title: Hyperacidification of vacuoles by the combined action of two different P-ATPases in the tonoplast determines flower color.
abstract: The acidification of endomembrane compartments is essential for enzyme activities, sorting, trafficking, and trans-membrane transport of various compounds. Vacuoles are mildly acidic in most plant cells because of the action of V-ATPase and/or pyrophosphatase proton pumps but are hyperacidified in specific cells by mechanisms that remained unclear. Here, we show that the blue petal color of petunia ph mutants is due to a failure to hyperacidify vacuoles. We report that PH1 encodes a P3B-ATPase, hitherto known as Mg2(+) transporters in bacteria only, that resides in the vacuolar membrane (tonoplast). In vivo nuclear magnetic resonance and genetic data show that PH1 is required and, together with the tonoplast H(+) P3A-ATPase PH5, sufficient to hyperacidify vacuoles. PH1 has no H(+) transport activity on its own but can physically interact with PH5 and boost PH5 H(+) transport activity. Hence, the hyperacidification of vacuoles in petals, and possibly other tissues, relies on a heteromeric P-ATPase pump.
authors.affiliation: Department of Molecular Cell Biology, Graduate School of Experimental Plant Sciences, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands.
authors.forename: Marianna
authors.initials: M
authors.lastname: Faraco
authors.affiliation: Department of Molecular Cell Biology, Graduate School of Experimental Plant Sciences, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands.
authors.forename: Cornelis
authors.initials: C
authors.lastname: Spelt
authors.affiliation: Department of Molecular Cell Biology, Graduate School of Experimental Plant Sciences, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands.
authors.forename: Mattijs
authors.initials: M
authors.lastname: Bliek
authors.affiliation: Department of Molecular Cell Biology, Graduate School of Experimental Plant Sciences, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands.
authors.forename: Walter
authors.initials: W
authors.lastname: Verweij
authors.affiliation: Department of Molecular Cell Biology, Graduate School of Experimental Plant Sciences, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands; National Institute for Basic Biology, Nishigonaka 38, Myodaiji, Okazaki, 444-8585 Aichi, Japan; Department of Basic Biology, The Graduate University for Advanced Studies (Sokendai), 444-8585 Okazaki, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hoshino
authors.affiliation: Dipartimento Scienze Agrarie e Ambientali, Produzione, Territorio, Agroenergia, Università degli Studi di Milano, Via G. Celoria 2, 20133 Milano, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Espen
authors.affiliation: Dipartimento Scienze Agrarie e Ambientali, Produzione, Territorio, Agroenergia, Università degli Studi di Milano, Via G. Celoria 2, 20133 Milano, Italy.
authors.forename: Bhakti
authors.initials: B
authors.lastname: Prinsi
authors.affiliation: Department of Molecular Cell Biology, Graduate School of Experimental Plant Sciences, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands.
authors.forename: Rinse
authors.initials: R
authors.lastname: Jaarsma
authors.affiliation: Department of Molecular Cell Biology, Graduate School of Experimental Plant Sciences, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands.
authors.forename: Eray
authors.initials: E
authors.lastname: Tarhan
authors.affiliation: Department of Molecular Cell Biology, Graduate School of Experimental Plant Sciences, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands.
authors.forename: Albertus H
authors.initials: AH
authors.lastname: de Boer
authors.affiliation: Di.S.Te.B.A., Università del Salento, Campus Ecotekne, 73100 Lecce, Italy.
authors.forename: Gian-Pietro
authors.initials: GP
authors.lastname: Di Sansebastiano
authors.affiliation: Department of Molecular Cell Biology, Graduate School of Experimental Plant Sciences, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands. Electronic address: ronald.koes@vu.nl.
authors.forename: Ronald
authors.initials: R
authors.lastname: Koes
authors.affiliation: Department of Molecular Cell Biology, Graduate School of Experimental Plant Sciences, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands. Electronic address: f.m.quattrocchio@vu.nl.
authors.forename: Francesca M
authors.initials: FM
authors.lastname: Quattrocchio
mesh_terms: D000595:Amino Acid Sequence; D035264:Flowers / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D009154:Mutation; D032306:Petunia / Q000201:enzymology / Q000378:metabolism*; D010802:Phylogeny; D010858:Pigmentation; D006180:Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D011522:Protons; D014617:Vacuoles / Q000201:enzymology / Q000378:metabolism*
chemical_list: D011522:Protons; D006180:Proton-Translocating ATPases