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

The genetic transformation of sunflower is very difficult. The protocols pu blished 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 meristema tic explants of germinating seedlings by a pectinase, before wounding, foll owed immediately by Agrobacterium tumefaciens cocultivation, enhanced beta- glucuronidase (GUS) gene expression in 14-day-old in vitro cultivated expla nts. Moreover, pectinase-treated explants showed a significant increase in interaction with bacteria compared to non-treated ones. This result suggest s facilitated access of the bacteria to competent sunflower cells, due to c ell-wall digestion by the pectinases. Furthermore, we show here, using comp etition experiments, that integrin-like proteins do not seem to be involved in the enhancement of bacterial binding to the cell explants.