Translational and post-translational regulation of polyamine metabolic enzymes in plants

Polyamines are small organic and basic polycations that perform essential regulatory functions in all living organisms. Fluctuations in polyamine content have been observed to occur during growth, development and under stress conditions, implying that polyamines play pivotal roles in diverse cellular and physiological processes. To achieve polyamine homeostasis, the entire metabolic pathway is subjected to a fine-tuned regulation of its biosynthetic and catabolic genes and enzymes. In this review, we describe and discuss the most important mechanisms implicated in the translational and post-translational regulation of polyamine metabolic enzymes in plants. At the translational level, we emphasize the role of polyamines in the modulation of upstream open reading frame (uORF) activities that control the translation of polyamine biosynthetic and catabolic mRNAs. At the post-translational level, different aspects of the regulation of polyamine metabolic proteins are depicted, such as the proteolytic activation of enzyme precursors, the importance of dimerization in protein stability as well as in protein intracellular localization. •Elements in the 5′-UTR negatively regulate translation of polyamine metabolic mRNAs.•Polyamines modulate uORF activity to control translation of their metabolic mRNAs.•Dimerization impacts the localization and activity of polyamine metabolic proteins.•Polyamine metabolic proteins with PEST sequences are targeted to the 26S-proteasome.•Proteolytic cleavage of enzyme precursors is necessary for polyamine biosynthesis.