title: Heterologous expression of a ketohexokinase in potato plants leads to inhibited rates of photosynthesis, severe growth retardation and abnormal leaf development.
abstract: In the present paper we investigated the effect of heterologous expression of a rat liver ketohexokinase in potato (Solanum tuberosum L.) plants with the aim of investigating the role of fructose 1-phosphate in plant metabolism. Plants were generated that contained appreciable activity of ketohexokinase but did not accumulate fructose 1-phosphate. They were, however, characterised by a severe growth retardation and abnormal leaf development. Studies of (14)CO(2) assimilation and metabolism, and of the levels of photosynthetic pigments, revealed that these lines exhibited restricted photosynthesis. Despite this fact, the levels of starch and soluble sugars remained relatively constant. Analysis of intermediates of starch and sucrose biosynthesis revealed large increases in the triose phosphate and fructose 1,6-bisphosphate pools but relatively unaltered levels of inorganic phosphate and 3-phosphoglycerate, and these lines were also characterised by an accumulation of glyceraldehyde. The transformants neither displayed consistent changes in the activities of Calvin cycle enzymes nor in enzymes of sucrose synthesis but displayed a metabolic profile partially reminiscent of that brought about by end-product limitation, but most likely caused by an inhibition of photosynthesis brought about by the accumulation of glyceraldehyde. Analysis of the metabolite contents in lamina and vein fractions of the leaf, and of the enzymes of carbohydrate oxidation indicate that the phloem-enriched veins of ketohexokinase-expressing leaves tend toward hypoxia and indicate a problem of phloem transport.
authors.affiliation: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Golm, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Geigenberger
authors.forename: Babette
authors.initials: B
authors.lastname: Regierer
authors.forename: Anna
authors.initials: A
authors.lastname: Lytovchenko
authors.forename: Andrea
authors.initials: A
authors.lastname: Leisse
authors.forename: Nicolas
authors.initials: N
authors.lastname: Schauer
authors.forename: Fransiska
authors.initials: F
authors.lastname: Springer
authors.forename: Jens
authors.initials: J
authors.lastname: Kossmann
authors.forename: Alisdair R
authors.initials: AR
authors.lastname: Fernie
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D005631:Fructokinases / Q000235:genetics* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D006593:Hexokinase / Q000235:genetics / Q000378:metabolism; D008099:Liver / Q000201:enzymology; D018515:Plant Leaves / Q000235:genetics*; D030821:Plants, Genetically Modified; D051381:Rats; D011198:Solanum tuberosum / Q000201:enzymology* / Q000254:growth & development / Q000502:physiology; D014158:Transcription, Genetic
chemical_list: D002734:Chlorophyll; D002245:Carbon Dioxide; D005631:Fructokinases; D006593:Hexokinase; C021475:ketohexokinase