1
|
Su H, Wang Y, Xu J, Omar AA, Grosser JW, Wang N. Cas12a RNP-mediated co-transformation enables transgene-free multiplex genome editing, long deletions, and inversions in citrus chromosome. FRONTIERS IN PLANT SCIENCE 2024; 15:1448807. [PMID: 39148610 PMCID: PMC11324552 DOI: 10.3389/fpls.2024.1448807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/13/2024] [Accepted: 07/19/2024] [Indexed: 08/17/2024]
Abstract
Introduction Citrus canker, caused by Xanthomonas citri subsp. citri (Xcc), is a devastating disease worldwide. Previously, we successfully generated canker-resistant Citrus sinensis cv. Hamlin lines in the T0 generation. This was achieved through the transformation of embryogenic protoplasts using the ribonucleoprotein (RNP) containing Cas12a and one crRNA to edit the canker susceptibility gene, CsLOB1, which led to small indels. Methods Here, we transformed embryogenic protoplasts of Hamlin with RNP containing Cas12a and three crRNAs. Results Among the 10 transgene-free genome-edited lines, long deletions were obtained in five lines. Additionally, inversions were observed in three of the five edited lines with long deletions, but not in any edited lines with short indel mutations, suggesting long deletions maybe required for inversions. Biallelic mutations were observed for each of the three target sites in four of the 10 edited lines when three crRNAs were used, demonstrating that transformation of embryogenic citrus protoplasts with Cas12a and three crRNAs RNP can be very efficient for multiplex editing. Our analysis revealed the absence of off-target mutations in the edited lines. These cslob1 mutant lines were canker- resistant and no canker symptoms were observed after inoculation with Xcc and Xcc growth was significantly reduced in the cslob1 mutant lines compared to the wild type plants. Discussion Taken together, RNP (Cas12a and three crRNAs) transformation of embryogenic protoplasts of citrus provides a promising solution for transgene-free multiplex genome editing with high efficiency and for deletion of long fragments.
Collapse
Affiliation(s)
- Hang Su
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
- Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
| | - Yuanchun Wang
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
- Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
| | - Jin Xu
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
- Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
| | - Ahmad A Omar
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
- Department of Horticultural Sciences, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
| | - Jude W Grosser
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
- Department of Horticultural Sciences, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
| | - Nian Wang
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
- Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
| |
Collapse
|
2
|
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.
Collapse
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
| |
Collapse
|
3
|
Ma H, Meng X, Xu K, Li M, Gmitter FG, Liu N, Gai Y, Huang S, Wang M, Wang M, Wang N, Xu H, Liu J, Sun X, Duan S. Highly efficient hairy root genetic transformation and applications in citrus. FRONTIERS IN PLANT SCIENCE 2022; 13:1039094. [PMID: 36388468 PMCID: PMC9647159 DOI: 10.3389/fpls.2022.1039094] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 10/10/2022] [Indexed: 06/16/2023]
Abstract
Highly efficient genetic transformation technology is greatly beneficial for crop gene function analysis and precision breeding. However, the most commonly used genetic transformation technology for woody plants, mediated by Agrobacterium tumefaciens, is time-consuming and inefficient, which limits its utility for gene function analysis. In this study, a simple, universal, and highly efficient genetic transformation technology mediated by A. rhizogenes K599 is described. This technology can be applied to multiple citrus genotypes, and only 2-8 weeks were required for the entire workflow. Genome-editing experiments were simultaneously conducted using 11 plasmids targeting different genomic positions and all corresponding transformants with the target knocked out were obtained, indicating that A. rhizogenes-mediated genome editing was highly efficient. In addition, the technology is advantageous for investigation of specific genes (such as ACD2) for obtaining "hard-to-get" transgenic root tissue. Furthermore, A. rhizogenes can be used for direct viral vector inoculation on citrus bypassing the requirement for virion enrichment in tobacco, which facilitates virus-induced gene silencing and virus-mediated gene expression. In summary, we established a highly efficient genetic transformation technology bypassing tissue culture in citrus that can be used for genome editing, gene overexpression, and virus-mediated gene function analysis. We anticipate that by reducing the cost, required workload, experimental period, and other technical obstacles, this genetic transformation technology will be a valuable tool for routine investigation of endogenous and exogenous genes in citrus.
