Biotechnology Letters, Vol.35, No.12, 2177-2183, 2013
Tissue-specifically regulated site-specific excision of selectable marker genes in bivalent insecticidal, genetically-modified rice
Marker-free, genetically-modified rice was created by the tissue-specifically regulated Cre/loxP system, in which the Cre recombinase gene and hygromycin phosphotransferase gene (hpt) were flanked by two directly oriented loxP sites. Cre expression was activated by the tissue-specific promoter OsMADS45 in flower or napin in seed, resulting in simultaneous excision of the recombinase and marker genes. Segregation of T-1 progeny was performed to select recombined plants. The excision was confirmed by PCR, Southern blot and sequence analyses indicating that efficiency varied from 10 to 53 % for OsMADS45 and from 12 to 36 % for napin. The expression of cry1Ac and vip3A was detected by RT-PCR analysis in marker-free transgenic rice. These results suggested that our tissue-specifically regulated Cre/loxP system could auto-excise marker genes from transgenic rice and alleviate public concerns about the security of GM crops.
Keywords:Auto-excision;Cre/loxP;cry1Ac and vip3A;Gene excision;Genetically-modified;Rice insect-resistant rice;Marker-free;Rice (GM)