Localization of NAD-isocitrate dehydrogenase and glutamate dehydrogenase in rice roots: candidates for providing carbon skeletons to NADH-glutamate synthase.
In rice roots, transient and cell-type-specific accumulation of both mRNA and protein for NADH-dependent glutamate synthase (NADH-GOGAT) occurs after the supply of NH(4) (+) ions. In order to better understand the origin of 2-oxoglutarate for this reaction, we focused on mitochondrial NAD-dependent isocitrate dehydrogenase (IDH) and glutamate dehydrogenase (GDH) in rice roots. Six rice cDNAs encoding a single catalytic (OsIDHa) and two regulatory (OsIDHc;1, OsIDHc;2) IDH subunits and three GDH proteins (OsGDH1-3) were isolated. These genes, except OsGDH3, were expressed in the roots. Real-time PCR analysis showed that OsIDHa and OsIDHc;1 transcripts, but not OsGDH1 and OsGDH2 transcripts, accumulated in a similar manner to NADH-GOGAT mRNA along the crown roots after the supply of different forms of inorganic nitrogen. Furthermore, immunolocalization studies revealed the NH(4) (+) induction of IDHa protein in two cell layers of the root surface, i.e. epidermis and exodermis, where NADH-GOGAT also accumulated. The possible relationship between NADH-GOGAT, IDH and GDH is discussed.
Abiko
Tomomi
T
Graduate School of Agricultural Science, Tohoku University, Aoba-ku, Sendai, Japan.
Obara
Mitsuhiro
M
Ushioda
Akiko
A
Hayakawa
Toshihiko
T
Hodges
Michael
M
Yamaya
Tomoyuki
T
D000595:Amino Acid Sequence; D001483:Base Sequence; D002244:Carbon / Q000737:chemistry*; D020134:Catalytic Domain; D017931:DNA Primers; D005969:Glutamate Dehydrogenase / Q000737:chemistry / Q000378:metabolism*; D050790:Glutamate Synthase (NADH) / Q000737:chemistry / Q000378:metabolism*; D007521:Isocitrate Dehydrogenase / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D012275:Oryza / Q000201:enzymology*; D018517:Plant Roots / Q000201:enzymology*; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D002244:Carbon; D007521:Isocitrate Dehydrogenase; D050790:Glutamate Synthase (NADH); D005969:Glutamate Dehydrogenase