Collapse
Affiliation(s)
- Haijie Ma
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou, Zhejiang, China
| | - Xinyue Meng
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou, Zhejiang, China
| | - Kai Xu
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou, Zhejiang, China
| | - Min Li
- 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 University, Ganzhou, Jiangxi, China
| | - Fred G. Gmitter
- Citrus Research and Education Center, Horticultural Sciences Department, University of Florida, Lake Alfred, FL, United States
| | - Ningge Liu
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou, Zhejiang, China
| | - Yunpeng Gai
- School of Grassland Science, Beijing Forestry University, Beijing, China
| | - Suya Huang
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou, Zhejiang, China
| | - Min Wang
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou, Zhejiang, China
| | - Min Wang
- 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 University, Ganzhou, Jiangxi, China
| | - Nian Wang
- Citrus Research and Education Center, Horticultural Sciences Department, University of Florida, Lake Alfred, FL, United States
| | - Hairen Xu
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou, Zhejiang, China
| | - Jinhua Liu
- Natural Medicine Institute of Zhejiang YangShengTang Co., LTD, Hangzhou, Zhejiang, China
| | - Xuepeng Sun
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou, Zhejiang, China
| | - Shuo Duan
- 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 University, Ganzhou, Jiangxi, China
| |
Collapse
|
4
|
Mahmoud LM, Kaur P, Stanton D, Grosser JW, Dutt M. A cationic lipid mediated CRISPR/Cas9 technique for the production of stable genome edited citrus plants. PLANT METHODS 2022; 18:33. [PMID: 35303912 PMCID: PMC8932238 DOI: 10.1186/s13007-022-00870-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Accepted: 03/05/2022] [Indexed: 05/09/2023]
Abstract
BACKGROUND The genetic engineering of crops has enhanced productivity in the face of climate change and a growing global population by conferring desirable genetic traits, including the enhancement of biotic and abiotic stress tolerance, to improve agriculture. The clustered regularly interspaced short palindromic repeats (CRISPR/Cas9) system has been found to be a promising technology for genomic editing. Protoplasts are often utilized for the development of genetically modified plants through in vitro integration of a recombinant DNA fragment into the plant genome. We targeted the citrus Nonexpressor of Pathogenesis-Related 3 (CsNPR3) gene, a negative regulator of systemic acquired resistance (SAR) that governs the proteasome-mediated degradation of NPR1 and developed a genome editing technique targeting citrus protoplast DNA to produce stable genome-edited citrus plants. RESULTS Here, we determined the best cationic lipid nanoparticles to deliver donor DNA and described a protocol using Lipofectamine™ LTX Reagent with PLUS Reagent to mediate DNA delivery into citrus protoplasts. A Cas9 construct containing a gRNA targeting the CsNPR3 gene was transfected into citrus protoplasts using the cationic lipid transfection agent Lipofectamine with or without polyethylene glycol (PEG, MW 6000). The optimal transfection efficiency for the encapsulation was 30% in Lipofectamine, 51% in Lipofectamine with PEG, and 2% with PEG only. Additionally, plasmid encapsulation in Lipofectamine resulted in the highest cell viability percentage (45%) compared with PEG. Nine edited plants were obtained and identified based on the T7EI assay and Sanger sequencing. The developed edited lines exhibited downregulation of CsNPR3 expression and upregulation of CsPR1. CONCLUSIONS Our results demonstrate that utilization of the cationic lipid-based transfection agent Lipofectamine is a viable option for the successful delivery of donor DNA and subsequent successful genome editing in citrus.
Collapse
Affiliation(s)
- Lamiaa M Mahmoud
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL, 33850, USA
- Pomology Department, Faculty of Agriculture, Mansoura University, Mansoura, Egypt
| | - Prabhjot Kaur
- Department of Horticulture, Michigan State University, East Lansing, MI, 48824, USA
| | - Daniel Stanton
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL, 33850, USA
| | - Jude W Grosser
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL, 33850, USA
| | - Manjul Dutt
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL, 33850, USA.
| |
Collapse
|
5
|
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] [Key Words] [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.
