bruna RE, García Véscovi E, González CF, Gadea J, Marano MR. A serralysin-like protein of Candidatus Liberibacter asiaticus modulates components of the bacterial extracellular matrix. Front Microbiol 2022; 13:1006962. [DOI: 10.3389/fmicb.2022.1006962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 09/26/2022] [Indexed: 11/13/2022] Open
Abstract
Huanglongbing (HLB), the current major threat for Citrus species, is caused by intracellular alphaproteobacteria of the genus Candidatus Liberibacter (CaL), with CaL asiaticus (CLas) being the most prevalent species. This bacterium inhabits phloem cells and is transmitted by the psyllid Diaphorina citri. A gene encoding a putative serralysin-like metalloprotease (CLIBASIA_01345) was identified in the CLas genome. The expression levels of this gene were found to be higher in citrus leaves than in psyllids, suggesting a function for this protease in adaptation to the plant environment. Here, we study the putative role of CLas-serralysin (Las1345) as virulence factor. We first assayed whether Las1345 could be secreted by two different surrogate bacteria, Rhizobium leguminosarum bv. viciae A34 (A34) and Serratia marcescens. The protein was detected only in the cellular fraction of A34 and S. marcescens expressing Las1345, and increased protease activity of those bacteria by 2.55 and 4.25-fold, respectively. In contrast, Las1345 expressed in Nicotiana benthamiana leaves did not show protease activity nor alterations in the cell membrane, suggesting that Las1345 do not function as a protease in the plant cell. Las1345 expression negatively regulated cell motility, exopolysaccharide production, and biofilm formation in Xanthomonas campestris pv. campestris (Xcc). This bacterial phenotype was correlated with reduced growth and survival on leaf surfaces as well as reduced disease symptoms in N. benthamiana and Arabidopsis. These results support a model where Las1345 could modify extracellular components to adapt bacterial shape and appendages to the phloem environment, thus contributing to virulence.
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Huang Y, Zhu F, Koh J, Stanton D, Chen S, Wang N. Proteomic and bioinformatic analyses of proteins in the outer membrane and extracellular compartments and outer membrane vesicles of Candidatus Liberibacter species. Front Microbiol 2022; 13:977710. [PMID: 36225379 PMCID: PMC9548881 DOI: 10.3389/fmicb.2022.977710] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 09/02/2022] [Indexed: 11/23/2022] Open
Abstract
Citrus Huanglongbing (HLB) is the most devastating citrus disease in the world. Candidatus Liberibacter asiaticus (Las) is the prevalent HLB pathogen, which is yet to be cultivated. A recent study demonstrates that Las does not contain pathogenicity factors that are directly responsible for HLB symptoms. Instead, Las triggers systemic and chronic immune responses, representing a pathogen-triggered immune disease. Importantly, overproduction of reactive oxygen species (ROS) causes systemic cell death of phloem tissues, thus causing HLB symptoms. Because Las resides in the phloem tissues, it is expected that phloem cell might recognize outer membrane proteins, outer membrane vesicle (OMV) proteins and extracellular proteins of Las to contribute to the immune responses. Because Las has not been cultivated, we used Liberibacter crescens (Lcr) as a surrogate to identify proteins in the OM fraction, OMV proteins and extracellular proteins by liquid chromatography with tandem mass spectrometry (LC–MS/MS). We observed OMVs of Lcr under scanning electron microscope, representing the first experimental evidence that Liberibacter can deliver proteins to the extracellular compartment. In addition, we also further analyzed LC–MS/MS data using bioinformatic tools. Our study provides valuable information regarding the biology of Ca. Liberibacter species and identifies many putative proteins that may interact with host proteins in the phloem tissues.
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Affiliation(s)
- Yixiao Huang
- Department of Plant Pathology, Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
| | - Fanchao Zhu
- Proteomics and Mass Spectrometry, Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, FL, United States
| | - Jin Koh
- Proteomics and Mass Spectrometry, Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, FL, United States
| | - Daniel Stanton
- Department of Plant Pathology, Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
| | - Sixue Chen
- Proteomics and Mass Spectrometry, Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, FL, United States
| | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
- *Correspondence: Nian Wang,
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Ma W, Pang Z, Huang X, Xu J, Pandey SS, Li J, Achor DS, Vasconcelos FNC, Hendrich C, Huang Y, Wang W, Lee D, Stanton D, Wang N. Citrus Huanglongbing is a pathogen-triggered immune disease that can be mitigated with antioxidants and gibberellin. Nat Commun 2022; 13:529. [PMID: 35082290 PMCID: PMC8791970 DOI: 10.1038/s41467-022-28189-9] [Citation(s) in RCA: 42] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 01/04/2022] [Indexed: 12/17/2022] Open
Abstract
Huanglongbing (HLB) is a devastating disease of citrus, caused by the phloem-colonizing bacterium Candidatus Liberibacter asiaticus (CLas). Here, we present evidence that HLB is an immune-mediated disease. We show that CLas infection of Citrus sinensis stimulates systemic and chronic immune responses in phloem tissue, including callose deposition, production of reactive oxygen species (ROS) such as H2O2, and induction of immunity-related genes. The infection also upregulates genes encoding ROS-producing NADPH oxidases, and downregulates antioxidant enzyme genes, supporting that CLas causes oxidative stress. CLas-triggered ROS production localizes in phloem-enriched bark tissue and is followed by systemic cell death of companion and sieve element cells. Inhibition of ROS levels in CLas-positive stems by NADPH oxidase inhibitor diphenyleneiodonium (DPI) indicates that NADPH oxidases contribute to CLas-triggered ROS production. To investigate potential treatments, we show that addition of the growth hormone gibberellin (known to have immunoregulatory activities) upregulates genes encoding H2O2-scavenging enzymes and downregulates NADPH oxidases. Furthermore, foliar spray of HLB-affected citrus with gibberellin or antioxidants (uric acid, rutin) reduces H2O2 concentrations and cell death in phloem tissues and reduces HLB symptoms. Thus, our results indicate that HLB is an immune-mediated disease that can be mitigated with antioxidants and gibberellin.
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Affiliation(s)
- Wenxiu Ma
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA
| | - Zhiqian Pang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA
| | - Xiaoen Huang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA
| | - Jin Xu
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA
| | - Sheo Shankar Pandey
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA
| | - Jinyun Li
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA
| | - Diann S Achor
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA
| | - Fernanda N C Vasconcelos
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA
| | - Connor Hendrich
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA
| | - Yixiao Huang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA
| | - Wenting Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA
| | - Donghwan Lee
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA
| | - Daniel Stanton
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA
| | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, USA.
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Pandey SS, Hendrich C, Andrade MO, Wang N. Candidatus Liberibacter: From Movement, Host Responses, to Symptom Development of Citrus Huanglongbing. PHYTOPATHOLOGY 2022; 112:55-68. [PMID: 34609203 DOI: 10.1094/phyto-08-21-0354-fi] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Candidatus Liberibacter spp. are fastidious α-proteobacteria that cause multiple diseases on plant hosts of economic importance, including the most devastating citrus disease: Huanglongbing (HLB). HLB was reported in Asia a century ago but has since spread worldwide. Understanding the pathogenesis of Candidatus Liberibacter spp. remains challenging as they are yet to be cultured in artificial media and infect the phloem, a sophisticated environment that is difficult to manipulate. Despite those challenges, tremendous progress has been made on Ca. Liberibacter pathosystems. Here, we first reviewed recent studies on genetic information of flagellar and type IV pili biosynthesis, their expression profiles, and movement of Ca. Liberibacter spp. inside the plant and insect hosts. Next, we reviewed the transcriptomic, proteomic, and metabolomic studies of susceptible and tolerant plant genotypes to Ca. Liberibacter spp. infection and how Ca. Liberibacter spp. adapt in plants. Analyses of the interactions between plants and Ca. Liberibacter spp. imply the involvement of immune response in the Ca. Liberibacter pathosystems. Lastly, we reviewed how Ca. Liberibacter spp. movement inside and interactions with plants lead to symptom development.
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Affiliation(s)
- Sheo Shankar Pandey
- Citrus Research and Education Center, Department of Microbiology and Cell Sciences, University of Florida, Lake Alfred, FL 33850, U.S.A
| | - Connor Hendrich
- Citrus Research and Education Center, Department of Microbiology and Cell Sciences, University of Florida, Lake Alfred, FL 33850, U.S.A
| | - Maxuel O Andrade
- Brazilian Biorenewables National Laboratory (LNBR), Brazilian Centre for Research in Energy and Materials (CNPEM), Campinas, SP, Brazil
| | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Sciences, University of Florida, Lake Alfred, FL 33850, U.S.A
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10
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Hu B, Rao MJ, Deng X, Pandey SS, Hendrich C, Ding F, Wang N, Xu Q. Molecular signatures between citrus and Candidatus Liberibacter asiaticus. PLoS Pathog 2021; 17:e1010071. [PMID: 34882744 PMCID: PMC8659345 DOI: 10.1371/journal.ppat.1010071] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Citrus Huanglongbing (HLB), also known as citrus greening, is one of the most devastating citrus diseases worldwide. Candidatus Liberibacter asiaticus (CLas) is the most prevalent strain associated with HLB, which is yet to be cultured in vitro. None of the commercial citrus cultivars are resistant to HLB. The pathosystem of Ca. Liberibacter is complex and remains a mystery. In this review, we focus on the recent progress in genomic research on the pathogen, the interaction of host and CLas, and the influence of CLas infection on the transcripts, proteins, and metabolism of the host. We have also focused on the identification of candidate genes for CLas pathogenicity or the improvements of HLB tolerance in citrus. In the end, we propose potentially promising areas for mechanistic studies of CLas pathogenicity, defense regulators, and genetic improvement for HLB tolerance/resistance in the future.
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Affiliation(s)
- Bin Hu
- Key Laboratory of Horticultural Plant Biology (Ministry of Education), Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Ministry of Agriculture), Huazhong Agricultural University, Wuhan, Hubei, China
| | - Muhammad Junaid Rao
- Key Laboratory of Horticultural Plant Biology (Ministry of Education), Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Ministry of Agriculture), Huazhong Agricultural University, Wuhan, Hubei, China
| | - Xiuxin Deng
- Key Laboratory of Horticultural Plant Biology (Ministry of Education), Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Ministry of Agriculture), Huazhong Agricultural University, Wuhan, Hubei, China
| | - Sheo Shankar Pandey
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, Florida, United States of America
| | - Connor Hendrich
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, Florida, United States of America
| | - Fang Ding
- Hubei Key Laboratory of Plant Pathology, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, Florida, United States of America
| | - Qiang Xu
- Key Laboratory of Horticultural Plant Biology (Ministry of Education), Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Ministry of Agriculture), Huazhong Agricultural University, Wuhan, Hubei, China
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Cai L, Jain M, Sena-Vélez M, Jones KM, Fleites LA, Heck M, Gabriel DW. Tad pilus-mediated twitching motility is essential for DNA uptake and survival of Liberibacters. PLoS One 2021; 16:e0258583. [PMID: 34644346 PMCID: PMC8513845 DOI: 10.1371/journal.pone.0258583] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 10/01/2021] [Indexed: 12/12/2022] Open
Abstract
Axenically cultured Liberibacter crescens (Lcr) is a closely related surrogate for uncultured plant pathogenic species of the genus Liberibacter, including ‘Candidatus L. asiaticus’ (CLas) and ‘Ca. L. solanacearum’ (CLso). All Liberibacters encode a completely conserved gene repertoire for both flagella and Tad (Tight Adherence) pili and all are missing genes critical for nucleotide biosynthesis. Both flagellar swimming and Tad pilus-mediated twitching motility in Lcr were demonstrated for the first time. A role for Tad pili in the uptake of extracellular dsDNA for food in Liberibacters was suspected because both twitching and DNA uptake are impossible without repetitive pilus extension and retraction, and no genes encoding other pilus assemblages or mechanisms for DNA uptake were predicted to be even partially present in any of the 35 fully sequenced Liberibacter genomes. Insertional mutations of the Lcr Tad pilus genes cpaA, cpaB, cpaE, cpaF and tadC all displayed such severely reduced growth and viability that none could be complemented. A mutation affecting cpaF (motor ATPase) was further characterized and the strain displayed concomitant loss of twitching, viability and reduced periplasmic uptake of extracellular dsDNA. Mutations of comEC, encoding the inner membrane competence channel, had no effect on either motility or growth but completely abolished natural transformation in Lcr. The comEC mutation was restored by complementation using comEC from Lcr but not from CLas strain psy62 or CLso strain RS100, indicating that unlike Lcr, these pathogens were not naturally competent for transformation. This report provides the first evidence that the Liberibacter Tad pili are dynamic and essential for both motility and DNA uptake, thus extending their role beyond surface adherence.
