Ethylene and in vitro culture of potato: suppression of ethylene generation vastly improves protoplast yield, plating efficiency and transient expression of an alien gene.

Ethylene release by potato shoots cultured in closed boxes was suppressed by the addition of silver thiosulfate to the culture medium. Shoots cultured in the presence of silver thiosulfate produced appreciably more tissue and the yield of protoplasts per unit tissue mass was vastly increased, resulting in an 8 fold increase of protoplast yield per shoot. Exposure of pricked leaves to macerating enzymes facilitated ethylene generation. Leaves of shoots which were previously cultured in silver thiosulfate containing medium generated much less ethylene than leaves from control shoots and this generation could be further reduced by the addition of acetylsalicylic acid during maceration. The capability of polyethylene glycol treated potato protoplasts to produce microcalli was vastly increased by the addition of silver thiosulfate during exposure of protoplasts to Ca(NO3)2 following the polyethylene glycol treatment. Similarly, when a plasmid (pCAP212) containing an expressible gene for chloramphenicol acetyltransferase was introduced into potato protoplasts through a polyethylene glycol treatment, the transient expression of acetyltransferase was very much increased by the addition of a short incubation of the protoplasts with silver thiosulfate.