Establishment of an Agrobacterium-mediated transformation system for Periploca sepium Bunge

Agrobacterium-mediated transformation of Periploca sepium Bunge using proliferated clonal shoots was investigated to identify important factors affecting the transformation efficiency. Agrobacterium tumefaciens strains EHA105 and LBA4404 were used, both of which harbored a pKAFCR21 binary vector, which contained two reporter genes (GUS and sGFP, encoding β-glucuronidase and the synthetic green-fluorescent protein with S65T mutation) and two marker genes (encoding neomycin phosphotransferase II and hygromycin phosphotransferase). The factors evaluated were Agrobacterium strain, co-cultivation treatment, and antibiotic selection regime. The results revealed that the transformation efficiency could be synergistically increased to as high as 50-60% by infecting explants with Agrobacterium strain EHA105/pKAFCR21 and co-cultivating in the presence of 150 mg l^-1 dithiothreitol, followed by selection at 100 mg l^-1 kanamycin. Genomic DNA PCR, Southern hybridization, and quantitative real-time reverse transcription PCR analyses confirmed that the transgenes (GUS or sGFP) had presented, integrated, and expressed in all the tested transformant plants. The optimized protocol provides a basis for further genetic alteration of P. sepium for medicinal compounds and cispolyisoprene production.