title: Phosphoenolpyruvate carboxykinase (PEPCK) deficiency affects the germination, growth and fruit sugar content in tomato (Solanum lycopersicum L.).
abstract: Phosphoenolpyruvate carboxykinase (PEPCK) is a key regulatory enzyme and is utilized in the gluconeogenesis pathway in plants. Although, its catalytic and regulatory properties are quite well understood, there are uncertainties regarding its physiological role in many plants tissues such as the flesh of developing fruits. To further understand the function of PEPCK in fruits and other tissues, RNAi transgenic tomato plants in which SlPEPCK transcription was down-regulated by either CaMV 35S constitutive promoter or the fruit-specific E8 promoter were generated and characterized on the basis of their phenotypic and metabolic aspects. In the PEPCK-deficient lines, prominent growth suppression of germinated seedlings was observed and other vegetative suppression appeared during the early stage of plant growth in the 35S promoter-driven lines. In particular, root elongation was most obviously suppressed in the germinated seedlings, indicating that the gluconeogenesis pathway is involved in the root growth of seedlings. Regarding the primary metabolism in fruit, the soluble sugar content tended to decrease, whereas the malate content tended to increase in ripening fruits of the RNAi lines compared with the wild type. These results indicate that activation of the gluconeogenesis pathway from organic acids to sugars occurs during ripening but is suppressed by the knocking down of the PEPCK gene, suggesting that PEPCK participates in determining the sugar/acid ratio in ripening fruit.
authors.affiliation: Graduate School of Life and Environment Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8572, Japan.
authors.forename: Yong-Xing
authors.initials: YX
authors.lastname: Huang
authors.affiliation: Graduate School of Life and Environment Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8572, Japan; Quantum Beam Science Center, Japan Atomic Energy Agency (JAEA), Watanuki 1233, Takasaki, Gunma 370-1292, Japan.
authors.forename: Yong-Gen
authors.initials: YG
authors.lastname: Yin
authors.affiliation: Graduate School of Life and Environment Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8572, Japan.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Sanuki
authors.affiliation: Graduate School of Life and Environment Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8572, Japan.
authors.forename: Naoya
authors.initials: N
authors.lastname: Fukuda
authors.affiliation: Graduate School of Life and Environment Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8572, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ezura
authors.affiliation: Graduate School of Life and Environment Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8572, Japan. Electronic address: matsukura.chiaki.fw@u.tsukuba.ac.jp.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Matsukura
mesh_terms: D050260:Carbohydrate Metabolism; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D018525:Germination / Q000502:physiology*; D018551:Solanum lycopersicum / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism / Q000502:physiology; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D030821:Plants, Genetically Modified; D014158:Transcription, Genetic
chemical_list: D019764:Phosphoenolpyruvate Carboxykinase (ATP)
keywords: Fruit; Gluconeogenesis; PEPCK; Seedling growth; Sugar content; Tomato