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Li R, Wang X, Hu Y, Huang G. Analysis of huanglongbing-associated RNA-seq data reveals disturbances in biological processes within Citrus spp. triggered by Candidatus Liberibacter asiaticus infection. FRONTIERS IN PLANT SCIENCE 2024; 15:1388163. [PMID: 38660443 PMCID: PMC11039969 DOI: 10.3389/fpls.2024.1388163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Accepted: 03/27/2024] [Indexed: 04/26/2024]
Abstract
Introduction Huanglongbing (HLB), a disease that's ubiquitous worldwide, wreaks havoc on the citrus industry. The primary culprit of HLB is the gram-negative bacterium Candidatus Liberibacter asiaticus (CLas) that infects the phloem, but its damaging mechanism is yet to be fully understood. Methods and results In this study, a multitude of tools including weighted correlation network analysis (WGCNA), protein-protein interaction (PPI) network analysis and gene expression profiling are employed to unravel the intricacies of its pathogenesis. The investigation pinpoints various central genes, such as the ethylene-responsive transcription factor 9 (ERF9) and thioredoxin reductase 1 (TrxR1), that are associated with CLas invasion and resultant disturbances in numerous biological operations. Additionally, the study uncovers a range of responses through the detection of differential expressed genes (DEGs) across different experiments. The discovery of core DEGs leads to the identification of pivotal genes such as the sieve element occlusion (SEO) and the wall-associated receptor kinase-like 15 (WAKL15). PPI network analysis highlights potential vital proteins, while GO and KEGG pathway enrichment analysis illustrate a significant impact on multiple defensive and metabolic pathways. Gene set enrichment analysis (GSEA) indicates significant alterations in biological processes such as leaf senescence and response to biotic stimuli. Discussion This all-encompassing approach extends valuable understanding into the pathogenesis of CLas, potentially aiding future research and therapeutic strategies for HLB.
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Affiliation(s)
- Ruimin Li
- College of Life Sciences, Gannan Normal University, Ganzhou, China
- China-USA Citrus Huanglongbing Joint Laboratory, National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, China
| | - Xinyou Wang
- College of Life Sciences, Gannan Normal University, Ganzhou, China
| | - Yanan Hu
- College of Life Sciences, Gannan Normal University, Ganzhou, China
| | - Guiyan Huang
- College of Life Sciences, Gannan Normal University, Ganzhou, China
- China-USA Citrus Huanglongbing Joint Laboratory, National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, China
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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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Fisher TW, Munyaneza JE, Brown JK. Sub-optimal temperatures lead to altered expression of stress-related genes and increased 'C andidatus Liberibacter solanacearum' accumulation in potato psyllid. FRONTIERS IN INSECT SCIENCE 2024; 3:1279365. [PMID: 38469510 PMCID: PMC10926459 DOI: 10.3389/finsc.2023.1279365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 11/23/2023] [Indexed: 03/13/2024]
Abstract
Introduction The potato psyllid Bactericera cockerelli is the insect vector of the fastidious bacterium 'Candidatus Liberibacter solanacearum'. The bacterium infects both B. cockerelli and plant species, causing zebra chip (ZC) disease of potato and vein-greening disease of tomato. Temperatures are known to influence the initiation and progression of disease symptom in the host plant, and seasonal transitions from moderate to high temperatures trigger psyllid dispersal migration to facilitate survival. Methods 'Ca. L. solanacearum' -infected and uninfected psyllids were reared at previously established 'permissible', optimal, and 'non-permissible' and temperatures of 18°C, 24°C, and 30°C, respectively. Gene expression profiles for 'Ca. L. solanacearum'-infected and -uninfected adult psyllids reared at different temperatures were characterized by Illumina RNA-Seq analysis. Bacterial genome copy number was quantified by real-time quantitative-PCR (qPCR) amplification. Results Relative gene expression profiles varied in psyllids reared at the three experimental temperatures. Psyllids reared at 18°C and 30°C exhibited greater fold-change increased expression of stress- and 'Ca. L. solanacearum' invasion-related proteins. Quantification by qPCR of bacterial genome copy number revealed that 'Ca. L. solanacearum' accumulation was significantly lower in psyllids reared at 18°C and 30°C, compared to 24°C. Discussion Temperature is a key factor in the life history of potato psyllid and multiplication/accumulation of 'Ca. L. solanacearum' in both the plant and psyllid host, influences the expression of genes associated with thermal stress tolerance, among others, and may have been instrumental in driving the co-evolution of the pathosystem.
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Affiliation(s)
- Tonja W. Fisher
- School of Plant Sciences, The University of Arizona, Tucson, AZ, United States
| | - Joseph E. Munyaneza
- United States Department of Agriculture-Agricultural Research Service (USDA-ARS), Yakima Agricultural Research Laboratory (YARL), Wapato, WA, United States
| | - Judith K. Brown
- School of Plant Sciences University of Arizona, Tucson, AZ, United States
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4
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Du P, Hu J, Du M, Gao X, Yang W, Zhang C, Zou X, Wang X, Li W. Interaction of a bacterial non-classically secreted RNase HⅠ with a citrus B-Box zinc finger protein delays flowering in Arabidopsis thaliana and suppresses the expression of FLOWERING LOCUS T. Microbiol Res 2024; 278:127541. [PMID: 37972521 DOI: 10.1016/j.micres.2023.127541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 10/21/2023] [Accepted: 10/31/2023] [Indexed: 11/19/2023]
Abstract
Ribonuclease HI (RNase HI) is well conserved across prokaryotes and eukaryotes, and has long been known to localize in the nucleic acid-containing cellular compartments for acting as an R-loop eraser but has never been determined to be a secreted protein. "Candidatus Liberibacter asiaticus" (CLas) is a fastidious α-proteobacterium that causes Huanglongbing (HLB), a devastating citrus disease often associated with flowering out of season. In this study, using the SecretomeP program coupled with an Escherichia coli-based alkaline phosphatase assay, we demonstrated that the CLas RNase HI (LasRNHⅠ) was a non-classically secreted protein. Further experiments identified that LasRNHⅠ could interact with a citrus B-box zinc finger protein CsBBX28 in the plant nucleolus. The in vitro assays indicated that CsBBX28 dramatically enhanced the R-loop-degrading activity of LasRNHⅠ. Remarkably, co-expression of CsBBX28 and LasRNHⅠ in Arabidopsis thaliana led to a much later flowering time than that of wild-type Arabidopsis, as well as that of the transgenic A. thaliana expressing only CsBBX28 or LasRNHⅠ, and lastingly and significantly repressed transcription of FLOWERING LOCUS T (FT), a floral pathway integrator. Similarly, ectopic expression of LasRNHⅠ in citrus greatly reduced the transcription level of FT. The data together disclosed the extracellular secretion of LasRNHⅠ, and that LasRNHⅠ physically interacted with CsBBX28 and served as a flowering repressor through suppressing the FT expression, suggesting a novel role of RNase HI in the bacteria interacting with the host plants.
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Affiliation(s)
- Peixiu Du
- Key Laboratory for Northern Urban Agriculture of Ministry of Agriculture and Rural Affairs, Beijing University of Agriculture, Beijing 102206, PR China; Innovative Institute of Chinese Medicine and Pharmacy, Shandong University of Traditional Chinese Medicine, Jinan 250355, PR China; Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, PR China
| | - Junxia Hu
- Department of Plant Protection, Beijing University of Agriculture, Beijing 102206, PR China
| | - Meixia Du
- Citrus Research Institute, Southwest University, Chongqing 400716, PR China
| | - Xiaoyu Gao
- Department of Plant Protection, Beijing University of Agriculture, Beijing 102206, PR China
| | - Wendi Yang
- Department of Plant Protection, Beijing University of Agriculture, Beijing 102206, PR China
| | - Chao Zhang
- College of Life Science, Hebei Agricultural University, Baoding 071001, PR China
| | - Xiuping Zou
- Citrus Research Institute, Southwest University, Chongqing 400716, PR China
| | - Xuefeng Wang
- Citrus Research Institute, Southwest University, Chongqing 400716, PR China
| | - Weimin Li
- Key Laboratory for Northern Urban Agriculture of Ministry of Agriculture and Rural Affairs, Beijing University of Agriculture, Beijing 102206, PR China; Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, PR China; Department of Plant Protection, Beijing University of Agriculture, Beijing 102206, PR China.