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Affiliation(s)
- Lulu Cai
- Plant Pathology Department, University of Florida, Gainesville, Florida, United States of America
| | - Mukesh Jain
- Plant Pathology Department, University of Florida, Gainesville, Florida, United States of America
| | - Marta Sena-Vélez
- Department of Biological Science, Florida State University, Tallahassee, Florida, United States of America
| | - Kathryn M. Jones
- Department of Biological Science, Florida State University, Tallahassee, Florida, United States of America
| | - Laura A. Fleites
- USDA Agricultural Research Service, Robert W. Holley Center for Agriculture and Health, Ithaca, New York, United States of America
| | - Michelle Heck
- USDA Agricultural Research Service, Robert W. Holley Center for Agriculture and Health, Ithaca, New York, United States of America
| | - Dean W. Gabriel
- Plant Pathology Department, University of Florida, Gainesville, Florida, United States of America
- * E-mail:
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12
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Wei X, Mira A, Yu Q, Gmitter FG. The Mechanism of Citrus Host Defense Response Repression at Early Stages of Infection by Feeding of Diaphorina citri Transmitting Candidatus Liberibacter asiaticus. FRONTIERS IN PLANT SCIENCE 2021; 12:635153. [PMID: 34168662 PMCID: PMC8218908 DOI: 10.3389/fpls.2021.635153] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 04/29/2021] [Indexed: 06/01/2023]
Abstract
Citrus Huanglongbing (HLB) is the most devastating disease of citrus, presumably caused by "Candidatus Liberibacter asiaticus" (CaLas). Although transcriptomic profiling of HLB-affected citrus plants has been studied extensively, the initial steps in pathogenesis have not been fully understood. In this study, RNA sequencing (RNA-seq) was used to compare very early transcriptional changes in the response of Valencia sweet orange (VAL) to CaLas after being fed by the vector, Diaphorina citri (Asian citrus psyllid, or ACP). The results suggest the existence of a delayed defense reaction against the infective vector in VAL, while the attack by the healthy vector prompted immediate and substantial transcriptomic changes that led to the rapid erection of active defenses. Moreover, in the presence of CaLas-infected psyllids, several downregulated differentially expressed genes (DEGs) were identified on the pathways, such as signaling, transcription factor, hormone, defense, and photosynthesis-related pathways at 1 day post-infestation (dpi). Surprisingly, a burst of DEGs (6,055) was detected at 5 dpi, including both upregulated and downregulated DEGs on the defense-related and secondary metabolic pathways, and severely downregulated DEGs on the photosynthesis-related pathways. Very interestingly, a significant number of those downregulated DEGs required ATP binding for the activation of phosphate as substrate; meanwhile, abundant highly upregulated DEGs were detected on the ATP biosynthetic and glycolytic pathways. These findings highlight the energy requirement of CaLas virulence processes. The emerging picture is that CaLas not only employs virulence strategies to subvert the host cell immunity, but the fast-replicating CaLas also actively rewires host cellular metabolic pathways to obtain the necessary energy and molecular building blocks to support virulence and the replication process. Taken together, the very early response of citrus to the CaLas, vectored by infective ACP, was evaluated for the first time, thus allowing the changes in gene expression relating to the primary mechanisms of susceptibility and host-pathogen interactions to be studied, and without the secondary effects caused by the development of complex whole plant symptoms.
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Affiliation(s)
- Xu Wei
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL, United States
- College of Horticulture and Landscape, Southwest University, Chongqing, China
| | - Amany Mira
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL, United States
- Department of Horticulture, Faculty of Agriculture, Tanta University, Tanta, Egypt
| | - Qibin Yu
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL, United States
| | - Fred G. Gmitter
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL, United States
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13
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Pandey SS, Nogales da Costa Vasconcelos F, Wang N. Spatiotemporal Dynamics of ' Candidatus Liberibacter asiaticus' Colonization Inside Citrus Plant and Huanglongbing Disease Development. PHYTOPATHOLOGY 2021; 111:921-928. [PMID: 33174821 DOI: 10.1094/phyto-09-20-0407-r] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
'Candidatus Liberibacter asiaticus' (CLas), the causal agent of citrus huanglongbing (HLB), colonizes inside the phloem and is naturally transmitted by the Asian citrus psyllid (ACP). Here, we investigated spatiotemporal CLas colonization in different tissues after ACP transmission. Of the nine plants successfully infected via ACP transmission, CLas was detected in the roots of all trees at 75 days postremoval of ACPs (DPR) but in the mature leaf of only one tree; this finding is consistent with the model that CLas moves passively from source to sink tissues. At 75 and 365 DPR, CLas was detected in 11.1 and 43.1% of mature leaves not fed on by ACPs during transmission, respectively, unveiling active movement to the source tissue. The difference in colonization timing of sink and source tissues indicates that CLas is capable of both passive and active movement, with passive movement being dominant. At 225 DPR, leaves fed on by ACPs during the young stage showed the highest ratio of HLB symptomatic leaves and the highest CLas titer, followed by leaves that emerged after ACP removal and mature leaves not fed on by ACPs. Importantly, our data showed that ACPs were unable to transmit CLas via feeding on mature leaves. It is estimated that it takes 3 years at most for CLas to infect the whole tree. Overall, spatiotemporal detection of CLas in different tissues after ACP transmission helps visualize the infection process of CLas in planta and subsequent HLB symptom development and provides evidence showing that young leaves should be the focus of HLB management.
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Affiliation(s)
- Sheo Shankar Pandey
- Citrus Research and Education Center, Department of Microbiology and Cell Science, University of Florida, Lake Alfred, FL 33850
| | | | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, University of Florida, Lake Alfred, FL 33850
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14
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Thapa SP, De Francesco A, Trinh J, Gurung FB, Pang Z, Vidalakis G, Wang N, Ancona V, Ma W, Coaker G. Genome-wide analyses of Liberibacter species provides insights into evolution, phylogenetic relationships, and virulence factors. MOLECULAR PLANT PATHOLOGY 2020; 21:716-731. [PMID: 32108417 PMCID: PMC7170780 DOI: 10.1111/mpp.12925] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 01/27/2020] [Accepted: 01/28/2020] [Indexed: 05/04/2023]
Abstract
'Candidatus Liberibacter' species are insect-transmitted, phloem-limited α-Proteobacteria in the order of Rhizobiales. The citrus industry is facing significant challenges due to huanglongbing, associated with infection from 'Candidatus Liberibacter asiaticus' (Las). In order to gain greater insight into 'Ca. Liberibacter' biology and genetic diversity, we have performed genome sequencing and comparative analyses of diverse 'Ca. Liberibacter' species, including those that can infect citrus. Our phylogenetic analysis differentiates 'Ca. Liberibacter' species and Rhizobiales in separate clades and suggests stepwise evolution from a common ancestor splitting first into nonpathogenic Liberibacter crescens followed by diversification of pathogenic 'Ca. Liberibacter' species. Further analysis of Las genomes from different geographical locations revealed diversity among isolates from the United States. Our phylogenetic study also indicates multiple Las introduction events in California and spread of the pathogen from Florida to Texas. Texan Las isolates were closely related, while Florida and Asian isolates exhibited the most genetic variation. We have identified conserved Sec translocon (SEC)-dependent effectors likely involved in bacterial survival and virulence of Las and analysed their expression in their plant host (citrus) and insect vector (Diaphorina citri). Individual SEC-dependent effectors exhibited differential expression patterns between host and vector, indicating that Las uses its effector repertoire to differentially modulate diverse organisms. Collectively, this work provides insights into the evolution of 'Ca. Liberibacter' species, the introduction of Las in the United States and identifies promising Las targets for disease management.
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Affiliation(s)
- Shree P. Thapa
- Department of Plant PathologyUniversity of CaliforniaDavisCAUSA
| | - Agustina De Francesco
- Department of Microbiology and Plant PathologyUniversity of CaliforniaRiversideCAUSA
| | - Jessica Trinh
- Department of Microbiology and Plant PathologyUniversity of CaliforniaRiversideCAUSA
| | - Fatta B. Gurung
- Citrus CenterDepartment of Agriculture, Agribusiness and Environmental SciencesTexas A&M University‐KingsvilleWeslacoTXUSA
| | - Zhiqian Pang
- Citrus Research and Education CenterDepartment of Microbiology and Cell ScienceUniversity of FloridaLake AlfredFLUSA
| | - Georgios Vidalakis
- Department of Microbiology and Plant PathologyUniversity of CaliforniaRiversideCAUSA
| | - Nian Wang
- Citrus Research and Education CenterDepartment of Microbiology and Cell ScienceUniversity of FloridaLake AlfredFLUSA
| | - Veronica Ancona
- Citrus CenterDepartment of Agriculture, Agribusiness and Environmental SciencesTexas A&M University‐KingsvilleWeslacoTXUSA
| | - Wenbo Ma
- Department of Microbiology and Plant PathologyUniversity of CaliforniaRiversideCAUSA
| | - Gitta Coaker
- Department of Plant PathologyUniversity of CaliforniaDavisCAUSA
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15
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Chen Y, Bendix C, Lewis JD. Comparative Genomics Screen Identifies Microbe-Associated Molecular Patterns from ' Candidatus Liberibacter' spp. That Elicit Immune Responses in Plants. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2020; 33:539-552. [PMID: 31790346 DOI: 10.1094/mpmi-11-19-0309-r] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Citrus huanglongbing (HLB), caused by phloem-limited 'Candidatus Liberibacter' bacteria, is a destructive disease threatening the worldwide citrus industry. The mechanisms of pathogenesis are poorly understood and no efficient strategy is available to control HLB. Here, we used a comparative genomics screen to identify candidate microbe-associated molecular patterns (MAMPs) from 'Ca. Liberibacter' spp. We identified the core genome from multiple 'Ca. Liberibacter' pathogens, and searched for core genes with signatures of positive selection. We hypothesized that genes encoding putative MAMPs would evolve to reduce recognition by the plant immune system, while retaining their essential functions. To efficiently screen candidate MAMP peptides, we established a high-throughput microtiter plate-based screening assay, particularly for citrus, that measured reactive oxygen species (ROS) production, which is a common immune response in plants. We found that two peptides could elicit ROS production in Arabidopsis and Nicotiana benthamiana. One of these peptides elicited ROS production and defense gene expression in HLB-tolerant citrus genotypes, and induced MAMP-triggered immunity against the bacterial pathogen Pseudomonas syringae. Our findings identify MAMPs that boost immunity in citrus and could help prevent or reduce HLB infection.
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Affiliation(s)
- Yuan Chen
- Plant Gene Expression Center, United States Department of Agriculture-Agricultural Research Service and Department of Plant and Microbial Biology, University of California-Berkeley, 800 Buchanan Street, Albany, CA 94710, U.S.A
| | - Claire Bendix
- Plant Gene Expression Center, United States Department of Agriculture-Agricultural Research Service and Department of Plant and Microbial Biology, University of California-Berkeley, 800 Buchanan Street, Albany, CA 94710, U.S.A
| | - Jennifer D Lewis
- Plant Gene Expression Center, United States Department of Agriculture-Agricultural Research Service and Department of Plant and Microbial Biology, University of California-Berkeley, 800 Buchanan Street, Albany, CA 94710, U.S.A
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16
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Jiang Y, Zhang CX, Chen R, He SY. Challenging battles of plants with phloem-feeding insects and prokaryotic pathogens. Proc Natl Acad Sci U S A 2019; 116:23390-23397. [PMID: 31712429 PMCID: PMC6876188 DOI: 10.1073/pnas.1915396116] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
For the past 4 decades, intensive molecular studies of mostly leaf mesophyll cell-infecting pathogens and chewing insects have led to compelling models of plant-pathogen and plant-insect interactions. Yet, some of the most devastating pathogens and insect pests live in or feed on the phloem, a systemic tissue belonging to the plant vascular system. Phloem tissues are difficult to study, and phloem-inhabiting pathogens are often impossible to culture, thus limiting our understanding of phloem-insect/pathogen interactions at a molecular level. In this Perspective, we highlight recent literature that reports significant advances in the understanding of phloem interactions with insects and prokaryotic pathogens and attempt to identify critical questions that need attention for future research. It is clear that study of phloem-insect/pathogen interactions represents an exciting frontier of plant science, and influx of new scientific expertise and funding is crucial to achieve faster progress in this important area of research that is integral to global food security.
