A new high-frequency Agrobacterium-mediated transformation technique for Sesamum indicum L. using de-embryonated cotyledon as explant

In spite of the economic importance of sesame (Sesamum indicum L.) and the recent availability of its genome sequence, a high-frequency transformation protocol is still not available. The only two existing Agrobacterium-mediated transformation protocols that are available have poor transformation efficiencies of less than 2 %. In the present study, we report a high-frequency, simple, and reproducible transformation protocol for sesame. Transformation was done using de-embryonated cotyledons via somatic embryogenic stages. All the critical parameters of transformation, like incubation period of explants in pre-regeneration medium prior to infection by Agrobacterium tumefaciens, cocultivation period, concentrations of acetosyringone in cocultivation medium, kanamycin concentration, and concentration of plant hormones, including 6-benzylaminopurine, have been optimized. This protocol is superior to the two existing protocols in its high regeneration and transformation efficiencies. The transformed sesame lines have been tested by PCR, RT-PCR for neomycin phosphotransferase II gene expression, and beta-glucuronidase (GUS) assay. The regeneration frequency and transformation efficiency are 57.33 and 42.66 %, respectively. T0 and T1 generation transgenic plants were analyzed, and several T1 plants homozygous for the transgenes were obtained.