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5
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Zhang S, Wang X, He J, Zhang S, Zhao T, Fu S, Zhou C. A Sec-dependent effector, CLIBASIA_04425, contributes to virulence in ' Candidatus Liberibater asiaticus'. FRONTIERS IN PLANT SCIENCE 2023; 14:1224736. [PMID: 37554557 PMCID: PMC10405523 DOI: 10.3389/fpls.2023.1224736] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Accepted: 07/05/2023] [Indexed: 08/10/2023]
Abstract
Citrus Huanglongbing (HLB) is the most destructive citrus disease worldwide, mainly caused by 'Candidatus Liberibacter asiaticus' (CLas). It encodes a large number of Sec-dependent effectors that contribute to HLB progression. In this study, an elicitor triggering ROS burst and cell death in Nicotiana benthamiana, CLIBASIA_04425 (CLas4425), was identified. Of particular interest, its cell death-inducing activity is associated with its subcellular localization and the cytoplasmic receptor Botrytis-induced kinase 1 (BIK1). Compared with CLas infected psyllids, CLas4425 showed higher expression level in planta. The transient expression of CLas4425 in N. benthamiana and its overexpression in Citrus sinensis enhanced plant susceptibility to Pseudomonas syringae pv. tomato DC3000 ΔhopQ1-1 and CLas, respectively. Furthermore, the salicylic acid (SA) level along with the expression of genes NPR1/EDS1/NDR1/PRs in SA signal transduction was repressed in CLas4425 transgenic citrus plants. Taken together, CLas4425 is a virulence factor that promotes CLas proliferation, likely by interfering with SA-mediated plant immunity. The results obtained facilitate our understanding of CLas pathogenesis.
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Affiliation(s)
- Shushe Zhang
- Citrus Research Institute, Southwest University/National Citrus Engineering Research Center, Chongqing, China
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Chinese Academy of Agriculture Sciences, Institute of Plant Protection, Beijing, China
| | - Xuefeng Wang
- Citrus Research Institute, Southwest University/National Citrus Engineering Research Center, Chongqing, China
| | - Jun He
- Citrus Research Institute, Southwest University/National Citrus Engineering Research Center, Chongqing, China
| | - Song Zhang
- Guangxi Citrus Breeding and Cultivation Engineering Technology Center Academy of Specialty Crops, Guangxi, Guilin, China
| | - Tingchang Zhao
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Chinese Academy of Agriculture Sciences, Institute of Plant Protection, Beijing, China
| | - Shimin Fu
- Citrus Research Institute, Southwest University/National Citrus Engineering Research Center, Chongqing, China
| | - Changyong Zhou
- Citrus Research Institute, Southwest University/National Citrus Engineering Research Center, Chongqing, China
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6
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Wang S, Du M, Dong L, Qu R, Ran D, Ma J, Wang X, Xu L, Li W, He Y, Zou X. Function and molecular mechanism analysis of CaLasSDE460 effector involved in the pathogenesis of "Candidatus Liberibacter asiaticus" in citrus. MOLECULAR HORTICULTURE 2023; 3:14. [PMID: 37789492 PMCID: PMC10514941 DOI: 10.1186/s43897-023-00062-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 07/10/2023] [Indexed: 10/05/2023]
Abstract
Citrus Huanglongbing (HLB), caused by Candidatus Liberibacter asiaticus (CaLas), is the most serious disease worldwide. CaLasSDE460 was previously characterized as a potential virulence factor of CaLas. However, the function and mechanism of CaLasSDE460 involved in CaLas against citrus is still elusive. Here, we showed that transgenic expression of CaLasSDE460 in Wanjincheng oranges (C. sinensis Osbeck) contributed to the early growth of CaLas and the development of symptoms. When the temperature increased from 25 °C to 32 °C, CaLas growth and symptom development in transgenic plants were slower than those in WT controls. RNA-seq analysis of transgenic plants showed that CaLasSDE460 affected multiple biological processes. At 25 °C, transcription activities of the "Protein processing in endoplasmic reticulum" and "Cyanoamino acid metabolism" pathways increased while transcription activities of many pathways decreased at 32 °C. 124 and 53 genes, separately annotated to plant-pathogen interaction and MAPK signaling pathways, showed decreased expression at 32 °C, compared with these (38 for plant-pathogen interaction and 17 for MAPK signaling) at 25 °C. Several important genes (MAPKKK14, HSP70b, NCED3 and WRKY33), remarkably affected by CaLasSDE460, were identified. Totally, our data suggested that CaLasSDE460 participated in the pathogenesis of CaLas through interfering transcription activities of citrus defense response and this interfering was temperature-dependent.
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Affiliation(s)
- Shuai Wang
- Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Citrus Research Institute, Southwest University/National Citrus Engineering Research Center, Chongqing, People's Republic of China
| | - Meixia Du
- Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Citrus Research Institute, Southwest University/National Citrus Engineering Research Center, Chongqing, People's Republic of China
| | - Liting Dong
- Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Citrus Research Institute, Southwest University/National Citrus Engineering Research Center, Chongqing, People's Republic of China
| | - Rongrong Qu
- Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Citrus Research Institute, Southwest University/National Citrus Engineering Research Center, Chongqing, People's Republic of China
| | - Danlu Ran
- Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Citrus Research Institute, Southwest University/National Citrus Engineering Research Center, Chongqing, People's Republic of China
| | - Juanjuan Ma
- Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Citrus Research Institute, Southwest University/National Citrus Engineering Research Center, Chongqing, People's Republic of China
| | - Xuefeng Wang
- Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Citrus Research Institute, Southwest University/National Citrus Engineering Research Center, Chongqing, People's Republic of China
| | - Lanzhen Xu
- Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Citrus Research Institute, Southwest University/National Citrus Engineering Research Center, Chongqing, People's Republic of China
| | - Weimin Li
- Key Laboratory for Northern Urban, Agriculture of Ministry of Agriculture and Rural Affairs, Beijing University of Agriculture, Beijing, People's Republic of China
| | - Yongrui He
- Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Citrus Research Institute, Southwest University/National Citrus Engineering Research Center, Chongqing, People's Republic of China
| | - Xiuping Zou
- Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Citrus Research Institute, Southwest University/National Citrus Engineering Research Center, Chongqing, People's Republic of China.
- Key Laboratory for Northern Urban, Agriculture of Ministry of Agriculture and Rural Affairs, Beijing University of Agriculture, Beijing, People's Republic of China.
