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Optimization of CRISPR/Cas9 genome editing in cotton by improved sgRNA expression

BACKGROUND: When developing CRISPR/Cas9 systems for crops, it is crucial to invest time characterizing the genome editing efficiency of the CRISPR/Cas9 cassettes, especially if the transformation system is difficult or time-consuming. Cotton is an important crop for the production of fiber, oil, and...

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Detalles Bibliográficos
Autores principales: Long, Lu, Guo, Dan-Dan, Gao, Wei, Yang, Wen-Wen, Hou, Li-Pan, Ma, Xiao-Nan, Miao, Yu-Chen, Botella, Jose Ramon, Song, Chun-Peng
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6169012/
https://www.ncbi.nlm.nih.gov/pubmed/30305839
http://dx.doi.org/10.1186/s13007-018-0353-0
Descripción
Sumario:BACKGROUND: When developing CRISPR/Cas9 systems for crops, it is crucial to invest time characterizing the genome editing efficiency of the CRISPR/Cas9 cassettes, especially if the transformation system is difficult or time-consuming. Cotton is an important crop for the production of fiber, oil, and biofuel. However, the cotton stable transformation is usually performed using Agrobacterium tumefaciens taking between 8 and 12 months to generate T(0) plants. Furthermore, cotton is a heterotetraploid and targeted mutagenesis is considered to be difficult as many genes are duplicated in this complex genome. The application of CRISPR/Cas9 in cotton is severely hampered by the long and technically challenging genetic transformation process, making it imperative to maximize its efficiency. RESULTS: In this study, we provide a new system to evaluate and validate the efficiency of CRISPR/Cas9 cassettes in cotton using a transient expression system. By using this system, we could select the most effective CRISPR/Cas9 cassettes before the stable transformation. We have also optimized the existing cotton CRISPR/Cas9 system to achieve vastly improved mutagenesis efficiency by incorporating an endogenous GhU6 promoter that increases sgRNA expression levels over the Arabidopsis AtU6-29 promoter. The 300 bp GhU6.3 promoter was cloned and validated using the transient expression system. When sgRNAs were expressed under the control of the GhU6.3 promoter in CRISPR/Cas9 cassettes, expression levels were 6–7 times higher than those provided by the AtU6-29 promoter and CRISPR/Cas9-mediated mutation efficiency was improved 4–6 times. CONCLUSIONS: This study provides essential improvements to maximize CRISPR/Cas9-mediated mutation efficiency by reducing risk and workload for the application of CRISPR/Cas9 approaches in the targeted mutagenesis of cotton. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s13007-018-0353-0) contains supplementary material, which is available to authorized users.