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Jia H, Omar AA, Xu J, Dalmendray J, Wang Y, Feng Y, Wang W, Hu Z, Grosser JW, Wang N. Generation of transgene-free canker-resistant Citrus sinensis cv. Hamlin in the T0 generation through Cas12a/CBE co-editing. FRONTIERS IN PLANT SCIENCE 2024; 15:1385768. [PMID: 38595767 PMCID: PMC11002166 DOI: 10.3389/fpls.2024.1385768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Accepted: 03/15/2024] [Indexed: 04/11/2024]
Abstract
Citrus canker disease affects citrus production. This disease is caused by Xanthomonas citri subsp. citri (Xcc). Previous studies confirmed that during Xcc infection, PthA4, a transcriptional activator like effector (TALE), is translocated from the pathogen to host plant cells. PthA4 binds to the effector binding elements (EBEs) in the promoter region of canker susceptibility gene LOB1 (EBEPthA4-LOBP) to activate its expression and subsequently cause canker symptoms. Previously, the Cas12a/CBE co-editing method was employed to disrupt EBEPthA4-LOBP of pummelo, which is highly homozygous. However, most commercial citrus cultivars are heterozygous hybrids and more difficult to generate homozygous/biallelic mutants. Here, we employed Cas12a/CBE co-editing method to edit EBEPthA4-LOBP of Hamlin (Citrus sinensis), a commercial heterozygous hybrid citrus cultivar grown worldwide. Binary vector GFP-p1380N-ttLbCas12a:LOBP1-mPBE:ALS2:ALS1 was constructed and shown to be functional via Xcc-facilitated agroinfiltration in Hamlin leaves. This construct allows the selection of transgene-free regenerants via GFP, edits ALS to generate chlorsulfuron-resistant regenerants as a selection marker for genome editing resulting from transient expression of the T-DNA via nCas9-mPBE:ALS2:ALS1, and edits gene(s) of interest (i.e., EBEPthA4-LOBP in this study) through ttLbCas12a, thus creating transgene-free citrus. Totally, 77 plantlets were produced. Among them, 8 plantlets were transgenic plants (#HamGFP1 - #HamGFP8), 4 plantlets were transgene-free (#HamNoGFP1 - #HamNoGFP4), and the rest were wild type. Among 4 transgene-free plantlets, three lines (#HamNoGFP1, #HamNoGFP2 and #HamNoGFP3) contained biallelic mutations in EBEpthA4, and one line (#HamNoGFP4) had homozygous mutations in EBEpthA4. We achieved 5.2% transgene-free homozygous/biallelic mutation efficiency for EBEPthA4-LOBP in C. sinensis cv. Hamlin, compared to 1.9% mutation efficiency for pummelo in a previous study. Importantly, the four transgene-free plantlets and 3 transgenic plantlets that survived were resistant against citrus canker. Taken together, Cas12a/CBE co-editing method has been successfully used to generate transgene-free canker-resistant C. sinensis cv. Hamlin in the T0 generation via biallelic/homozygous editing of EBEpthA4 of the canker susceptibility gene LOB1.
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Affiliation(s)
- Hongge Jia
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL, United States
| | - Ahmad A. Omar
- Citrus Research and Education Center, Horticultural Sciences Department, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL, United States
- Biochemistry Department, Faculty of Agriculture, Zagazig University, Zagazig, Egypt
| | - Jin Xu
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL, United States
| | - Javier Dalmendray
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL, United States
| | - Yuanchun Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL, United States
| | - Yu Feng
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL, United States
| | - Wenting Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL, United States
| | - Zhuyuan Hu
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL, United States
| | - Jude W. Grosser
- Citrus Research and Education Center, Horticultural Sciences Department, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL, United States
| | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL, United States
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Manchanda P, Kaur H, Khan F, Sidhu GS, Hunjan MS, Chhuneja P, Bains NS. RETRACTED ARTICLE: Agroinfiltration-based transient genome editing for targeting phytoene desaturase gene in kinnow mandarin (C. reticulata Blanco). Mol Biotechnol 2023:10.1007/s12033-023-00980-z. [PMID: 38041775 DOI: 10.1007/s12033-023-00980-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 11/01/2023] [Indexed: 12/03/2023]
Affiliation(s)
- Pooja Manchanda
- School of Agricultural Biotechnology, Punjab Agricultural University, Ludhiana, 141004, India.