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7
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Du J, Wang Q, Shi H, Zhou C, He J, Wang X. A prophage-encoded effector from "Candidatus Liberibacter asiaticus" targets ASCORBATE PEROXIDASE6 in citrus to facilitate bacterial infection. MOLECULAR PLANT PATHOLOGY 2023; 24:302-316. [PMID: 36692022 PMCID: PMC10013806 DOI: 10.1111/mpp.13296] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Revised: 01/03/2023] [Accepted: 01/03/2023] [Indexed: 05/21/2023]
Abstract
Citrus huanglongbing (HLB), associated with the unculturable phloem-limited bacterium "Candidatus Liberibacter asiaticus" (CLas), is the most devastating disease in the citrus industry worldwide. However, the pathogenicity of CLas remains poorly understood. In this study, we show that AGH17488, a secreted protein encoded by the prophage region of the CLas genome, suppresses plant immunity via targeting the host ASCORBATE PEROXIDASE6 (APX6) protein in Nicotiana benthamiana and Citrus sinensis. The transient expression of AGH17488 reduced the chloroplast localization of APX6 and its enzyme activity, inhibited the accumulation of reactive oxygen species (H2 O2 and O2 - ) and the lipid oxidation endproduct malondialdehyde in plants, and promoted the proliferation of Pseudomonas syringae pv. tomato DC3000 and Xanthomonas citri subsp. citri. This study reveals a novel mechanism underlying how CLas uses a prophage-encoded effector, AGH17488, to target a reactive oxygen species accumulation-related gene, APX6, in the host to facilitate its infection.
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Affiliation(s)
- Jiao Du
- National Citrus Engineering Research CenterCitrus Research Institute, Southwest UniversityChongqingChina
- Fruit Tree and Melon Information Research CenterZhengzhou Fruit Research Institute, Chinese Academy of Agricultural SciencesZhengzhouChina
| | - Qiying Wang
- National Citrus Engineering Research CenterCitrus Research Institute, Southwest UniversityChongqingChina
| | - Hongwei Shi
- National Citrus Engineering Research CenterCitrus Research Institute, Southwest UniversityChongqingChina
| | - Changyong Zhou
- National Citrus Engineering Research CenterCitrus Research Institute, Southwest UniversityChongqingChina
| | - Jun He
- National Citrus Engineering Research CenterCitrus Research Institute, Southwest UniversityChongqingChina
| | - Xuefeng Wang
- National Citrus Engineering Research CenterCitrus Research Institute, Southwest UniversityChongqingChina
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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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9
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Reyes Caldas PA, Zhu J, Breakspear A, Thapa SP, Toruño TY, Perilla-Henao LM, Casteel C, Faulkner CR, Coaker G. Effectors from a Bacterial Vector-Borne Pathogen Exhibit Diverse Subcellular Localization, Expression Profiles, and Manipulation of Plant Defense. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2022; 35:1067-1080. [PMID: 35952362 PMCID: PMC9844206 DOI: 10.1094/mpmi-05-22-0114-r] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Climate change is predicted to increase the prevalence of vector-borne disease due to expansion of insect populations. 'Candidatus Liberibacter solanacearum' is a phloem-limited pathogen associated with multiple economically important diseases in solanaceous crops. Little is known about the strategies and pathogenicity factors 'Ca. L. solanacearum' uses to colonize its vector and host. We determined the 'Ca. L. solanacearum' effector repertoire by predicting proteins secreted by the general secretory pathway across four different 'Ca. L. solanacearum' haplotypes, investigated effector localization in planta, and profiled effector expression in the vector and host. The localization of 'Ca. L. solanacearum' effectors in Nicotiana spp. revealed diverse eukaryotic subcellular targets. The majority of tested effectors were unable to suppress plant immune responses, indicating they possess unique activities. Expression profiling in tomato and the psyllid Bactericera cockerelli indicated 'Ca. L. solanacearum' differentially interacts with its host and vector and can switch effector expression in response to these environments. This study reveals 'Ca. L. solanacearum' effectors possess complex expression patterns, target diverse host organelles and the majority are unable to suppress host immune responses. A mechanistic understanding of 'Ca. L. solanacearum' effector function will reveal novel targets and provide insight into phloem biology. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
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Affiliation(s)
| | - Jie Zhu
- Plant Pathology Department, University of California, Davis, CA, U.S.A
| | | | - Shree P. Thapa
- Plant Pathology Department, University of California, Davis, CA, U.S.A
| | - Tania Y. Toruño
- Plant Pathology Department, University of California, Davis, CA, U.S.A
- Rijk Zwaan Breeding B.V, Burgemeester Crezéelaan 40, De Lier, 2678 KX, The Netherlands
| | | | - Clare Casteel
- Plant Pathology Department, University of California, Davis, CA, U.S.A
- School of Integrative Plant Science, Plant-Microbe Biology and Plant Pathology Section, Cornell University, Ithaca, NY, U.S.A
| | | | - Gitta Coaker
- Plant Pathology Department, University of California, Davis, CA, U.S.A
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10
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Shen P, Li X, Fu S, Zhou C, Wang X. A " Candidatus Liberibacter asiaticus"-secreted polypeptide suppresses plant immune responses in Nicotiana benthamiana and Citrus sinensis. FRONTIERS IN PLANT SCIENCE 2022; 13:997825. [PMID: 36352861 PMCID: PMC9638108 DOI: 10.3389/fpls.2022.997825] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 08/23/2022] [Indexed: 05/22/2023]
Abstract
Citrus Huanglongbing (HLB), known as the most economically devastating disease in citrus industry, is mainly caused by phloem-restricted Gram-negative bacterium "Candidatus Liberibacter asiaticus" (CLas). To date, CLas is still unculturable in vitro, which has been dramatically delaying the research on its pathogenesis, and only few Sec-dependent effectors (SDEs) have been identified to elucidate the pathogenesis of CLas. Here, we confirmed that a CLas-secreted Sec-dependent polypeptide, namely SECP8 (CLIBASIA_05330), localized in nucleus, cytoplasm and cytoplasmic membrane, and showed remarkably higher transcript abundance in citrus than in psyllids. Potato virus X (PVX)-mediated transient expression assays indicated that mSECP8 (the mature form of SECP8) suppressed pro-apoptotic mouse protein BAX and Phytophthora infestans elicitin INF1-triggered hypersensitive response (HR) associated phenotypes, including cell death, H2O2 accumulation and callose deposition. Intriguingly, mSECP8 also inhibited SDE1 (CLIBASIA_05315)-induced water-soaked and dwarfing symptoms in Nicotiana benthamiana. In addition, mSECP8 can promote the susceptibility of transgenic Wanjincheng orange (Citrus sinensis) to CLas invasion and further HLB symptom development, and it contributes to the proliferation of Xanthomonas citri subsp. citri (Xcc). Moreover, the expression of ten immunity-related genes were significantly down-regulated in mSECP8 transgenic citrus than those in wide-type (WT) plants. Overall, we propose that mSECP8 may serve as a novel broad-spectrum suppressor of plant immunity, and provide the first evidence counteractive effect among CLas effectors. This study will enrich and provide new evidences for elucidating the pathogenic mechanisms of CLas in citrus host.
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Affiliation(s)
| | | | | | - Changyong Zhou
- National Citrus Engineering Research Center, Citrus Research Institute, Southwest University, Chongqing, China
| | - Xuefeng Wang
- National Citrus Engineering Research Center, Citrus Research Institute, Southwest University, Chongqing, China
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11
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CLIBASIA_00460 Disrupts Hypersensitive Response and Interacts with Citrus Rad23 Proteins. Int J Mol Sci 2022; 23:ijms23147846. [PMID: 35887193 PMCID: PMC9324546 DOI: 10.3390/ijms23147846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Revised: 07/11/2022] [Accepted: 07/13/2022] [Indexed: 12/10/2022] Open
Abstract
'Candidatus Liberibacter asiaticus' (CLas) is a bacterium that causes Huanglongbing, also known as citrus greening, in citrus plants. 'Candidatus Liberibacter solanacearum' (Lso) is a close relative of CLas and in the US it infects solanaceous crops, causing zebra chip disease in potato. Previously, we have identified the Lso hypothetical protein effector 1 (Lso-HPE1). This protein uses a signal peptide for secretion; disrupts programmed cell death; and interacts with tomato RAD23c, d, and e proteins, but not with RAD23a. In this study, we evaluated whether CLIBASIA_00460, the CLas homolog of Lso-HPE1 interacted with citrus RAD23 proteins and disrupted their programmed cell death. Based on the yeast two-hybrid assay results, CLIBASIA_00460 interacted with citrus RAD23c and RAD23d, but not with citrus RAD23b. These results were confirmed using bimolecular fluorescence complementation assays, which showed that these interactions occurred in cell puncta, but not in the nucleus or cytoplasm. Additionally, CLIBASIA_00460 was able to disrupt the PrfD1416V-induced hypersensitive response. Therefore, based on the similar interactions between Lso-HPE1 and CLIBASIA_00460 with the host RAD23 proteins and their ability to inhibit cell death in plants, we propose that these effectors may have similar functions during plant infection.
