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Subedi A, Minsavage GV, Roberts PD, Goss EM, Sharma A, Jones JB. Insights into bs5 resistance mechanisms in pepper against Xanthomonas euvesicatoria through transcriptome profiling. BMC Genomics 2024; 25:711. [PMID: 39044136 PMCID: PMC11267861 DOI: 10.1186/s12864-024-10604-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2024] [Accepted: 07/08/2024] [Indexed: 07/25/2024] Open
Abstract
BACKGROUND Bacterial spot of pepper (BSP), caused by four different Xanthomonas species, primarily X. euvesicatoria (Xe), poses a significant challenge in pepper cultivation. Host resistance is considered the most important approach for BSP control, offering long-term protection and sustainability. While breeding for resistance to BSP for many years focused on dominant R genes, introgression of recessive resistance has been a more recent focus of breeding programs. The molecular interactions underlying recessive resistance remain poorly understood. RESULTS In this study, transcriptomic analyses were performed to elucidate defense responses triggered by Xe race P6 infection by two distinct pepper lines: the Xe-resistant line ECW50R containing bs5, a recessive resistance gene that confers resistance to all pepper Xe races, and the Xe-susceptible line ECW. The results revealed a total of 3357 upregulated and 4091 downregulated genes at 0, 1, 2, and 4 days post-inoculation (dpi), with the highest number of differentially expressed genes (DEGs) observed at 2 dpi. Pathway analysis highlighted DEGs in key pathways such as plant-pathogen interaction, MAPK signaling pathway, plant hormone signal transduction, and photosynthesis - antenna proteins, along with cysteine and methionine metabolism. Notably, upregulation of genes associated with PAMP-Triggered Immunity (PTI) was observed, including components like FLS2, Ca-dependent pathways, Rboh, and reactive oxygen species (ROS) generation. In support of these results, infiltration of ECW50R leaves with bacterial suspension of Xe led to observable hydrogen peroxide accumulation without a rapid increase in electrolyte leakage, suggestive of the absence of Effector-Triggered Immunity (ETI). Furthermore, the study confirmed that bs5 does not disrupt the effector delivery system, as evidenced by incompatible interactions between avirulence genes and their corresponding dominant resistant genes in the bs5 background. CONCLUSION Overall, these findings provide insights into the molecular mechanisms underlying bs5-mediated resistance in pepper against Xe and suggest a robust defense mechanism in ECW50R, primarily mediated through PTI. Given that bs5 provides early strong response for resistance, combining this resistance with other dominant resistance genes will enhance the durability of resistance to BSP.
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Affiliation(s)
- Aastha Subedi
- Department of Plant Pathology, University of Florida, Gainesville, FL, USA
| | - Gerald V Minsavage
- Department of Plant Pathology, University of Florida, Gainesville, FL, USA
| | - Pamela D Roberts
- Southwest Florida Research & Education Center, University of Florida, Immokalee, FL, USA
| | - Erica M Goss
- Department of Plant Pathology, University of Florida, Gainesville, FL, USA
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Anuj Sharma
- Department of Plant Pathology, University of Florida, Gainesville, FL, USA
- Department of Horticultural Sciences, Gulf Coast Research and Education Center, University of Florida, Wimauma, FL, USA
| | - Jeffrey B Jones
- Department of Plant Pathology, University of Florida, Gainesville, FL, USA.
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Su H, Wang Y, Xu J, Omar AA, Grosser JW, Calovic M, Zhang L, Feng Y, Vakulskas CA, Wang N. Generation of the transgene-free canker-resistant Citrus sinensis using Cas12a/crRNA ribonucleoprotein in the T0 generation. Nat Commun 2023; 14:3957. [PMID: 37402755 DOI: 10.1038/s41467-023-39714-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 06/26/2023] [Indexed: 07/06/2023] Open
Abstract
Citrus canker caused by Xanthomonas citri subsp. citri (Xcc) is a destructive citrus disease worldwide. Generating disease-resistant cultivars is the most effective, environmentally friendly and economic approach for disease control. However, citrus traditional breeding is lengthy and laborious. Here, we develop transgene-free canker-resistant Citrus sinensis lines in the T0 generation within 10 months through transformation of embryogenic protoplasts with Cas12a/crRNA ribonucleoprotein to edit the canker susceptibility gene CsLOB1. Among the 39 regenerated lines, 38 are biallelic/homozygous mutants, demonstrating a 97.4% biallelic/homozygous mutation rate. No off-target mutations are detected in the edited lines. Canker resistance of the cslob1-edited lines results from both abolishing canker symptoms and inhibiting Xcc growth. The transgene-free canker-resistant C. sinensis lines have received regulatory approval by USDA APHIS and are exempted from EPA regulation. This study provides a sustainable and efficient citrus canker control solution and presents an efficient transgene-free genome-editing strategy for citrus and other crops.
