title: The Arabidopsis polyamine oxidase/dehydrogenase 5 interferes with cytokinin and auxin signaling pathways to control xylem differentiation.
abstract: In plants, the polyamines putrescine, spermidine, spermine (Spm), and thermospermine (Therm-Spm) participate in several physiological processes. In particular, Therm-Spm is involved in the control of xylem differentiation, having an auxin antagonizing effect. Polyamine oxidases (PAOs) are FAD-dependent enzymes involved in polyamine catabolism. In Arabidopsis, five PAOs are present, among which AtPAO5 catalyzes the back-conversion of Spm, Therm-Spm, and N1-acetyl-Spm to spermidine. In the present study, it is shown that two loss-of-function atpao5 mutants and a 35S::AtPAO5 Arabidopsis transgenic line present phenotypical differences from the wild-type plants with regard to stem and root elongation, differences that are accompanied by changes in polyamine levels and the number of xylem vessels. It is additionally shown that cytokinin treatment, which up-regulates AtPAO5 expression in roots, differentially affects protoxylem differentiation in 35S::AtPAO5, atpao5, and wild-type roots. Together with these findings, Therm-Spm biosynthetic genes, as well as auxin-, xylem-, and cytokinin-related genes (such as ACL5, SAMDC4, PIN1, PIN6, VND6, VND7, ATHB8, PHB, CNA, PXY, XTH3, XCP1, and AHP6) are shown to be differentially expressed in the various genotypes. These data suggest that AtPAO5, being involved in the control of Therm-Spm homeostasis, participates in the tightly controlled interplay between auxin and cytokinins that is necessary for proper xylem differentiation.
authors.affiliation: Department of Sciences, University 'ROMA TRE', Rome, Italy.
authors.forename: Osama
authors.initials: O
authors.lastname: Alabdallah
authors.affiliation: Department of Sciences, University 'ROMA TRE', Rome, Italy.
authors.forename: Abdellah
authors.initials: A
authors.lastname: Ahou
authors.affiliation: Department of Sciences, University 'ROMA TRE', Rome, Italy.
authors.forename: Namrata
authors.initials: N
authors.lastname: Mancuso
authors.affiliation: Department of Sciences, University 'ROMA TRE', Rome, Italy.
authors.forename: Valerio
authors.initials: V
authors.lastname: Pompili
authors.affiliation: Department of Biochemical Sciences 'A. Rossi Fanelli', University of Rome 'La Sapienza', Rome, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Macone
authors.affiliation: Società Agricola Floramiata Servizi srl, 53025 Piancastagnaio, Siena, Italy.
authors.forename: Dimitre
authors.initials: D
authors.lastname: Pashkoulov
authors.affiliation: Department of Sciences, University 'ROMA TRE', Rome, Italy.
authors.forename: Pasquale
authors.initials: P
authors.lastname: Stano
authors.affiliation: Department of Sciences, University 'ROMA TRE', Rome, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Cona
authors.affiliation: Department of Sciences, University 'ROMA TRE', Rome, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Angelini
authors.affiliation: Department of Sciences, University 'ROMA TRE', Rome, Italy.
authors.forename: Paraskevi
authors.initials: P
authors.lastname: Tavladoraki
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002454:Cell Differentiation; D003583:Cytokinins / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D050891:Oxidoreductases Acting on CH-NH2 Group Donors / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D052584:Xylem / Q000166:cytology / Q000201:enzymology / Q000235:genetics; D000097667:Polyamine Oxidase
chemical_list: D029681:Arabidopsis Proteins; D003583:Cytokinins; D007210:Indoleacetic Acids; D050891:Oxidoreductases Acting on CH-NH2 Group Donors; C000624495:PAO5 protein, Arabidopsis; D000097667:Polyamine Oxidase
keywords: Auxin; cytokinins; metaxylem; polyamine oxidases; polyamines; protoxylem; thermospermine; xylem.