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Affiliation(s)
- Yanjuan Jiang
- CAS Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Kunming 650223, China;
- Center of Economic Botany, Core Botanical Gardens, Chinese Academy of Sciences, Kunming 650223, China
- Department of Energy, Plant Research Laboratory, Michigan State University, East Lansing, MI 48824
- Howard Hughes Medical Institute, Michigan State University, East Lansing, MI 48824
| | - Chuan-Xi Zhang
- State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Molecular Biology of Crop Pathogens and Insect Pests, Institute of Insect Science, Zhejiang University, Hangzhou 310058, China
| | - Rongzhi Chen
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430070, China
| | - Sheng Yang He
- Department of Energy, Plant Research Laboratory, Michigan State University, East Lansing, MI 48824;
- Howard Hughes Medical Institute, Michigan State University, East Lansing, MI 48824
- Department of Plant Biology, Michigan State University, East Lansing, MI 48824
- Plant Resilience Institute, Michigan State University, East Lansing, MI 48824
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17
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Shi Q, Pitino M, Zhang S, Krystel J, Cano LM, Shatters RG, Hall DG, Stover E. Temporal and spatial detection of Candidatus Liberibacter asiaticus putative effector transcripts during interaction with Huanglongbing-susceptible, -tolerant, and -resistant citrus hosts. BMC PLANT BIOLOGY 2019; 19:122. [PMID: 30940073 PMCID: PMC6444692 DOI: 10.1186/s12870-019-1703-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 03/06/2019] [Indexed: 05/06/2023]
Abstract
BACKGROUND Citrus Huanglongbing (HLB) is a bacterial disease with high economic significance. The associated agent Candidatus Liberibacter asiaticus is a fastidious, phloem-limited, intracellular bacterium that is transmitted by an insect vector the Asian citrus psyllid (ACP). The genome of Ca. L. asiaticus contains protein secretion machinery that suggests host cell modulation capacity of this bacterium. RESULTS A total of 28 candidate effectors, an important class of secreted proteins, were predicted from the Ca. L. asiaticus genome. Sequence specific primers were designed for reverse transcription (RT) and quantitative PCR (qPCR), and expression was validated for 20 of the effector candidates in infected citrus with multiple genetic background. Using detached leaf inoculation, the mRNA of effectors was detected from 6 h to 7 days post ACP exposure. It was observed that higher bacterial titers were associated with a larger number of effectors showing amplification across all samples. The effectors' expression were compared in citrus hosts with various levels of HLB tolerance, including susceptible Duncan grapefruit and Washington navel orange, tolerant citron and Cleopatra mandarin, and resistant Pomeroy trifoliate and Carrizo citrange. Across all genotypes relatively high expression was observed for CLIBASIA_03695, CLIBASIA_00460, CLIBASIA_00420, CLIBASIA_04580, CLIBASIA_05320, CLIBASIA_04425, CLIBASIA_00525 and CLIBASIA_05315 in either a host-specific or -nonspecific manners. The two genotypes in each HLB-response group also show effector-expression profiles that seem to be different. In a companion study, the expression of effectors was compared between leaves and roots of own-rooted citrus that had been Ca. L. asiaticus-infected for more than a year. Results indicated relatively high expression of CLIBASIA_03875, CLIBASIA_04800 and CLIBASIA_05640 in all leaf and some root tissues of citron, Duncan and Cleopatra. CONCLUSION This temporal and spatial expression analysis of Ca. L. asiaticus effectors identified candidates possibly critical for early bacterial colonization, host tolerance suppression and long-term survival which are all worthy of further investigation.
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Affiliation(s)
- Qingchun Shi
- U.S. Horticultural Research Laboratory, Agricultural Research Service, United States Department of Agriculture, Fort Pierce, FL USA
| | - Marco Pitino
- Institute of Food and Agricultural Sciences, Department of Plant Pathology, Indian River Research and Education Center, University of Florida, Fort Pierce, FL USA
| | - Shujian Zhang
- U.S. Horticultural Research Laboratory, Agricultural Research Service, United States Department of Agriculture, Fort Pierce, FL USA
| | - Joseph Krystel
- U.S. Horticultural Research Laboratory, Agricultural Research Service, United States Department of Agriculture, Fort Pierce, FL USA
| | - Liliana M. Cano
- Institute of Food and Agricultural Sciences, Department of Plant Pathology, Indian River Research and Education Center, University of Florida, Fort Pierce, FL USA
| | - Robert G. Shatters
- U.S. Horticultural Research Laboratory, Agricultural Research Service, United States Department of Agriculture, Fort Pierce, FL USA
| | - David G. Hall
- U.S. Horticultural Research Laboratory, Agricultural Research Service, United States Department of Agriculture, Fort Pierce, FL USA
| | - Ed Stover
- U.S. Horticultural Research Laboratory, Agricultural Research Service, United States Department of Agriculture, Fort Pierce, FL USA
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The Ferredoxin-Like Protein FerR Regulates PrbP Activity in Liberibacter asiaticus. Appl Environ Microbiol 2019; 85:AEM.02605-18. [PMID: 30552192 DOI: 10.1128/aem.02605-18] [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: 10/27/2018] [Accepted: 12/08/2018] [Indexed: 12/26/2022] Open
Abstract
In Liberibacter asiaticus, PrbP is an important transcriptional accessory protein that regulates gene expression through interactions with the RNA polymerase β-subunit and a specific sequence on the promoter region. The constitutive expression of prbP observed upon chemical inactivation of PrbP-DNA interactions in vivo indicated that the expression of prbP was not autoregulated at the level of transcription. This observation suggested that a modulatory mechanism via protein-protein interactions may be involved. In silico genome association analysis identified FerR (CLIBASIA_01505), a putative ferredoxin-like protein, as a PrbP-interacting protein. Using a bacterial two-hybrid system and immunoprecipitation assays, interactions between PrbP and FerR were confirmed. In vitro transcription assays were used to show that FerR can increase the activity of PrbP by 16-fold when present in the PrbP-RNA polymerase reaction mixture. The FerR protein-protein interaction surface was predicted by structural modeling and followed by site-directed mutagenesis. Amino acids V20, V23, and C40 were identified as the most important residues in FerR involved in the modulation of PrbP activity in vitro The regulatory mechanism of FerR abundance was examined at the transcription level. In contrast to prbP of L. asiaticus (prbP Las), mRNA levels of ferR of L. asiaticus (ferR Las) are induced by an increase in osmotic pressure. The results of this study revealed that the activity of the transcriptional activator PrbPLas is modulated via interactions with FerRLas The induction of ferR Las expression by osmolarity provides insight into the mechanisms of adjusting gene expression in response to host environmental signals in L. asiaticus IMPORTANCE The rapid spread and aggressive progression of huanglongbing (HLB) in the major citrus-producing areas have raised global recognition of and vigilance to this disease. As a result, the causative agent, Liberibacter asiaticus, has been investigated from various perspectives. However, gene expression regulatory mechanisms that are important for the survival and persistence of this intracellular pathogen remain largely unexplored. PrbP is a transcriptional accessory protein important for L. asiaticus survival in the plant host. In this study, we investigated the interactions between PrbP in L. asiaticus (PrbPLas) and a ferredoxin-like protein (FerR) in L. asiaticus, FerRLas We show that the presence of FerR stabilizes and augments the activity of PrbPLas In addition, we demonstrate that the expression of ferR is induced by increases in osmolarity in Liberibacter crescens Altogether, these results suggest that FerRLas and PrbPLas may play important roles in the regulation of gene expression in response to changing environmental signals during L. asiaticus infection in the citrus host.
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Jain M, Munoz-Bodnar A, Zhang S, Gabriel DW. A Secreted 'Candidatus Liberibacter asiaticus' Peroxiredoxin Simultaneously Suppresses Both Localized and Systemic Innate Immune Responses In Planta. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2018; 31:1312-1322. [PMID: 29953333 DOI: 10.1094/mpmi-03-18-0068-r] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The oxidative (H2O2) burst is a seminal feature of the basal plant defense response to attempted pathogen invasions. In 'Candidatus Liberibacter asiaticus' UF506, expression of the SC2 prophage-encoded secreted peroxidase (F489_gp15) increases bacterial fitness and delays symptom progression in citrus. Two chromosomal 1-Cys peroxiredoxin genes, CLIBASIA_RS00940 (Lasprx5) and CLIBASIA_RS00445 (Lasbcp), are conserved among all sequenced 'Ca. L. asiaticus' strains, including those lacking prophages. Both LasBCP and LasdPrx5 have only a single conserved peroxidatic Cys (CP/SH) and lack the resolving Cys (CR/SH). Lasprx5 appeared to be a housekeeping gene with similar moderate transcript abundance in both 'Ca. L. asiaticus'-infected psyllids and citrus. By contrast, Lasbcp was expressed only in planta, similar to the expression of the SC2 peroxidase. Since 'Ca. L. asiaticus' is uncultured, Lasbcp and Lasprx5 were functionally validated in a cultured surrogate species, Liberibacter crescens, and both genes significantly increased oxidative stress tolerance and cell viability in culture. LasBCP was nonclassically secreted and, in L. crescens, conferred 214-fold more resistance to tert-butyl hydroperoxide (tBOOH) than wild type. Transient overexpression of Lasbcp in tobacco suppressed H2O2-mediated transcriptional activation of RbohB, the key gatekeeper of the systemic plant defense signaling cascade. Lasbcp expression did not interfere with the perception of 'Ca. L. asiaticus' flagellin (flg22Las) but interrupted the downstream activation of RbohB and stereotypical deposition of callose in tobacco. Critically, LasBCP also protected against tBOOH-induced peroxidative degradation of lipid membranes in planta, preventing subsequent accumulation of antimicrobial oxylipins that can also trigger the localized hypersensitive cell death response.
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Affiliation(s)
- Mukesh Jain
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, U.S.A
| | | | - Shujian Zhang
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, U.S.A
| | - Dean W Gabriel
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, U.S.A
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Importance of Remotely-Sensed Vegetation Variables for Predicting the Spatial Distribution of African Citrus Triozid (Trioza erytreae) in Kenya. ISPRS INTERNATIONAL JOURNAL OF GEO-INFORMATION 2018. [DOI: 10.3390/ijgi7110429] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Citrus is considered one of the most important fruit crops globally due to its contribution to food and nutritional security. However, the production of citrus has recently been in decline due to many biological, environmental, and socio-economic constraints. Amongst the biological ones, pests and diseases play a major role in threatening citrus quantity and quality. The most damaging disease in Kenya, is the African citrus greening disease (ACGD) or Huanglongbing (HLB) which is transmitted by the African citrus triozid (ACT), Trioza erytreae. HLB in Kenya is reported to have had the greatest impact on citrus production in the highlands, causing yield losses of 25% to 100%. This study aimed at predicting the occurrence of ACT using an ecological habitat suitability modeling approach. Specifically, we tested the contribution of vegetation phenological variables derived from remotely-sensed (RS) data combined with bio-climatic and topographical variables (BCL) to accurately predict the distribution of ACT in citrus-growing areas in Kenya. A MaxEnt (maximum entropy) suitability modeling approach was used on ACT presence-only data. Forty-seven (47) ACT observations were collected while 23 BCL and 12 RS covariates were used as predictor variables in the MaxEnt modeling. The BCL variables were extracted from the WorldClim data set, while the RS variables were predicted from vegetation phenological time-series data (spanning the years 2014–2016) and annually-summed land surface temperature (LST) metrics (2014–2016). We developed two MaxEnt models; one including both the BCL and the RS variables (BCL-RS) and another with only the BCL variables. Further, we tested the relationship between ACT habitat suitability and the surrounding land use/land cover (LULC) proportions using a random forest regression model. The results showed that the combined BCL-RS model predicted the distribution and habitat suitability for ACT better than the BCL-only model. The overall accuracy for the BCL-RS model result was 92% (true skills statistic: TSS = 0.83), whereas the BCL-only model had an accuracy of 85% (TSS = 0.57). Also, the results revealed that the proportion of shrub cover surrounding citrus orchards positively influenced the suitability probability of the ACT. These results provide a resourceful tool for precise, timely, and site-specific implementation of ACGD control strategies.
