Expression of CodA gene from Escherichia coli confering a negative selection phenotype on transgenic Artemisia annua / 中草药

ABSTRACT

Objective To explore the feasibility of utilizing the cytosine deaminase A (CodA) gene as an effective negative selectable marker in Artemisia annua for gene targeting.Methods The PCR procedure was employed to amplify CodA gene from Escherichia coli.After being cloned and sequenced, the gene was inserted into a plant expression vector, pROKⅡ, and then introduced into Agrobacterium tumefaciens LBA4404 (pAL4404).The leaf disks of A.annua were transformed by the co-cultivation protocol, after which the transformed calli were selected and green shoots of A. annua were regenerated on N6 medium supplemented with 25 ?g/mL Kanamycin (Kan).Then the Kan-resistant transgenic shoots were transplanted onto the MS medium containing 500 ?g/mL 5-fluocytosine (5-FC) plus 25 ?g/mL Kan and continuously cultured for up to two weeks.Results The transgenic shoots have totally died while untransformed shoots still kept normal growth, indicating that A.annua cells introduced into the CodA gene had conferred an expected negative selection phenotype.When detected by RT-PCR, the transgenic shoots displayed a CodA-positive amplified band, but untransformed shoots gave no such CodA-specific amplified pattern.This result suggested that CodA gene had transcribed into corresponding mRNA in A.annua cells with furtherly verifying the result of phenotypic assay.Conclusion The CodA gene can be utilized as an effective negative selectable marker in A.annua for gene targeting.