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Valentine M, Butruille D, Achard F, Beach S, Brower-Toland B, Cargill E, Hassebrock M, Rinehart J, Ream T, Chen Y. Simultaneous genetic transformation and genome editing of mixed lines in soybean ( Glycine max) and maize ( Zea mays). ABIOTECH 2024; 5:169-183. [PMID: 38974857 PMCID: PMC11224177 DOI: 10.1007/s42994-024-00173-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Accepted: 06/02/2024] [Indexed: 07/09/2024]
Abstract
Robust genome editing technologies are becoming part of the crop breeding toolbox. Currently, genome editing is usually conducted either at a single locus, or multiple loci, in a variety at one time. Massively parallel genomics platforms, multifaceted genome editing capabilities, and flexible transformation systems enable targeted variation at nearly any locus, across the spectrum of genotypes within a species. We demonstrate here the simultaneous transformation and editing of many genotypes, by targeting mixed seed embryo explants with genome editing machinery, followed by re-identification through genotyping after plant regeneration. Transformation and Editing of Mixed Lines (TREDMIL) produced transformed individuals representing 101 of 104 (97%) mixed elite genotypes in soybean; and 22 of 40 (55%) and 9 of 36 (25%) mixed maize female and male elite inbred genotypes, respectively. Characterization of edited genotypes for the regenerated individuals identified over 800 distinct edits at the Determinate1 (Dt1) locus in samples from 101 soybean genotypes and 95 distinct Brown midrib3 (Bm3) edits in samples from 17 maize genotypes. These results illustrate how TREDMIL can help accelerate the development and deployment of customized crop varieties for future precision breeding. Supplementary Information The online version contains supplementary material available at 10.1007/s42994-024-00173-5.
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Affiliation(s)
- Michelle Valentine
- Bayer Crop Science, 700 Chesterfield Parkway W, Chesterfield, MO 63017 USA
| | - David Butruille
- Bayer Crop Science, 700 Chesterfield Parkway W, Chesterfield, MO 63017 USA
| | - Frederic Achard
- Bayer Crop Science, 700 Chesterfield Parkway W, Chesterfield, MO 63017 USA
| | - Steven Beach
- Bayer Crop Science, 700 Chesterfield Parkway W, Chesterfield, MO 63017 USA
| | | | - Edward Cargill
- Bayer Crop Science, 700 Chesterfield Parkway W, Chesterfield, MO 63017 USA
| | - Megan Hassebrock
- Bayer Crop Science, 700 Chesterfield Parkway W, Chesterfield, MO 63017 USA
| | - Jennifer Rinehart
- Bayer Crop Science, 700 Chesterfield Parkway W, Chesterfield, MO 63017 USA
| | - Thomas Ream
- Bayer Crop Science, 700 Chesterfield Parkway W, Chesterfield, MO 63017 USA
| | - Yurong Chen
- Bayer Crop Science, 700 Chesterfield Parkway W, Chesterfield, MO 63017 USA
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Ye X, Shrawat A, Moeller L, Rode R, Rivlin A, Kelm D, Martinell BJ, Williams EJ, Paisley A, Duncan DR, Armstrong CL. Agrobacterium-mediated direct transformation of wheat mature embryos through organogenesis. FRONTIERS IN PLANT SCIENCE 2023; 14:1202235. [PMID: 37324676 PMCID: PMC10264787 DOI: 10.3389/fpls.2023.1202235] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 05/11/2023] [Indexed: 06/17/2023]
Abstract
Transgenic plant production in monocotyledonous species has primarily relied on embryogenic callus induction from both immature and mature embryos as the pathway for plant regeneration. We have efficiently regenerated fertile transgenic wheat plants through organogenesis after Agrobacterium-mediated direct transformation of mechanically isolated mature embryos from field-grown seed. Centrifugation of the mature embryos in the presence of Agrobacterium was found to be essential for efficient T-DNA delivery to the relevant regenerable cells. The inoculated mature embryos formed multiple buds/shoots on high-cytokinin medium, which directly regenerated into transgenic shoots on hormone-free medium containing glyphosate for selection. Rooted transgenic plantlets were obtained within 10-12 weeks after inoculation. Further optimization of this transformation protocol resulted in significant reduction of chimeric plants to below 5%, as indicated by leaf GUS staining and T1 transgene segregation analysis. Direct transformation of wheat mature embryos has substantial advantages over traditional immature embryo-based transformation systems, including long-term storability of the mature dry explants, scalability, and greatly improved flexibility and consistency in transformation experiments.