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12
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Du J, Wang Q, Zeng C, Zhou C, Wang X. A prophage-encoded nonclassical secretory protein of "Candidatus Liberibacter asiaticus" induces a strong immune response in Nicotiana benthamiana and citrus. MOLECULAR PLANT PATHOLOGY 2022; 23:1022-1034. [PMID: 35279937 PMCID: PMC9190977 DOI: 10.1111/mpp.13206] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 02/14/2022] [Accepted: 02/23/2022] [Indexed: 05/04/2023]
Abstract
Huanglongbing (HLB), associated with "Candidatus Liberibacter asiaticus" (CLas), is a globally devastating plant disease. The highly reduced genome of CLas encodes a number of secretory proteins. The conserved prophage-encoded protein AGH17470 is herein identified as a nonclassical secretory protein. We confirmed that the N-terminal and C-terminal sequences jointly determine the secretion of AGH17470. The transient expression of AGH17470 protein in Nicotiana benthamiana caused hypersensitive response (HR) cell death in infiltrated leaves and systemically infected leaves as well as the dwarfing of the entire plant, suggesting that AGH17470 is involved in the plant immune response, growth, and development. Overexpression of AGH17470 in N. benthamiana and citrus plants up-regulated the transcription of pathogenesis-related and salicylic acid (SA)-signalling pathway genes and promoted SA accumulation. Furthermore, transient expression of AGH17470 enhanced the resistance of sweet orange to Xanthomonas citri subsp. citri. To our knowledge, AGH17470 is the first prophage-encoded secretory protein demonstrated to elicit an HR and induce a strong plant immune response. The findings have increased our understanding of prophage-encoded secretory protein genes, and the results provide clues as to the plant defence response against CLas.
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Affiliation(s)
- Jiao Du
- National Citrus Engineering Research CenterCitrus Research InstituteSouthwest UniversityChongqingChina
| | - Qiying Wang
- National Citrus Engineering Research CenterCitrus Research InstituteSouthwest UniversityChongqingChina
| | - Chunhua Zeng
- National Citrus Engineering Research CenterCitrus Research InstituteSouthwest UniversityChongqingChina
| | - Changyong Zhou
- National Citrus Engineering Research CenterCitrus Research InstituteSouthwest UniversityChongqingChina
| | - Xuefeng Wang
- National Citrus Engineering Research CenterCitrus Research InstituteSouthwest UniversityChongqingChina
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13
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Du M, Wang S, Dong L, Qu R, Zheng L, He Y, Chen S, Zou X. Overexpression of a " Candidatus Liberibacter Asiaticus" Effector Gene CaLasSDE115 Contributes to Early Colonization in Citrus sinensis. Front Microbiol 2022; 12:797841. [PMID: 35265048 PMCID: PMC8899593 DOI: 10.3389/fmicb.2021.797841] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Accepted: 12/20/2021] [Indexed: 11/29/2022] Open
Abstract
Huanglongbing (HLB), caused by "Candidatus liberibacter asiaticus" (CaLas), is one of the most devastating diseases in citrus but its pathogenesis remains poorly understood. Here, we reported the role of the CaLasSDE115 (CLIBASIA_05115) effector, encoded by CaLas, during pathogen-host interactions. Bioinformatics analyses showed that CaLasSDE115 was 100% conserved in all reported CaLas strains but had sequence differences compared with orthologs from other "Candidatus liberibacter." Prediction of protein structures suggested that the crystal structure of CaLasSDE115 was very close to that of the invasion-related protein B (IalB), a virulence factor from Bartonella henselae. Alkaline phosphatase (PhoA) assay in E. coli further confirmed that CaLasSDE115 was a Sec-dependent secretory protein while subcellular localization analyses in tobacco showed that the mature protein of SDE115 (mSDE115), without its putative Sec-dependent signal peptide, was distributed in the cytoplasm and the nucleus. Expression levels of CaLasSDE115 in CaLas-infected Asian citrus psyllid (ACP) were much higher (∼45-fold) than those in CaLas-infected Wanjincheng oranges, with the expression in symptomatic leaves being significantly higher than that in asymptomatic ones. Additionally, the overexpression of mSDE115 favored CaLas proliferation during the early stages (2 months) of infection while promoting the development of symptoms. Hormone content and gene expression analysis of transgenic plants also suggested that overexpressing mSDE115 modulated the transcriptional regulation of genes involved in systemic acquired resistance (SAR) response. Overall, our data indicated that CaLasSDE115 effector contributed to the early colonization of citrus by the pathogen and worsened the occurrence of Huanglongbing symptoms, thereby providing a theoretical basis for further exploring the pathogenic mechanisms of Huanglongbing disease in citrus.
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Affiliation(s)
| | | | | | | | | | | | | | - Xiuping Zou
- National Citrus Engineering Research Center, Citrus Research Institute, Southwest University, Chongqing, China
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14
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De Francesco A, Lovelace AH, Shaw D, Qiu M, Wang Y, Gurung F, Ancona V, Wang C, Levy A, Jiang T, Ma W. Transcriptome Profiling of ' Candidatus Liberibacter asiaticus' in Citrus and Psyllids. PHYTOPATHOLOGY 2022; 112:116-130. [PMID: 35025694 DOI: 10.1094/phyto-08-21-0327-fi] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
'Candidatus Liberibacter asiaticus' (Las) is an emergent bacterial pathogen that is associated with the devastating citrus huanglongbing (HLB). Vectored by the Asian citrus psyllid, Las colonizes the phloem tissue of citrus, causing severe damage to infected trees. So far, cultivating pure Las culture in axenic media has not been successful, and dual-transcriptome analyses aiming to profile gene expression in both Las and its hosts have a low coverage of the Las genome because of the low abundance of bacterial RNA in total RNA extracts from infected tissues. Therefore, a lack of understanding of the Las transcriptome remains a significant knowledge gap. Here, we used a bacterial cell enrichment procedure and confidently determined the expression profiles of approximately 84% of the Las genes. Genes that exhibited high expression in citrus include transporters, ferritin, outer membrane porins, specific pilins, and genes involved in phage-related functions, cell wall modification, and stress responses. We also found 106 genes to be differentially expressed in citrus versus Asian citrus psyllids. Genes related to transcription or translation and resilience to host defense response were upregulated in citrus, whereas genes involved in energy generation and the flagella system were expressed to higher levels in psyllids. Finally, we determined the relative expression levels of potential Sec-dependent effectors, which are considered as key virulence factors of Las. This work advances our understanding of HLB biology and offers novel insight into the interactions of Las with its plant host and insect vector.
