POLYAMINE CATABOLISM IN ARABIDOPSIS THALIANA

The until now characterised plant polyamine oxidases (PAO), such as the apoplastic maize PAO(ZmPAO), are involved in the terminal catabolism of spermine (Spm) and spermidine (Spd), contrary tothe animal PAOs which oxidise Spm and Spd through a polyamine back-conversion pathway. InArabidopsis thaliana, five putative PAO genes (AtPAO1-5) are present with a varying sequencehomology (23%-45%) to ZmPAO and predicted subcellular localization (cytosolic and peroxisomal).Biochemical characterization of recombinant AtPAO1, AtPAO2 and AtPAO4 showed that theseenzymes are active not only towards the common polyamines Spd and Spm, but also towards the stress related uncommon polyamines thermine and thermospermine. It was also demonstrated that theseenzymes participate in a polyamine back-conversion pathway which was indeed detected in vivo.Characterization of Arabidopsis knock out mutants and Arabidopsis plants transformed with35SCaMVprom:AtPAO, AtPAOprom:GUS and 35SCaMVprom: AtPAOGFP constructs for allAtPAOs is in progress both under physiological and environmental stress conditions to obtaininformation on AtPAO expression pattern, subcellular localization and physiological role.POSSIBL