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Affiliation(s)
- Hang Su
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, USA
| | - Yuanchun Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, USA
| | - 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, USA
| | - Ahmad A Omar
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, USA
- Biochemistry Department, Faculty of Agriculture, Zagazig University, Zagazig, Egypt
| | - Jude W Grosser
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, USA
| | - Milica Calovic
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, USA
| | - Liyang Zhang
- Integrated DNA Technologies, Inc, Coralville, IA, USA
| | - Yu Feng
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, USA
| | | | - 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, USA.
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de Souza-Neto RR, Vasconcelos FNDC, Teper D, Carvalho IGB, Takita MA, Benedetti CE, Wang N, de Souza AA. The Expansin Gene CsLIEXP1 Is a Direct Target of CsLOB1 in Citrus. PHYTOPATHOLOGY 2023; 113:1266-1277. [PMID: 36825333 DOI: 10.1094/phyto-11-22-0424-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: 06/18/2023]
Abstract
Transcription activator-like effectors are key virulence factors of Xanthomonas. They are secreted into host plant cells and mimic transcription factors inducing the expression of host susceptibility (S) genes. In citrus, CsLOB1 is a direct target of PthA4, the primary effector associated with citrus canker symptoms. CsLOB1 is a transcription factor, and its expression is required for canker symptoms induced by Xanthomonas citri subsp. citri. Several genes are up-regulated by PthA4; however, only CsLOB1 was described as an S gene induced by PthA4. Here, we investigated whether other up-regulated genes could be direct targets of PthA4 or CsLOB1. Seven up-regulated genes by PthA4 were investigated; however, an expansin-coding gene was more induced than CsLOB1. In Nicotiana benthamiana transient expression experiments, we demonstrate that the expansin-coding gene, referred here to as CsLOB1-INDUCED EXPANSIN 1 (CsLIEXP1), is not a direct target of PthA4, but CsLOB1. Interestingly, CsLIEXP1 was induced by CsLOB1 even without the predicted CsLOB1 binding site, which suggested that CsLOB1 has other unknown binding sites. We also investigated the minimum promoter regulated by CsLOB1, and this region and LOB1 domain were conserved among citrus species and relatives, which suggests that the interaction PthA4-CsLOB1-CsLIEXP1 is conserved in citrus species and relatives. This is the first study that experimentally demonstrated a CsLOB1 downstream target and lays the foundation to identify other new targets. In addition, we demonstrated that the CsLIEXP1 is a putative S gene indirectly induced by PthA4, which may serve as the target for genome editing to generate citrus canker-resistant varieties.
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Affiliation(s)
- Reinaldo Rodrigues de Souza-Neto
- Citrus Research Center "Sylvio Moreira", Agronomic Institute-IAC, Brazil
- Departament of Genetics, Evolution and Bioagents, Institute of Biology, University of Campinas, Brazil
| | | | - Doron Teper
- Department of Plant Pathology and Weed Research, Institute of Plant Protection, Agricultural Research Organization, Volcani Center, Israel
| | | | | | - Celso Eduardo Benedetti
- Brazilian Biosciences National Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), Brazil
| | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, U.S.A
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Long Y, Luo R, Xu Z, Cheng S, Li L, Ma H, Bao M, Li M, Ouyang Z, Wang N, Duan S. A Fluorescent Reporter-Based Evaluation Assay for Antibacterial Components Against Xanthomonas citri subsp. citri. Front Microbiol 2022; 13:864963. [PMID: 35602035 PMCID: PMC9114712 DOI: 10.3389/fmicb.2022.864963] [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: 01/29/2022] [Accepted: 04/05/2022] [Indexed: 11/13/2022] Open
Abstract
Xanthomonas citri subsp. citri (Xcc) is the agent of citrus bacterial canker (CBC) disease, which has significantly reduced citrus quantity and quality in many producing areas worldwide. Copper-based bactericides are the primary products for CBC control and management, but the problems derived from copper-resistant and environmental contamination have become issues of anxiety. Thus, there is a need to find alternative antibacterial products instead of relying on a single type of agent. This study developed a method to evaluate the inhibition of antibacterial agents using the fluorescence-labeled recombinant Xcc strain (Xcc-eYFP). The optimization of timelines and parameters for the evaluation of antibacterial agents involved the use of a Spark™ multimode microplate reader. This evaluation and screening method can be applied to bactericides, cocktail-mixture formulations, antagonistic bacteria, and derived metabolites. The results showed that the minimum inhibitory concentration (MIC) of commercial bactericides determined by fluorescence agrees with the MIC values determined by the conventional method. A screened cocktail-mixture bactericide presents more activity than the individual agents during the protective effects. Notably, this method has been further developed in the screening of Xcc-antagonistic bacterial strains. In summary, we provide a validated strategy for screening and evaluation of different antibacterial components for inhibition against Xcc for CBC control and management.