Collapse
|
6
|
Jia H, Omar AA, Orbović V, Wang N. Biallelic Editing of the LOB1 Promoter via CRISPR/Cas9 Creates Canker-Resistant 'Duncan' Grapefruit. PHYTOPATHOLOGY 2022; 112:308-314. [PMID: 34213958 DOI: 10.1094/phyto-04-21-0144-r] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Citrus canker caused by Xanthomonas citri subsp. citri is one of the most devastating citrus diseases worldwide. Generating disease-resistant citrus varieties is considered one of the most efficient and environmentally friendly measures for controlling canker. X. citri subsp. citri causes canker symptoms by inducing the expression of canker susceptibility gene LOB1 via PthA4, a transcription activator-like (TAL) effector, by binding to the effector binding element (EBE) in the promoter region. In previous studies, canker-resistant plants were generated by mutating the coding region or the EBE of LOB1. However, homozygous or biallelic canker-resistant plants have not been generated for commercial citrus varieties, such as grapefruit (Citrus paradisi), which usually contain two alleles of LOB1 and thus, have two types of LOB1 promoter sequences: TI LOBP and TII LOBP. Two different sgRNAs were used to target both EBE types. Both 35S promoter and Yao promoter were used to drive the expression of SpCas9p to modify EBEPthA4-LOBP in grapefruit. Using 'Duncan' grapefruit epicotyls as explants, 19 genome-edited grapefruit plants were generated with one biallelic mutant line (#DunYao7). X. citri subsp. citri caused canker symptoms on wild-type and nonbiallelic mutant plants but not on #DunYao7. XccPthA4 mutant containing the designer TAL effector dLOB1.5, which recognizes a conserved sequence in both wild-type and #DunYao7, caused canker symptoms on both wild-type and #DunYao7. No off-target mutations were detected in #DunYao7. This study represents the first time that CRISPR-mediated genome editing has been successfully used to generate disease-resistant plants for 'Duncan' grapefruit, paving the way for using disease-resistant varieties to control canker.
Collapse
Affiliation(s)
- Hongge Jia
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred 33850, U.S.A
| | - Ahmad A Omar
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred 33850, U.S.A
- Biochemistry Department, Faculty of Agriculture, Zagazig University, Zagazig 44519, Egypt
| | - Vladimir Orbović
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred 33850, U.S.A
| | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred 33850, U.S.A
| |
Collapse
|
7
|
Jia H, Wang Y, Su H, Huang X, Wang N. LbCas12a-D156R Efficiently Edits LOB1 Effector Binding Elements to Generate Canker-Resistant Citrus Plants. Cells 2022; 11:cells11030315. [PMID: 35159125 PMCID: PMC8834406 DOI: 10.3390/cells11030315] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 01/07/2022] [Accepted: 01/14/2022] [Indexed: 12/17/2022] Open
Abstract
Citrus canker caused by Xanthomonas citri subsp. citri (Xcc) is an economically important disease in most citrus production regions worldwide. Xcc secretes a transcriptional activator like effector (TALE) PthA4 to bind to the effector binding elements (EBEs) in the promoter region of canker susceptibility gene LOB1 to activate its expression, which in turn causes canker symptoms. Editing the EBE region with Cas9/gRNA has been used to generate canker resistant citrus plants. However, most of the EBE-edited lines generated contain indels of 1–2 bp, which has higher possibility to be overcome by PthA4 adaptation. The adaptation capacity of TALEs inversely correlates with the number of mismatches with the EBE. LbCas12a/crRNA is known to generate longer deletion than Cas9. In this study, we used a temperature-tolerant and more efficient LbCas12a variant (ttLbCas12a), harboring the single substitution D156R, to modify the EBE region of LOB1. We first constructed GFP-p1380N-ttLbCas12a:LOBP, which was shown to be functional via Xcc-facilitated agroinfiltration in Pummelo (Citrus maxima) leaves. Subsequently, we stably expressed ttLbCas12a:LOBP in Pummelo. Eight transgenic lines were generated, with seven lines showing 100% mutations of the EBE, among which one line is homozygous. The EBE-edited lines had the ttLbCas12a-mediated deletions of up to 10 bp. Importantly, the seven lines were canker resistant and no off-targets were detected. In summary, ttLbCas12a can be used to efficiently generate biallelic/homozygous citrus mutant lines with short deletions, thus providing a useful tool for the functional study and breeding of citrus.
Collapse
|
8
|
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.
