High yields of viable pea protoplasts were produced from suspension cultured cells derived from calli formed from embryogenic tissues or leaves and the conditions for the optimum expression of chloramphenicol acetyltransferase (CAT) fused to the phenylalanine ammonia-lyase gene of Pisum sativum (pPAL1-15) were investigated by transient assay after electroporation. A fungal elicitor isolated from a pea pathogen, Mycosphaerella pinodes, and the reduced from of glutathione induced the expression of PAL promoter but orthovanadate, a plasma membrane ATPase inhibitor, considerably suppressed the gene expression. Rice protoplasts were also prepared from the suspension cultured cells derived from embryonic tissues, and the effects of elicitors on the expression of CAT in pPAL1-15-electroporated rice protoplasts were examined. No distinctive induction of CAT activity was observed by the treatment of rice protoplasts with a chitosan oligomer elicitor.