Geigenberger P., Regierer B., Nunes-Nesi A., Leisse A., Urbanczyk-Wochniak E., Springer F., Van Dongen J.T., Kossmann J., Fernie A.R.
Max Planck Institute of Molecular Plant Physiology, 14476 Golm, Germany; Institute for Plant Biotechnology, Botany and Zoology Department, Stellenbosch University, Maiteland 7601, South Africa
Geigenberger, P., Max Planck Institute of Molecular Plant Physiology, 14476 Golm, Germany; Regierer, B., Max Planck Institute of Molecular Plant Physiology, 14476 Golm, Germany; Nunes-Nesi, A., Max Planck Institute of Molecular Plant Physiology, 14476 Golm, Germany; Leisse, A., Max Planck Institute of Molecular Plant Physiology, 14476 Golm, Germany; Urbanczyk-Wochniak, E., Max Planck Institute of Molecular Plant Physiology, 14476 Golm, Germany; Springer, F., Max Planck Institute of Molecular Plant Physiology, 14476 Golm, Germany; Van Dongen, J.T., Max Planck Institute of Molecular Plant Physiology, 14476 Golm, Germany; Kossmann, J., Institute for Plant Biotechnology, Botany and Zoology Department, Stellenbosch University, Maiteland 7601, South Africa; Fernie, A.R., Max Planck Institute of Molecular Plant Physiology, 14476 Golm, Germany
Pyrimidine nucleotides are of general importance for many aspects of cell function, but their role in the regulation of biosynthetic processes is still unclear. In this study, we investigate the influence of a decreased expression of UMP synthase (UMPS), a key enzyme in the pathway of de novo pyrimidine synthesis, on biosynthetic processes in growing potato (Solanum tuberosum) tubers. Transgenic plants were generated expressing UMPS in the antisense orientation under the control of the tuber-specific patatin promoter. Lines were selected with markedly decreased expression of UMPS in the tubers. Decreased expression of UMPS restricted the use of externally supplied orotate for de novo pyrimidine synthesis in tuber tissue, whereas the uridine-salvaging pathway was stimulated. This shift in the pathways of UMP synthesis was accompanied by increased levels of tuber uridine nucleotides, increased fluxes of [ 14C]sucrose to starch and cell wall synthesis, and increased amounts of starch and cell wall components in the tubers, whereas there were no changes in uridine nucleotide levels in leaves. Decreased expression of UMPS in tubers led to an increase in transcript levels of carbamoylphosphate synthase, uridine kinase, and uracil phosphoribosyltransferase, the latter two encoding enzymes in the pyrimidine salvage pathways. Thus, the results show that antisense inhibition of the de novo pathway of pyrimidine synthesis leads to a compensatory stimulation of the less energy-consuming salvage pathways, probably via increased expression and activity of uridine kinase and uracil phosphoribosyl-transferase. This results in increased uridine nucleotide pool levels in tubers and improved biosynthetic performance. © 2005 American Society of Plant Biologists.
Cells; Growth kinetics; Plants (botany); Starch; Tissue; Pyrimidine salvage pathway; Pyrimidine synthesis; Transgenic plants; Uracil phosphoribosyl-transferase; Biosynthesis; Biosynthesis; Cells; Growth; Plants; Starch; Tissue; Solanum tuberosum; antisense oligonucleotide; multienzyme complex; orotate phosphoribosyltransferase; orotic acid; orotidine 5' phosphate decarboxylase; pyrimidine derivative; uridine; uridine 5' phosphate synthase; uridine 5'-monophosphate synthase; article; biosynthesis; down regulation; enzyme activation; gene expression regulation; genetics; growth, development and aging; metabolism; physiology; plant tuber; potato; promoter region; signal transduction; transgenic plant; upregulation; Down-Regulation; Enzyme Activation; Gene Expression Regulation, Plant; Multienzyme Complexes; Oligoribonucleotides, Antisense; Orotate Phosphoribosyltransferase; Orotic Acid; Orotidine-5'-Phosphate Decarboxylase; Plant Tubers; Plants, Genetically Modified; Promoter Regions (Genetics); Pyrimidines; Signal Transduction; Solanum tuberosum; Up-Regulation; Uridine