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21
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Hilf ME, Luo W. Dynamics of 'Candidatus Liberibacter asiaticus' Colonization of New Growth of Citrus. PHYTOPATHOLOGY 2018; 108:1165-1171. [PMID: 29757704 DOI: 10.1094/phyto-12-17-0408-r] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
'Candidatus Liberibacter asiaticus' is a phloem-colonizing intracellular bacterial pathogen of citrus associated with the disease huanglongbing. A study of patterns of colonization and bacterial population growth in new growth of different citrus types was conducted by pruning infected citron, sweet orange, sour orange, mandarin, citrange, and Citrus macrophylla trees to force the growth of axillary and adventitious shoots. The first three leaves on newly emerged shoots were collected at 30, 60, and 90 days to assess colonization and population growth of 'Ca. L. asiaticus' using real time PCR (qPCR). Single trials were conducted with mandarin and citron, two trials each for citrange, sour orange and sweet orange, and four trials for C. macrophylla. In citron the proportion of colonized leaves increased significantly over time, with 67, 85, and 96% of leaves colonized at 30, 60, and 90 days, respectively. For the other citrus types, the exact proportion of colonized leaves differed, but colonization exceeded 60% in mandarin, sour orange, and citrange, and exceeded 80% at 30 days in two trials with sweet orange and three trials with C. macrophylla, but there was no significant increase in the proportion of colonized leaves at 60 and 90 days. Bacteria were readily detected by 30 days in new leaves of all citrus types. Differences in the growth of the bacterial population between citrus types and at different times of the year were noted, but common trends were apparent. In general, bacterial titers peaked at 60 days, except in leaves of C. macrophylla where bacterial titers peaked at 30 days. The early and consistently high proportion of leaf colonization observed for new growth of sweet orange during two trials and for C. macrophylla during three trials indicates a near synchronous colonization of new leaves by 30 days.
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Affiliation(s)
- Mark E Hilf
- First author: U.S. Department of Agriculture-Agriculture Research Service (USDA-ARS), 2001 South Rock Road, Fort Pierce, FL 34945; and second author: USDA-ARS, Fort Pierce, Florida and North Carolina State University, Center for Integrated Pest Management, Raleigh 27606
| | - Weiqi Luo
- First author: U.S. Department of Agriculture-Agriculture Research Service (USDA-ARS), 2001 South Rock Road, Fort Pierce, FL 34945; and second author: USDA-ARS, Fort Pierce, Florida and North Carolina State University, Center for Integrated Pest Management, Raleigh 27606
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Tang J, Ding Y, Nan J, Yang X, Sun L, Zhao X, Jiang L. Transcriptome sequencing and ITRAQ reveal the detoxification mechanism of Bacillus GJ1, a potential biocontrol agent for Huanglongbing. PLoS One 2018; 13:e0200427. [PMID: 30091977 PMCID: PMC6084860 DOI: 10.1371/journal.pone.0200427] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 06/26/2018] [Indexed: 11/18/2022] Open
Abstract
Huanglongbing (HLB) is the most serious disease affecting citrus production worldwide. No HLB-resistant citrus varieties exist. The HLB pathogen Candidatus Liberibacter asiaticus is nonculturable, increasing the difficulty of preventing and curing the disease. We successfully screened the biocontrol agent Bacillus GJ1 for the control of HLB in nursery-grown citrus plants. RNA sequencing (RNA-seq) of the transcriptome and isobaric tags for relative and absolute quantification of the proteome revealed differences in the detoxification responses of Bacillus GJ1-treated and -untreated Ca. L. asiaticus-infected citrus. Phylogenetic tree alignment showed that GJ1 was classified as B. amyloliquefaciens. The effect of eliminating the HLB pathogen was measured using real-time quantitative polymerase chain reaction (qPCR) and PCR. The results indicate that the rate of detoxification reached 50% after seven irrigations, of plants with an OD600nm≈1 Bacillus GJ1 suspension. Most importantly, photosynthesis-antenna proteins, photosynthesis, plant-pathogen interactions, and protein processing in the endoplasmic reticulum were significantly upregulated (padj < 0.05), as shown by the KEGG enrichment analysis of the transcriptomes; nine of the upregulated genes were validated by qPCR. Transcription factor analysis of the transcriptomes was performed, and 10 TFs were validated by qPCR. Cyanoamino acid metabolism, regulation of autophagy, isoflavonoid biosynthesis, starch and sucrose metabolism, protein export, porphyrin and chlorophyll metabolism, and carotenoid biosynthesis were investigated by KEGG enrichment analysis of the proteome, and significant differences were found in the expression of the genes involved in those pathways. Correlation analysis of the proteome and transcriptome showed common entries for the significantly different expression of proteins and the significantly different expression of genes in the GO and KEGG pathways, respectively. The above results reveal important information about the detoxification pathways.
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Affiliation(s)
- Jizhou Tang
- College of Horticulture and Forestry, Key Laboratory of Horticultural Plant Biology of Ministry of Education, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Yuanxi Ding
- College of Horticulture and Forestry, Key Laboratory of Horticultural Plant Biology of Ministry of Education, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Jing Nan
- College of Horticulture and Forestry, Key Laboratory of Horticultural Plant Biology of Ministry of Education, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Xiangyu Yang
- College of Horticulture and Forestry, Key Laboratory of Horticultural Plant Biology of Ministry of Education, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Liang Sun
- College of Horticulture and Forestry, Key Laboratory of Horticultural Plant Biology of Ministry of Education, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Xiuyun Zhao
- College of life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China.,State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Ling Jiang
- College of Horticulture and Forestry, Key Laboratory of Horticultural Plant Biology of Ministry of Education, Huazhong Agricultural University, Wuhan, Hubei, China.,National Indoor Conservation Center of Virus-free Germplasm of Fruit Crops, Huazhong Agricultural University, Wuhan, Hubei, China
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23
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Shi Q, Febres VJ, Zhang S, Yu F, McCollum G, Hall DG, Moore GA, Stover E. Identification of Gene Candidates Associated with Huanglongbing Tolerance, Using 'Candidatus Liberibacter asiaticus' Flagellin 22 as a Proxy to Challenge Citrus. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2018; 31:200-211. [PMID: 29148926 DOI: 10.1094/mpmi-04-17-0084-r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The 22-amino acid (flg22) pathogen-associated molecular pattern from the flagellin of Xanthomonas citri subsp. citri has been shown to induce defense responses correlated with citrus canker resistance. Here, flg22 of 'Candidatus Liberibacter asiaticus', the putative causal agent of Huanglongbing (HLB), elicited differential defense responses that were weaker than those from Xcc-flg22, between those of the HLB-tolerant mandarin cultivar Sun Chu Sha and susceptible grapefruit cultivar Duncan. Transcriptomics was used to compare the effect of CLas-flg22 and Xcc-flg22 between the citrus genotypes and identified 86 genes induced only by CLas-flg22 in the tolerant mandarin. Expression of 16 selected genes was validated, by reverse transcription-quantitative polymerase chain reaction, and was evaluated in citrus during 'Ca. L. asiaticus' infection. Differential expression of a number of genes occurred between tolerant and susceptible citrus infected with 'Ca. L. asiaticus', suggesting their involvement in HLB tolerance. In addition, several genes were similarly regulated by CLas-flg22 and 'Ca. L. asiaticus' treatments, while others were oppositely regulated in the tolerant mandarin, suggesting similarity and interplay between CLas-flg22 and 'Ca. L. asiaticus'-triggered defenses. Genes identified are valuable in furthering the study of HLB tolerance mechanisms and, potentially, for screening for HLB-tolerant citrus using CLas-flg22 as a pathogen proxy.
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Affiliation(s)
- Qingchun Shi
- 1 U.S. Horticultural Research Laboratory, USDA/ARS, Fort Pierce, FL, U.S.A
| | - Vicente J Febres
- 2 Horticultural Sciences Department, University of Florida, Gainesville, FL, U.S.A.; and
| | - Shujian Zhang
- 1 U.S. Horticultural Research Laboratory, USDA/ARS, Fort Pierce, FL, U.S.A
| | - Fahong Yu
- 3 Interdisciplinary Center for Biotechnology Research, University of Florida
| | - Greg McCollum
- 1 U.S. Horticultural Research Laboratory, USDA/ARS, Fort Pierce, FL, U.S.A
| | - David G Hall
- 1 U.S. Horticultural Research Laboratory, USDA/ARS, Fort Pierce, FL, U.S.A
| | - Gloria A Moore
- 2 Horticultural Sciences Department, University of Florida, Gainesville, FL, U.S.A.; and
| | - Ed Stover
- 1 U.S. Horticultural Research Laboratory, USDA/ARS, Fort Pierce, FL, U.S.A
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24
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Bendix C, Lewis JD. The enemy within: phloem-limited pathogens. MOLECULAR PLANT PATHOLOGY 2018; 19:238-254. [PMID: 27997761 PMCID: PMC6638166 DOI: 10.1111/mpp.12526] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 12/06/2016] [Accepted: 12/08/2016] [Indexed: 05/06/2023]
Abstract
The growing impact of phloem-limited pathogens on high-value crops has led to a renewed interest in understanding how they cause disease. Although these pathogens cause substantial crop losses, many are poorly characterized. In this review, we present examples of phloem-limited pathogens that include intracellular bacteria with and without cell walls, and viruses. Phloem-limited pathogens have small genomes and lack many genes required for core metabolic processes, which is, in part, an adaptation to the unique phloem environment. For each pathogen class, we present multiple case studies to highlight aspects of disease caused by phloem-limited pathogens. The pathogens presented include Candidatus Liberibacter asiaticus (citrus greening), Arsenophonus bacteria, Serratia marcescens (cucurbit yellow vine disease), Candidatus Phytoplasma asteris (Aster Yellows Witches' Broom), Spiroplasma kunkelii, Potato leafroll virus and Citrus tristeza virus. We focus on commonalities in the virulence strategies of these pathogens, and aim to stimulate new discussions in the hope that widely applicable disease management strategies can be found.
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Affiliation(s)
- Claire Bendix
- United States Department of AgriculturePlant Gene Expression CenterAlbanyCA94710USA
| | - Jennifer D. Lewis
- United States Department of AgriculturePlant Gene Expression CenterAlbanyCA94710USA
- Department of Plant and Microbial BiologyUniversity of California, BerkeleyBerkeleyCA94720USA
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25
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Wang N, Pierson EA, Setubal JC, Xu J, Levy JG, Zhang Y, Li J, Rangel LT, Martins J. The Candidatus Liberibacter-Host Interface: Insights into Pathogenesis Mechanisms and Disease Control. ANNUAL REVIEW OF PHYTOPATHOLOGY 2017. [PMID: 28637377 DOI: 10.1146/annurev-phyto-080516-035513] [Citation(s) in RCA: 165] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
"Candidatus Liberibacter" species are associated with economically devastating diseases of citrus, potato, and many other crops. The importance of these diseases as well as the proliferation of new diseases on a wider host range is likely to increase as the insects vectoring the "Ca. Liberibacter" species expand their territories worldwide. Here, we review the progress on understanding pathogenesis mechanisms of "Ca. Liberibacter" species and the control approaches for diseases they cause. We discuss the Liberibacter virulence traits, including secretion systems, putative effectors, and lipopolysaccharides (LPSs), as well as other important traits likely to contribute to disease development, e.g., flagella, prophages, and salicylic acid hydroxylase. The pathogenesis mechanisms of Liberibacters are discussed. Liberibacters secrete Sec-dependent effectors (SDEs) or other virulence factors into the phloem elements or companion cells to interfere with host targets (e.g., proteins or genes), which cause cell death, necrosis, or other phenotypes of phloem elements or companion cells, leading to localized cell responses and systemic malfunction of phloem. Receptors on the remaining organelles in the phloem, such as plastid, vacuole, mitochondrion, or endoplasmic reticulum, interact with secreted SDEs and/or other virulence factors secreted or located on the Liberibacter outer membrane to trigger cell responses. Some of the host genes or proteins targeted by SDEs or other virulence factors of Liberibacters serve as susceptibility genes that facilitate compatibility (e.g., promoting pathogen growth or suppressing immune responses) or disease development. In addition, Liberibacters trigger plant immunity response via pathogen-associated molecular patterns (PAMPs, such as lipopolysaccharides), which leads to premature cell death, callose deposition, or phloem protein accumulation, causing a localized response and/or systemic effect on phloem transportation. Physical presence of Liberibacters and their metabolic activities may disturb the function of phloem, via disrupting osmotic gradients, or the integrity of phloem conductivity. We also review disease management strategies, including promising new technologies. Citrus production in the presence of Huanglongbing is possible if the most promising management approaches are integrated. HLB management is discussed in the context of local, area-wide, and regional Huanglongbing/Asian Citrus Psyllid epidemiological zones. For zebra chip disease control, aggressive psyllid management enables potato production, although insecticide resistance is becoming an issue. Meanwhile, new technologies such as clustered regularly interspaced short palindromic repeat (CRISPR)-derived genome editing provide an unprecedented opportunity to provide long-term solutions.
