title: Mild reductions in mitochondrial NAD-dependent isocitrate dehydrogenase activity result in altered nitrate assimilation and pigmentation but do not impact growth.
abstract: Transgenic tomato (Solanum lycopersicum) plants were generated expressing a fragment of the mitochondrial NAD-dependent isocitrate dehydrogenase gene (SlIDH1) in the antisense orientation. The transgenic plants displayed a mild reduction in the activity of the target enzyme in the leaves but essentially no visible alteration in growth from the wild-type. Fruit size and yield were, however, reduced. These plants were characterized by relatively few changes in photosynthetic parameters, but they displayed a minor decrease in maximum photosynthetic efficiency (Fv/Fm). Furthermore, a clear reduction in flux through the tricarboxylic acid (TCA) cycle was observed in the transformants. Additionally, biochemical analyses revealed that the transgenic lines exhibited considerably altered metabolism, being characterized by slight decreases in the levels of amino acids, intermediates of the TCA cycle, photosynthetic pigments, starch, and NAD(P)H levels, but increased levels of nitrate and protein. Results from these studies show that even small changes in mitochondrial NAD-dependent isocitrate dehydrogenase activity lead to noticeable alterations in nitrate assimilation and suggest the presence of different strategies by which metabolism is reprogrammed to compensate for this deficiency.
authors.affiliation: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, Germany.
authors.forename: Agata
authors.initials: A
authors.lastname: Sienkiewicz-Porzucek
authors.forename: Ronan
authors.initials: R
authors.lastname: Sulpice
authors.forename: Sonia
authors.initials: S
authors.lastname: Osorio
authors.forename: Ina
authors.initials: I
authors.lastname: Krahnert
authors.forename: Andrea
authors.initials: A
authors.lastname: Leisse
authors.forename: Ewa
authors.initials: E
authors.lastname: Urbanczyk-Wochniak
authors.forename: Michael
authors.initials: M
authors.lastname: Hodges
authors.forename: Alisdair R
authors.initials: AR
authors.lastname: Fernie
authors.forename: Adriano
authors.initials: A
authors.lastname: Nunes-Nesi
mesh_terms: D002952:Citric Acid Cycle / Q000235:genetics / Q000502:physiology; D007521:Isocitrate Dehydrogenase / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D018551:Solanum lycopersicum / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology*; D009566:Nitrates / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D010788:Photosynthesis / Q000235:genetics / Q000502:physiology; D010802:Phylogeny; D010858:Pigmentation / Q000235:genetics / Q000502:physiology; D010940:Plant Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D009566:Nitrates; D010940:Plant Proteins; D007521:Isocitrate Dehydrogenase