Transient expression of β-glucuronidase following biolistic delivery of foreign DNA into coffee tissues.

Some conditions related to the transient expression of β-glucuronidase in biolistically-treated Coffea spp. tissues were investigated, and subsequently used in a promoter study. Bombardments were performed on different types of tissue (leaves, somatic embryos and suspension cultures) of genotypes of C. arabica, C. canephora and Arabusta, using 4 different promoter sequences. Tobacco leaves were used as a comparison. In general, similar large variation and mean values of transient expression were observed between coffee and tobacco leaves. With regard to the coffee tissues effect, transient expression was best detectable and most frequently observed with bombarded leaves of microcuttings. Disturbing endogenous light blue staining was found with control treatments of somatic embryos. For the three coffee species tested, the most effective promoter was the EF1α-A1 promoter of Arabidopsis thaliana.