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Affiliation(s)
- Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, Florida 33850;
| | - Elizabeth A Pierson
- Department of Horticultural Sciences, Texas A&M University, College Station, Texas 77843
| | - João Carlos Setubal
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, SP, 05508-000, Brazil
| | - Jin Xu
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, Florida 33850;
| | - Julien G Levy
- Department of Horticultural Sciences, Texas A&M University, College Station, Texas 77843
| | - Yunzeng Zhang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, Florida 33850;
| | - Jinyun Li
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, Florida 33850;
| | - Luiz Thiberio Rangel
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, SP, 05508-000, Brazil
| | - Joaquim Martins
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, SP, 05508-000, Brazil
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26
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Li J, Pang Z, Trivedi P, Zhou X, Ying X, Jia H, Wang N. 'Candidatus Liberibacter asiaticus' Encodes a Functional Salicylic Acid (SA) Hydroxylase That Degrades SA to Suppress Plant Defenses. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2017; 30:620-630. [PMID: 28488467 DOI: 10.1094/mpmi-12-16-0257-r] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Pathogens from the fastidious, phloem-restricted 'Candidatus Liberibacter' species cause the devastating Huanglongbing (HLB) disease in citrus worldwide and cause diseases on many solanaceous crops and plants in the Apiaceae family. However, little is known about the pathogenic mechanisms due to the difficulty in culturing the corresponding 'Ca. Liberibacter' species. Here, we report that the citrus HLB pathogen 'Ca. L. asiaticus' uses an active salicylate hydroxylase SahA to degrade salicylic acid (SA) and suppress plant defenses. Purified SahA protein displays strong enzymatic activity to degrade SA and its derivatives. Overexpression of SahA in transgenic tobacco plants abolishes SA accumulation and hypersensitive response (HR) induced by nonhost pathogen infection. By degrading SA, 'Ca. L. asiaticus' not only enhances the susceptibility of citrus plants to both nonpathogenic and pathogenic Xanthomonas citri but also attenuates the responses of citrus plants to exogenous SA. In addition, foliar spraying of 2,1,3-benzothiadiazole and 2,6-dichloroisonicotinic acid, SA functional analogs not degradable by SahA, displays comparable (and even better) effectiveness with SA in suppressing 'Ca. L. asiaticus' population growth and HLB disease progression in infected citrus trees under field conditions. This study demonstrates one or more pathogens suppress plant defenses by degrading SA and establish clues for developing novel SA derivatives-based management approaches to control the associated plant diseases.
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Affiliation(s)
- Jinyun Li
- Citrus Research and Education Center, Department of Microbiology and Cell Science, University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, U.S.A
| | - Zhiqian Pang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, U.S.A
| | - Pankaj Trivedi
- Citrus Research and Education Center, Department of Microbiology and Cell Science, University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, U.S.A
| | - Xiaofeng Zhou
- Citrus Research and Education Center, Department of Microbiology and Cell Science, University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, U.S.A
| | - Xiaobao Ying
- Citrus Research and Education Center, Department of Microbiology and Cell Science, University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, U.S.A
| | - Hongge Jia
- Citrus Research and Education Center, Department of Microbiology and Cell Science, University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, U.S.A
| | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, U.S.A
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Moreira LM, Soares MR, Facincani AP, Ferreira CB, Ferreira RM, Ferro MIT, Gozzo FC, Felestrino ÉB, Assis RAB, Garcia CCM, Setubal JC, Ferro JA, de Oliveira JCF. Proteomics-based identification of differentially abundant proteins reveals adaptation mechanisms of Xanthomonas citri subsp. citri during Citrus sinensis infection. BMC Microbiol 2017; 17:155. [PMID: 28693412 PMCID: PMC5504864 DOI: 10.1186/s12866-017-1063-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 07/01/2017] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Xanthomonas citri subsp. citri (Xac) is the causal agent of citrus canker. A proteomic analysis under in planta infectious and non-infectious conditions was conducted in order to increase our knowledge about the adaptive process of Xac during infection. RESULTS For that, a 2D-based proteomic analysis of Xac at 1, 3 and 5 days after inoculation, in comparison to Xac growth in NB media was carried out and followed by MALDI-TOF-TOF identification of 124 unique differentially abundant proteins. Among them, 79 correspond to up-regulated proteins in at least one of the three stages of infection. Our results indicate an important role of proteins related to biofilm synthesis, lipopolysaccharides biosynthesis, and iron uptake and metabolism as possible modulators of plant innate immunity, and revealed an intricate network of proteins involved in reactive oxygen species adaptation during Plants` Oxidative Burst response. We also identified proteins previously unknown to be involved in Xac-Citrus interaction, including the hypothetical protein XAC3981. A mutant strain for this gene has proved to be non-pathogenic in respect to classical symptoms of citrus canker induced in compatible plants. CONCLUSIONS This is the first time that a protein repertoire is shown to be active and working in an integrated manner during the infection process in a compatible host, pointing to an elaborate mechanism for adaptation of Xac once inside the plant.
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Affiliation(s)
- Leandro M Moreira
- Departamento de Ciências Biológicas (DECBI), Instituto de Ciências Exatas e Biológicas (ICEB), Universidade Federal de Ouro Preto (UFOP), Ouro Preto, MG, Brazil. .,Núcleo de Pesquisas em Ciências Biológicas (NUPEB), Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil.
| | - Márcia R Soares
- Departamento de Bioquímica (DBq), Instituto de Química (IQ), Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ, Brazil
| | - Agda P Facincani
- Faculdade de Ciências Agrárias e Veterinárias de Jaboticabal, UNESP - Universidade Estadual Paulista, Departamento de Tecnologia, Jaboticabal, SP, Brazil.
| | - Cristiano B Ferreira
- Faculdade de Ciências Agrárias e Veterinárias de Jaboticabal, UNESP - Universidade Estadual Paulista, Departamento de Tecnologia, Jaboticabal, SP, Brazil
| | - Rafael M Ferreira
- Faculdade de Ciências Agrárias e Veterinárias de Jaboticabal, UNESP - Universidade Estadual Paulista, Departamento de Tecnologia, Jaboticabal, SP, Brazil
| | - Maria I T Ferro
- Faculdade de Ciências Agrárias e Veterinárias de Jaboticabal, UNESP - Universidade Estadual Paulista, Departamento de Tecnologia, Jaboticabal, SP, Brazil
| | - Fábio C Gozzo
- Instituto de Química, Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil
| | - Érica B Felestrino
- Núcleo de Pesquisas em Ciências Biológicas (NUPEB), Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil
| | - Renata A B Assis
- Núcleo de Pesquisas em Ciências Biológicas (NUPEB), Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil
| | - Camila Carrião M Garcia
- Departamento de Ciências Biológicas (DECBI), Instituto de Ciências Exatas e Biológicas (ICEB), Universidade Federal de Ouro Preto (UFOP), Ouro Preto, MG, Brazil.,Núcleo de Pesquisas em Ciências Biológicas (NUPEB), Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil
| | - João C Setubal
- Departamento de Bioquímica (DB), Instituto de Química (IQ), Universidade de São Paulo (USP), São Paulo, SP, Brazil.,Biocomplexity Institute, Virginia Tech, Blacksburg, VA, USA
| | - Jesus A Ferro
- Faculdade de Ciências Agrárias e Veterinárias de Jaboticabal, UNESP - Universidade Estadual Paulista, Departamento de Tecnologia, Jaboticabal, SP, Brazil
| | - Julio C F de Oliveira
- Departamento de Ciências Biológicas (DCB), Universidade Federal de São Paulo (UNIFESP), Diadema, SP, Brazil
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28
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Jain M, Fleites LA, Gabriel DW. A Small Wolbachia Protein Directly Represses Phage Lytic Cycle Genes in " Candidatus Liberibacter asiaticus" within Psyllids. mSphere 2017; 2:e00171-17. [PMID: 28608866 PMCID: PMC5463029 DOI: 10.1128/mspheredirect.00171-17] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 04/20/2017] [Indexed: 01/17/2023] Open
Abstract
Huanglongbing (HLB) is a severe disease of citrus caused by an uncultured alphaproteobacterium "Candidatus Liberibacter asiaticus" and transmitted by Asian citrus psyllids (Diaphorina citri). Two prophage genomes, SC1 and SC2, integrated in "Ca. Liberibacter asiaticus" strain UF506 were described previously, and very similar prophages are found resident in the majority of "Ca. Liberibacter asiaticus" strains described worldwide. The SC1 lytic cycle is marked by upregulation of prophage late genes, including a functional holin (SC1_gp110); these late genes are activated when "Ca. Liberibacter asiaticus" is in planta, but not when infecting the psyllid host. We previously reported that the holin promoter is strongly and constitutively active in Liberibacter crescens (a cultured proxy for uncultured "Ca. Liberibacter asiaticus") but is suppressed in a dose-dependent manner by crude aqueous extracts from D. citri applied exogenously. Here we report that the suppressor activity of the crude psyllid extract was heat labile and abolished by proteinase K treatment, indicating a proteinaceous repressor and of a size smaller than 30 kDa. The repressor was affinity captured from D. citri aqueous extracts using biotinylated holin promoter DNA immobilized on magnetic beads and subjected to liquid chromatography-tandem mass spectrometry (LC-MS/MS). Protein database interrogation was used to identify a small DNA-binding protein encoded by a gene carried by Wolbachia strain wDi, a resident endosymbiont of D. citri as the repressor. The in vitro-translated Wolbachia repressor protein was able to penetrate L. crescens cells, bind to "Ca. Liberibacter asiaticus" promoter DNA, and partially suppress holin promoter-driven β-glucuronidase (GUS) activity, indicating potential involvement of an additional interacting partner(s) or posttranslational modification(s) for complete suppression. Expression of the Wolbachia repressor protein appeared to be constitutive irrespective of "Ca. Liberibacter asiaticus" infection status of the insect host. IMPORTANCE Host acquisition of a new microbial species can readily perturb the dynamics of preexisting microbial associations. Molecular cross talk between microbial associates may be necessary for efficient resource allocation and enhanced survival. Classic examples involve quorum sensing (QS), which detects population densities and is both used and coopted to control expression of bacterial genes, including host adaptation factors. We report that a 56-amino-acid repressor protein made by the resident psyllid endosymbiont Wolbachia can enter cells of Liberibacter crescens, a cultured proxy for the uncultured psyllid endosymbiont "Ca. Liberibacter asiaticus" and repress "Ca. Liberibacter asiaticus" phage lytic cycle genes. Such repression in "Ca. Liberibacter asiaticus" may be critical to survival of both endosymbionts, since phage-mediated lysis would likely breach the immunogenic threshold of the psyllid, invoking a systemic and nonspecific innate immune reaction.