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Affiliation(s)
- Yunfei Long
- China-USA Citrus Huanglongbing Joint Laboratory, National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, China
| | - Ruifang Luo
- China-USA Citrus Huanglongbing Joint Laboratory, National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, China
| | - Zhou Xu
- China-USA Citrus Huanglongbing Joint Laboratory, National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, China
| | - Shuyuan Cheng
- China-USA Citrus Huanglongbing Joint Laboratory, National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, China
| | - Ling Li
- China-USA Citrus Huanglongbing Joint Laboratory, National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, China
| | - Haijie Ma
- College of Agricultural and Food Sciences, Zhejiang A&F University, Hangzhou, China
| | - Minli Bao
- China-USA Citrus Huanglongbing Joint Laboratory, National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, China
| | - Min Li
- China-USA Citrus Huanglongbing Joint Laboratory, National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, China
| | - Zhigang Ouyang
- China-USA Citrus Huanglongbing Joint Laboratory, National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, China
| | - Nian Wang
- Department of Microbiology and Cell Science, Citrus Research and Education Center, University of Florida, Lake Alfred, FL, United States
| | - Shuo Duan
- China-USA Citrus Huanglongbing Joint Laboratory, National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, China
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Duan S, Long Y, Cheng S, Li J, Ouyang Z, Wang N. Rapid Evaluation of the Resistance of Citrus Germplasms Against Xanthomonas citri subsp. citri. PHYTOPATHOLOGY 2022; 112:765-774. [PMID: 34495678 DOI: 10.1094/phyto-04-21-0175-r] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Xanthomonas citri subsp. citri (Xcc) is the causal agent of citrus bacterial canker (CBC), one of the most devastating citrus diseases. Most commercial citrus varieties are susceptible to CBC. However, some citrus varieties and wild citrus germplasms are CBC resistant and are promising in genetic increases in citrus resistance against CBC. We aimed to evaluate citrus germplasms for resistance against CBC. First, we developed a rapid evaluation method based on enhanced yellow fluorescent protein (eYFP)-labeled Xcc. The results demonstrated that eYFP does not affect the growth and virulence of Xcc. Xcc-eYFP allows measurement of bacterial titers but is more efficient and rapid than the plate colony counting method. Next, we evaluated citrus germplasms collected in China. Based on symptoms and bacterial titers, we identified that two citrus germplasms ('Ichang' papeda and 'Huapi' kumquat) are resistant, whereas eight citrus germplasms ('Chongyi' wild mandarin, 'Mangshan' wild mandarin, 'Ledong' kumquat, 'Dali' citron, 'Yiliang' citron, 'Longyan' kumquat, 'Bawang' kumquat, and 'Daoxian' wild mandarin) are tolerant. In summary, we have developed a rapid evaluation method to test the resistance of citrus plants against CBC. This method was successfully used to identify two highly canker-resistant citrus germplasms and eight citrus germplasms with canker tolerance. These results could be leveraged in traditional breeding contexts or be used to identify canker resistance genes to increase the disease resistance of commercial citrus varieties via biotechnological approaches.
