Germline transformation of Shepherd's purse (Capsella bursa-pastoris) by the ‘floral dip’ method as a tool for evolutionary and developmental biology

Capsella bursa-pastoris is an attractive model system for evolutionary and developmental biology. To facilitate future studies on gene function, the ‘floral dip’ method was adapted to achieve germline transformation of C. bursa-pastoris. The GFP and BASTA-resistance (BAR r) genes were used as markers for screening or selecting, respectively, putative transgenic C. bursa-pastoris plants and the β-glucuronidase (GUS) gene as well as the GFP gene for monitoring transgene expression level. We tested two Agrobacterium strains, LBA4404 and GV3101, for their ability to transform C. bursa-pastoris. In contrast to Arabidopsis thaliana, for which both strains were able to transform different ecotypes, only GV3101 gave satisfactory transformation rates with C. bursa-pastoris. Furthermore, we evaluated the effects of different concentrations of sucrose and the surfactant Silwet L-77 on the efficiency to generate transgenic C. bursa-pastoris plants and identified an efficient medium containing 10% (w/v) sucrose and 0.02–0.05% (v/v) Silwet L-77. Using Southern hybridisation, we confirmed the integration of the marker gene in the plant genome and the stable heredity of the introduced genes in the next generation.