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Affiliation(s)
- Agustina De Francesco
- Department of Microbiology and Plant Pathology, University of California, Riverside, CA 92521, U.S.A
| | - Amelia H Lovelace
- The Sainsbury Laboratory, Norwich Research Park, NR4 7UH, United Kingdom
| | - Dipan Shaw
- Department of Computer Science and Engineering, University of California, Riverside, CA 92521, U.S.A
| | - Min Qiu
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
| | - Yuanchao Wang
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
| | - Fatta Gurung
- Citrus Center, Department of Agriculture, Agribusiness and Environmental Sciences, Texas A&M University-Kingsville, Weslaco, TX 78599, U.S.A
| | - Veronica Ancona
- Citrus Center, Department of Agriculture, Agribusiness and Environmental Sciences, Texas A&M University-Kingsville, Weslaco, TX 78599, U.S.A
| | - Chunxia Wang
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, U.S.A
| | - Amit Levy
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, U.S.A
| | - Tao Jiang
- Department of Computer Science and Engineering, University of California, Riverside, CA 92521, U.S.A
| | - Wenbo Ma
- Department of Microbiology and Plant Pathology, University of California, Riverside, CA 92521, U.S.A
- The Sainsbury Laboratory, Norwich Research Park, NR4 7UH, United Kingdom
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15
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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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16
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Merli ML, Padgett-Pagliai KA, Cuaycal AE, Garcia L, Marano MR, Lorca GL, Gonzalez CF. ' Candidatus Liberibacter asiaticus' Multimeric LotP Mediates Citrus sinensis Defense Response Activation. Front Microbiol 2021; 12:661547. [PMID: 34421834 PMCID: PMC8371691 DOI: 10.3389/fmicb.2021.661547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 07/06/2021] [Indexed: 11/13/2022] Open
Abstract
‘Candidatus Liberibacter asiaticus’ is known as the most pathogenic organism associated with citrus greening disease. Since its publicized emergence in Florida in 2005, ‘Ca. L. asiaticus’ remains unculturable. Currently, a limited number of potential disease effectors have been identified through in silico analysis. Therefore, these potential effectors remain poorly characterized and do not fully explain the complexity of symptoms observed in citrus trees infected with ‘Ca. L. asiaticus.’ LotP has been identified as a potential effector and have been partially characterized. This protein retains structural homology to the substrate binding domain of the Lon protease. LotP interacts with chaperones like GroEL, Hsp40, DnaJ, and ClpX and may exercise its biological role through interactions with different proteins involved in proteostasis networks. Here, we evaluate the interactome of LotP—revealing a new protein–protein interaction target (Lon-serine protease) and its effect on citrus plant tissue integrity. We found that via protein–protein interactions, LotP can enhance Lon protease activity, increasing the degradation rate of its specific targets. Infiltration of purified LotP strained citrus plant tissue causing photoinhibition and chlorosis after several days. Proteomics analysis of LotP tissues recovering after the infiltration revealed a large abundance of plant proteins associated with the stabilization and processing of mRNA transcripts, a subset of important transcription factors; and pathways associated with innate plant defense were highly expressed. Furthermore, interactions and substrate binding module of LotP suggest potential interactions with plant proteins, most likely proteases.
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Affiliation(s)
- Marcelo L Merli
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Science, University of Florida, Gainesville, FL, United States
| | - Kaylie A Padgett-Pagliai
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Science, University of Florida, Gainesville, FL, United States
| | - Alexandra E Cuaycal
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Science, University of Florida, Gainesville, FL, United States
| | - Lucila Garcia
- Instituto de Biología Molecular y Celular de Rosario (IBR), Consejo Nacional de Investigaciones Científicas y Tecnológicas, Rosario, Argentina
| | - Maria Rosa Marano
- Instituto de Biología Molecular y Celular de Rosario (IBR), Consejo Nacional de Investigaciones Científicas y Tecnológicas, Rosario, Argentina
| | - Graciela L Lorca
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Science, University of Florida, Gainesville, FL, United States
| | - Claudio F Gonzalez
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Science, University of Florida, Gainesville, FL, United States
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17
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Kan CC, Mendoza-Herrera A, Levy J, Hull JJ, Fabrick JA, Tamborindeguy C. HPE1, an Effector from Zebra Chip Pathogen Interacts with Tomato Proteins and Perturbs Ubiquitinated Protein Accumulation. Int J Mol Sci 2021; 22:9003. [PMID: 34445707 PMCID: PMC8396652 DOI: 10.3390/ijms22169003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 08/10/2021] [Accepted: 08/16/2021] [Indexed: 12/20/2022] Open
Abstract
The gram-negative bacterial genus Liberibacter includes economically important pathogens, such as 'Candidatus Liberibacter asiaticus' that cause citrus greening disease (or Huanglongbing, HLB) and 'Ca. Liberibacter solanacearum' (Lso) that cause zebra chip disease in potato. Liberibacter pathogens are fastidious bacteria transmitted by psyllids. Pathogen manipulation of the host' and vector's immune system for successful colonization is hypothesized to be achieved by Sec translocon-dependent effectors (SDE). In previous work, we identified hypothetical protein effector 1 (HPE1), an SDE from Lso, that acts as a suppressor of the plant's effector-triggered immunity (ETI)-like response. In this study, using a yeast two-hybrid system, we identify binding interactions between tomato RAD23 proteins and HPE1. We further show that HPE1 interacts with RAD23 in both nuclear and cytoplasmic compartments in planta. Immunoblot assays show that HPE1 is not ubiquitinated in the plant cell, but rather the expression of HPE1 induced the accumulation of other ubiquitinated proteins. A similar accumulation of ubiquitinated proteins is also observed in Lso infected tomato plants. Finally, earlier colonization and symptom development following Lso haplotype B infection are observed in HPE1 overexpressing plants compared to wild-type plants. Overall, our results suggest that HPE1 plays a role in virulence in Lso pathogenesis, possibly by perturbing the ubiquitin-proteasome system via direct interaction with the ubiquitin-like domain of RAD23 proteins.
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Affiliation(s)
- Chia-Cheng Kan
- Department of Entomology, Texas A&M University, College Station, TX 77843, USA; (C.-C.K.); (A.M.-H.)
| | - Azucena Mendoza-Herrera
- Department of Entomology, Texas A&M University, College Station, TX 77843, USA; (C.-C.K.); (A.M.-H.)
| | - Julien Levy
- Department of Horticultural Sciences, Texas A&M University, College Station, TX 77843, USA;
| | - J. Joe Hull
- USDA-ARS, Arid Land Agricultural Research Center, Maricopa, AZ 85138, USA; (J.J.H.); (J.A.F.)
| | - Jeffery A. Fabrick
- USDA-ARS, Arid Land Agricultural Research Center, Maricopa, AZ 85138, USA; (J.J.H.); (J.A.F.)
| | - Cecilia Tamborindeguy
- Department of Entomology, Texas A&M University, College Station, TX 77843, USA; (C.-C.K.); (A.M.-H.)
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18
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" Candidatus Liberibacter asiaticus" Secretes Nonclassically Secreted Proteins That Suppress Host Hypersensitive Cell Death and Induce Expression of Plant Pathogenesis-Related Proteins. Appl Environ Microbiol 2021; 87:AEM.00019-21. [PMID: 33579681 PMCID: PMC8091116 DOI: 10.1128/aem.00019-21] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although emerging evidence indicates that bacteria extracellularly export many cytoplasmic proteins referred to as non-classically secreted proteins (ncSecPs) for their own benefit, the mechanisms and functional significance of the ncSecPs in extracellular milieu remain elusive. "Candidatus Liberibacter asiaticus" (CLas) is a fastidious Gram-negative bacterium that causes Huanglongbing (HLB), the most globally devastating citrus disease. In this study, using the SecretomeP program coupled with an Escherichia coli alkaline phosphatase assay, we identified 27 ncSecPs from the CLas genome. Further, we demonstrated that 10 of these exhibited significantly higher levels of gene expression in citrus than in psyllid hosts, and particularly suppressed hypersensitive response (HR)-based cell death and H2O2 overaccumulation in Nicotiana benthamiana, indicating their opposing effects on early plant defenses. However, these proteins also dramatically enhanced the gene expression of pathogenesis-related 1 protein (PR-1), PR-2, and PR-5, essential components of plant defense mechanisms. Additional experiments disclosed that the increased expression of these PR genes, in particular PR-1 and PR-5, could negatively regulate HR-based cell death development and H2O2 accumulation. Remarkably, CLas infection clearly induced gene expression of PR-1, PR-2, and PR-5 in both HLB-tolerant and HLB-susceptible species of citrus plants. Taken together, we hypothesized that CLas has evolved an arsenal of ncSecPs that function cooperatively to overwhelm the early plant defenses by inducing host PR genes.IMPORTANCE In this study, we present a combined computational and experimental methodology that allows a rapid and efficient identification of the ncSecPs from bacteria, in particular the unculturable bacteria like CLas. Meanwhile, the study determined that a number of CLas ncSecPs suppressed HR-based cell death, and thus indicated a novel role for the bacterial ncSecPs in extracellular milieu. More importantly, these ncSecPs were found to suppress cell death presumably by utilizing host PR proteins. The data overall provide a novel clue to understand the CLas pathogenesis and also suggest a new way by which phytopathogens manipulate host cellular machinery to establish infection.