Collapse
|
9
|
Lobato-Gómez M, Hewitt S, Capell T, Christou P, Dhingra A, Girón-Calva PS. Transgenic and genome-edited fruits: background, constraints, benefits, and commercial opportunities. HORTICULTURE RESEARCH 2021; 8:166. [PMID: 34274949 PMCID: PMC8286259 DOI: 10.1038/s41438-021-00601-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 04/14/2021] [Accepted: 05/20/2021] [Indexed: 05/14/2023]
Abstract
Breeding has been used successfully for many years in the fruit industry, giving rise to most of today's commercial fruit cultivars. More recently, new molecular breeding techniques have addressed some of the constraints of conventional breeding. However, the development and commercial introduction of such novel fruits has been slow and limited with only five genetically engineered fruits currently produced as commercial varieties-virus-resistant papaya and squash were commercialized 25 years ago, whereas insect-resistant eggplant, non-browning apple, and pink-fleshed pineapple have been approved for commercialization within the last 6 years and production continues to increase every year. Advances in molecular genetics, particularly the new wave of genome editing technologies, provide opportunities to develop new fruit cultivars more rapidly. Our review, emphasizes the socioeconomic impact of current commercial fruit cultivars developed by genetic engineering and the potential impact of genome editing on the development of improved cultivars at an accelerated rate.
Collapse
Affiliation(s)
- Maria Lobato-Gómez
- Department of Crop and Forest Sciences, University of Lleida-Agrotecnio CERCA Center, Lleida, 25198, Spain
| | - Seanna Hewitt
- Department of Horticulture, Washington State University, PO Box, 646414, Pullman, WA, USA
| | - Teresa Capell
- Department of Crop and Forest Sciences, University of Lleida-Agrotecnio CERCA Center, Lleida, 25198, Spain
| | - Paul Christou
- Department of Crop and Forest Sciences, University of Lleida-Agrotecnio CERCA Center, Lleida, 25198, Spain
- ICREA, Catalan Institute for Research and Advanced Studies, 08010, Barcelona, Spain
| | - Amit Dhingra
- Department of Horticulture, Washington State University, PO Box, 646414, Pullman, WA, USA
| | - Patricia Sarai Girón-Calva
- Department of Crop and Forest Sciences, University of Lleida-Agrotecnio CERCA Center, Lleida, 25198, Spain.
| |
Collapse
|
10
|
Huang X, Wang Y, Xu J, Wang N. Development of multiplex genome editing toolkits for citrus with high efficacy in biallelic and homozygous mutations. PLANT MOLECULAR BIOLOGY 2020; 104:297-307. [PMID: 32748081 DOI: 10.1007/s11103-020-01043-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Accepted: 07/28/2020] [Indexed: 05/21/2023]
Abstract
KEY MESSAGE We have developed multiplex genome editing toolkits for citrus that significantly improve citrus genome editing efficacy. CRISPR/Cas systems have been engineered for genome editing in many organisms, including plants. However, the gene editing efficiency in citrus via CRISPR technology remains too low to be implemented for genetic improvement in practice. Moreover, it is very difficult to obtain homozygous or biallelic knockout mutants in citrus. Here, we have developed multiplex genome editing toolkits for citrus including PEG-mediated protoplast transformation, a GFP reporter system that allows the rapid assessment of CRISPR constructs, citrus U6 promoters with improved efficacy, and tRNA-mediated or Csy4-mediated multiplex genome editing. Using the toolkits, we successfully conducted genome modification of embryogenic protoplast cells and epicotyl tissues. We have achieved a biallelic mutation rate of 44.4% and a homozygous mutation rate of 11.1%, representing a significant improvement in citrus genome editing efficacy. In addition, our study lays the foundation for nontransgenic genome editing of citrus.
Collapse
Affiliation(s)
- Xiaoen Huang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), 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 (IFAS), 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 (IFAS), 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 (IFAS), University of Florida, Lake Alfred, FL, USA.
| |
Collapse
|
11
|
Poles L, Licciardello C, Distefano G, Nicolosi E, Gentile A, La Malfa S. Recent Advances of In Vitro Culture for the Application of New Breeding Techniques in Citrus. PLANTS (BASEL, SWITZERLAND) 2020; 9:E938. [PMID: 32722179 PMCID: PMC7465985 DOI: 10.3390/plants9080938] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 07/21/2020] [Accepted: 07/22/2020] [Indexed: 12/15/2022]
Abstract
Citrus is one of the most important fruit crops in the world. This review will discuss the recent findings related to citrus transformation and regeneration protocols of juvenile and adult explants. Despite the many advances that have been made in the last years (including the use of inducible promoters and site-specific recombination systems), transformation efficiency, and regeneration potential still represent a bottleneck in the application of the new breeding techniques in commercial citrus varieties. The influence of genotype, explant type, and other factors affecting the regeneration and transformation of the most used citrus varieties will be described, as well as some examples of how these processes can be applied to improve fruit quality and resistance to various pathogens and pests, including the potential of using genome editing in citrus. The availability of efficient regeneration and transformation protocols, together with the availability of the source of resistance, is made even more important in light of the fast diffusion of emerging diseases, such as Huanglongbing (HLB), which is seriously challenging citriculture worldwide.
