Isolation and characterization of senescence-induced cDNAs encoding deoxyhypusine synthase and eucaryotic translation initiation factor 5A from tomato.
Full-length cDNA clones encoding deoxyhypusine synthase (DHS) and eucaryotic initiation factor 5A (eIF-5A) have been isolated from a cDNA expression library prepared from tomato leaves (Lycopersicon esculentum, cv. Match) exposed to environmental stress. DHS mediates the first of two enzymatic reactions that activate eIF-5A by converting a conserved lysine to the unusual amino acid, deoxyhypusine. Recombinant protein obtained by expressing tomato DHS cDNA in Escherichia coli proved capable of carrying out the deoxyhypusine synthase reaction in vitro in the presence of eIF-5A. Of particular interest is the finding that DHS mRNA and eIF-5A mRNA show a parallel increase in abundance in senescing tomato flowers, senescing tomato fruit, and environmentally stressed tomato leaves exhibiting programmed cell death. Western blot analyses indicated that DHS protein also increases at the onset of senescence. It is apparent from previous studies with yeast and mammalian cells that hypusine-modified eIF-5A facilitates the translation of a subset of mRNAs mediating cell division. The present study provides evidence for senescence-induced DHS and eIF-5A in tomato tissues that may facilitate the translation of mRNA species required for programmed cell death.
Department of Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
T W
TW
Wang
L
L
Lu
D
D
Wang
J E
JE
Thompson
D000375:Aging; D000595:Amino Acid Sequence; D001105:Archaea / Q000235:genetics; D001483:Base Sequence; D017124:Conserved Sequence; D018076:DNA, Complementary; D005658:Fungi / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D015723:Gene Library; D006801:Humans; D018551:Solanum lycopersicum / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D008239:Lysine; D008969:Molecular Sequence Data; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000235:genetics* / Q000378:metabolism; D010448:Peptide Initiation Factors / Q000235:genetics* / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D018547:Plant Stems / Q000378:metabolism; D010944:Plants / Q000235:genetics; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D000097574:Eukaryotic Translation Initiation Factor 5A
D018076:DNA, Complementary; D008239:Lysine; D000587:Oxidoreductases Acting on CH-NH Group Donors; D010448:Peptide Initiation Factors; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D000097574:Eukaryotic Translation Initiation Factor 5A; C063507:deoxyhypusine synthase