title: Oxalate synthesis in leaves is associated with root uptake of nitrate and its assimilation in spinach (Spinacia oleracea L.) plants.
abstract: BACKGROUND
  Excessive accumulation of oxalate in numerous vegetables adversely affects their quality as food. While it is known that nitrate could effectively stimulate oxalate accumulation in many vegetables, little information is available about the mechanism of nitrate-induced oxalate accumulation. In this study, we examined the association of oxalate synthesis with nitrate uptake and assimilation in two genotypes of spinach (Spinacia oleracea L.), Heizhenzhu and Weilv.
  
  
  RESULTS
  Increasing nitrate levels resulted in enhanced synthesis of oxalate, as well as increased root uptake of nitrate and leaf activities of nitrate reductase (NR) and glutamine synthetase (GS) for both genotypes. Correlation analysis revealed that oxalate accumulation in spinach leaves was positively related with rate of nitrate uptake by roots, as well as leaf activities of NR and GS. Addition of plasmalemma H(+)-ATPase inhibitor sodium vanadate (Na3VO4) significantly decreased leaf oxalate accumulation in both genotypes. Presence of NR or GS inhibitors led to reduction of leaf oxalate contents, GS/NR activities and decreased nitrate uptake rate. Significantly higher levels of nitrate root uptake, leaf NR and GS activities were observed in the high-oxalate genotype Heizhenzhu than in Weilv.
  
  
  CONCLUSIONS
  Oxalate synthesis in leaves of spinach is not only positively associated with root uptake of nitrate, but also with its assimilation within the plants.
authors.affiliation: MOE Key Laboratory of Environment Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Xiao Xia
authors.initials: XX
authors.lastname: Liu
authors.affiliation: MOE Key Laboratory of Environment Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Zhou
authors.affiliation: MOE Key Laboratory of Environment Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Agricultural Experimental Station, Zhejiang University, Hangzhou 310058, China.
authors.forename: Rong
authors.initials: R
authors.lastname: Jin
authors.affiliation: MOE Key Laboratory of Environment Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.|Key Laboratory of Subtropical Soil Science and Plant Nutrition of Zhejiang Province, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Ling Li
authors.initials: LL
authors.lastname: Lu
authors.affiliation: MOE Key Laboratory of Environment Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.|Key Laboratory of Subtropical Soil Science and Plant Nutrition of Zhejiang Province, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Chong Wei
authors.initials: CW
authors.lastname: Jin
authors.affiliation: MOE Key Laboratory of Environment Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.|Agricultural Experimental Station, Zhejiang University, Hangzhou 310058, China.
authors.forename: Xian Yong
authors.initials: XY
authors.lastname: Lin
mesh_terms: D001692:Biological Transport; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D005974:Glutamate-Ammonia Ligase / Q000235:genetics / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D050901:Nitrate Reductase / Q000235:genetics / Q000378:metabolism; D009566:Nitrates / Q000737:chemistry / Q000378:metabolism*; D019815:Oxalic Acid / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors; D018724:Spinacia oleracea / Q000737:chemistry* / Q000378:metabolism*; D014638:Vanadates / Q000494:pharmacology
chemical_list: D009566:Nitrates; D014638:Vanadates; D019815:Oxalic Acid; D050901:Nitrate Reductase; D006180:Proton-Translocating ATPases; D005974:Glutamate-Ammonia Ligase
keywords: genotype; nitrate reduction; nitrate uptake; oxalate; spinach