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Ye X, Vaghchhipawala Z, Williams EJ, Fu C, Liu J, Lu F, Hall EL, Guo SX, Frank L, Gilbertson LA. Cre-mediated autoexcision of selectable marker genes in soybean, cotton, canola and maize transgenic plants. PLANT CELL REPORTS 2023; 42:45-55. [PMID: 36316413 DOI: 10.1007/s00299-022-02935-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 10/10/2022] [Indexed: 06/16/2023]
Abstract
Efficient selectable marker gene autoexcision in transgenic plants of soybean, cotton, canola, and maize is achieved by effective Cre recombinase expression. Selectable marker genes are often required for efficient generation of transgenic plants in plant transformation but are not desired once the transgenic events are obtained. We have developed Cre/loxP autoexcision systems to remove selectable marker genes in soybean, cotton, canola and maize. We tested a set of vectors with diverse promoters and identified promising promoters to drive cre expression for each of the four crops. We evaluated both the efficiency of generating primary transgenic events with low transgene copy numbers, and the frequency of marker-free progeny in the next generation. The best performing vectors gave no obvious decrease in the transformation frequency in each crop and generated homozygous marker-free progeny in the next generation. We found that effective expression of Cre recombinase for marker gene autoexcision can be species dependent. Among the vectors tested, the best autoexcision frequency (41%) in soybean transformation came from using the soybean RSP1 promoter for cre expression. The cre gene expressed by soybean RSP1 promoter with an Arabidopsis AtpE intron delivered the best autoexcision frequency (69%) in cotton transformation. The cre gene expressed by the embryo-specific eUSP88 promoter from Vicia faba conferred the best marker excision frequency (32%) in canola transformation. Finally, the cre gene expressed by the rice CDC45-1 promoter resulted in 44% autoexcision in maize transformation. The Cre/loxP recombinase system enables the generation of selectable marker-free transgenic plants for commercial product development in four agriculturally important crops and provides further improvement opportunities for more specific and better marker excision efficiency.
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Affiliation(s)
- Xudong Ye
- Bayer Crop Science, 700 Chesterfield Pkwy, St. Louis, MO, 63017, USA.
| | | | - Edward J Williams
- Bayer Crop Science, 700 Chesterfield Pkwy, St. Louis, MO, 63017, USA
- Wisconsin Crop Innovation Center, 8520 University Green, Middleton, WI, 53562, USA
| | - Changlin Fu
- Bayer Crop Science, 700 Chesterfield Pkwy, St. Louis, MO, 63017, USA
| | - Jinyuan Liu
- Bayer Crop Science, 700 Chesterfield Pkwy, St. Louis, MO, 63017, USA
| | - Fengming Lu
- Bayer Crop Science, 700 Chesterfield Pkwy, St. Louis, MO, 63017, USA
| | - Erin L Hall
- Bayer Crop Science, 700 Chesterfield Pkwy, St. Louis, MO, 63017, USA
| | - Shirley X Guo
- Bayer Crop Science, 700 Chesterfield Pkwy, St. Louis, MO, 63017, USA
| | - LaRee Frank
- Bayer Crop Science, 700 Chesterfield Pkwy, St. Louis, MO, 63017, USA
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Ye X, Shrawat A, Williams E, Rivlin A, Vaghchhipawala Z, Moeller L, Kumpf J, Subbarao S, Martinell B, Armstrong C, Saltarikos MA, Somers D, Chen Y. Commercial scale genetic transformation of mature seed embryo explants in maize. FRONTIERS IN PLANT SCIENCE 2022; 13:1056190. [PMID: 36523626 PMCID: PMC9745677 DOI: 10.3389/fpls.2022.1056190] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 11/07/2022] [Indexed: 06/17/2023]
Abstract
A novel, efficient maize genetic transformation system was developed using Agrobacterium-mediated transformation of embryo explants from mature seeds. Seeds from field grown plants were sterilized and crushed to isolate embryo explants consisting of the coleoptile, leaf primordia, and shoot apical meristem which were then purified from the ground seed bulk preparation. The infection of relevant tissues of seed embryo explants (SEEs) by Agrobacterium was improved by the centrifugation of the explants. Transgenic plants were obtained by multiple bud induction on high cytokinin media, followed by plant regeneration on hormone-free medium. Three different selectable markers (cp4 epsps, aadA, and nptII) were successfully used for producing transgenic plants. Stable integration of transgenes in the maize genome was demonstrated by molecular analyses and germline transmission of the inserted transgenes to the next generation was confirmed by pollen segregation and progeny analysis. Phenotypic evidence for chimeric transgenic tissue was frequently observed in initial experiments but was significantly reduced by including a second bud induction step with optimized cytokinin concentration. Additional improvements, including culturing explants at an elevated temperature during bud induction led to the development of a revolutionary system for efficient transgenic plant production and genome editing. To our knowledge, this is the first report of successful transgenic plant regeneration through Agrobacterium-mediated transformation of maize mature SEEs. This system starts with mature seed that can be produced in large volumes and the SEEs explants are storable. It has significant advantages in terms of scalability and flexibility over methods that rely on immature explants.
