Pectolytic enzyme treatment of sunflower explants prior to wounding and cocultivation with Agrobacterium tumefaciens, enhances efficiency of transient β-glucuronidase expression

The genetic transformation of sunflower is very difficult. The protocols published so far combined wounding of meristematic axes by microprojectils or glass beads and gene transfer by Agrobacterium tumefaciens . The yields of transgenic plants were well below 0.1% in all cases. Treatment of meristematic explants of germinating seedlings by a pectinase, before wounding, followed immediately by Agrobacterium tumefaciens cocultivation, enhanced β -glucuronidase (GUS) gene expression in 14-day-old in vitro cultivated explants. Moreover, pectinase-treated explants showed a significant increase in interaction with bacteria compared to non-treated ones. This result suggests facilitated access of the bacteria to competent sunflower cells, due to cell-wall digestion by the pectinases. Furthermore, we show here, using competition experiments, that integrin-like proteins do not seem to be involved in the enhancement of bacterial binding to the cell explants.