title: Effects of NAD kinase 2 overexpression on primary metabolite profiles in rice leaves under elevated carbon dioxide.
abstract: The concentration of carbon dioxide (CO2) in the atmosphere is projected to double by the end of the 21st century. In C3 plants, elevated CO2 concentrations promote photosynthesis but inhibit the assimilation of nitrate into organic nitrogen compounds. Several steps of nitrate assimilation depend on the availability of ATP and sources of reducing power, such as nicotinamide adenine dinucleotide phosphate (NADPH). Plastid-localised NAD kinase 2 (NADK2) plays key roles in increasing the ATP/ADP and NADP(H)/NAD(H) ratios. Here we examined the effects of NADK2 overexpression on primary metabolism in rice (Oryza sativa) leaves in response to elevated CO2. By using capillary electrophoresis mass spectrometry, we showed that the primary metabolite profile of NADK2-overexpressing plants clearly differed from that of wild-type plants under ambient and elevated CO2. In NADK2-overexpressing leaves, expression of the genes encoding glutamine synthetase and glutamate synthase was up-regulated, and the levels of Asn, Gln, Arg, and Lys increased in response to elevated CO2. The present study suggests that overexpression of NADK2 promotes the biosynthesis of nitrogen-rich amino acids under elevated CO2.
authors.affiliation: Institute for Environmental Science and Technology, Saitama University, Sakura-ku, Saitama, Japan; Department of Food and Applied Life Sciences, Yamagata University, Tsuruoka, Yamagata, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Onda
authors.forename: A
authors.initials: A
authors.lastname: Miyagi
authors.forename: K
authors.initials: K
authors.lastname: Takahara
authors.forename: H
authors.initials: H
authors.lastname: Uchimiya
authors.forename: M
authors.initials: M
authors.lastname: Kawai-Yamada
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D012275:Oryza / Q000201:enzymology* / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D018515:Plant Leaves / Q000201:enzymology* / Q000378:metabolism*
chemical_list: D002245:Carbon Dioxide; D017853:Phosphotransferases (Alcohol Group Acceptor); C021844:NAD kinase
keywords: Carbon dioxide; NAD kinase 2; chloroplast; nitrogen assimilation; primary metabolites; rice