The members of Arabidopsis thaliana PAO gene family exhibit distinct tissue- and organ-specific expression pattern during seedling growth and flower development

Polyamine oxidases (PAOs) are FAD-dependent enzymes involved in polyamine catabolism. In Arabidopsis thaliana, five PAOs (AtPAO1-5) are present with cytosolic or peroxisomal localization. Here, we present a detailed study of the expression pattern of AtPAO1, AtPAO2, AtPAO3 and AtPAO5 during seedling and flower growth and development through analysis of promoter activity in AtPAO::beta-glucuronidase (GUS) transgenic Arabidopsis plants. The results reveal distinct expression patterns for each studied member of the AtPAO gene family. AtPAO1 is mostly expressed in the transition region between the meristematic and the elongation zone of roots and anther tapetum, AtPAO2 in the quiescent center, columella initials and pollen, AtPAO3 in columella, guard cells and pollen, and AtPAO5 in the vascular system of roots and hypocotyls. Furthermore, treatment with the plant hormone abscisic acid induced expression of AtPAO1 in root tip and AtPAO2 in guard cells. These data suggest distinct physiological role(s) for each member of the AtPAO gene family.