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Affiliation(s)
- Shuo Duan
- Citrus Huanglongbing Joint Laboratory, National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, Jiangxi 341000, China
| | - Yunfei Long
- Citrus Huanglongbing Joint Laboratory, National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, Jiangxi 341000, China
| | - Shuyuan Cheng
- Citrus Huanglongbing Joint Laboratory, National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, Jiangxi 341000, China
| | - Jinyun Li
- Citrus Research and Education Center, Department of Microbiology and Cell Science, University of Florida, Lake Alfred, FL 33850, U.S.A
| | - Zhigang Ouyang
- Citrus Huanglongbing Joint Laboratory, National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, Jiangxi 341000, China
| | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, University of Florida, Lake Alfred, FL 33850, U.S.A
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6
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Huang X, Wang Y, Wang N. Highly Efficient Generation of Canker-Resistant Sweet Orange Enabled by an Improved CRISPR/Cas9 System. FRONTIERS IN PLANT SCIENCE 2022; 12:769907. [PMID: 35087548 PMCID: PMC8787272 DOI: 10.3389/fpls.2021.769907] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 12/09/2021] [Indexed: 06/02/2023]
Abstract
Sweet orange (Citrus sinensis) is the most economically important species for the citrus industry. However, it is susceptible to many diseases including citrus bacterial canker caused by Xanthomonas citri subsp. citri (Xcc) that triggers devastating effects on citrus production. Conventional breeding has not met the challenge to improve disease resistance of sweet orange due to the long juvenility and other limitations. CRISPR-mediated genome editing has shown promising potentials for genetic improvements of plants. Generation of biallelic/homozygous mutants remains difficult for sweet orange due to low transformation rate, existence of heterozygous alleles for target genes, and low biallelic editing efficacy using the CRISPR technology. Here, we report improvements in the CRISPR/Cas9 system for citrus gene editing. Based on the improvements we made previously [dicot codon optimized Cas9, tRNA for multiplexing, a modified sgRNA scaffold with high efficiency, citrus U6 (CsU6) to drive sgRNA expression], we further improved our CRISPR/Cas9 system by choosing superior promoters [Cestrum yellow leaf curling virus (CmYLCV) or Citrus sinensis ubiquitin (CsUbi) promoter] to drive Cas9 and optimizing culture temperature. This system was able to generate a biallelic mutation rate of up to 89% for Carrizo citrange and 79% for Hamlin sweet orange. Consequently, this system was used to generate canker-resistant Hamlin sweet orange by mutating the effector binding element (EBE) of canker susceptibility gene CsLOB1, which is required for causing canker symptoms by Xcc. Six biallelic Hamlin sweet orange mutant lines in the EBE were generated. The biallelic mutants are resistant to Xcc. Biallelic mutation of the EBE region abolishes the induction of CsLOB1 by Xcc. This study represents a significant improvement in sweet orange gene editing efficacy and generating disease-resistant varieties via CRISPR-mediated genome editing. This improvement in citrus genome editing makes genetic studies and manipulations of sweet orange more feasible.
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Teper D, Wang N. Consequences of adaptation of TAL effectors on host susceptibility to Xanthomonas. PLoS Genet 2021; 17:e1009310. [PMID: 33465093 PMCID: PMC7845958 DOI: 10.1371/journal.pgen.1009310] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 01/29/2021] [Accepted: 12/11/2020] [Indexed: 12/03/2022] Open
Abstract
Transcription activator-like effectors (TALEs) are virulence factors of Xanthomonas that induce the expression of host susceptibility (S) genes by specifically binding to effector binding elements (EBEs) in their promoter regions. The DNA binding specificity of TALEs is dictated by their tandem repeat regions, which are highly variable between different TALEs. Mutation of the EBEs of S genes is being utilized as a key strategy to generate resistant crops against TALE-dependent pathogens. However, TALE adaptations through rearrangement of their repeat regions is a potential obstacle for successful implementation of this strategy. We investigated the consequences of TALE adaptations in the citrus pathogen Xanthomonas citri subsp. citri (Xcc), in which PthA4 is the TALE required for pathogenicity, whereas CsLOB1 is