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Free keywords:
Amino Acids/*analysis
Cell Respiration
Citric Acid Cycle/physiology
Cytosol/enzymology/metabolism
DNA, Complementary
Gene Expression Regulation, Enzymologic
Gene Expression Regulation, Plant
Isocitrate Dehydrogenase/*metabolism
Ketoglutaric Acids/metabolism
Lycopersicon esculentum/*genetics/growth & development/*metabolism
NADP/metabolism
Nitrogen/metabolism
*Photosynthesis/genetics
Pigmentation
Pigments, Biological/metabolism
Plant Leaves/enzymology/metabolism
Plants, Genetically Modified/metabolism
Polymerase Chain Reaction
RNA, Plant/genetics
Abstract:
Transgenic tomato (Solanum lycopersicum) plants were generated targeting the cytosolic NADP-dependent isocitrate dehydrogenase gene (SlICDH1) via the RNA interference approach. The resultant transformants displayed a relatively mild reduction in the expression and activity of the target enzyme in the leaves. However, biochemical analyses revealed that the transgenic lines displayed a considerable shift in metabolism, being characterized by decreases in the levels of the TCA cycle intermediates, total amino acids, photosynthetic pigments, starch and NAD(P)H. The plants showed little change in photosynthesis with the exception of a minor decrease in maximum photosynthetic efficiency (F (v)/F (m)), and a small decrease in growth compared to the wild type. These results reveal that even small changes in cytosolic NADP-dependent isocitrate dehydrogenase activity lead to noticeable alterations in the activities of enzymes involved in primary nitrate assimilation and in the synthesis of 2-oxoglutarate derived amino acids. These data are discussed within the context of current models for the role of the various isoforms of isocitrate dehydrogenase within plant amino acid metabolism.