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19
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Zhang W, Zhu Z, Du P, Zhang C, Yan H, Wang W, Li W. NtRBP45, a nuclear RNA-binding protein of Nicotiana tabacum, facilitates post-transcriptional gene silencing. PLANT DIRECT 2020; 4:e00294. [PMID: 33615112 PMCID: PMC7880056 DOI: 10.1002/pld3.294] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 11/10/2020] [Accepted: 11/17/2020] [Indexed: 06/12/2023]
Abstract
The tobacco RBP45 is a nuclear RNA binding protein (RBP). In this study, we identified that the gene expression of NtRBP45 was significantly up-regulated upon the Tobacco mosaic virus infection and the central region of the protein accounted for its nuclear localization. In particular, using a green fluorescent protein-based transient suppression assay, we uncovered that the transiently overexpressed NtRBP45 was able to enhance local post-transcriptional gene silencing (PTGS), facilitate siRNA accumulation, and compromise the RNA silencing suppression mediated by Tomato aspermy virus 2b protein. Deletion mutagenesis showed that both the N- and C-terminal regions of NtRBP45 were necessary for enhancing PTGS. The data overall indicated a novel RNA silencing factor that might participate in antiviral defense.
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Affiliation(s)
- Wangbin Zhang
- College of Plant ScienceTarim UniversityAlarPR China
- Southern Xinjiang Key Laboratory of IPMTarim UniversityAlarPR China
| | - Zongcai Zhu
- College of Plant ScienceTarim UniversityAlarPR China
- Biotechnology Research InstituteChinese Academy of Agricultural SciencesBeijingPR China
| | - Peixiu Du
- Biotechnology Research InstituteChinese Academy of Agricultural SciencesBeijingPR China
| | - Chao Zhang
- Biotechnology Research InstituteChinese Academy of Agricultural SciencesBeijingPR China
| | - Hailin Yan
- College of Plant ScienceTarim UniversityAlarPR China
- Biotechnology Research InstituteChinese Academy of Agricultural SciencesBeijingPR China
| | - Wenguo Wang
- Key Laboratory of Development and Application of Rural Renewable EnergyMinistry of Agriculture and Rural AffairsChengduPR China
| | - Weimin Li
- Biotechnology Research InstituteChinese Academy of Agricultural SciencesBeijingPR China
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20
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Zhang C, Du P, Yan H, Zhu Z, Wang X, Li W. A Sec-Dependent Secretory Protein of the Huanglongbing-Associated Pathogen Suppresses Hypersensitive Cell Death in Nicotiana benthamiana. Front Microbiol 2020; 11:594669. [PMID: 33329478 PMCID: PMC7734103 DOI: 10.3389/fmicb.2020.594669] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Accepted: 11/04/2020] [Indexed: 11/13/2022] Open
Abstract
"Candidatus Liberibacter asiaticus" (CLas) is a phloem-restricted Gram-negative bacterium that is the causal agent of citrus huanglongbing (HLB). In this study, we identified a CLas-encoded Sec-dependent secretory protein CLIBASIA_04405 that could contribute to the pathogenicity of this bacterium. The gene expression level of CLIBASIA_04405 was significantly higher in citrus than in psyllids. Transient overexpression of the mature CLIBASIA_04405 protein (m4405) in Nicotiana benthamiana leaves could suppress hypersensitive response (HR)-based cell death and H2O2 accumulation triggered by the mouse BAX and the Phytophthora infestans INF1. An alanine-substitution mutagenesis assay revealed the essential of amino acid clusters EKR45-47 and DE64-65 in cell death suppression. Challenge inoculation of the transgenic N. benthamiana-expressing m4405 with Pseudomonas syringae DC3000ΔhopQ1-1 demonstrated the greatly reduced bacterial proliferation. Remarkably, transcriptome profiling and RT-qPCR analysis disclosed that the gene expression of six small heat shock proteins (sHSPs), a set of plant defense regulators, were significantly elevated in the transgenic m4405 lines compared with those in wild-type N. benthamiana. In addition, the transgenic m4405 lines displayed phenotypes of dwarfism and leaf deformation. Altogether, these data indicated that m4405 was a virulence factor of CLas.
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Affiliation(s)
- Chao Zhang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Peixiu Du
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Hailin Yan
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China.,College of Plant Science, Tarim University, Alar, China
| | - Zongcai Zhu
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China.,College of Plant Science, Tarim University, Alar, China
| | - Xuefeng Wang
- Citrus Research Institute, Southwest University, Chongqing, China
| | - Weimin Li
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
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21
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Zhang WB, Yan HL, Zhu ZC, Zhang C, Du PX, Zhao WJ, Li WM. Genome-wide identification of the Sec-dependent secretory protease genes in Erwinia amylovora and analysis of their expression during infection of immature pear fruit. J Zhejiang Univ Sci B 2020; 21:716-726. [PMID: 32893528 DOI: 10.1631/jzus.b2000281] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The general secretory (Sec) pathway represents a common mechanism by which bacteria secrete proteins, including virulence factors, into the extracytoplasmic milieu. However, there is little information about this system, as well as its associated secretory proteins, in relation to the fire blight pathogen Erwinia amylovora. In this study, data mining revealed that E. amylovora harbors all of the essential components of the Sec system. Based on this information, we identified putative Sec-dependent secretory proteases in E. amylovora on a genome-wide scale. Using the programs SignalP, LipoP, and Phobius, a total of 15 putative proteases were predicted to contain the N-terminal signal peptides (SPs) that might link them to the Sec-dependent pathway. The activities of the predicted SPs were further validated using an Escherichia coli-based alkaline phosphatase (PhoA) gene fusion system that confirmed their extracytoplasmic property. Transcriptional analyses showed that the expression of 11 of the 15 extracytoplasmic protease genes increased significantly when E. amylovora was used to inoculate immature pears, suggesting their potential roles in plant infection. The results of this study support the suggestion that E. amylovora might employ the Sec system to secrete a suite of proteases to enable successful infection of plants, and shed new light on the interaction of E. amylovora with host plants.
