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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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Archer L, Kunwar S, Alferez F, Batuman O, Albrecht U. Trunk Injection of Oxytetracycline for Huanglongbing Management in Mature Grapefruit and Sweet Orange Trees. PHYTOPATHOLOGY 2023; 113:1010-1021. [PMID: 36474420 DOI: 10.1094/phyto-09-22-0330-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
Huanglongbing (HLB) is a devastating bacterial disease associated with 'Candidatus Liberibacter asiaticus'. The location of the pathogen within the vasculature of the tree has left growers with limited options for the effective management of the disease. Trunk injection is a crop protection technique that applies therapeutics directly into the xylem of woody tree species and allows for their systemic uptake and transport, which may provide more effective management of vascular diseases such as HLB. In this study, mature 'Valencia' and 'Hamlin' sweet orange (Citrus sinensis) and 'Duncan' grapefruit (C. paradisi) trees were injected with oxytetracycline (OTC) in the spring and/or fall to evaluate the effects of injection timing and response to injection. In addition to seasonal evaluations of tree health and bacterial titer, preharvest fruit drop, yield, and fruit quality were measured at harvest to determine the effects of OTC injection. The benefits associated with injection included a reduction in fruit drop, an increase in fruit yield and fruit size, and improvements in juice quality. However, results varied due to the timing of injection and were not consistent across all three varieties. Residue analysis at different time points after injection suggests that trunk injection effectively delivers therapeutics to mature citrus trees. This study provides fundamental information on the short-term benefits associated with trunk injection of OTC for HLB management in citrus groves. The potential for use of trunk injection at the commercial scale and the possible risks are discussed.
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Affiliation(s)
- Leigh Archer
- Horticultural Sciences Department, University of Florida, Southwest Florida Research and Education Center, University of Florida/IFAS, Immokalee, FL 34142
| | - Sanju Kunwar
- Plant Pathology Department, University of Florida, Southwest Florida Research and Education Center, University of Florida/IFAS, Immokalee, FL 34142
| | - Fernando Alferez
- Horticultural Sciences Department, University of Florida, Southwest Florida Research and Education Center, University of Florida/IFAS, Immokalee, FL 34142
| | - Ozgur Batuman
- Plant Pathology Department, University of Florida, Southwest Florida Research and Education Center, University of Florida/IFAS, Immokalee, FL 34142
| | - Ute Albrecht
- Horticultural Sciences Department, University of Florida, Southwest Florida Research and Education Center, University of Florida/IFAS, Immokalee, FL 34142
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Ribeiro C, Xu J, Hendrich C, Pandey SS, Yu Q, Gmitter FG, Wang N. Seasonal Transcriptome Profiling of Susceptible and Tolerant Citrus Cultivars to Citrus Huanglongbing. PHYTOPATHOLOGY 2023; 113:286-298. [PMID: 36001783 DOI: 10.1094/phyto-05-22-0179-r] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Citrus huanglongbing (HLB) caused by 'Candidatus Liberibacter asiaticus' (CLas) is the most devastating citrus disease worldwide. Most commercial citrus cultivars are susceptible to HLB, with a few more tolerant exceptions such as 'LB8-9' Sugar Belle mandarin. Transcriptomic analyses have been widely used to investigate the potential mechanisms for disease susceptibility, resistance, or tolerance. Previous transcriptomic studies related to HLB mostly focused on single time point data collection. We hypothesize that changes in day length and temperature throughout the seasons have profound effects on citrus-CLas interactions. Here, we conducted RNA-seq analyses on HLB-susceptible Valencia sweet orange and HLB-tolerant mandarin 'LB8-9' in winter, spring, summer, and fall. Significant variations in differentially expressed genes (DEGs) related to HLB were observed among the four seasons. For both cultivars, the highest number of DEGs were found in the spring. CLas infection stimulates the expression of immune-related genes such as NBS-LRR, RLK, RLCK, CDPK, MAPK pathway, reactive oxygen species (ROS), and PR genes in both cultivars, consistent with the model that HLB is a pathogen-triggered immune disease. HLB-positive mandarin 'LB8-9' trees contained higher concentrations of maltose and sucrose, which are known to scavenge ROS. In addition, mandarin 'LB8-9' showed higher expression of genes involved in phloem regeneration, which might contribute to its HLB tolerance. This study shed light on the pathogenicity mechanism of the HLB pathosystem and the tolerance mechanism against HLB, providing valuable insights into HLB management.
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Affiliation(s)
- Camila Ribeiro
- Citrus Research & Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL 33850
| | - Jin Xu
- Citrus Research & Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL 33850
| | - Connor Hendrich
- Citrus Research & Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL 33850
| | - Sheo Shankar Pandey
- Citrus Research & Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL 33850
| | - Qibin Yu
- Citrus Research & Education Center, Plant Molecular and Cellular Biology Program, Horticultural Sciences Department, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL 33850
| | - Frederick G Gmitter
- Citrus Research & Education Center, Plant Molecular and Cellular Biology Program, Horticultural Sciences Department, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL 33850
| | - Nian Wang
- Citrus Research & Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL 33850
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Yang C, Ancona V. An Overview of the Mechanisms Against " Candidatus Liberibacter asiaticus": Virulence Targets, Citrus Defenses, and Microbiome. Front Microbiol 2022; 13:850588. [PMID: 35391740 PMCID: PMC8982080 DOI: 10.3389/fmicb.2022.850588] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Accepted: 02/18/2022] [Indexed: 12/01/2022] Open
Abstract
Citrus Huanglongbing (HLB) or citrus greening, is the most destructive disease for citrus worldwide. It is caused by the psyllid-transmitted, phloem-limited bacteria "Candidatus Liberibacter asiaticus" (CLas). To date, there are still no effective practical strategies for curing citrus HLB. Understanding the mechanisms against CLas can contribute to the development of effective approaches for combatting HLB. However, the unculturable nature of CLas has hindered elucidating mechanisms against CLas. In this review, we summarize the main aspects that contribute to the understanding about the mechanisms against CLas, including (1) CLas virulence targets, focusing on inhibition of virulence genes; (2) activation of citrus host defense genes and metabolites of HLB-tolerant citrus triggered by CLas, and by agents; and (3) we also review the role of citrus microbiome in combatting CLas. Finally, we discuss novel strategies to continue studying mechanisms against CLas and the relationship of above aspects.