Collapse
Affiliation(s)
- Lara Poles
- Food and Environment (Di3A), Department of Agriculture, University of Catania, Via Valdisavoia 5, 95123 Catania, Italy; (L.P.); (G.D.); (E.N.); (S.L.M.)
- CREA, Research Centre for Olive, Fruit and Citrus Crops, Corso Savoia 190, 95024 Acireale, Italy;
| | - Concetta Licciardello
- CREA, Research Centre for Olive, Fruit and Citrus Crops, Corso Savoia 190, 95024 Acireale, Italy;
| | - Gaetano Distefano
- Food and Environment (Di3A), Department of Agriculture, University of Catania, Via Valdisavoia 5, 95123 Catania, Italy; (L.P.); (G.D.); (E.N.); (S.L.M.)
| | - Elisabetta Nicolosi
- Food and Environment (Di3A), Department of Agriculture, University of Catania, Via Valdisavoia 5, 95123 Catania, Italy; (L.P.); (G.D.); (E.N.); (S.L.M.)
| | - Alessandra Gentile
- Food and Environment (Di3A), Department of Agriculture, University of Catania, Via Valdisavoia 5, 95123 Catania, Italy; (L.P.); (G.D.); (E.N.); (S.L.M.)
- College of Horticulture and Landscape, Hunan Agricultural University, Changsha 410128, China
| | - Stefano La Malfa
- Food and Environment (Di3A), Department of Agriculture, University of Catania, Via Valdisavoia 5, 95123 Catania, Italy; (L.P.); (G.D.); (E.N.); (S.L.M.)
| |
Collapse
|
12
|
Long Q, Xie Y, He Y, Li Q, Zou X, Chen S. Abscisic Acid Promotes Jasmonic Acid Accumulation and Plays a Key Role in Citrus Canker Development. FRONTIERS IN PLANT SCIENCE 2019; 10:1634. [PMID: 31921273 PMCID: PMC6934002 DOI: 10.3389/fpls.2019.01634] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 11/20/2019] [Indexed: 05/06/2023]
Abstract
Antagonism between jasmonic acid (JA) and salicylic acid (SA) plays pivotal roles in the fine-tuning of plant immunity against pathogen infection. In this study, we compared the phytohormonal responses to Xanthomonas citri subsp. citri (Xcc) between the citrus canker-susceptible (S) cultivar Wanjincheng orange (Citrus sinensis Osbeck) and -resistant (R) cultivar Jindan (Fortunella crassifolia Swingle). Upon Xcc infection, SA and JA were strongly induced in Jindan (R) and Wanjincheng orange (S), respectively, and JA appeared to contribute to citrus disease susceptibility by antagonizing SA-mediated effective defenses. A homologous gene encoding the allene oxide synthase (AOS) 1-2 enzyme, which catalyzes the first committed step in JA biosynthesis, was specifically upregulated in Wanjincheng orange (S) but not in Jindan (R). A promoter sequence analysis showed that abscisic acid (ABA)-responsive elements are enriched in the AOS1-2 of Wanjincheng orange (S) but not in Jindan (R). Accordingly, ABA treatments could induce AOS1-2 expression and JA accumulation, leading to enhanced citrus disease susceptibility in Wanjincheng orange (S), while the synthesis inhibitor sodium tungstate had the opposite effects. Moreover, ABA was specifically induced by Xcc infection in Wanjincheng orange (S) but not in Jindan (R). Thus, Xcc appeared to hijack host ABA biosynthesis to promote JA accumulation, which in turn suppressed effectual SA-mediated defenses to favor disease development in citrus. Our findings provide new insights into the molecular mechanisms underlying the differential citrus-canker resistance in citrus cultivars, and a new strategy for the biotechnological improvement of citrus canker resistance was discussed.