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Affiliation(s)
- Mukesh Jain
- Department of Plant Pathology, University of Florida, Gainesville, Florida, USA
| | - Laura A Fleites
- Department of Plant Pathology, University of Florida, Gainesville, Florida, USA
| | - Dean W Gabriel
- Department of Plant Pathology, University of Florida, Gainesville, Florida, USA
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29
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Dalio RJD, Magalhães DM, Rodrigues CM, Arena GD, Oliveira TS, Souza-Neto RR, Picchi SC, Martins PMM, Santos PJC, Maximo HJ, Pacheco IS, De Souza AA, Machado MA. PAMPs, PRRs, effectors and R-genes associated with citrus-pathogen interactions. ANNALS OF BOTANY 2017; 119:749-774. [PMID: 28065920 PMCID: PMC5571375 DOI: 10.1093/aob/mcw238] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2016] [Revised: 07/08/2016] [Accepted: 10/22/2016] [Indexed: 05/08/2023]
Abstract
BACKGROUND Recent application of molecular-based technologies has considerably advanced our understanding of complex processes in plant-pathogen interactions and their key components such as PAMPs, PRRs, effectors and R-genes. To develop novel control strategies for disease prevention in citrus, it is essential to expand and consolidate our knowledge of the molecular interaction of citrus plants with their pathogens. SCOPE This review provides an overview of our understanding of citrus plant immunity, focusing on the molecular mechanisms involved in the interactions with viruses, bacteria, fungi, oomycetes and vectors related to the following diseases: tristeza, psorosis, citrus variegated chlorosis, citrus canker, huanglongbing, brown spot, post-bloom, anthracnose, gummosis and citrus root rot.
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Affiliation(s)
- Ronaldo J. D. Dalio
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Diogo M. Magalhães
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Carolina M. Rodrigues
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Gabriella D. Arena
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Tiago S. Oliveira
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Reinaldo R. Souza-Neto
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Simone C. Picchi
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Paula M. M. Martins
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Paulo J. C. Santos
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Heros J. Maximo
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Inaiara S. Pacheco
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Alessandra A. De Souza
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Marcos A. Machado
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
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30
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Ding F, Duan Y, Yuan Q, Shao J, Hartung JS. Serological detection of 'Candidatus Liberibacter asiaticus' in citrus, and identification by GeLC-MS/MS of a chaperone protein responding to cellular pathogens. Sci Rep 2016; 6:29272. [PMID: 27381064 PMCID: PMC4933950 DOI: 10.1038/srep29272] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 06/15/2016] [Indexed: 11/09/2022] Open
Abstract
We describe experiments with antibodies against 'Candidatus Liberibacter asiaticus used to detect the pathogen in infected plants. We used scFv selected to bind epitopes exposed on the surface of the bacterium in tissue prints, with secondary monoclonal antibodies directed at a FLAG epitope included at the carboxyl end of the scFv. Unexpectedly, the anti-FLAG secondary antibody produced positive results with CaLas diseased samples when the primary scFv were not used. The anti-FLAG monoclonal antibody (Mab) also identified plants infected with other vascular pathogens. We then identified a paralogous group of secreted chaperone proteins in the HSP-90 family that contained the amino acid sequence DDDDK identical to the carboxy-terminal sequence of the FLAG epitope. A rabbit polyclonal antibody against one of the same epitopes combined with a goat anti-rabbit secondary antibody produced very strong purple color in individual phloem cells, as expected for this pathogen. These results were entirely specific for CaLas-infected citrus. The simplicity, cost and ability to scale the tissue print assay makes this an attractive assay to complement PCR-based assays currently in use. The partial FLAG epitope may itself be useful as a molecular marker for the rapid screening of citrus plants for the presence of vascular pathogens.
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Affiliation(s)
- Fang Ding
- Hubei Key Laboratory of Plant Pathology, Huazhong Agricultural University, Wuhan 430070 P. R. China
- USDA ARS MPPL 10300 Baltimore Ave., Beltsville, MD 20705 USA
| | - Yongping Duan
- USDA ARS USHRL 2001 South Rock Road, Fort Pierce, FL 34945 USA
| | - Qing Yuan
- Sichuan Medical University, Luzhou, Sichuan, 646000 P. R. China
| | - Jonathan Shao
- USDA ARS MPPL 10300 Baltimore Ave., Beltsville, MD 20705 USA
| | - John S. Hartung
- USDA ARS MPPL 10300 Baltimore Ave., Beltsville, MD 20705 USA
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da Graça JV, Douhan GW, Halbert SE, Keremane ML, Lee RF, Vidalakis G, Zhao H. Huanglongbing: An overview of a complex pathosystem ravaging the world's citrus. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2016; 58:373-87. [PMID: 26466921 DOI: 10.1111/jipb.12437] [Citation(s) in RCA: 141] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 10/12/2015] [Indexed: 05/24/2023]
Abstract
Citrus huanglongbing (HLB) has become a major disease and limiting factor of production in citrus areas that have become infected. The destruction to the affected citrus industries has resulted in a tremendous increase to support research that in return has resulted in significant information on both applied and basic knowledge concerning this important disease to the global citrus industry. Recent research indicates the relationship between citrus and the causal agent of HLB is shaped by multiple elements, in which host defense responses may also play an important role. This review is intended to provide an overview of the importance of HLB to a wider audience of plant biologists. Recent advances on host-pathogen interactions, population genetics and vectoring of the causal agent are discussed.
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Affiliation(s)
- John V da Graça
- Texas A&M University-Kingsville Citrus Center, Weslaco, Texas 78599, USA
| | - Greg W Douhan
- Department of Plant Pathology and Microbiology, University of California, Riverside, California 92521, USA
| | - Susan E Halbert
- Florida Department of Agriculture and Consumer Services, Division of Plant Industry, P.O. Box 147100, Gainesville, Florida 32614, USA
| | - Manjunath L Keremane
- USDA ARS National Clonal Germplasm Repository for Citrus and Dates, Riverside, California 92507, USA
| | - Richard F Lee
- USDA ARS National Clonal Germplasm Repository for Citrus and Dates, Riverside, California 92507, USA
| | - Georgios Vidalakis
- Department of Plant Pathology and Microbiology, University of California, Riverside, California 92521, USA
| | - Hongwei Zhao
- College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
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SGT1 is required in PcINF1/SRC2-1 induced pepper defense response by interacting with SRC2-1. Sci Rep 2016; 6:21651. [PMID: 26898479 PMCID: PMC4761932 DOI: 10.1038/srep21651] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 01/28/2016] [Indexed: 02/06/2023] Open
Abstract
PcINF1 was previously found to induce pepper defense response by interacting with SRC2-1, but the underlying mechanism remains uninvestigated. Herein, we describe the involvement of SGT1 in the PcINF1/SRC2-1-induced immunity. SGT1 was observed to be up-regulated by Phytophthora capsici inoculation and synergistically transient overexpression of PcINF1/SRC2-1 in pepper plants. SGT1-silencing compromised HR cell death, blocked H2O2 accumulation, and downregulated HR-associated and hormones-dependent marker genes’ expression triggered by PcINF1/SRC2-1 co-overexpression. The interaction between SRC2-1 and SGT1 was found by the yeast two hybrid system and was further confirmed by bimolecular fluorescence complementation and co-immunoprecipitation analyses. The SGT1/SRC2-1 interaction was enhanced by transient overexpression of PcINF1 and Phytophthora capsici inoculation, and SGT1-silencing attenuated PcINF1/SRC2-1 interaction. Additionally, by modulating subcellular localizations of SRC2-1, SGT1, and the interacting complex of SGT1/SRC2-1, it was revealed that exclusive nuclear targeting of the SGT1/SRC2-1 complex blocks immunity triggered by formation of SGT1/SRC2-1, and a translocation of the SGT1/SRC2-1 complex from the plasma membrane and cytoplasm to the nuclei upon the inoculation of P. capsici. Our data demonstrate that the SGT1/SRC2-1 interaction, and its nucleocytoplasmic partitioning, is involved in pepper’s immunity against P. capsici, thus providing a molecular link between Ca2+ signaling associated SRC2-1 and SGT1-mediated defense signaling.
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Hao G, Pitino M, Duan Y, Stover E. Reduced Susceptibility to Xanthomonas citri in Transgenic Citrus Expressing the FLS2 Receptor From Nicotiana benthamiana. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2016; 29:132-42. [PMID: 26554734 DOI: 10.1094/mpmi-09-15-0211-r] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Overexpression of plant pattern-recognition receptors by genetic engineering provides a novel approach to enhance plant immunity and broad-spectrum disease resistance. Citrus canker disease associated with Xanthomonas citri is one of the most important diseases damaging citrus production worldwide. In this study, we cloned the FLS2 gene from Nicotiana benthamiana cDNA and inserted it into the binary vector pBinPlus/ARS to transform Hamlin sweet orange and Carrizo citrange. Transgene presence was confirmed by polymerase chain reaction (PCR) and gene expression of NbFLS2 was compared by reverse transcription quantitative PCR. Reactive oxygen species (ROS) production in response to flg22Xcc was detected in transgenic Hamlin but not in nontransformed controls. Low or no ROS production was detected from nontransformed Hamlin seedlings challenged with flg22Xcc. Transgenic plants highly expressing NbFLS2 were selected and were evaluated for resistance to canker incited by X. citri 3213. Our results showed that the integration and expression of the NbFLS2 gene in citrus can increase canker resistance and defense-associated gene expression when challenged with X. citri. These results suggest that canker-susceptible Citrus genotypes lack strong basal defense induced by X. citri flagellin and the resistance of these genotypes can be enhanced by transgenic expression of the flagellin receptor from a resistant species.
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Affiliation(s)
- Guixia Hao
- U. S. Horticultural Research Laboratory, USDA-ARS, Fort Pierce, FL 34945, U.S.A
| | - Marco Pitino
- U. S. Horticultural Research Laboratory, USDA-ARS, Fort Pierce, FL 34945, U.S.A
| | - Yongping Duan
- U. S. Horticultural Research Laboratory, USDA-ARS, Fort Pierce, FL 34945, U.S.A
| | - Ed Stover
- U. S. Horticultural Research Laboratory, USDA-ARS, Fort Pierce, FL 34945, U.S.A
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34
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Yuan Q, Jordan R, Brlansky RH, Minenkova O, Hartung J. Development of single chain variable fragment (scFv) antibodies against surface proteins of 'Ca. Liberibacter asiaticus'. J Microbiol Methods 2015; 122:1-7. [PMID: 26744234 DOI: 10.1016/j.mimet.2015.12.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 12/22/2015] [Accepted: 12/23/2015] [Indexed: 10/22/2022]
Abstract
'Candidatus Liberibacter asiaticus' is the causal agent of citrus huanglongbing, the most serious disease of citrus worldwide. We have developed and applied immunization and affinity screening methods to develop a primary library of recombinant single chain variable fragment (scFv) antibodies in an M13 vector, pKM19. The antibody population is enriched for antibodies that bind antigens of 'Ca. Liberibacter asiaticus'. The primary library has more than 10(7) unique antibodies and the genes that encode them. We have screened this library for antibodies that bind to specifically-chosen proteins that are present on the surface of 'Ca. Liberibacter asiaticus'. These proteins were used as targets for affinity-based selection of scFvs that bind to the major outer membrane protein, OmpA; the polysaccharide capsule protein KpsF; a protein component of the type IV pilus (CapF); and, two flagellar proteins FlhA and FlgI. These scFvs have been used in ELISA and dot blot assays against purified protein antigens and 'Ca. Liberibacter asiaticus' infected plant extracts. We have also recloned many of these scFvs into a plasmid expression vector designed for the production of scFvs. Screening of these scFvs was more efficient when phage-bound, rather than soluble scFvs, were used. We have demonstrated a technology to produce antibodies at will and against any protein target encoded by 'Ca. Liberibacter asiaticus'. Applications could include advanced diagnostic methods for huanglongbing and the development of immune labeling reagents for in planta applications.
