Influence of pretreatments with inhibitors of putrescine synthesis on polyamine metabolism and differentiation processes of maize calluses

Abstract

The effect of short treatments with 10 mM DL-α-difluoromethylornithine (DFMO) and DL-α-difluoromethylarginine (DFMA), irreversible inhibitors of putrescine synthesis on growth, plant regeneration and endogenous polyamine content of maize ( Zea mays L.) callus cultures was investigated. The effect of exogenous putrescine and the enzymatic activities of arginine decarboxylase (ADC) and ornithine decarboxylase (ODC) were also studied. Of all the assayed treatments, only DFMA significantly decreased callus growth versus control. Enzymatic activity was markedly decreased by the addition of the respective inhibitors in all the treatments. Furthermore, a decrease in ODC and ADC activities was observed when DFMA and DFMO were added respectively to the medium. Whereas a predominance of ODC activity was detected in maintenance medium, ADC activity was the prevalent in differentiation medium. Moreover, DFMO pretreated calluses led to a marked increase in the number of buds with respect to all the other treatments and maintained the capacity of the calluses to regenerate plants. By contrast, although DFMA pretreated calluses raied the number of regenerated plants versus control, the number of buds were decreased and the calluses tended to be eliminated at the end of the differentiation period. The combined addition of putrescine and inhibitors reduced the regeneration rate and the enzymatic activities of the calluses. Nevertheless, the addition of putrescine to the control medium increased the regeneration rate and the number of plants. Differences in endogenous polyamine content (especially putrescine), depending on the treatments, were also observed.