Collapse
Affiliation(s)
| | | | | | | | - Xiuping Zou
- Citrus Research Institute, Southwest University/Chinese Academy of Agricultural Sciences, Chongqing, China
| | - Shanchun Chen
- Citrus Research Institute, Southwest University/Chinese Academy of Agricultural Sciences, Chongqing, China
| |
Collapse
|
13
|
Citrus Taste Modification Potentials by Genetic Engineering. Int J Mol Sci 2019; 20:ijms20246194. [PMID: 31817978 PMCID: PMC6940753 DOI: 10.3390/ijms20246194] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 11/25/2019] [Accepted: 12/04/2019] [Indexed: 12/22/2022] Open
Abstract
Citrus fruits are mainly consumed as fresh fruit and processed juice products. They serve as nutritional and a tasty diet in our daily life. However, the formidable bitterness and delayed bitterness significantly impact the citrus industry attributable to the two major bitter compounds naringin and limonin. The extremely sour and acidic also negatively affects the sensory quality of citrus products. Citrus breeding programs have developed different strategies to improve citrus quality and a wealth of studies have aimed to uncover the genetic and biochemical basis of citrus flavor. In this minireview, we outline the major genes characterized to be involved in pathways shaping the sweet, bitter, or sour taste in citrus, and discuss briefly about the possible approaches to modify citrus taste by genetic engineering.
Collapse
|
14
|
Sun L, Ke F, Nie Z, Wang P, Xu J. Citrus Genetic Engineering for Disease Resistance: Past, Present and Future. Int J Mol Sci 2019; 20:E5256. [PMID: 31652763 PMCID: PMC6862092 DOI: 10.3390/ijms20215256] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Revised: 10/20/2019] [Accepted: 10/21/2019] [Indexed: 11/16/2022] Open
Abstract
Worldwide, citrus is one of the most important fruit crops and is grown in more than 130 countries, predominantly in tropical and subtropical areas. The healthy progress of the citrus industry has been seriously affected by biotic and abiotic stresses. Several diseases, such as canker and huanglongbing, etc., rigorously affect citrus plant growth, fruit quality, and yield. Genetic engineering technologies, such as genetic transformation and genome editing, represent successful and attractive approaches for developing disease-resistant crops. These genetic engineering technologies have been widely used to develop citrus disease-resistant varieties against canker, huanglongbing, and many other fungal and viral diseases. Recently, clustered regularly interspaced short palindromic repeats (CRISPR)-based systems have made genome editing an indispensable genetic manipulation tool that has been applied to many crops, including citrus. The improved CRISPR systems, such as CRISPR/CRISPR-associated protein (Cas)9 and CRISPR/Cpf1 systems, can provide a promising new corridor for generating citrus varieties that are resistant to different pathogens. The advances in biotechnological tools and the complete genome sequence of several citrus species will undoubtedly improve the breeding for citrus disease resistance with a much greater degree of precision. Here, we attempt to summarize the recent successful progress that has been achieved in the effective application of genetic engineering and genome editing technologies to obtain citrus disease-resistant (bacterial, fungal, and virus) crops. Furthermore, we also discuss the opportunities and challenges of genetic engineering and genome editing technologies for citrus disease resistance.
Collapse
Affiliation(s)
- Lifang Sun
- Institute of Citrus Research, Zhejiang Academy of Agricultural Sciences, Taizhou 318026, China.
- National Center for Citrus Variety Improvement, Zhejiang Branch, Taizhou 318026, China.
| | - Fuzhi Ke
- Institute of Citrus Research, Zhejiang Academy of Agricultural Sciences, Taizhou 318026, China.
- National Center for Citrus Variety Improvement, Zhejiang Branch, Taizhou 318026, China.
| | - Zhenpeng Nie
- Institute of Citrus Research, Zhejiang Academy of Agricultural Sciences, Taizhou 318026, China.
- National Center for Citrus Variety Improvement, Zhejiang Branch, Taizhou 318026, China.
| | - Ping Wang
- Institute of Citrus Research, Zhejiang Academy of Agricultural Sciences, Taizhou 318026, China.
- National Center for Citrus Variety Improvement, Zhejiang Branch, Taizhou 318026, China.
| | - Jianguo Xu
- Institute of Citrus Research, Zhejiang Academy of Agricultural Sciences, Taizhou 318026, China.
- National Center for Citrus Variety Improvement, Zhejiang Branch, Taizhou 318026, China.
| |
Collapse
|