the corresponding susceptibility gene, on host resistance. Seven TALEs, containing two-to-nine mismatching-repeats to the EBEPthA4 that were unable to induce CsLOB1 expression, were introduced into Xcc pthA4:Tn5 and adaptation was simulated by repeated inoculations into and isolations from sweet orange for a duration of 30 cycles. While initially all strains failed to promote disease, symptoms started to appear between 9–28 passages in four TALEs, which originally harbored two-to-five mismatches. Sequence analysis of adapted TALEs identified deletions and mutations within the TALE repeat regions which enhanced putative affinity to the CsLOB1 promoter. Sequence analyses suggest that TALEs adaptations result from recombinations between repeats of the TALEs. Reintroduction of these adapted TALEs into Xcc pthA4:Tn5 restored the ability to induce the expression of CsLOB1, promote disease symptoms and colonize host plants. TALEs harboring seven-to-nine mismatches were unable to adapt to overcome the incompatible interaction. Our study experimentally documented TALE adaptations to incompatible EBE and provided strategic guidance for generation of disease resistant crops against TALE-dependent pathogens. Mutation of the EBEs of susceptibility (S) genes via genome editing and utilization of naturally occurring EBE variants have been used to generate disease resistant plants. However, TALE adaptations may lead to resistance loss, limiting the long-term efficacy of the strategy. We utilized an experimental evolution approach to test TALEs adaptations in the Xanthomonas citri-citrus pathosystem using designer TALEs that cannot recognize the EBE of host targets. We identified adaptive TALE mutations and deletions that occurred during less than 30 cycles of repeated infections, which reconstituted the virulence on the host. Adaptive variants originated from TALEs that harbored a small number of mismatches (≤5) to the EBE, whereas designer TALEs that harbored larger number of mismatches (≥7) to the EBE failed to adapt in the duration of this study. Our study experimentally demonstrates adaptive rearrangements of TALEs during host adaptation and suggests that the potential durability in the resistance of modified crops should be a significant factor to be considered prior to their introduction into the field.
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Affiliation(s)
- Doron Teper
- 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
| | - 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
- * E-mail:
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Teper D, Xu J, Li J, Wang N. The immunity of Meiwa kumquat against Xanthomonas citri is associated with a known susceptibility gene induced by a transcription activator-like effector. PLoS Pathog 2020; 16:e1008886. [PMID: 32931525 PMCID: PMC7518600 DOI: 10.1371/journal.ppat.1008886] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 09/25/2020] [Accepted: 08/14/2020] [Indexed: 12/22/2022] Open
Abstract
Citrus canker caused by Xanthomonas citri subsp. citri (Xcc) is one of the most devastating diseases in citrus. Meiwa kumquat (Fortunella crassifolia) has shown a durable resistance against Xcc. Here, we aimed to characterize the mechanisms responsible for such a durable resistance by characterizing the transcriptional and physiological responses of Meiwa kumquat to Xcc. Inoculation of Meiwa kumquat with Xcc promoted immune responses such as upregulation of PR genes, accumulation of salicylic acid, hypersensitive response (HR)-like cell death and early leaf abscission. Hypertrophy and hyperplasia symptoms, which are known to be caused by Xcc-induction of the canker susceptibility gene LOB1 through the transcription activator-like effector (TALE) PthA4, always appear prior to the development of cell death. Mutation of pthA4 in Xcc abolished the induction of LOB1, canker symptoms, cell death, and leaf abscission and reduced the expression of PR genes in inoculated kumquat leaves without reducing Xcc titers in planta. Transcriptome analysis demonstrated that PthA4 promotes plant biotic and abiotic stress responses and the biosynthesis of abscisic acid. Transcriptional induction of LOB1 homologs in Meiwa kumquat by Xcc pthA4 mutant strains carrying a repertoire of designer TALEs promoted the elicitation of HR-like phenotype and leaf abscission, suggesting that kumquat response to Xcc is associated with upregulation of LOB1. Our study suggests a novel mechanism of plant resistance to Xanthomonas via elicitation of immune responses by upregulation of a host susceptibility gene.
