An Efficient Agrobacterium-Mediated Genetic Transformation Method for Solanum betaceum Cav. Embryogenic Callus

Somatic embryogenesis in Solanum betaceum (tamarillo) has proven to be an effective model system for studying morphogenesis, since optimized plant regeneration protocols are available, and embryogenic competent cell lines can be induced from different explants. Nevertheless, an efficient genetic transformation system for embryogenic callus (EC) has not yet been implemented for this species. Here, an optimized faster protocol of genetic transformation using Agrobacterium tumefaciens is described for EC. The sensitivity of EC to three antibiotics was determined, and kanamycin proved to be the best selective agent for tamarillo callus. Two Agrobacterium strains, EHA105 and LBA4404, both harboring the p35SGUSINT plasmid, carrying the reporter gene for β-glucuronidase (gus) and the marker gene neomycin phosphotransferase (nptII), were used to test the efficiency of the process. To increase the success of the genetic transformation, a cold-shock treatment, coconut water, polyvinylpyrrolidone and an appropriate selection schedule based on antibiotic resistance were employed. The genetic transformation was evaluated by GUS assay and PCR-based techniques, and a 100% efficiency rate was confirmed in the kanamycin-resistant EC clumps. Genetic transformation with the EHA105 strain resulted in higher values for gus insertion in the genome. The protocol presented provides a useful tool for functional gene analysis and biotechnology approaches.

Agrobacterium tumefaciens-mediated transformation of Dendrobium lasianthera J.J.Sm: An important medicinal orchid

A protocol for genetic transformation mediated by Agrobacterium tumefaciens and production of transgenic Dendrobium lasianthera has been developed for the first time. The 8-week-old protocorm explants were used as target of transformation with Agrobacterium tumefaciens strain LBA4404 carrying plasmid pG35SKNAT1. Several parameters such as infection period, Agrobacterium density, concentration of acetosyringone, and co-cultivation period were evaluated for the transformation efficiency. The data were analyzed using one-way analysis of variance (ANOVA) and Duncan's Multiple Range Test (DMRT) with p < 0.05. Subsequently, KNAT1 gene expression was confirmed by polymerase chain reaction (PCR) analysis. The highest efficiency of transformation (70%) obtained from protocorm explants infected with Agrobacterium culture was at the OD₆₀₀ concentration of 0.6 for 30 min, and co-cultivated with acetosyringone 100 µM for 5 days. The results of confirmation by PCR analysis show that the KNAT1 gene has been integrated and expressed in the genome of Dendrobium lasianthera transgenic.