title: Polyols in grape berry: transport and metabolic adjustments as a physiological strategy for water-deficit stress tolerance in grapevine.
abstract: Polyols are important metabolites that often function as carbon and energy sources and/or osmoprotective solutes in some plants. In grapevine, and in the grape berry in particular, the molecular aspects of polyol transport and metabolism and their physiological relevance are virtually unknown to date. Here, the biochemical function of a grapevine fruit mesocarp polyol transporter (VvPLT1) was characterized after its heterologous expression in yeast. This H(+)-dependent plasma membrane carrier transports mannitol (K m=5.4mM) and sorbitol (K m=9.5mM) over a broad range of polyols and monosaccharides. Water-deficit stress triggered an increase in the expression of VvPLT1 at the fully mature stage, allowing increased polyol uptake into pulp cells. Plant polyol dehydrogenases are oxireductases that reversibly oxidize polyols into monosaccharides. Mannitol catabolism in grape cells (K m=30.1mM mannitol) and mature berry mesocarps (K m=79mM) was, like sorbitol dehydrogenase activity, strongly inhibited (50-75%) by water-deficit stress. Simultaneously, fructose reduction into polyols via mannitol and sorbitol dehydrogenases was stimulated, contributing to their higher intracellular concentrations in water-deficit stress. Accordingly, the concentrations of mannitol, sorbitol, galactinol, myo-inositol, and dulcitol were significantly higher in berry mesocarps from water-deficit-stressed Tempranillo grapevines. Metabolomic profiling of the berry pulp by GC-TOF-MS also revealed many other changes in its composition induced by water deficit. The impact of polyols on grape berry composition and plant response to water deficit stress, via modifications in polyol transport and metabolism, was analysed by integrating metabolomics with transcriptional analysis and biochemical approaches.
authors.affiliation: Centro de Investigação e de Tecnologias Agro-Ambientais e Biológicas (CITAB-UM), Portugal Grupo de Investigação em Biologia Vegetal Aplicada e Inovação Agroalimentar (AgroBioPlant), Departamento de Biologia, Universidade do Minho, 4710-057 Braga, Portugal.
authors.forename: Artur
authors.initials: A
authors.lastname: Conde
authors.affiliation: Instituto de Tecnologia Química e Biológica, Apartado 127, 2781-901 Oeiras, Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Regalado
authors.affiliation: Grupo de Investigação em Biologia Vegetal Aplicada e Inovação Agroalimentar (AgroBioPlant), Departamento de Biologia, Universidade do Minho, 4710-057 Braga, Portugal.
authors.forename: Diana
authors.initials: D
authors.lastname: Rodrigues
authors.affiliation: Instituto de Tecnologia Química e Biológica, Apartado 127, 2781-901 Oeiras, Portugal Instituto Superior de Agronomia, Universidade Técnica de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal.
authors.forename: J Miguel
authors.initials: JM
authors.lastname: Costa
authors.affiliation: Department of Plant Sciences, UC Davis, One Shields Ave, Davis, CA 95616, USA.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Blumwald
authors.affiliation: Instituto de Tecnologia Química e Biológica, Apartado 127, 2781-901 Oeiras, Portugal Instituto Superior de Agronomia, Universidade Técnica de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal.
authors.forename: M Manuela
authors.initials: MM
authors.lastname: Chaves
authors.affiliation: Centro de Investigação e de Tecnologias Agro-Ambientais e Biológicas (CITAB-UM), Portugal Grupo de Investigação em Biologia Vegetal Aplicada e Inovação Agroalimentar (AgroBioPlant), Departamento de Biologia, Universidade do Minho, 4710-057 Braga, Portugal geros@bio.uminho.pt.
authors.forename: Hernâni
authors.initials: H
authors.lastname: Gerós
mesh_terms: D000595:Amino Acid Sequence; D001693:Biological Transport, Active; D050260:Carbohydrate Metabolism; D005638:Fruit / Q000378:metabolism*; D008969:Molecular Sequence Data; D064587:Osmoregulation; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013312:Stress, Physiological / Q000502:physiology*; D027843:Vitis / Q000235:genetics / Q000378:metabolism*; D014867:Water / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D014867:Water
keywords: Grape berry metabolome; VvPLT1; osmoprotection; polyol metabolism; polyol transport; polyol/sugar ratio; water-deficit stress.