Effects of inhibitors of polyamine biosynthesis on growth and organization of meristematic centers in Petunia protoplast cultures

Abstract

We examined the effects of inhibitors of the polyamine biosynthetic enzymes arginine decarboxylase (ADC), ornithine decarboxylase (ODC) and spermidine synthase (Spd synthase) on growth and organogenesis in cultures derived from mesophyll protoplasts of Petunia hybrida Vilm cv. Fire Chief. Both processes were dramatically inhibited when protoplasts were cultured in a mixture of dl-α-difluoromethylarginine (DFMA) and dl-ga-difluoromethylornithine (DFMO), specific inhibitors of ADC and ODC respectively, and cyclohexylamine sulfate (CHA) an inhibitor of Spd synthase. The inhibition was partially reversed by addition of micromolar amounts of both putrescine and spermidine. Treatment with DFMA markedly inhibited organization of meristematic centers and reduced levels of free and bound putrescine, while treatment with CHA was less effective. In contrast, treatment with DFMO promoted growth and organization with concomitant increases in bound putrescine and spermidine. The results suggest that putrescine synthesized via ADC is involved in growth and organogenesis.