Elimination of selectable marker genes with chemical-inducible cre/loxP system and cytosine deaminase in plant

Abstract

Elimination of selectable marker genes is essential technique for the relaxation of consumer concerns on genetically modified organisms (GMOs) and gene stacking. In this study, a self-removable selectable marker cassette consists of glucocorticoid-regulated Cre/loxP recombination system, nptii and a negative selection marker cytosine deaminase (codA) gene was constructed between the strong plant promoter CaMV 35S promoter and a β-glucuronidase (GUS) gene. By the induction of cre expression with glucocorticoid hormone dexamethasone, the cassette was eliminated and GUS reporter gene was activated. The eliminated region was confirmed by PCR. Cells still carrying selectable markers were killed by codA that converts non-toxic 5-fluorocytosine to toxic 5-fluorouracil.