title: Post-transcriptional regulation of nitrate reductase by light is abolished by an N-terminal deletion.
abstract: Higher plant nitrate reductases (NRs) carry an N-terminal domain whose sequence is not conserved in NRs from other organisms. A gene composed of a full-length tobacco NR cDNA with an internal deletion of 168 bp in the 5' end fused to the cauliflower mosaic virus 35S promoter and appropriate termination signals was constructed and designated as delta NR. An NR-deficient mutant of Nicotiana plumbaginifolia was transformed with this delta NR gene. In transgenic plants expressing this construct, NR activity was restored and normal growth resulted. Apart from a higher thermosensitivity, no appreciable modification of the kinetic parameters of the enzyme was detectable. The post-transcriptional regulation of NR by light was abolished in delta NR transformants. Consequently, deregulated production of glutamine and asparagine was detected in delta NR transformants. The absence of in vitro delta NR activity modulation by ATP suggests the impairment of delta NR phosphorylation and thereby suppression of delta NR post-translational regulation. These data imply that post-transcriptional control of NR expression is important for the flow of the nitrate assimilatory pathway.
authors.affiliation: Laboratoire de Biologie Cellulaire, Institut National de la Recherche Agronomique, Centre de Versailles, Versailles, France.
authors.forename: L
authors.initials: L
authors.lastname: Nussaume
authors.forename: M
authors.initials: M
authors.lastname: Vincentz
authors.forename: C
authors.initials: C
authors.lastname: Meyer
authors.forename: J P
authors.initials: JP
authors.lastname: Boutin
authors.forename: M
authors.initials: M
authors.lastname: Caboche
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D001216:Asparagine / Q000096:biosynthesis; D001483:Base Sequence; D017124:Conserved Sequence; D003624:Darkness; D015971:Gene Expression Regulation, Enzymologic / Q000528:radiation effects*; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects*; D017343:Genes, Plant / Q000235:genetics*; D005816:Genetic Complementation Test; D005973:Glutamine / Q000096:biosynthesis; D006720:Homozygote; D008027:Light; D008969:Molecular Sequence Data; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics*; D010455:Peptides / Q000032:analysis; D010766:Phosphorylation; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D011499:Protein Processing, Post-Translational; D012323:RNA Processing, Post-Transcriptional; D018749:RNA, Plant / Q000032:analysis; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000201:enzymology / Q000235:genetics*; D015003:Yeasts / Q000235:genetics
chemical_list: D010455:Peptides; D018749:RNA, Plant; D005973:Glutamine; D001216:Asparagine; D000255:Adenosine Triphosphate; D009565:Nitrate Reductases; D050901:Nitrate Reductase