Mohammed Rafi, Mohamed ElSiddig, Maitha Aldarmaki, Mariam Al Nuaimi, Suja George, Khaled M A Amiri
{"title":"Application of a multiplex CRISPR/Cas9 strategy for elimination of selection markers from transgenic plants.","authors":"Mohammed Rafi, Mohamed ElSiddig, Maitha Aldarmaki, Mariam Al Nuaimi, Suja George, Khaled M A Amiri","doi":"10.3389/fgeed.2025.1633104","DOIUrl":null,"url":null,"abstract":"<p><p>Selectable marker genes (SMGs) are essential for identifying transgenic plants but raise concerns regarding biosafety, regulatory compliance, and public acceptance. In this study, we used a CRISPR/Cas9-based strategy to eliminate the SMG from transgenic tobacco plants. Leaf discs from plants carrying DsRED (SMG) and aminoglycoside phosphotransferase (gene of interest, GOI) were re-transformed with a CRISPR vector containing four gRNAs designed to target both flanking regions of the SMG cassette. Approximately 20% of the regenerated shoots exhibited loss of red fluorescence, and PCR and sequencing analyses confirmed that about half of these carried a smaller amplicon, indicating a successful SMG excision efficiency of around 10%. Mutation analysis further revealed the presence of small indels at gRNA target sites, in addition to the deletion of SMG cassette. Quantitative real-time PCR (qPCR) analysis confirmed the absence of DsRED expression in SMG-deleted lines, while the Cas9 and GOI remained actively expressed. The SMG-free plants displayed normal growth, flowering, and seed production, indicating CRISPR marker excision had no adverse effects on plant development and fertility. In addition, Cas9-free, marker-free transgenic plants were recovered through segregation in T1 generation. This approach is adaptable to various transgenic plant species and provides a practical solution for generating marker-free transgenic crops, thereby enhancing their acceptance and commercialization.</p>","PeriodicalId":73086,"journal":{"name":"Frontiers in genome editing","volume":"7 ","pages":"1633104"},"PeriodicalIF":4.4000,"publicationDate":"2025-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12440875/pdf/","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Frontiers in genome editing","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.3389/fgeed.2025.1633104","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2025/1/1 0:00:00","PubModel":"eCollection","JCR":"Q1","JCRName":"BIOTECHNOLOGY & APPLIED MICROBIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Selectable marker genes (SMGs) are essential for identifying transgenic plants but raise concerns regarding biosafety, regulatory compliance, and public acceptance. In this study, we used a CRISPR/Cas9-based strategy to eliminate the SMG from transgenic tobacco plants. Leaf discs from plants carrying DsRED (SMG) and aminoglycoside phosphotransferase (gene of interest, GOI) were re-transformed with a CRISPR vector containing four gRNAs designed to target both flanking regions of the SMG cassette. Approximately 20% of the regenerated shoots exhibited loss of red fluorescence, and PCR and sequencing analyses confirmed that about half of these carried a smaller amplicon, indicating a successful SMG excision efficiency of around 10%. Mutation analysis further revealed the presence of small indels at gRNA target sites, in addition to the deletion of SMG cassette. Quantitative real-time PCR (qPCR) analysis confirmed the absence of DsRED expression in SMG-deleted lines, while the Cas9 and GOI remained actively expressed. The SMG-free plants displayed normal growth, flowering, and seed production, indicating CRISPR marker excision had no adverse effects on plant development and fertility. In addition, Cas9-free, marker-free transgenic plants were recovered through segregation in T1 generation. This approach is adaptable to various transgenic plant species and provides a practical solution for generating marker-free transgenic crops, thereby enhancing their acceptance and commercialization.