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Affiliation(s)
- Doron Teper
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, United States of America
| | - Jin Xu
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, United States of America
| | - Jinyun Li
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, United States of America
| | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, United States of America
- * E-mail:
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Identification of Appropriate Reference Genes for Normalizing miRNA Expression in Citrus Infected by Xanthomonas citri subsp. citri. Genes (Basel) 2019; 11:genes11010017. [PMID: 31877985 PMCID: PMC7017248 DOI: 10.3390/genes11010017] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 12/13/2019] [Accepted: 12/16/2019] [Indexed: 01/01/2023] Open
Abstract
MicroRNAs (miRNAs) are short noncoding RNA molecules that regulate gene expression at the posttranscriptional level. Reverse transcription-quantitative PCR (RT-qPCR) is one of the most common methods used for quantification of miRNA expression, and the levels of expression are normalized by comparing with reference genes. Thus, the selection of reference genes is critically important for accurate quantification. The present study was intended to identify appropriate miRNA reference genes for normalizing the level of miRNA expression in Citrus sinensis L. Osbeck and Citrus reticulata Blanco infected by Xanthomonas citri subsp. citri, which caused citrus canker disease. Five algorithms (Delta Ct, geNorm, NormFinder, BestKeeper and RefFinder) were used for screening reference genes, and two quantification approaches, poly(A) extension RT-qPCR and stem-loop RT-qPCR, were used to determine the most appropriate method for detecting expression patterns of miRNA. An overall comprehensive ranking output derived from the multi-algorithms showed that poly(A)-tailed miR162-3p/miR472 were the best reference gene combination for miRNA RT-qPCR normalization in citrus canker research. Candidate reference gene expression profiles determined by poly(A) RT-qPCR were more consistent in the two citrus species. To the best of our knowledge, this is the first systematic comparison of two miRNA quantification methods for evaluating reference genes. These results highlight the importance of rigorously assessing candidate reference genes and clarify some contradictory results in miRNA research on citrus.
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Medina CA, Reyes PA, Trujillo CA, Gonzalez JL, Bejarano DA, Montenegro NA, Jacobs JM, Joe A, Restrepo S, Alfano JR, Bernal A. The role of type III effectors from Xanthomonas axonopodis pv. manihotis in virulence and suppression of plant immunity. MOLECULAR PLANT PATHOLOGY 2018; 19:593-606. [PMID: 28218447 PMCID: PMC6638086 DOI: 10.1111/mpp.12545] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Revised: 01/25/2017] [Accepted: 02/15/2017] [Indexed: 05/29/2023]
Abstract
Xanthomonas axonopodis pv. manihotis (Xam) causes cassava bacterial blight, the most important bacterial disease of cassava. Xam, like other Xanthomonas species, requires type III effectors (T3Es) for maximal virulence. Xam strain CIO151 possesses 17 predicted T3Es belonging to the Xanthomonas outer protein (Xop) class. This work aimed to characterize nine Xop effectors present in Xam CIO151 for their role in virulence and modulation of plant immunity. Our findings demonstrate the importance of XopZ, XopX, XopAO1 and AvrBs2 for full virulence, as well as a redundant function in virulence between XopN and XopQ in susceptible cassava plants. We tested their role in pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI) using heterologous systems. AvrBs2, XopR and XopAO1 are capable of suppressing PTI. ETI suppression activity was only detected for XopE4 and XopAO1. These results demonstrate the overall importance and diversity in functions of major virulence effectors AvrBs2 and XopAO1 in Xam during cassava infection.
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Affiliation(s)
- Cesar Augusto Medina
- Universidad de los Andes, Laboratorio de Micología y Fitopatología de la Universidad de los Andes111711 BogotáColombia
| | - Paola Andrea Reyes
- Universidad de los Andes, Laboratorio de Micología y Fitopatología de la Universidad de los Andes111711 BogotáColombia
| | - Cesar Augusto Trujillo
- Universidad de los Andes, Laboratorio de Micología y Fitopatología de la Universidad de los Andes111711 BogotáColombia
| | - Juan Luis Gonzalez
- Universidad de los Andes, Laboratorio de Micología y Fitopatología de la Universidad de los Andes111711 BogotáColombia
| | - David Alejandro Bejarano
- Universidad de los Andes, Laboratorio de Micología y Fitopatología de la Universidad de los Andes111711 BogotáColombia
| | - Nathaly Andrea Montenegro