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Affiliation(s)
- Qing Yuan
- Molecular Plant Pathology Lab, USDA-ARS, Beltsville, MD 20705, United States
| | - Ramon Jordan
- United States National Arboretum, USDA-ARS, Beltsville, MD 20705, United States
| | - Ronald H Brlansky
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, United States
| | | | - John Hartung
- Molecular Plant Pathology Lab, USDA-ARS, Beltsville, MD 20705, United States
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Jain M, Fleites LA, Gabriel DW. Prophage-Encoded Peroxidase in 'Candidatus Liberibacter asiaticus' Is a Secreted Effector That Suppresses Plant Defenses. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2015; 28:1330-7. [PMID: 26313412 DOI: 10.1094/mpmi-07-15-0145-r] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
'Candidatus Liberibacter asiaticus' is transmitted by psyllids and causes huanglongbing (HLB), a lethal disease of citrus. Most pathogenic 'Ca. L. asiaticus' strains carry two nearly identical prophages similar to SC1 and SC2 in strain UF506. SC2 was observed to replicate as a moderately high-copy excision plasmid encoding a reactive oxygen species-scavenging peroxidase (SC2_gp095), a predicted lysogenic conversion factor. SC2_gp095 was expressed at significantly higher levels in periwinkle than in citrus and was suppressed in psyllids. SC2_gp095 was cloned in a shuttle vector and transformed into Escherichia coli and Liberibacter crescens, a culturable proxy for 'Ca. L. asiaticus'. Transformed L. crescens cells showed 20 to 25% enhanced resistance to H₂O₂on agar plates, 47% greater enzymatic activity, and enhanced growth in liquid cultures. A nonclassical secretion potential was predicted for SC2_gp095 and secretion from L. crescens was confirmed by enzymatic and Western blot analyses. Transient expression of SC2_gp095 in planta resulted in strong transcriptional downregulation of RbohB, the key gatekeeper of the H₂O₂-mediated defense signaling in plants, helping explain the surprisingly long incubation period (years) before HLB symptoms appear in 'Ca. L. asiaticus'-infected citrus. 'Ca. L. asiaticus' peroxidase is likely a secreted, horizontally acquired effector that suppresses host symptom development, a tactic used by most biotrophic plant pathogens.
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Affiliation(s)
- Mukesh Jain
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611-0680, U.S.A
| | - Laura A Fleites
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611-0680, U.S.A
| | - Dean W Gabriel
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611-0680, U.S.A
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36
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Rawat N, Kiran SP, Du D, Gmitter FG, Deng Z. Comprehensive meta-analysis, co-expression, and miRNA nested network analysis identifies gene candidates in citrus against Huanglongbing disease. BMC PLANT BIOLOGY 2015; 15:184. [PMID: 26215595 PMCID: PMC4517500 DOI: 10.1186/s12870-015-0568-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Accepted: 07/07/2015] [Indexed: 05/20/2023]
Abstract
BACKGROUND Huanglongbing (HLB), the most devastating disease of citrus, is associated with infection by Candidatus Liberibacter asiaticus (CaLas) and is vectored by the Asian citrus psyllid (ACP). Recently, the molecular basis of citrus-HLB interactions has been examined using transcriptome analyses, and these analyses have identified many probe sets and pathways modulated by CaLas infection among different citrus cultivars. However, lack of consistency among reported findings indicates that an integrative approach is needed. This study was designed to identify the candidate probe sets in citrus-HLB interactions using meta-analysis and gene co-expression network modelling. RESULTS Twenty-two publically available transcriptome studies on citrus-HLB interactions, comprising 18 susceptible (S) datasets and four resistant (R) datasets, were investigated using Limma and RankProd methods of meta-analysis. A combined list of 7,412 differentially expressed probe sets was generated using a Teradata in-house Structured Query Language (SQL) script. We identified the 65 most common probe sets modulated in HLB disease among different tissues from the S and R datasets. Gene ontology analysis of these probe sets suggested that carbohydrate metabolism, nutrient transport, and biotic stress were the core pathways that were modulated in citrus by CaLas infection and HLB development. We also identified R-specific probe sets, which encoded leucine-rich repeat proteins, chitinase, constitutive disease resistance (CDR), miraculins, and lectins. Weighted gene co-expression network analysis (WGCNA) was conducted on 3,499 probe sets, and 21 modules with major hub probe sets were identified. Further, a miRNA nested network was created to examine gene regulation of the 3,499 target probe sets. Results suggest that csi-miR167 and csi-miR396 could affect ion transporters and defence response pathways, respectively. CONCLUSION Most of the potential candidate hub probe sets were co-expressed with gibberellin pathway (GA)-related probe sets, implying the role of GA signalling in HLB resistance. Our findings contribute to the integration of existing citrus-HLB transcriptome data that will help to elucidate the holistic picture of the citrus-HLB interaction. The citrus probe sets identified in this analysis signify a robust set of HLB-responsive candidates that are useful for further validation.
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Affiliation(s)
- Nidhi Rawat
- University of Florida, Institute of Food and Agricultural Sciences, Gulf Coast Research and Education Center, Wimauma, FL, 33598, USA.
| | - Sandhya P Kiran
- Ocimum BioSolutions, Banjara Hills Road No. 1, VI Floor Reliance Classic, Hyderabad, 500039, India.
| | - Dongliang Du
- University of Florida, Institute of Food and Agricultural Sciences, Citrus Research and Education Center, Lake Alfred, FL, 33850, USA.
| | - Fred G Gmitter
- University of Florida, Institute of Food and Agricultural Sciences, Citrus Research and Education Center, Lake Alfred, FL, 33850, USA.
| | - Zhanao Deng
- University of Florida, Institute of Food and Agricultural Sciences, Gulf Coast Research and Education Center, Wimauma, FL, 33598, USA.
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Wang S, Sun Z, Wang H, Liu L, Lu F, Yang J, Zhang M, Zhang S, Guo Z, Bent AF, Sun W. Rice OsFLS2-Mediated Perception of Bacterial Flagellins Is Evaded by Xanthomonas oryzae pvs. oryzae and oryzicola. MOLECULAR PLANT 2015; 8:1024-37. [PMID: 25617720 DOI: 10.1016/j.molp.2015.01.012] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 01/10/2015] [Accepted: 01/11/2015] [Indexed: 05/26/2023]
Abstract
Bacterial flagellins are often recognized by the receptor kinase FLAGELLIN SENSITIVE2 (FLS2) and activate MAMP-triggered immunity in dicotyledonous plants. However, the capacity of monocotyledonous rice to recognize flagellins of key rice pathogens and its biological relevance remain poorly understood. We demonstrate that ectopically expressed OsFLS2 in Arabidopsis senses the eliciting flg22 peptide and in vitro purified Acidovorax avenae (Aa) flagellin in an expression level-dependent manner, but does not recognize purified flagellins or derivative flg22(Xo) peptides of Xanthomonas oryzae pvs. oryzae (Xoo) and oryzicola (Xoc). Consistently, the flg22 peptide and purified Aa flagellin, but not Xoo/Xoc flagellins, induce various immune responses such as defense gene induction and MAPK activation in rice. Perception of flagellin by rice does induce strong resistance to Xoo infection, as shown after pre-treatment of rice leaves with Aa flagellin. OsFLS2 was found to differ from AtFLS2 in its perception specificities or sensitivities to different flg22 sequences. In addition, post-translational modification of Xoc flagellin was altered by deletion of glycosyltransferase-encoding rbfC, but this had little effect on Xoc motility and rpfC mutation did not detectably reduce Xoc virulence on rice. Deletion of flagellin-encoding fliC from Xoo/Xoc blocked swimming motility but also did not significantly alter Xoo/Xoc virulence. These results suggest that Xoo/Xoc carry flg22-region amino acid changes that allow motility while evading the ancient flagellin detection system in rice, which retains recognition capacity for other bacterial pathogens.
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Affiliation(s)
- Shanzhi Wang
- Department of Plant Pathology, China Agricultural University, 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China; Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing 100193, China
| | - Zhe Sun
- Department of Plant Pathology, China Agricultural University, 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China; Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing 100193, China
| | - Huiqin Wang
- Department of Plant Pathology, China Agricultural University, 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China; Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing 100193, China
| | - Lijuan Liu
- Department of Plant Pathology, China Agricultural University, 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China; Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing 100193, China
| | - Fen Lu
- Department of Plant Pathology, China Agricultural University, 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China; Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing 100193, China
| | - Jun Yang
- Department of Plant Pathology, China Agricultural University, 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China; Rice Research Institute, Shandong Academy of Agricultural Science, Jinan 250100, Shandong Province, China
| | - Min Zhang
- College of Bioscience and Biotechnology, Hunan Agricultural University, Changsha 410128, Hunan Province, China
| | - Shiyong Zhang
- Rice Research Institute, Shandong Academy of Agricultural Science, Jinan 250100, Shandong Province, China
| | - Zejian Guo
- Department of Plant Pathology, China Agricultural University, 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China; Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing 100193, China
| | - Andrew F Bent
- Department of Plant Pathology, University of Wisconsin, Madison, WI 53706, USA
| | - Wenxian Sun
- Department of Plant Pathology, China Agricultural University, 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China; Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing 100193, China.
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Vyas M, Fisher TW, He R, Nelson W, Yin G, Cicero JM, Willer M, Kim R, Kramer R, May GA, Crow JA, Soderlund CA, Gang DR, Brown JK. Asian Citrus Psyllid Expression Profiles Suggest Candidatus Liberibacter Asiaticus-Mediated Alteration of Adult Nutrition and Metabolism, and of Nymphal Development and Immunity. PLoS One 2015; 10:e0130328. [PMID: 26091106 PMCID: PMC4474670 DOI: 10.1371/journal.pone.0130328] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 05/19/2015] [Indexed: 11/29/2022] Open
Abstract
The Asian citrus psyllid (ACP) Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is the insect vector of the fastidious bacterium Candidatus Liberibacter asiaticus (CLas), the causal agent of citrus greening disease, or Huanglongbing (HLB). The widespread invasiveness of the psyllid vector and HLB in citrus trees worldwide has underscored the need for non-traditional approaches to manage the disease. One tenable solution is through the deployment of RNA interference technology to silence protein-protein interactions essential for ACP-mediated CLas invasion and transmission. To identify psyllid interactor-bacterial effector combinations associated with psyllid-CLas interactions, cDNA libraries were constructed from CLas-infected and CLas-free ACP adults and nymphs, and analyzed for differential expression. Library assemblies comprised 24,039,255 reads and yielded 45,976 consensus contigs. They were annotated (UniProt), classified using Gene Ontology, and subjected to in silico expression analyses using the Transcriptome Computational Workbench (TCW) (http://www.sohomoptera.org/ACPPoP/). Functional-biological pathway interpretations were carried out using the Kyoto Encyclopedia of Genes and Genomes databases. Differentially expressed contigs in adults and/or nymphs represented genes and/or metabolic/pathogenesis pathways involved in adhesion, biofilm formation, development-related, immunity, nutrition, stress, and virulence. Notably, contigs involved in gene silencing and transposon-related responses were documented in a psyllid for the first time. This is the first comparative transcriptomic analysis of ACP adults and nymphs infected and uninfected with CLas. The results provide key initial insights into host-parasite interactions involving CLas effectors that contribute to invasion-virulence, and to host nutritional exploitation and immune-related responses that appear to be essential for successful ACP-mediated circulative, propagative CLas transmission.
