Induction of ascorbate peroxidase by ethylene and hydrogen peroxide during growth of cultured soybean cells

In cultured soybean cells, a transient ethylene burst in the pre-stationary phase was followed by an induction of ascorbate peroxidase (AsPOX) in the stationary phase. Treatment of cells with the ethylene antagonist, silver thiosulfate (STS), resulted in the suppression of enzyme activity. Application of the ethylene releasing agent 2-chloroethylphosphonic acid (CEPA) in the medium led to an increased enzyme activity when treated in the pre-stationary phase. On the contrary, a remarkable inhibitory effect on enzyme activity was elicited by 1,3-dimethyl-2-thiourea (DMTU), trapping the hydrogen peroxide generated when treated in the stationary phase. Likewise, a steady level of AsPOX transcript was reduced by STS treatment. Furthermore, its effect appeared to be more rapid and prominent during the pre-stationary phase. It is suggested that the induction of AsPOX in cultured soybean cells during the stationary phase could result, at least in part, by the hydrogen peroxide generated as a result of preceding ethylene production.