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- Title
Highly-expressed polyamine oxidases catalyze polyamine back conversion in <italic>Brachypodium distachyon</italic>.
- Authors
Takahashi, Yoshihiro; Ono, Kaede; Akamine, Yuuta; Asano, Takuya; Ezaki, Masatoshi; Mouri, Itsupei
- Abstract
To understand the polyamine (PA) catabolic pathways in <italic>Brachypodium distachyon</italic>, we focused on the flavin-containing polyamine oxidase enzymes (PAO), and characterized them at the molecular and biochemical levels. Five <italic>PAO</italic> isoforms were identified from database searches, and we named them BdPAO1 to BdPAO5. By gene expression analysis using above-ground tissues such as leaf, stem and inflorescence, it was revealed that <italic>BdPAO2</italic> is the most abundant PAO gene in normal growth conditions, followed by <italic>BdPAO3</italic> and <italic>BdPAO4. BdPAO1</italic> and <italic>BdPAO5</italic> were expressed at very low levels. All <italic>Arabidopsis thaliana</italic> and rice orthologs belonging to the same clade as BdPAO2, BdPAO3 and BdPAO4 have conserved peroxisome-targeting signal sequences at their C-termini. Amino acid sequences of BdPAO2 and BdPAO4 also showed such a sequence, but BdPAO3 did not. We selected the gene with the highest expression level (<italic>BdPAO2</italic>) and the peroxisome-targeting signal lacking PAO (<italic>BdPAO3</italic>) for biochemical analysis of substrate specificity and catabolic pathways. BdPAO2 catalyzed conversion of spermine (Spm) or thermospermine to spermidine (Spd), and Spd to putrescine, but its most-favored substrate was Spd. In contrast, BdPAO3 favored Spm as substrate and catalyzed conversion of tetraamines to Spd. These results indicated that the major PAOs in <italic>B. distachyon</italic> have back-conversion activity.
- Subjects
POLYAMINES; BRACHYPODIUM; FLAVINS; INFLORESCENCES; GENE expression in plants
- Publication
Journal of Plant Research, 2018, Vol 131, Issue 2, p341
- ISSN
0918-9440
- Publication type
Article
- DOI
10.1007/s10265-017-0989-2