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Affiliation(s)
- Chuanyu Yang
- Department of Agriculture, Agribusiness, and Environmental Sciences, Citrus Center, Texas A&M University-Kingsville, Weslaco, TX, United States
| | - Veronica Ancona
- Department of Agriculture, Agribusiness, and Environmental Sciences, Citrus Center, Texas A&M University-Kingsville, Weslaco, TX, United States
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Li X, Ruan H, Zhou C, Meng X, Chen W. Controlling Citrus Huanglongbing: Green Sustainable Development Route Is the Future. FRONTIERS IN PLANT SCIENCE 2021; 12:760481. [PMID: 34868155 PMCID: PMC8636133 DOI: 10.3389/fpls.2021.760481] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 10/06/2021] [Indexed: 05/12/2023]
Abstract
Huanglongbing (HLB) is the most severe bacterial disease of citrus crops caused by Candidatus Liberibacter spp. It causes a reduction in fruit yield, poor fruit quality, and even plants death. Due to the lack of effective medicine, HLB is also called citrus "AIDS." Currently, it is essential for the prevention and control of HLB to use antibiotics and pesticides while reducing the spread of HLB by cultivating pathogen-free seedlings, removing disease trees, and killing Asian citrus psyllid (ACP). New compounds [e.g., antimicrobial peptides (AMPs) and nanoemulsions] with higher effectiveness and less toxicity were also found and they have made significant achievements. However, further evaluation is required before these new antimicrobial agents can be used commercially. In this review, we mainly introduced the current strategies from the aspects of physical, chemical, and biological and discussed their environmental impacts. We also proposed a green and ecological strategy for controlling HLB basing on the existing methods and previous research results.
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Affiliation(s)
- Xue Li
- MOE Key Laboratory of Laser Life Science, Institute of Laser Life Science, Guangzhou, China
- Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou, China
| | - Huaqin Ruan
- State Key Laboratory of Biocontrol and Guangdong Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Chengqian Zhou
- Neuroscience Laboratory, Hugo Moser Research Institute at Kennedy Krieger, Baltimore, MD, United States
| | - Xiangchun Meng
- Key Laboratory of South Subtropical Fruit Biology and Genetic Resource Utilization (MOA), Guangzhou, China
- Key Laboratory of Tropical and Subtropical Fruit Tree Research, Guangzhou, China
- Institute of Fruit Tree Research, Guangdong Academy of Agricultural Science, Guangzhou, China
| | - Wenli Chen
- MOE Key Laboratory of Laser Life Science, Institute of Laser Life Science, Guangzhou, China
- Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou, China
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Nan J, Zhang S, Zhan P, Jiang L. Discovery of Novel GMPS Inhibitors of Candidatus Liberibacter Asiaticus by Structure Based Design and Enzyme Kinetic. BIOLOGY 2021; 10:biology10070594. [PMID: 34203217 PMCID: PMC8301025 DOI: 10.3390/biology10070594] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 06/24/2021] [Accepted: 06/25/2021] [Indexed: 12/12/2022]
Abstract
Simple Summary The spread of citrus Huanglongbing caused significant damage to the world’s citrus industry. Thermotherapy and chemical agents were used to control this disease; however, the effectiveness of these treatments is frequently inconsistent. In addition, CLas cannot be cultured in vitro. Therefore, structure-based virtual screening is a novel method to find compounds that work against CLas. This study used CLas GMPS as a target for high-throughput screening and selected some compounds which have a higher binding affinity to test their inhibition of CLas GMPS. Finally, two molecules were identified as the lead compound to control citrus HLB. Abstract Citrus production is facing an unprecedented problem because of huanglongbing (HLB) disease. Presently, no effective HLB-easing method is available when citrus becomes infected. Guanosine 5′-monophosphate synthetase (GMPS) is a key protein in the de novo synthesis of guanine nucleotides. GMPS is used as an attractive target for developing agents that are effective against the patogen infection. In this research, homology modeling, structure-based virtual screening, and molecular docking were used to discover the new inhibitors against CLas GMPS. Enzyme assay showed that folic acid and AZD1152 showed high inhibition at micromole concentrations, with AZD1152 being the most potent molecule. The inhibition constant (Ki) value of folic acid and AZD1152 was 51.98 µM and 4.05 µM, respectively. These results suggested that folic acid and AZD1152 could be considered as promising candidates for the development of CLas agents.
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Affiliation(s)
- Jing Nan
- Ministry of Education Key Laboratory of Plant Biology, Huazhong Agricultural University, Wuhan 430070, China; (J.N.); (P.Z.)
| | - Shaoran Zhang
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China;
| | - Ping Zhan
- Ministry of Education Key Laboratory of Plant Biology, Huazhong Agricultural University, Wuhan 430070, China; (J.N.); (P.Z.)
| | - Ling Jiang
- Ministry of Education Key Laboratory of Plant Biology, Huazhong Agricultural University, Wuhan 430070, China; (J.N.); (P.Z.)
- Correspondence:
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