Delivery of N-methyltransferase and 11S globulin promoters of Coffea canephora Pex Fr. by tissue electroporation and analysis of transformational events

A tissue electroporation system was optimized to deliver transgenes, and the expression of reporter gene driven by coffee N-methyltransferase (NMT) and 11S globulin promoters in somatic embryos of Coffea canephora was achieved. Plant transformation vector pCAMBIA 1301 was adopted for electroporation. Transient as well as stable expression of uidA gene was detected after electroporation using field strengths of 500 V/cm, 900 mu F capacitance and 100 mu g/ml of plasmid DNA. The efficiency of tissue electroporation was dependent on the type and developmental stage of the plant material. Spermidine treatment during electroporation increased transformation frequency twofold. Histochemical staining of GUS activity confirmed the expression of uidA gene in somatic embryos and endosperm tissues of C canephora. Electroporation with pPCGB 959 (11S globulin promoter) resulted in 32% of explants showing GUS expression in endosperm tissues. The study demonstrated the ability of these promoters to drive the expression of the reporter gene. The results may be helpful for using these promoters to alter the expression of the NMT gene family through transcriptional gene silencing by RNA-directed DNA methylation, and also for using 11S globulin promoter for silencing NMT genes in a tissue-specific manner in transgenic coffee plants.