- Universidad de los Andes, Laboratorio de Micología y Fitopatología de la Universidad de los Andes111711 BogotáColombia
| | - Jonathan M. Jacobs
- Institut de Recherche pour le De´veloppement (IRD), CiradUniversite´ Montpellier, Interactions Plantes Microorganismes Environnement (IPME), 34394MontpellierFrance
| | - Anna Joe
- Center for Plant Science InnovationUniversity of NebraskaLincolnNE68588‐0660USA
- Department of Plant PathologyUniversity of NebraskaLincolnNE68588‐0722USA
- Present address:
Department of Plant Pathology and the Genome CenterUniversity of California, Davis, CA 95616, USA, and Joint BioEnergy Institute and Physical Biosciences Division, Lawrence Berkeley National LaboratoryBerkeleyCA94720USA
| | - Silvia Restrepo
- Universidad de los Andes, Laboratorio de Micología y Fitopatología de la Universidad de los Andes111711 BogotáColombia
| | - James R. Alfano
- Center for Plant Science InnovationUniversity of NebraskaLincolnNE68588‐0660USA
- Department of Plant PathologyUniversity of NebraskaLincolnNE68588‐0722USA
| | - Adriana Bernal
- Universidad de los Andes, Laboratorio de Micología y Fitopatología de la Universidad de los Andes111711 BogotáColombia
- Present address:
Novozymes, Inc., DavisCA95618USA
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Duan S, Jia H, Pang Z, Teper D, White F, Jones J, Zhou C, Wang N. Functional characterization of the citrus canker susceptibility gene CsLOB1. MOLECULAR PLANT PATHOLOGY 2018; 19:1908-1916. [PMID: 29461671 PMCID: PMC6638005 DOI: 10.1111/mpp.12667] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Revised: 01/29/2018] [Accepted: 02/16/2018] [Indexed: 05/08/2023]
Abstract
Xanthomonas citri ssp. citri (Xcc) is an important plant-pathogenic bacterium that causes citrus canker disease worldwide. PthA, a transcriptional activator-like (TAL) effector, directs the expression of the canker susceptibility gene CsLOB1. Here, we report our recent progress in the functional characterization of CsLOB1. Subcellular localization analysis of CsLOB1 protein in citrus protoplast revealed that CsLOB1 is primarily localized in the nucleus. We showed that CsLOB1 expression driven by dexamethasone (DEX) in CsLOB1-GR transgenic plants is associated with pustule formation following treatment with DEX. Pustule formation was not observed in DEX-treated wild-type plants and in non-treated CsLOB1-GR transgenic plants. Water soaking is typically associated with symptoms of citrus canker. Weaker water soaking was observed with pustule formation in CsLOB1-GR transgenic plants following DEX treatment. When CsLOB1-GR-transgenic Duncan grapefruit leaves were inoculated with Xcc306ΔpthA4 and treated with DEX, typical canker symptoms, including hypertrophy, hyperplasia and water soaking symptoms, were observed on DEX-treated transgenic plant leaves, but not on mock-treated plants. Twelve citrus genes that are induced by PthA4 are also stimulated by the DEX-induced expression of CsLOB1. As CsLOB1 acts as a transcriptional factor, we identified putative targets of CsLOB1 via bioinformatic and electrophoretic mobility shift assays. Cs2g20600, which encodes a zinc finger C3HC4-type RING finger protein, has been identified to be a direct target of CsLOB1. This study advances our understanding of the function of CsLOB1 and the molecular mechanism of how Xcc causes canker symptoms via CsLOB1.
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Affiliation(s)
- Shuo Duan
- Citrus Research InstituteSouthwest University, Chongqing400712, China
- Department of Microbiology and Cell Science, Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS)University of FloridaLake AlfredFL 33850USA
| | - Hongge Jia
- Department of Microbiology and Cell Science, Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS)University of FloridaLake AlfredFL 33850USA
| | - Zhiqian Pang
- Department of Microbiology and Cell Science, Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS)University of FloridaLake AlfredFL 33850USA
| | - Doron Teper
- Department of Microbiology and Cell Science, Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS)University of FloridaLake AlfredFL 33850USA
| | - Frank White
- Department of Plant PathologyUniversity of FloridaGainesvilleFL 32611USA
| | - Jeffrey Jones
- Department of Plant PathologyUniversity of FloridaGainesvilleFL 32611USA
| | - Changyong Zhou
- Citrus Research InstituteSouthwest University, Chongqing400712, China
| | - Nian Wang
- Department of Microbiology and Cell Science, Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS)University of FloridaLake AlfredFL 33850USA
- China‐USA Citrus Huanglongbing Joint Laboratory (A joint laboratory of The University of Florida's Institute of Food and Agricultural Sciences and Gannan Normal University)National Navel Orange Engineering Research Center, Gannan Normal UniversityGanzhouJiangxiChina
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