title: Polyamine Oxidase5 Regulates Arabidopsis Growth through Thermospermine Oxidase Activity.
abstract: The major plant polyamines (PAs) are the tetraamines spermine (Spm) and thermospermine (T-Spm), the triamine spermidine, and the diamine putrescine. PA homeostasis is governed by the balance between biosynthesis and catabolism; the latter is catalyzed by polyamine oxidase (PAO). Arabidopsis (Arabidopsis thaliana) has five PAO genes, AtPAO1 to AtPAO5, and all encoded proteins have been biochemically characterized. All AtPAO enzymes function in the back-conversion of tetraamine to triamine and/or triamine to diamine, albeit with different PA specificities. Here, we demonstrate that AtPAO5 loss-of-function mutants (pao5) contain 2-fold higher T-Spm levels and exhibit delayed transition from vegetative to reproductive growth compared with that of wild-type plants. Although the wild type and pao5 are indistinguishable at the early seedling stage, externally supplied low-dose T-Spm, but not other PAs, inhibits aerial growth of pao5 mutants in a dose-dependent manner. Introduction of wild-type AtPAO5 into pao5 mutants rescues growth and reduces the T-Spm content, demonstrating that AtPAO5 is a T-Spm oxidase. Recombinant AtPAO5 catalyzes the conversion of T-Spm and Spm to triamine spermidine in vitro. AtPAO5 specificity for T-Spm in planta may be explained by coexpression with T-Spm synthase but not with Spm synthase. The pao5 mutant lacking T-Spm oxidation and the acl5 mutant lacking T-Spm synthesis both exhibit growth defects. This study indicates a crucial role for T-Spm in plant growth and development.
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8577, Japan (D.W.K., K.W., C.M., S.I., T.K.);Faculty of Pharmaceutical Sciences, Josai University, Sakado, Saitama 370-0290, Japan (M.N.);University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041 (A.J.M.); andBiodiversity and Climate Research Center, D-60325 Frankfurt am Main, Germany (T.B.).
authors.forename: Dong Wook
authors.initials: DW
authors.lastname: Kim
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8577, Japan (D.W.K., K.W., C.M., S.I., T.K.);Faculty of Pharmaceutical Sciences, Josai University, Sakado, Saitama 370-0290, Japan (M.N.);University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041 (A.J.M.); andBiodiversity and Climate Research Center, D-60325 Frankfurt am Main, Germany (T.B.).
authors.forename: Kanako
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8577, Japan (D.W.K., K.W., C.M., S.I., T.K.);Faculty of Pharmaceutical Sciences, Josai University, Sakado, Saitama 370-0290, Japan (M.N.);University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041 (A.J.M.); andBiodiversity and Climate Research Center, D-60325 Frankfurt am Main, Germany (T.B.).
authors.forename: Chihiro
authors.initials: C
authors.lastname: Murayama
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8577, Japan (D.W.K., K.W., C.M., S.I., T.K.);Faculty of Pharmaceutical Sciences, Josai University, Sakado, Saitama 370-0290, Japan (M.N.);University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041 (A.J.M.); andBiodiversity and Climate Research Center, D-60325 Frankfurt am Main, Germany (T.B.).
authors.forename: Sho
authors.initials: S
authors.lastname: Izawa
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8577, Japan (D.W.K., K.W., C.M., S.I., T.K.);Faculty of Pharmaceutical Sciences, Josai University, Sakado, Saitama 370-0290, Japan (M.N.);University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041 (A.J.M.); andBiodiversity and Climate Research Center, D-60325 Frankfurt am Main, Germany (T.B.).
authors.forename: Masaru
authors.initials: M
authors.lastname: Niitsu
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8577, Japan (D.W.K., K.W., C.M., S.I., T.K.);Faculty of Pharmaceutical Sciences, Josai University, Sakado, Saitama 370-0290, Japan (M.N.);University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041 (A.J.M.); andBiodiversity and Climate Research Center, D-60325 Frankfurt am Main, Germany (T.B.).
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Michael
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8577, Japan (D.W.K., K.W., C.M., S.I., T.K.);Faculty of Pharmaceutical Sciences, Josai University, Sakado, Saitama 370-0290, Japan (M.N.);University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041 (A.J.M.); andBiodiversity and Climate Research Center, D-60325 Frankfurt am Main, Germany (T.B.).
authors.forename: Thomas
authors.initials: T
authors.lastname: Berberich
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8577, Japan (D.W.K., K.W., C.M., S.I., T.K.);Faculty of Pharmaceutical Sciences, Josai University, Sakado, Saitama 370-0290, Japan (M.N.);University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041 (A.J.M.); andBiodiversity and Climate Research Center, D-60325 Frankfurt am Main, Germany (T.B.) kusano@ige.tohoku.ac.jp.
authors.forename: Tomonobu
authors.initials: T
authors.lastname: Kusano