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Affiliation(s)
- Wang-Bin Zhang
- College of Plant Science, Tarim University, Alar 843300, China.,Southern Xinjiang Key Laboratory of Integrated Pest Management, Tarim University, Alar 843300, China
| | - Hai-Lin Yan
- College of Plant Science, Tarim University, Alar 843300, China.,Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Zong-Cai Zhu
- College of Plant Science, Tarim University, Alar 843300, China.,Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Chao Zhang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Pei-Xiu Du
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Wen-Jun Zhao
- Chinese Academy of Inspection and Quarantine, Beijing 100176, China
| | - Wei-Min Li
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
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Heterologous Expression of the Constitutive Disease Resistance 2 and 8 Genes from Poncirus trifoliata Restored the Hypersensitive Response and Resistance of Arabidopsis cdr1 Mutant to Bacterial Pathogen Pseudomonas syringae. PLANTS 2020; 9:plants9070821. [PMID: 32629813 PMCID: PMC7412121 DOI: 10.3390/plants9070821] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 06/19/2020] [Accepted: 06/29/2020] [Indexed: 01/23/2023]
Abstract
Huanglongbing (HLB), also known as citrus greening, is the most destructive disease of citrus worldwide. In the United States, this disease is associated with a phloem-restricted bacterium, Candidatus Liberibacter asiaticus. Commercial citrus cultivars are susceptible to HLB, but Poncirus trifoliata, a close relative of Citrus, is highly tolerant of HLB. Isolating P. trifoliata gene(s) controlling its HLB tolerance followed by expressing the gene(s) in citrus is considered a potential cisgenic approach to engineering citrus for tolerance to HLB. Previous gene expression studies indicated that the constitutive disease resistance (CDR) genes in P. trifoliata (PtCDRs) may play a vital role in its HLB tolerance. This study was designed to use Arabidopsis mutants as a model system to confirm the function of PtCDRs in plant disease resistance. PtCDR2 and PtCDR8 were amplified from P. trifoliata cDNA and transferred into the Arabidopsis cdr1 mutant, whose resident CDR1 gene was disrupted by T-DNA insertion. The PtCDR2 and PtCDR8 transgenic Arabidopsis cdr1 mutant restored its hypersensitive response to the bacterial pathogen Pseudomonas syringae pv. tomato strain DC3000 (Pst DC3000) expressing avrRpt2. The defense marker gene PATHOGENESIS RELATED 1 (PR1) expressed at much higher levels in the PtCDR2 or PtCDR8 transgenic cdr1 mutant than in the non-transgenic cdr1 mutant with or without pathogen infection. Multiplication of Pst DC3000 bacteria in Arabidopsis was inhibited by the expression of PtCDR2 and PtCDR8. Our results showed that PtCDR2 and PtCDR8 were functional in Arabidopsis and played a positive role in disease resistance and demonstrated that Arabidopsis mutants can be a useful alternate system for screening Poncirus genes before making the time-consuming effort to transfer them into citrus, a perennial woody plant that is highly recalcitrant for Agrobacterium or biolistic-mediated transformation.
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Levy JG, Gross R, Mendoza-Herrera A, Tang X, Babilonia K, Shan L, Kuhl JC, Dibble MS, Xiao F, Tamborindeguy C. Lso-HPE1, an Effector of ' Candidatus Liberibacter solanacearum', Can Repress Plant Immune Response. PHYTOPATHOLOGY 2020; 110:648-655. [PMID: 31697198 DOI: 10.1094/phyto-07-19-0252-r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
'Candidatus Liberibacter solanacearum' is a plant pathogen affecting the families Solanaceae and Apiaceae in different parts of the world. 'Ca. L. solanacearum' is a Gram-negative, fastidious α-proteobacterium that is vectored by different psyllid species. Plant-pathogenic bacteria are known for interfering with the host physiology or defense mechanisms, often by secreting bacterial effectors. Effector proteins are critical for virulence; therefore, the identification of effectors could help with disease management. In this study, we characterized the Sec-translocon-dependent 'Ca. L. solanacearum'-hypothetical protein effector 1 (Lso-HPE1). We compared this protein sequence in the different 'Ca. L. solanacearum' haplotypes. We predicted the signal peptide and validated its function using Escherichia coli's alkaline phosphatase fusion assay. Agrobacterium tumefaciens-mediated transient expression in Nicotiana benthamiana demonstrated that Lso-HPE1 from 'Ca. L. solanacearum' haplotypes A and B were able to inhibit the induction of cell death in plants. We also compared gene expression of the Lso-HPE1- transcripts in 'Ca. L. solanacearum' haplotypes A and B in tomato and in the vector Bactericera cockerelli. This work validates the identification of a Sec-translocon-dependent 'Ca. L. solanacearum' protein possibly involved in suppression of plant cell death.
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Affiliation(s)
- Julien G Levy
- Department of Horticultural Sciences, Texas A&M University, College Station, TX 77843
| | - Rachel Gross
- Department of Plant Sciences, University of Idaho, Moscow, ID 83844
| | | | - Xiaotian Tang
- Department of Entomology, Texas A&M University, College Station, TX 77843
| | - Kevin Babilonia
- Institute for Plant Genomics and Biotechnology, Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843
| | - Libo Shan
- Institute for Plant Genomics and Biotechnology, Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843
| | - Joseph C Kuhl
- Department of Plant Sciences, University of Idaho, Moscow, ID 83844
| | | | - Fangming Xiao
- Department of Plant Sciences, University of Idaho, Moscow, ID 83844
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Li H, Ying X, Shang L, Redfern B, Kypraios N, Xie X, Xu F, Wang S, Zhang J, Jian H, Yu H, Lv D. Heterologous Expression of CLIBASIA_03915/CLIBASIA_04250 by Tobacco Mosaic Virus Resulted in Phloem Necrosis in the Senescent Leaves of Nicotiana benthamiana. Int J Mol Sci 2020; 21:E1414. [PMID: 32093101 PMCID: PMC7073121 DOI: 10.3390/ijms21041414] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Revised: 02/15/2020] [Accepted: 02/17/2020] [Indexed: 12/02/2022] Open
Abstract
Huanglongbing (HLB), also known as citrus greening, is the most notorious citrus disease worldwide. Candidatus Liberibacter asiaticus (CaLas) is a phloem-restricted bacterium associated with HLB. Because there is no mutant library available, the pathogenesis of CaLas is obscure. In this study, we employed tobacco mosaic virus (TMV) to express two mature secretion proteins CLIBASIA_03915 (m03915) and CLIBASIA_04250 (m04250) in Nicotiana benthamiana (N. benthamiana). Phloem necrosis was observed in the senescent leaves of N. benthamiana that expressed the two low molecular weight proteins, while no phloem necrosis was observed in the plants that expressed the control, green fluorescent protein (GFP). Additionally, no phloem necrosis was observed in the senescent leaves of N. benthamiana that expressed the null mutation of m03915 and frameshifting m04250. The subcellular localizations of m03915 and m04250 were determined by fusion with GFP using confocal microscopy. The subcellular localization of m03915 was found to be as free GFP without a nuclear localization sequence (NLS). However, m04250 did have an NLS. Yeast two-hybrid (Y2H) was carried out to probe the citrus proteins interacting with m03915 and m04250. Six citrus proteins were found to interact with m03915. The identified proteins were involved in the metabolism of compounds, transcription, response to abiotic stress, ubiquitin-mediated protein degradation, etc. The prey of m04250 was involved in the processing of specific pre-mRNAs. Identification of new virulence factors of CaLas will give insight into the pathogenesis of CaLas, and therefore, it will eventually help develop the HLB-resistant citrus.
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Affiliation(s)
- Hui Li
- College of Agronomy and Biotechnology, Southwest University, Chongqing 400715, China; (H.L.); (L.S.); (H.J.)
