TRANSIENT GENE-EXPRESSION IN CASSAVA SOMATIC EMBRYOS BY TISSUE ELECTROPORATION

Embryogenic cassava (Manihot esculenta Crantz) tissues were transformed with the P-glucuronidase (GUS) gene by electroporation, Physiological and developmental state of the tissues, electric field strength and incubation temperature and duration were observed to be the most important factors influencing transient expression. Optimised frequencies of GUS expression were obtained when tissue pieces bearing torpedo-stage embryos were preincubated at 37 degrees C for 1 h, in sodium aspartate buffer containing plasmid DNA and electroporated with a single electric pulse (750 V/cm, 960 mu F capacitance). The system was efficient and reproducible and, under these conditions, it was possible to obtain expression in 75% of the tissue pieces electroporated, with an average of 174 (+/-35.6) GUS spots per replicate (of approximately 20 pieces), These results suggests that tissue electroporation could have a general application as a facile gene transfer method.