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Affiliation(s)
- Xudong Ye
- Plant Biotechnology, Bayer Crop Science, W. St. Louis, MO, United States
| | - Ashok Shrawat
- Plant Biotechnology, Bayer Crop Science, W. St. Louis, MO, United States
| | - Edward Williams
- Agracetus Campus, Monsanto Company, Middleton, WI, United States
| | - Anatoly Rivlin
- Agracetus Campus, Monsanto Company, Middleton, WI, United States
| | | | - Lorena Moeller
- Plant Biotechnology, Bayer Crop Science, W. St. Louis, MO, United States
| | - Jennifer Kumpf
- Mystic Research, Monsanto Company, Mystic, CT, United States
| | - Shubha Subbarao
- Plant Biotechnology, Bayer Crop Science, W. St. Louis, MO, United States
| | - Brian Martinell
- Plant Biotechnology, Bayer Crop Science, W. St. Louis, MO, United States
| | - Charles Armstrong
- Plant Biotechnology, Bayer Crop Science, W. St. Louis, MO, United States
| | | | - David Somers
- Mystic Research, Monsanto Company, Mystic, CT, United States
| | - Yurong Chen
- Plant Biotechnology, Bayer Crop Science, W. St. Louis, MO, United States
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Demonstration of targeted crossovers in hybrid maize using CRISPR technology. Commun Biol 2022; 5:53. [PMID: 35027641 PMCID: PMC8758740 DOI: 10.1038/s42003-022-03004-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 12/23/2021] [Indexed: 12/17/2022] Open
Abstract
Naturally occurring chromosomal crossovers (CO) during meiosis are a key driver of genetic diversity. The ability to target CO at specific allelic loci in hybrid plants would provide an advantage to the plant breeding process by facilitating trait introgression, and potentially increasing the rate of genetic gain. We present the first demonstration of targeted CO in hybrid maize utilizing the CRISPR Cas12a system. Our experiments showed that stable and heritable targeted CO can be produced in F1 somatic cells using Cas12a at a significantly higher rate than the natural CO in the same interval. Molecular characterization of the recombinant plants demonstrated that the targeted CO were driven by the non-homologous end joining (NHEJ) or HDR repair pathways, presumably during the mitotic cell cycle. These results are a step towards the use of RNA-guided nuclease technology to simplify the creation of targeted genome combinations in progeny and accelerate breeding. Kouranov et al. demonstrate Cas12a-mediated targeted chromosomal crossover (CO) in transgenic hybrid maize plants and produce heritable crossover in F1 plants when Cas12a transgene is segregated away. The authors also report that the frequency of LbCas12a-mediated CO is higher than control natural CO in the same intervals in the progeny of 4 different events.
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Chen Y, Lange A, Vaghchhipawala Z, Ye X, Saltarikos A. Direct Germline Transformation of Cotton Meristem Explants With No Selection. FRONTIERS IN PLANT SCIENCE 2020; 11:575283. [PMID: 33072151 PMCID: PMC7543975 DOI: 10.3389/fpls.2020.575283] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 09/04/2020] [Indexed: 05/27/2023]
Abstract
Regeneration of transgenic plants without selectable markers can facilitate the development and commercialization of trait stacking products. A wide range of strategies have been developed to eliminate selectable markers to produce marker-free transgenic plants. The most widely used marker free approach is probably the Agrobacterium-based 2 T-DNA strategy where the gene-of-interest (GOI) and selectable marker gene are delivered from independent T-DNAs (Darbani et al., 2007). The selectable marker gene is segregated away from the GOI in subsequent generations. However, the efficiency of this 2 T-DNA system is much less than the traditional 1 T-DNA system due to the inefficiency of T-DNA co-transformation and high rate of con-integration between the GOI and selectable marker gene T-DNAs. In contrast, no selection transformation utilizes a single T-DNA carrying the GOI and thus eliminates the need to remove the selectable marker insert and potentially provides a viable alternative marker-free system. In this study, we reported the successful regeneration of transgenic cotton plants through Agrobacterium inoculation of seed meristem explants without the use of selective agents. Regeneration of putative transgenic plants were identified by GUS histo-chemical assay. The germline transmission of transgene to progeny was determined by segregation of pollen grains, immature embryos and T1 plants by GUS expression. The results were further confirmed by Southern analyses. The marker-free transformation frequency in this no selection system was similar to current meristem transformation system with selection (0.2%-0.7%). The strategy for further improvement of this system and its implication in improving cotton transformation pipeline and in developing transgene-free genome editing technology is discussed.
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