| | - Harleen Kaur
- School of Agricultural Biotechnology, Punjab Agricultural University, Ludhiana, 141004, India
| | - Faishal Khan
- School of Agricultural Biotechnology, Punjab Agricultural University, Ludhiana, 141004, India
| | - Gurupkar S Sidhu
- School of Agricultural Biotechnology, Punjab Agricultural University, Ludhiana, 141004, India
| | - Mandeep S Hunjan
- Department of Plant Pathology, Punjab Agricultural University, Ludhiana, 141004, India
| | - Parveen Chhuneja
- School of Agricultural Biotechnology, Punjab Agricultural University, Ludhiana, 141004, India
| | - Navtej S Bains
- School of Agricultural Biotechnology, Punjab Agricultural University, Ludhiana, 141004, India
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Shantharaj D, Minsavage GV, Orbović V, Moore GA, Holmes DR, Römer P, Horvath DM, Lahaye T, Jones JB. A promoter trap in transgenic citrus mediates recognition of a broad spectrum of Xanthomonas citri pv. citri TALEs, including in planta-evolved derivatives. PLANT BIOTECHNOLOGY JOURNAL 2023; 21:2019-2032. [PMID: 37421233 PMCID: PMC10502743 DOI: 10.1111/pbi.14109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2023] [Revised: 06/09/2023] [Accepted: 06/12/2023] [Indexed: 07/10/2023]
Abstract
Citrus bacterial canker (CBC), caused by Xanthomonas citri subsp. citri (Xcc), causes dramatic losses to the citrus industry worldwide. Transcription activator-like effectors (TALEs), which bind to effector binding elements (EBEs) in host promoters and activate transcription of downstream host genes, contribute significantly to Xcc virulence. The discovery of the biochemical context for the binding of TALEs to matching EBE motifs, an interaction commonly referred to as the TALE code, enabled the in silico prediction of EBEs for each TALE protein. Using the TALE code, we engineered a synthetic resistance (R) gene, called the Xcc-TALE-trap, in which 14 tandemly arranged EBEs, each capable of autonomously recognizing a particular Xcc TALE, drive the expression of Xanthomonas avrGf2, which encodes a bacterial effector that induces plant cell death. Analysis of a corresponding transgenic Duncan grapefruit showed that transcription of the cell death-inducing executor gene, avrGf2, was strictly TALE-dependent and could be activated by several different Xcc TALE proteins. Evaluation of Xcc strains from different continents showed that the Xcc-TALE-trap mediates resistance to this global panel of Xcc isolates. We also studied in planta-evolved TALEs (eTALEs) with novel DNA-binding domains and found that these eTALEs also activate the Xcc-TALE-trap, suggesting that the Xcc-TALE-trap is likely to confer durable resistance to Xcc. Finally, we show that the Xcc-TALE-trap confers resistance not only in laboratory infection assays but also in more agriculturally relevant field studies. In conclusion, transgenic plants containing the Xcc-TALE-trap offer a promising sustainable approach to control CBC.
