title: A vacuolar H(+)-pyrophosphatase differential activation and energy coupling integrate the responses of weeds and crops to drought stress.
abstract: BACKGROUND
  Cyperus rotundus L. is a C4 weed of large vegetative and reproductive vigor endowed with competitive advantages over most crop species mainly under adverse environmental conditions. Vacuole functions are critical for the mechanisms of drought resistance, and here the modulation of the primary system of vacuolar ion transport is investigated during a transient water stress imposed to this weed and to C4 crop species (Zea mays L.).
  
  
  METHODS
  The vacuolar H(+) pumps, the H(+)-ATPase and H(+)-PPiase, expression, activities and the energy coupling were spectrophotometrically investigated as key elements in the differential drought-resistance mechanisms developed by weeds and crops.
  
  
  RESULTS
  In C. rotundus tonoplasts, ATP hydrolysis was more sensitive to drought than its coupled H(+) transport, which was in turn at least 3-folds faster than that mediated by the H(+)-PPiase. Its PPi hydrolysis was only slightly affected by severe water deficit, contrasting with the disruption induced in the PPi-dependent H(+)-gradient. This effect was antagonized by plant rehydration as the H(+)-PPiase activity was highly stimulated, reassuming a coupled PPi-driven H(+) pumping. Maize tonoplasts exhibited 2-4 times lower hydrolytic activities than that of C. rotundus, but were able to overactivate specifically PPi-dependent H(+) pumping in response to stress relief, resulting in an enhanced H(+)-pumps coupling efficiency.
  
  
  CONCLUSIONS
  These results together with immunoanalysis revealed profiles consistent with pre- and post-translational changes occurring on the tonoplast H(+)-pumps, which differ between weeds and crops upon water deficit.
  
  
  CONCLUSIONS
  The evidences highlight an unusual modulation of the H(+)-PPiase energy coupling as a key biochemical change related to environmental stresses adaptive capacity of plants.
authors.affiliation: Laboratório de Biologia Celular e Tecidual, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, RJ, Brazil; Núcleo de Desenvolvimento de Insumos Biológicos para Agricultura (NUDIBA), Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, RJ, Brazil.
authors.forename: Josimara Barcelos
authors.initials: JB
authors.lastname: Venancio
authors.affiliation: Instituto Federal Fluminense, Macaé, RJ, Brazil.
authors.forename: Michelle Guedes
authors.initials: MG
authors.lastname: Catunda
authors.affiliation: Instituto Federal Fluminense, Bom Jesus do Itabapoana, RJ, Brazil.
authors.forename: Juarez
authors.initials: J
authors.lastname: Ogliari
authors.affiliation: Laboratório de Biologia Celular e Tecidual, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, RJ, Brazil; Núcleo de Desenvolvimento de Insumos Biológicos para Agricultura (NUDIBA), Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, RJ, Brazil.
authors.forename: Janaína Aparecida Hottz
authors.initials: JA
authors.lastname: Rima
authors.affiliation: Laboratório de Fisiologia e Bioquímica de Microorganismos, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, RJ, Brazil.
authors.forename: Anna Lvovna
authors.initials: AL
authors.lastname: Okorokova-Facanha
authors.affiliation: Laboratório de Fisiologia e Bioquímica de Microorganismos, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, RJ, Brazil.
authors.forename: Lev Alexandrovitich
authors.initials: LA
authors.lastname: Okorokov
authors.affiliation: Laboratório de Biologia Celular e Tecidual, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, RJ, Brazil; Núcleo de Desenvolvimento de Insumos Biológicos para Agricultura (NUDIBA), Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, RJ, Brazil. Electronic address: arnoldo@uenf.br.
authors.forename: Arnoldo Rocha
authors.initials: AR
authors.lastname: Facanha
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D015153:Blotting, Western; D018556:Crops, Agricultural / Q000378:metabolism*; D055864:Droughts; D006868:Hydrolysis; D043564:Inorganic Pyrophosphatase / Q000502:physiology*; D057685:Plant Weeds / Q000378:metabolism*; D025262:Vacuolar Proton-Translocating ATPases / Q000502:physiology; D014617:Vacuoles / Q000201:enzymology*
chemical_list: D000255:Adenosine Triphosphate; D025262:Vacuolar Proton-Translocating ATPases; D043564:Inorganic Pyrophosphatase
keywords: Cytoplasmic pyrophosphate; Electrochemical gradient; Membrane-bound pyrophosphatase; Metabolic energy; Phosphate pool dynamics; V-type ATPase