Bridging the Gap between Plant and Mammalian Polyamine Catabolism: A Novel Peroxisomal Polyamine Oxidase Responsible for a Full Back-Conversion Pathway in Arabidopsis    

Abstract

In contrast to animals, where polyamine (PA) catabolism efficiently converts spermine (Spm) to putrescine (Put), plants have been considered to possess a PA catabolic pathway producing 1,3-diaminopropane, D 1 -pyrroline, the corresponding aldehyde, and hydrogen peroxide but unable to back-convert Spm to Put. Arabidopsis (Arabidopsis thaliana) genome contains at least five putative PA oxidase (PAO) members with yet-unknown localization and physiological role(s). AtPAO1 was recently identified as an enzyme similar to the mammalian Spm oxidase, which converts Spm to spermidine (Spd). In this work, we have performed in silico analysis of the five Arabidopsis genes and have identified PAO3 (AtPAO3) as a nontypical PAO, in terms of homology, compared to other known PAOs. We have expressed the gene AtPAO3 and have purified a protein corresponding to it using the inducible heterologous expression system of Escherichia coli. AtPAO3 catalyzed the sequential conversion/ oxidation of Spm to Spd, and of Spd to Put, thus exhibiting functional homology to the mammalian PAOs. The best substrate for this pathway was Spd, whereas the N 1 -acetyl-derivatives of Spm and Spd were oxidized less efficiently. On the other hand, no activity was detected when diamines (agmatine, cadaverine, and Put) were used as substrates. Moreover, although AtPAO3 does not exhibit significant similarity to the other known PAOs, it is efficiently inhibited by guazatine, a potent PAO inhibitor. AtPAO3 contains a peroxisomal targeting motif at the C terminus, and it targets green fluorescence protein to peroxisomes when fused at the N terminus but not at the C terminus. These results reveal that AtPAO3 is a peroxisomal protein and that the C terminus of the protein contains the sorting information. The overall data reinforce the view that plants and mammals possess a similar PA oxidation system, concerning both the subcellular localization and the mode of its action.

Arabidopsis mutant plants with diverse defects in polyamine metabolism show unequal sensitivity to exogenous cadaverine probably based on their spermine content

“…Even in plant, PA back-conversion activity was reported for AtPAO1, an isoform of five Arabidopsis PAOs ). More recently, it was evidenced that AtPAO3 and AtPAO4 catalyze a PA backconversion reaction; AtPAO3 catalyzes the oxidation of Spm to Put via Spd, while AtPAO4 converts Spm to Spd, but not to Put (Moschou et al 2008;Kamada-Nobusada et al 2008). Furthermore, knowledge on Plant PAOs have started to be accumulated (Moschou et al 2008;KamadaNobusada et al 2008;Takahashi et al 2010;Fincato et al 2011;Ono et al 2012).…”

Perturbation of Polyamine Catabolism Can Strongly Affect Root Development and Xylem Differentiation

“…In monocotyledons, PAOs oxidize the carbon at the endo-side of the N 4 -nitrogen of Spd and Spm, producing ABAL and N-(3-aminopropyl)-ABAL, respectively, in addition to DAP and H 2 O 2 (Cona et al, 2006;Angelini et al, 2010). In Arabidopsis, PAOs, namely AtPAO1 , AtPAO2 (Fincato et al, 2011), AtPAO3 (Moschou et al, 2008c), and AtPAO4 (Kamada-Nobusada et al, 2008), oxidize the carbon at the exo-side of the N 4 -nitrogen of Spd and Spm, giving rise to an interconversion catabolism, with the production of Spd from Spm and Put from Spd, in addition to 3-aminopropionaldehyde and H 2 O 2 . Thus, H 2 O 2 is the only shared compound in all the amine oxidase-catalyzed reactions.…”

Polyamine metabolism and lipoxygenase activity during Fusarium oxysporum f. sp. ricini -Castor interaction

“…The 'spermine signaling pathway' involves accumulation of spermine in the apoplast, upregulation of a subset of defence-related genes such as those encoding pathogenesis-related (PR) proteins, PR-1, PR-2, PR-3 and PR-5 (Yamakawa et al 1998) and mitogen-activated protein kinases, and a type of programmed cell death known as the hypersensitive response. This response is triggered by spermine-derived H 2 O 2 , produced through the action of polyamine oxidase (PAO) localized in the apoplast (Kusano et al 2008;Moschou et al 2008). Taken together, these data indicate double-edged roles of spermine in cell survival: as a free radical scavenger in the nucleus and as a source of free radicals in the apoplast, the interaction of spermine with other molecules is involved in the cell death.…”