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Affiliation(s)
| | | | - Vladimir Orbović
- Citrus Research and Education CenterUniversity of FloridaLake AlfredFLUSA
| | - Gloria A. Moore
- Department of Horticultural SciencesUniversity of FloridaGainesvilleFLUSA
| | - Danalyn R. Holmes
- Zentrum für Molekularbiologie der Pflanzen (ZMBP)Eberhard‐Karls‐Universität TübingenTübingenGermany
| | - Patrick Römer
- Genetics, Department of BiologyLudwig‐Maximilians‐University MunichMartinsriedGermany
- Present address:
Avicare+KöthenGermany
| | | | - Thomas Lahaye
- Zentrum für Molekularbiologie der Pflanzen (ZMBP)Eberhard‐Karls‐Universität TübingenTübingenGermany
- Genetics, Department of BiologyLudwig‐Maximilians‐University MunichMartinsriedGermany
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Huang X, Jia H, Xu J, Wang Y, Wen J, Wang N. Transgene-free genome editing of vegetatively propagated and perennial plant species in the T0 generation via a co-editing strategy. NATURE PLANTS 2023; 9:1591-1597. [PMID: 37723203 DOI: 10.1038/s41477-023-01520-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2023] [Accepted: 08/22/2023] [Indexed: 09/20/2023]
Abstract
Transgene-free plant genome editing in the T0 generation is highly desirable but challenging1,2. Here we achieved such a goal using a co-editing strategy via Agrobacterium-mediated transient expression of cytosine base editor to edit ALS encoding acetolactate synthase to confer herbicide chlorsulfuron resistance as a selection marker, Cas12a/CRISPR RNA for editing gene(s) of interest, and green fluorescent protein for selecting transgene-free transformants. The biallelic/homozygous transgene-free mutation rates for target genes among herbicide-resistant transformants ranged from 1.9% to 42.1% in tomato, tobacco, potato and citrus. This co-editing strategy is particularly useful for transgene-free genome editing of vegetatively propagated and perennial plant species in the T0 generation.
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Affiliation(s)
- Xiaoen Huang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, USA
| | - Hongge Jia
- 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
| | - 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
| | - Jiawen Wen
- Citrus Research and Education Center, Department of Plant Pathology, 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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Sardar A. Genetic amelioration of fruit and vegetable crops to increase biotic and abiotic stress resistance through CRISPR Genome Editing. FRONTIERS IN PLANT SCIENCE 2023; 14:1260102. [PMID: 37841604 PMCID: PMC10570431 DOI: 10.3389/fpls.2023.1260102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 08/28/2023] [Indexed: 10/17/2023]
Abstract
Environmental changes and increasing population are major concerns for crop production and food security as a whole. To address this, researchers had focussed on the improvement of cereals and pulses and have made considerable progress till the beginning of this decade. However, cereals and pulses together, without vegetables and fruits, are inadequate to meet the dietary and nutritional demands of human life. Production of good quality vegetables and fruits is highly challenging owing to their perishable nature and short shelf life as well as abiotic and biotic stresses encountered during pre- and post-harvest. Genetic engineering approaches to produce good quality, to increase shelf life and stress-resistance, and to change the time of flowering and fruit ripening by introducing foreign genes to produce genetically modified crops were quite successful. However, several biosafety concerns, such as the risk of transgene-outcrossing, limited their production, marketing, and consumption. Modern genome editing techniques, like the CRISPR/Cas9 system, provide a perfect solution in this scenario, as it can produce transgene-free genetically edited plants. Hence, these genetically edited plants can easily satisfy the biosafety norms for crop production and consumption. This review highlights the potential of the CRISPR/Cas9 system for the successful generation of abiotic and biotic stress resistance and thereby improving the quality, yield, and overall productivity of vegetables and fruits.
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Affiliation(s)
- Atish Sardar
- Department of Botany, Jogesh Chandra Chaudhuri College, West Bengal, Kolkata, India
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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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Teper D, White FF, Wang N. The Dynamic Transcription Activator-Like Effector Family of Xanthomonas. PHYTOPATHOLOGY 2023; 113:651-666. [PMID: 36449529 DOI: 10.1094/phyto-10-22-0365-kd] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Transcription activator-like effectors (TALEs) are bacterial proteins that are injected into the eukaryotic nucleus to act as transcriptional factors and function as key virulence factors of the phytopathogen Xanthomonas. TALEs are translocated into plant host cells via the type III secretion system and induce the expression of host susceptibility (S) genes to facilitate disease. The unique modular DNA binding domains of TALEs comprise an array of nearly identical direct repeats that enable binding to DNA targets based on the recognition of a single nucleotide target per repeat. The very nature of TALE structure and function permits the proliferation of TALE genes and evolutionary adaptations in the host to counter TALE function, making the TALE-host interaction the most dynamic story in effector biology. The TALE genes appear to be a relatively young effector gene family, with a presence in all virulent members of some species and absent in others. Genome sequencing has revealed many TALE genes throughout the xanthomonads, and relatively few have been associated with a cognate S gene. Several species, including Xanthomonas oryzae pv. oryzae and X. citri pv. citri, have near absolute requirement for TALE gene function, while the genes appear to be just now entering the disease interactions with new fitness contributions to the pathogens of tomato and pepper among others. Deciphering the simple and effective DNA binding mechanism also has led to the development of DNA manipulation tools in fields of gene editing and transgenic research. In the three decades since their discovery, TALE research remains at the forefront of the study of bacterial evolution, plant-pathogen interactions, and synthetic biology. We also discuss critical questions that remain to be addressed regarding TALEs.
