Polyamines: essential factors for growth and survival

Abstract

Polyamines are low molecular weight, aliphatic polycations found in the cells of all living organisms. Due to their positive charges, polyamines bind to macromolecules such as DNA, RNA, and proteins. They are involved in diverse processes, including regulation of gene expression, translation, cell proliferation, modulation of cell signalling, and membrane stabilization. They also modulate the activities of certain sets of ion channels. Because of these multifaceted functions, the homeostasis of polyamines is crucial and is ensured through regulation of biosynthesis, catabolism, and transport. Through isolation of the genes involved in plant polyamine biosynthesis and loss-of-function experiments on the corresponding genes, their essentiality for growth is reconfirmed. Polyamines are also involved in stress responses and diseases in plants, indicating their importance for plant survival. This review summarizes the recent advances in polyamine research in the field of plant science compared with the knowledge obtained in microorganisms and animal systems.

Increased Polyamine Biosynthesis Enhances Stress Tolerance by Preventing the Accumulation of Reactive Oxygen Species: T-DNA Mutational Analysis of Oryza sativa Lysine Decarboxylase-like Protein 1

“…PAs have also been described as membrane protectors (Alcázar et al, 2006;Kusano et al, 2008), a property that is consistent with the observation that the addition of spermine dramatically inhibited H 2 O 2 -induced ion leakage in WT plants (Fig. 10B).…”

“…Above a certain threshold level, PAs can be harmful to plant cells and can induce cell death. Because of this, intracellular free PA concentrations are tightly regulated at various steps, including de novo synthesis, conjugation, degradation, and transport (Kusano et al, 2008). In the osldc-like 1 HM mutant, free putrescine was increased by only 25%, whereas there was a 3.18-fold increase in conjugated putrescine (Figs.…”

“…In plants, PAs are present as free bases or conjugated to small molecules, mainly hydroxycinnamic acids, and to various macromolecules such as proteins (Alcázar et al, 2006). It was recently suggested that there is a reverse PA pathway in plants from spermine to putrescine (Kusano et al, 2008). The biosynthetic pathway that converts putrescine into spermidine and spermine is also important in conferring plant stress tolerance (Capell et al, 2004).…”

“…Cadaverine is synthesized from lysine by lysine decarboxylase (LDC) (Bagni and Tassoni, 2001;Flores et al, 1989). PAs localize to the cytoplasm as well as organelles such as vacuoles, mitochondria, and chloroplasts (Kusano et al, 2008).…”

“…Cadaverine, which is relatively less abundant, is present in various bacteria and in several higher plant families such as Gramineae, Poaceae, Solanaceae, and in particular, Leguminosae (Ohe et al, 2009). The long-standing observation that putrescine levels increase in response to potassium deficiency has led investigators to examine changes in PA levels following exposure to single or combinations of stress (Groppa and Benavides, 2008;Kusano et al, 2008). In many cases, stress leads to an accumulation of free or conjugated PAs, which indicates that PA biosynthesis may be an integral component of plant stress responses.…”