Role of ethylene on induction and expression of carrot somatic embryogenesis: relationship with polyamine metabolism

Abstract

The effects of ethylene on somatic embryogenesis were investigated during the induction phase (with auxin) and expression phase (without auxin) in carrot ( Daucus carota L.) cell cultures. The addition of 2-chloroethylphosphonic acid (CEPA), an exogenous source of ethylene, during the induction phase or after day 7 of the expression phase did not affect the level of somatic embryogenesis. However, an increase of ethylene concentration at the begining of the expression phase inhibited embryo formation. During this same period, ethylene reduced the polyamine formation from [U- 14C]arginine by inhibiting the activities of arginine decarboxylase (ADC, EC 4.1.1.19) and S-adenosylmethionine decarboxylase (SAMDC, EC 4.1.1.50). Furthermore, the addition of exogenous spermidine to ethylene-treated cells can restore the embryogenic potential of carrot cells. The results demonstrate that there is a physiological relationship between ethylene, polyamine biosynthesis and somatic embryogenesis.