SAM levels, gene expression of SAM synthetase, methionine synthase and ACC oxidase, and ethylene emission from N. suaveolens flowers.
S'adenosyl-L: -methionine (SAM) is a ubiquitous methyl donor and a precursor in the biosynthesis of ethylene, polyamines, biotin, and nicotianamine in plants. Only limited information is available regarding its synthesis (SAM cycle) and its concentrations in plant tissues. The SAM concentrations in flowers of Nicotiana suaveolens were determined during day/night cycles and found to fluctuate rhythmically between 10 and 50 nmol g(-1) fresh weight. Troughs of SAM levels were measured in the evening and night, which corresponds to the time when the major floral scent compound, methyl benzoate, is synthesized by a SAM dependent methyltransferase (NsBSMT) and when this enzyme possesses its highest activity. The SAM synthetase (NsSAMS1) and methionine synthase (NsMS1) are enzymes, among others, which are involved in the synthesis and regeneration of SAM. Respective genes were isolated from a N. suaveolens petal cDNA library. Transcript accumulation patterns of both SAM regenerating enzymes matched perfectly those of the bifunctional NsBSMT; maximum mRNA accumulations of NsMS1 and NsSAMS1 were attained in the evening. Ethylene, which is synthesized from SAM, reached only low levels of 1-2 ppbv in N. suaveolens flowers. It is emitted in a burst at the end of the life span of the flowers, which correlates with the increased expression of the 1-aminocyclopropane-1-carboxylate oxidase (NsACO).
Roeder
Susanna
S
Department of Biological Sciences, Institute of Biological Sciences, University of Rostock, Albert-Einstein-Strasse 3, Rostock, Germany.
Dreschler
Katharina
K
Wirtz
Markus
M
Cristescu
Simona M
SM
van Harren
Frans J M
FJ
Hell
Rüdiger
R
Piechulla
Birgit
B
D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / Q000145:classification / Q000235:genetics / Q000378:metabolism; D000594:Amino Acid Oxidoreductases / Q000145:classification / Q000235:genetics / Q000378:metabolism; D015152:Blotting, Northern; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D005030:Ethylenes / Q000378:metabolism*; D035264:Flowers / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D015723:Gene Library; D008716:Methionine Adenosyltransferase / Q000145:classification / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D012436:S-Adenosylmethionine / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D013997:Time Factors; D014026:Nicotiana / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
D018076:DNA, Complementary; D005030:Ethylenes; D010940:Plant Proteins; D012436:S-Adenosylmethionine; C036216:ethylene; D000594:Amino Acid Oxidoreductases; C059460:1-aminocyclopropane-1-carboxylic acid oxidase; D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; D008716:Methionine Adenosyltransferase