title: Binding of spermidine to a unique protein in thin-layer tobacco tissue culture.
abstract: The mechanism by which spermidine induces the appearances of floral buds in thin-layer tobacco (Nicotiana tabacum) tissue culture was studied by following the fate of the radioactive compound.  [3H]Spermidine was taken up rapidly by the tissue, and after a brief lag, a portion was bound to trichloroacetic acid precipitable macromolecules.  Such binding increased to a maximum on day 4 of culture, coinciding with the onset of bud differentiation, and declined thereafter until shortly before flowering.  About 82% of the label in the trichloroacetic acid precipitate remained as spermidine, 14% was metabolized to putrescine, 3% to spermine, and 1% to gamma-aminobutyric acid.  Spermidine was covalently bound to a protein with a molecular size of about 18 kilodaltons.  Hydrolysis of this protein and analysis of the labeled entities revealed 81% spermidine, 16% putrescine, and 3% spermine.  This post-translational modification of a unique protein by attachment of spermidine may be causally connected to the appearance of flower buds in thin-layer tobacco cultures.
authors.affiliation: Department of Biology, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: A
authors.initials: A
authors.lastname: Apelbaum
authors.forename: Z N
authors.initials: ZN
authors.lastname: Canellakis
authors.forename: P B
authors.initials: PB
authors.lastname: Applewhite
authors.forename: R
authors.initials: R
authors.lastname: Kaur-Sawhney
authors.forename: A W
authors.initials: AW
authors.lastname: Galston
mesh_terms: D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D046508:Culture Techniques; D006868:Hydrolysis; D008970:Molecular Weight; D010940:Plant Proteins / Q000032:analysis / Q000378:metabolism*; D010947:Plants, Toxic; D011485:Protein Binding; D011700:Putrescine / Q000032:analysis / Q000378:metabolism; D013095:Spermidine / Q000378:metabolism*; D013096:Spermine / Q000032:analysis / Q000378:metabolism; D013997:Time Factors; D014026:Nicotiana / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism*; D014316:Tritium; D005680:gamma-Aminobutyric Acid / Q000032:analysis / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D014316:Tritium; D013096:Spermine; D005680:gamma-Aminobutyric Acid; D013095:Spermidine; D011700:Putrescine