title: Subcellular and tissue localization of NAD kinases from Arabidopsis: compartmentalization of de novo NADP biosynthesis.
abstract: The de novo biosynthesis of the triphosphopyridine NADP is catalyzed solely by the ubiquitous NAD kinase family. The Arabidopsis (Arabidopsis thaliana) genome contains two genes encoding NAD+ kinases (NADKs), annotated as NADK1, NADK2, and one gene encoding a NADH kinase, NADK3, the latter isoform preferring NADH as a substrate. Here, we examined the tissue-specific and developmental expression patterns of the three NADKs using transgenic plants stably transformed with NADK promoter::glucuronidase (GUS) reporter gene constructs. We observed distinct spatial and temporal patterns of GUS activity among the NADK::GUS plants. All three NADK::GUS transgenes were expressed in reproductive tissue, whereas NADK1::GUS activity was found mainly in the roots, NADK2::GUS in leaves, and NADK3::GUS was restricted primarily to leaf vasculature and lateral root primordia. We also examined the subcellular distribution of the three NADK isoforms using NADK-green fluorescent protein (GFP) fusion proteins expressed transiently in Arabidopsis suspension-cultured cells. NADK1 and NADK2 were found to be localized to the cytosol and plastid stroma, respectively, consistent with previous work, whereas NADK3 localized to the peroxisomal matrix via a novel type 1 peroxisomal targeting signal. The specific subcellular and tissue distribution profiles among the three NADK isoforms and their possible non-overlapping roles in NADP(H) biosynthesis in plant cells are discussed.
authors.affiliation: Department of Biology, Queen's University, Kingston, ON K7L 3N6, Canada.
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Waller
authors.forename: Preetinder K
authors.initials: PK
authors.lastname: Dhanoa
authors.forename: Uwe
authors.initials: U
authors.lastname: Schumann
authors.forename: Robert T
authors.initials: RT
authors.lastname: Mullen
authors.forename: Wayne A
authors.initials: WA
authors.lastname: Snedden
mesh_terms: D020816:Amino Acid Motifs; D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology* / Q000254:growth & development; D002451:Cell Compartmentation; D002463:Cell Membrane Permeability; D035264:Flowers / Q000166:cytology / Q000201:enzymology; D018525:Germination / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000378:metabolism; D009249:NADP / Q000096:biosynthesis*; D009928:Organ Specificity; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry / Q000378:metabolism*; D018515:Plant Leaves / Q000166:cytology / Q000201:enzymology / Q000254:growth & development; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000201:enzymology
chemical_list: D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D009249:NADP; D017853:Phosphotransferases (Alcohol Group Acceptor); C021844:NAD kinase