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Affiliation(s)
- Meenal Vyas
- School of Plant Sciences, The University of Arizona, Tucson, Arizona, United States of America
| | - Tonja W. Fisher
- School of Plant Sciences, The University of Arizona, Tucson, Arizona, United States of America
| | - Ruifeng He
- Institute of Biological Chemistry, Washington State University, Pullman, Washington, United States of America
| | - William Nelson
- BIO5, The University of Arizona, Tucson, Arizona, United States of America
| | - Guohua Yin
- School of Plant Sciences, The University of Arizona, Tucson, Arizona, United States of America
| | - Joseph M. Cicero
- School of Plant Sciences, The University of Arizona, Tucson, Arizona, United States of America
| | - Mark Willer
- BIO5, The University of Arizona, Tucson, Arizona, United States of America
| | - Ryan Kim
- National Center for Genome Resources, Santa Fe, New Mexico, United States of America
| | - Robin Kramer
- National Center for Genome Resources, Santa Fe, New Mexico, United States of America
| | - Greg A. May
- National Center for Genome Resources, Santa Fe, New Mexico, United States of America
| | - John A. Crow
- National Center for Genome Resources, Santa Fe, New Mexico, United States of America
| | - Carol A. Soderlund
- BIO5, The University of Arizona, Tucson, Arizona, United States of America
| | - David R. Gang
- Institute of Biological Chemistry, Washington State University, Pullman, Washington, United States of America
| | - Judith K. Brown
- School of Plant Sciences, The University of Arizona, Tucson, Arizona, United States of America
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Fisher TW, Vyas M, He R, Nelson W, Cicero JM, Willer M, Kim R, Kramer R, May GA, Crow JA, Soderlund CA, Gang DR, Brown JK. Comparison of potato and asian citrus psyllid adult and nymph transcriptomes identified vector transcripts with potential involvement in circulative, propagative liberibacter transmission. Pathogens 2014; 3:875-907. [PMID: 25436509 PMCID: PMC4282890 DOI: 10.3390/pathogens3040875] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 10/18/2014] [Accepted: 10/20/2014] [Indexed: 01/01/2023] Open
Abstract
The potato psyllid (PoP) Bactericera cockerelli (Sulc) and Asian citrus psyllid (ACP) Diaphorina citri Kuwayama are the insect vectors of the fastidious plant pathogen, Candidatus Liberibacter solanacearum (CLso) and Ca. L. asiaticus (CLas), respectively. CLso causes Zebra chip disease of potato and vein-greening in solanaceous species, whereas, CLas causes citrus greening disease. The reliance on insecticides for vector management to reduce pathogen transmission has increased interest in alternative approaches, including RNA interference to abate expression of genes essential for psyllid-mediated Ca. Liberibacter transmission. To identify genes with significantly altered expression at different life stages and conditions of CLso/CLas infection, cDNA libraries were constructed for CLso-infected and -uninfected PoP adults and nymphal instars. Illumina sequencing produced 199,081,451 reads that were assembled into 82,224 unique transcripts. PoP and the analogous transcripts from ACP adult and nymphs reported elsewhere were annotated, organized into functional gene groups using the Gene Ontology classification system, and analyzed for differential in silico expression. Expression profiles revealed vector life stage differences and differential gene expression associated with Liberibacter infection of the psyllid host, including invasion, immune system modulation, nutrition, and development.
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Affiliation(s)
- Tonja W Fisher
- School of Plant Sciences, The University of Arizona, Tucson, AZ 85721, USA.
| | - Meenal Vyas
- School of Plant Sciences, The University of Arizona, Tucson, AZ 85721, USA.
| | - Ruifeng He
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA.
| | | | - Joseph M Cicero
- School of Plant Sciences, The University of Arizona, Tucson, AZ 85721, USA.
| | - Mark Willer
- BIO5, The University of Arizona, Tucson, AZ 85721, USA.
| | - Ryan Kim
- National Center for Genome Resources, 2935 Rodeo Park Drive East, Santa Fe, NM 87505, USA.
| | - Robin Kramer
- National Center for Genome Resources, 2935 Rodeo Park Drive East, Santa Fe, NM 87505, USA.
| | - Greg A May
- National Center for Genome Resources, 2935 Rodeo Park Drive East, Santa Fe, NM 87505, USA.
| | - John A Crow
- National Center for Genome Resources, 2935 Rodeo Park Drive East, Santa Fe, NM 87505, USA.
| | | | - David R Gang
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA.
| | - Judith K Brown
- School of Plant Sciences, The University of Arizona, Tucson, AZ 85721, USA.
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Hao G, Pitino M, Ding F, Lin H, Stover E, Duan Y. Induction of innate immune responses by flagellin from the intracellular bacterium, 'Candidatus Liberibacter solanacearum'. BMC PLANT BIOLOGY 2014; 14:211. [PMID: 25091183 PMCID: PMC4422280 DOI: 10.1186/s12870-014-0211-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 07/24/2014] [Indexed: 05/09/2023]
Abstract
BACKGROUND 'Candidatus Liberibacter solanacearum' (Lso) is a phloem-limited alphaproteobacterium associated with the devastating zebra chip disease of potato (Solanum tuberosum). Like other members of Liberibacter, Lso-ZC1 encodes a flagellin domain-containing protein (Fla Lso ) with a conserved 22 amino-acid peptide (flg22 Lso ). To understand the innate immune responses triggered by this unculturable intracellular bacterium, we studied the pathogen-associated molecular patterns (PAMPs) that triggered immunity in Nicotiana benthamiana, using the flg22 Lso peptide and the full length fla Lso gene. RESULTS Our results showed that the expression of fla Lso via Agrobacterium-mediated transient expression induced a slow necrotic cell death in the inoculated leaves of N. benthamiana, which was coupled with a burst of reactive oxygen species (ROS) production. Moreover, the expression of several representative genes involved in innate immunity was transiently up-regulated by the flg22 Lso in N. benthamiana. The Fla Lso , however, induced stronger up-regulation of these representative genes compared to the flg22 Lso , especially that of flagellin receptor FLAGELLIN SENSING2 (FLS2) and respiratory burst oxidase (RbohB) in N. benthamiana. Although neither cell death nor ROS were induced by the synthetic flg22 Lso , a weak callose deposition was observed in infiltrated leaves of tobacco, tomato, and potato plants. CONCLUSION The flagellin of Lso and its functional domain, flg22 Lso share characteristics of pathogen-associated molecular patterns, and trigger unique innate immune responses in N. benthamiana. Slow and weak activation of the innate immune response in host plants by the flagellin of Lso may reflect the nature of its intracellular life cycle. Our findings provide new insights into the role of the Lso flagellin in the development of potato zebra chip disease and potential application in breeding for resistance.
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Affiliation(s)
- Guixia Hao
- U. S. Horticultural Research Laboratory, USDA-ARS, 2001 South Rock Rd, Fort Pierce, FL, 34945, USA.
| | - Marco Pitino
- U. S. Horticultural Research Laboratory, USDA-ARS, 2001 South Rock Rd, Fort Pierce, FL, 34945, USA.
| | - Fang Ding
- U. S. Horticultural Research Laboratory, USDA-ARS, 2001 South Rock Rd, Fort Pierce, FL, 34945, USA.
| | - Hong Lin
- San Joaquin Valley Agricultural Sciences Center, USDA-ARS, Parlier, CA, 93648, USA.
| | - Ed Stover
- U. S. Horticultural Research Laboratory, USDA-ARS, 2001 South Rock Rd, Fort Pierce, FL, 34945, USA.
| | - Yongping Duan
- U. S. Horticultural Research Laboratory, USDA-ARS, 2001 South Rock Rd, Fort Pierce, FL, 34945, USA.
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Wulff NA, Zhang S, Setubal JC, Almeida NF, Martins EC, Harakava R, Kumar D, Rangel LT, Foissac X, Bové JM, Gabriel DW. The complete genome sequence of 'Candidatus Liberibacter americanus', associated with Citrus huanglongbing. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2014; 27:163-76. [PMID: 24200077 DOI: 10.1094/mpmi-09-13-0292-r] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Liberibacter spp. form a Rhizobiaceae clade of phloem-limited pathogens of limited host range. Two obligately parasitic species have been sequenced: 'Candidatus Liberibacter asiaticus', which causes citrus huanglongbing (HLB) worldwide, and 'Ca. L. solanacearum', which causes potato "zebra chip" disease. A third (proposed) species, Liberibacter crescens, was isolated from mountain papaya, grown in axenic culture, and sequenced. In an effort to identify common host determinants, the complete genomic DNA sequence of a second HLB species, 'Ca. L. americanus' strain 'São Paulo' was determined. The circular genome of 1,195,201 bp had an average 31.12% GC content and 983 predicted protein encoding genes, 800 (81.4%) of which had a predicted function. There were 658 genes common to all sequenced Liberibacter spp. and only 8 genes common to 'Ca. L. americanus' and 'Ca. L. asiaticus' but not found in 'Ca. L. solanacearum'. Surprisingly, most of the lipopolysaccharide biosynthetic genes were missing from the 'Ca. L. americanus' genome, as well as OmpA and a key regulator of flagellin, all indicating a 'Ca. L. americanus' strategy of avoiding production of major pathogen-associated molecular patterns present in 'Ca. L. asiaticus' and 'Ca. L. solanacearum'. As with 'Ca. L. asiaticus', one of two 'Ca. L. americanus' prophages replicated as an excision plasmid and carried potential lysogenic conversion genes that appeared fragmentary or degenerated in 'Ca. L. solanacearum'.
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Hao G, Boyle M, Zhou L, Duan Y. The intracellular citrus huanglongbing bacterium, 'Candidatus Liberibacter asiaticus' encodes two novel autotransporters. PLoS One 2013; 8:e68921. [PMID: 23874813 PMCID: PMC3708911 DOI: 10.1371/journal.pone.0068921] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Accepted: 06/04/2013] [Indexed: 01/09/2023] Open
Abstract
Proteins secreted by the type V secretion system (T5SS), known as autotransporters, are large extracellular virulence proteins localized to the bacterial poles. In this study, we characterized two novel autotransporter proteins of 'Candidatus Liberibacter asiaticus' (Las), and redesignated them as LasAI and LasAII in lieu of the previous names HyvI and HyvII. As a phloem-limited, intracellular bacterial pathogen, Las has a significantly reduced genome and causes huanglongbing (HLB), a devastating disease of citrus worldwide. Bioinformatic analyses revealed that LasAI and LasAII share the structural features of an autotransporter family containing large repeats of a passenger domain and a unique C-terminal translocator domain. When fused to the GFP gene and expressed in E. coli, the LasAI C-terminus and the full length LasAII were localized to the bacterial poles, similar to other members of autotransporter family. Despite the absence of a typical signal peptide, LasAI was found to localize at the cell surface by immuno-dot blot using a monoclonal antibody against the partial LasAI protein. Its surface localization was also confirmed by the removal of the LasAI antigen using a proteinase K treatment of the intact bacterial cells. When co-inoculated with a P19 gene silencing suppressor and transiently expressed in tobacco leaves, the GFP-LasAI translocator targeted to the mitochondria. This is the first report that Las encodes novel autotransporters that target to mitochondria when expressed in the plants. These findings may lead to a better understanding of the pathogenesis of this intracellular bacterium.
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Affiliation(s)
- Guixia Hao
- United States Horticultural Research Laboratory, United States Department of Agriculture-Agriculture Research Service, Fort Pierce, Florida, United States of America
| | - Michael Boyle
- Smithsonian Marine Station, Fort Pierce, Florida, United States of America
| | - Lijuan Zhou
- United States Horticultural Research Laboratory, United States Department of Agriculture-Agriculture Research Service, Fort Pierce, Florida, United States of America
| | - Yongping Duan
- United States Horticultural Research Laboratory, United States Department of Agriculture-Agriculture Research Service, Fort Pierce, Florida, United States of America
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Wang N, Trivedi P. Citrus huanglongbing: a newly relevant disease presents unprecedented challenges. PHYTOPATHOLOGY 2013; 103:652-65. [PMID: 23441969 DOI: 10.1094/phyto-12-12-0331-rvw] [Citation(s) in RCA: 179] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Citrus huanglongbing (HLB) is one of the oldest citrus diseases and has been known for over a century. HLB is caused by 'Candidatus Liberibacter' spp. that are phloem-limited, fastidious α-proteobacteria and infect hosts in different Kingdoms (i.e., Animalia and Plantae). When compared with well-characterized, cultivatable plant-pathogenic Gram-negative bacteria, the interactions of uncultured insect-vectored plant-pathogenic bacteria, including 'Ca. Liberibacter' spp., with their hosts remain poorly understood. 'Ca. Liberibacter' spp. have been known to cause HLB, which has been rapidly spreading worldwide, resulting in dramatic economic losses. HLB presents an unprecedented challenge to citrus production. In this review, we focus on the most recent research on citrus, 'Candidatus Liberibacter asiaticus', and psyllid interactions, specifically considering the following topics: evolutionary relationships among 'Ca. Liberibacter' spp., genetic diversity, host range, genome analysis, transmission, virulence mechanisms, and the ecological importance of HLB. Currently, no efficient management strategy is available to control HLB, although some promising progress has been made. Further studies are needed to understand citrus, 'Ca. L. asiaticus', and psyllid interactions to design innovative management strategies. Although HLB has been problematic for over a century, we can only win the battle against HLB with a coordinated and deliberate effort by the citrus industry, citrus growers, researchers, legislatures, and governments.
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Affiliation(s)
- Nian Wang
- Cirtrus Research Education Center, Department of Microbiology and Cell Science, University of Florida, Lake Alfred 33850, USA.
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