title: Involvement of the Putative N-Acetylornithine Deacetylase from Arabidopsis thaliana in Flowering and Fruit Development.
abstract: In eukaryotic cells, the non-proteinogenic amino acid ornithine is the precursor of arginine and polyamines (PAs). The final step of ornithine biosynthesis occurs in plants via a cyclic pathway catalyzed by N(2)-acetylornithine:N-acetylglutamate acetyltransferase (NAOGAcT). An alternative route for ornithine formation, the linear pathway, has been reported for enteric bacteria and a few other organisms; the acetyl group of N(2)-acetylornithine is released as acetate by N(2)-acetylornithine deacetylase (NAOD). NAOD activity has never been demonstrated in plants, although many putative NAOD-like genes have been identified. In this investigation, we examined the effect of down-regulation of the putative Arabidopsis thaliana NAOD gene by using AtNAOD-silenced (sil#17) and T-DNA insertional mutant (atnaod) plants. The ornithine content was consistently reduced in sil#17 and atnaod plants compared with wild-type plants, suggesting that in addition to NAOGAcT action, AtNAOD contributes to the regulation of ornithine levels in plant cells. Ornithine depletion was associated with altered levels of putrescine and spermine. Reduced AtNAOD expression resulted in alterations at the reproductive level, causing early flowering and impaired fruit setting. In this regard, the highest level of AtNAOD expression was observed in unfertilized ovules. Our findings suggest that AtNAOD acts as a positive regulator of fruit setting and agree with those obtained in tomato auxin-synthesizing parthenocarpic plants, where induction of SlNAOD was associated with the onset of ovary growth. Thus, here we have uncovered the first hints of the functions of AtNAOD by connecting its role in flower and fruit development with the regulation of ornithine and PA levels.
authors.affiliation: Department of Biotechnology, University of Verona, Strada Le Grazie 15, 37134 Verona, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Molesini
authors.affiliation: Consiglio per la Ricerca e la Sperimentazione in Agricoltura, CRA-ORT Centro di Ricerca per l'Orticoltura, via Cavalleggeri 25, 84098 Pontecagnano-Faiano (Salerno), Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Mennella
authors.affiliation: Department of Biotechnology, University of Verona, Strada Le Grazie 15, 37134 Verona, Italy.
authors.forename: Flavio
authors.initials: F
authors.lastname: Martini
authors.affiliation: Consiglio per la Ricerca e la Sperimentazione in Agricoltura, CRA-ORT Centro di Ricerca per l'Orticoltura, via Cavalleggeri 25, 84098 Pontecagnano-Faiano (Salerno), Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Francese
authors.affiliation: Department of Biotechnology, University of Verona, Strada Le Grazie 15, 37134 Verona, Italy tiziana.pandolfini@univr.it.
authors.forename: Tiziana
authors.initials: T
authors.lastname: Pandolfini
mesh_terms: D000581:Amidohydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001120:Arginine / Q000378:metabolism; D004269:DNA, Bacterial; D035264:Flowers / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D005638:Fruit / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009952:Ornithine / Q000378:metabolism; D010641:Phenotype; D016415:Sequence Alignment
chemical_list: D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; C036483:T-DNA; D001120:Arginine; D009952:Ornithine; D000581:Amidohydrolases; C000605520:N2-acetylornithine deacetylase, Arabidopsis; C018732:N-acetylornithine deacetylase
keywords: Early flowering; Flower fertility; Fruit development; Ornithine; Polyamines