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Affiliation(s)
- Doron Teper
- Department of Plant Pathology and Weed Research, Agricultural Research Organization, Volcani Institute, Rishon LeZion, Israel
| | - Frank F White
- Department of Plant Pathology, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Gainesville, FL, U.S.A
| | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, IFAS, University of Florida, Lake Alfred, FL, U.S.A
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Bowen JK, Brummell DA, Gapper NE. Biotechnological approaches for reducing fruit losses caused by pathogenic infection. Curr Opin Biotechnol 2022; 78:102795. [PMID: 36116332 DOI: 10.1016/j.copbio.2022.102795] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 08/09/2022] [Accepted: 08/12/2022] [Indexed: 12/14/2022]
Abstract
Fruit loss due to disease occurs in both the field and postharvest. Knowledge of host immune responses and pathogen virulence is enabling the formulation of increasingly sophisticated strategies for disease control. Traditional genetic modification, typically involving overexpression of genes involved in pathogen perception and defence responses, is beginning to be superseded by CRISPR-Cas9 manipulation of host susceptibility targets. Moreover, the refinement of RNA interference (RNAi) strategies, including spray-induced gene silencing (SIGS), is allowing more nuanced control options. These latter approaches have the advantage over earlier technologies in that either they do not result in the generation of genetically modified organisms (RNAi-based SIGS), or the genetic manipulation used leaves no trace of introduced genetic material (gene editing). Thus, these strategies may be more widely acceptable for deployment for future disease control.
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Affiliation(s)
- Joanna K Bowen
- The New Zealand Institute for Plant and Food Research Limited, Mount Albert Research Centre, Private Bag 92169, Auckland 1142, New Zealand
| | - David A Brummell
- The New Zealand Institute for Plant and Food Research Limited, Food Industry Science Centre, Private Bag 11600, Palmerston North 4442, New Zealand
| | - Nigel E Gapper
- The New Zealand Institute for Plant and Food Research Limited, Mount Albert Research Centre, Private Bag 92169, Auckland 1142, New Zealand.
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Huang X, Wang Y, Wang N. Base Editors for Citrus Gene Editing. Front Genome Ed 2022; 4:852867. [PMID: 35296063 PMCID: PMC8919994 DOI: 10.3389/fgeed.2022.852867] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 02/10/2022] [Indexed: 11/22/2022] Open
Abstract
Base editors, such as adenine base editors (ABE) and cytosine base editors (CBE), provide alternatives for precise genome editing without generating double-strand breaks (DSBs), thus avoiding the risk of genome instability and unpredictable outcomes caused by DNA repair. Precise gene editing mediated by base editors in citrus has not been reported. Here, we have successfully adapted the ABE to edit the TATA box in the promoter region of the canker susceptibility gene LOB1 from TATA to CACA in grapefruit (Citrus paradise) and sweet orange (Citrus sinensis). TATA-edited plants are resistant to the canker pathogen Xanthomonas citri subsp. citri (Xcc). In addition, CBE was successfully used to edit the acetolactate synthase (ALS) gene in citrus. ALS-edited plants were resistant to the herbicide chlorsulfuron. Two ALS-edited plants did not show green fluorescence although the starting construct for transformation contains a GFP expression cassette. The Cas9 gene was undetectable in the herbicide-resistant citrus plants. This indicates that the ALS edited plants are transgene-free, representing the first transgene-free gene-edited citrus using the CRISPR technology. In summary, we have successfully adapted the base editors for precise citrus gene editing. The CBE base editor has been used to generate transgene-free citrus via transient expression.
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