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Chongqing 400715, China
| | - Xiaobao Ying
- Gulf Coast Research and Education Center, University of Florida, Wimauma, FL 33598, USA; (X.Y.); (B.R.); (N.K.)
| | - Lina Shang
- College of Agronomy and Biotechnology, Southwest University, Chongqing 400715, China; (H.L.); (L.S.); (H.J.)
| | - Bryce Redfern
- Gulf Coast Research and Education Center, University of Florida, Wimauma, FL 33598, USA; (X.Y.); (B.R.); (N.K.)
| | - Nicholas Kypraios
- Gulf Coast Research and Education Center, University of Florida, Wimauma, FL 33598, USA; (X.Y.); (B.R.); (N.K.)
| | - Xuejun Xie
- Changzhou Institute of Technology, Changzhou 213032, China;
| | - FeiFei Xu
- Heilongjiang Academy of Agricultural Sciences, Harbin 10086, China (S.W.); (J.Z.); (H.Y.)
| | - Shaopeng Wang
- Heilongjiang Academy of Agricultural Sciences, Harbin 10086, China (S.W.); (J.Z.); (H.Y.)
| | - Jinghua Zhang
- Heilongjiang Academy of Agricultural Sciences, Harbin 10086, China (S.W.); (J.Z.); (H.Y.)
| | - Hongju Jian
- College of Agronomy and Biotechnology, Southwest University, Chongqing 400715, China; (H.L.); (L.S.); (H.J.)
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Chongqing 400715, China
| | - Hongtao Yu
- Heilongjiang Academy of Agricultural Sciences, Harbin 10086, China (S.W.); (J.Z.); (H.Y.)
| | - Dianqiu Lv
- College of Agronomy and Biotechnology, Southwest University, Chongqing 400715, China; (H.L.); (L.S.); (H.J.)
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Chongqing 400715, China
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25
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Zhang C, Wang X, Liu X, Fan Y, Zhang Y, Zhou X, Li W. A Novel ' Candidatus Liberibacter asiaticus'-Encoded Sec-Dependent Secretory Protein Suppresses Programmed Cell Death in Nicotiana benthamiana. Int J Mol Sci 2019; 20:E5802. [PMID: 31752214 PMCID: PMC6888338 DOI: 10.3390/ijms20225802] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 11/12/2019] [Accepted: 11/15/2019] [Indexed: 12/28/2022] Open
Abstract
'Candidatus Liberibacter asiaticus' (CLas) is one of the causal agents of citrus Huanglongbing (HLB), a bacterial disease of citrus trees that greatly reduces fruit yield and quality. CLas strains produce an array of currently uncharacterized Sec-dependent secretory proteins. In this study, the conserved chromosomally encoded protein CLIBASIA_03875 was identified as a novel Sec-dependent secreted protein. We show that CLIBASIA_03875 contains a putative Sec- secretion signal peptide (SP), a 29 amino acid residue located at the N-terminus, with a mature protein (m3875) of 22 amino acids found to localize in multiple subcellular components of the leaf epidermal cells of Nicotiana benthamiana. When overexpressed via a Potato virus X (PVX)-based expression vector in N. benthamiana, m3875 suppressed programmed cell death (PCD) and the H2O2 accumulation triggered by the pro-apoptotic mouse protein BAX and the Phytophthora infestans elicitin INF1. Overexpression also resulted in a phenotype of dwarfing, leaf deformation and mosaics, suggesting that m3875 has roles in plant immune response, growth, and development. Substitution mutagenesis of the charged amino acid (D7, R9, R11, and K22) with alanine within m3875 did not recover the phenotypes for PCD and normal growth. In addition, the transiently overexpressed m3875 regulated the transcriptional levels of N. benthamiana orthologs of CNGCs (cyclic nucleotide-gated channels), BI-1 (Bax-inhibitor 1), and WRKY33 that are involved in plant defense mechanisms. To our knowledge, m3875 is the first PCD suppressor identified from CLas. Studying the function of this protein provides insight as to how CLas attenuates the host immune responses to proliferate and cause Huanglongbing disease in citrus plants.
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Affiliation(s)
- Chao Zhang
- Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100094, China;
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (X.L.); (Y.F.); (Y.Z.)
| | - Xuefeng Wang
- Citrus Research Institute, Southwest University, Chongqing 400712, China;
| | - Xuelu Liu
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (X.L.); (Y.F.); (Y.Z.)
- Citrus Research Institute, Southwest University, Chongqing 400712, China;
| | - Yanyan Fan
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (X.L.); (Y.F.); (Y.Z.)
- College of Life Science, Shandong Normal University, Jinan 250014, China
| | - Yongqiang Zhang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (X.L.); (Y.F.); (Y.Z.)
| | - Xueping Zhou
- Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100094, China;
| | - Weimin Li
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (X.L.); (Y.F.); (Y.Z.)
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Ying X, Wan M, Hu L, Zhang J, Li H, Lv D. Identification of the Virulence Factors of Candidatus Liberibacter asiaticus via Heterologous Expression in Nicotiana benthamiana using Tobacco Mosaic Virus. Int J Mol Sci 2019; 20:E5575. [PMID: 31717281 PMCID: PMC6888081 DOI: 10.3390/ijms20225575] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 10/31/2019] [Accepted: 11/04/2019] [Indexed: 12/12/2022] Open
Abstract
Huanglongbing (HLB), also known as citrus greening, is the most destructive disease of citrus worldwide. HLB is associated with the non-culturable bacterium, Candidatus Liberibacter asiaticus (CaLas) in the United States. The virulence mechanism of CaLas is largely unknown, partly because of the lack of a mutant library. In this study, Tobacco mosaic virus (TMV) and Nicotiana benthamiana (N. benthamiana) were used for large-scale screening of the virulence factors of CaLas. Agroinfiltration of 60 putative virulence factors in N. benthamiana led to the identification of four candidates that caused severe symptoms in N. benthamiana, such as growth inhibition and cell death. CLIBASIA_05150 and CLIBASIA_04065C (C-terminal of CLIBASIA_04065) could cause cell death in the infiltrated leaves at five days post infiltration. Two low-molecular-weight candidates, CLIBASIA_00470 and CLIBASIA_04025, could inhibit plant growth. By converting start codon to stop codon or frameshifting, the four genes lost their harmful effects to N. benthamiana. It indicated that the four virulence factors functioned at the protein level rather than at the RNA level. The subcellular localization of the four candidates was determined by confocal laser scanning microscope. CLIBASIA_05150 located in the Golgi apparatus; CLIBASIA_04065 located in the mitochondrion; CLIBASIA_00470 and CLIBASIA_04025 distributed in cells as free GFP. The host proteins interacting with the four virulence factors were identified by yeast two-hybrid. The host proteins interacting with CLIBASIA_00470 and CLIBASIA_04025 were overlapping. Based on the phenotypes, the subcellular localization and the host proteins identified by yeast two-hybrid, CLIBASIA_00470 and CLIBASIA_04025, functioned redundantly. The hypothesis of CaLas virulence was proposed. CaLas affects citrus development and suppresses citrus disease resistance, comprehensively, in a complicated manner. Ubiquitin-mediated protein degradation might play a vital role in CaLas virulence. Deep characterization of the interactions between the identified virulence factors and their prey will shed light on HLB. Eventually, it will help in developing HLB-resistant citrus and save the endangered citrus industry worldwide.
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Affiliation(s)
- Xiaobao Ying
- Gulf Coast Research and Education Center, University of Florida, Wimauma, FL 33598, USA;
| | - Mengyuan Wan
- College of Agronomy and Biotechnology, Southwest University, Beibei, Chongqing 400715, China;
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Beibei, Chongqing 400715, China
| | - Linshuang Hu
- Heilongjiang Academy of Agricultural Sciences, Harbin 10086, China; (L.H.); (J.Z.)
| | - Jinghua Zhang
- Heilongjiang Academy of Agricultural Sciences, Harbin 10086, China; (L.H.); (J.Z.)
| | - Hui Li
- College of Agronomy and Biotechnology, Southwest University, Beibei, Chongqing 400715, China;
| | - Dianqiu Lv
- College of Agronomy and Biotechnology, Southwest University, Beibei, Chongqing 400715, China;
- State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Beibei, Chongqing 400715, China
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