Enhanced cystathionine beta-lyase activity in transgenic potato plants does not force metabolite flow towards methionine.
Cystathionine beta-lyase (CbL) catalyses the second step in higher-plant methionine biosynthesis. To further characterise the role of CbL in methionine biosynthesis, transgenic potato (Solanum tuberosum L.) plants were generated that express a potato cystathionine beta-lyase (StCbL; EC 4.4.1.8) under the control of the cauliflower mosaic virus 35 S promoter. Transgenic potato lines showed no visible phenotype but revealed an accumulation of both CbL transcript and protein. The enzymatic activity of CbL in these lines was up to 2.5-fold higher than that of wild-type plants. GC-MS measurements of aspartate-derived metabolites, however, showed no significant changes in content of amino acids and pathway intermediates when transgenic and wild-type plants were compared. CbL over-expression did not change the expression patterns and gene products of other pathway-relevant genes as evident from RNA and protein blot analyses. Despite the essential role of CbL in plant growth and development, the data presented indicate that the homologous over-expression of CbL is not in itself able to enhance metabolic flux towards methionine biosynthesis.
Maimann
S
S
Max-Planck-Institut für Molekulare Pflanzenphysiologie, Golm, Germany.
Hoefgen
R
R
Hesse
H
H
D001224:Aspartic Acid / Q000378:metabolism; D003540:Cystathionine / Q000008:administration & dosage; D015971:Gene Expression Regulation, Enzymologic; D008190:Lyases / Q000235:genetics / Q000378:metabolism*; D008715:Methionine / Q000096:biosynthesis*; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011198:Solanum tuberosum / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development
D010940:Plant Proteins; D001224:Aspartic Acid; D003540:Cystathionine; D008715:Methionine; D008190:Lyases; C019965:cystathionine beta-lyase