title: An Arabidopsis FAD pyrophosphohydrolase, AtNUDX23, is involved in flavin homeostasis.
abstract: Although flavins, riboflavin (RF), FMN and FAD, are essential for primary and secondary metabolism in plants, the metabolic regulation of flavins is still largely unknown. Recently, we found that an Arabidopsis Nudix hydrolase, AtNUDX23, has FAD pyrophosphohydrolase activity and is distributed in plastids. Levels of RF and FAD but not FMN in Arabidopsis leaves significantly increased under continuous light and decreased in the dark. The transcript levels of AtNUDX23 as well as genes involved in flavin metabolism (AtFADS, AtRibF1, AtRibF2, AtFMN/FHy, LS and AtRibA) significantly increased under continuous light. The pyrophosphohydrolase activity toward FAD was enhanced in AtNUDX23-overexpressing (OX-NUDX23) plants and reduced in AtNUDX23-suppressed (KD-nudx23) plants, compared with the control plants. Interestingly intracellular levels of RF, FMN and FAD significantly decreased in not only OX-NUDX23 but also KD-nudx23 plants. The transcript levels of the flavin metabolic genes also decreased in both plants. Similarly, the increase in intracellular levels on treatment with flavins caused a reduction in the transcript levels of genes involved in flavin metabolism. These results suggest that negative feedback regulation of the metabolism of flavins through the hydrolysis of FAD by AtNUDX23 in plastids is involved in flavin homeostasis in plant cells.
authors.affiliation: Department of Advanced Bioscience, Faculty of Agriculture, Kinki University, Nakamachi, Nara, 631-8505 Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Maruta
authors.forename: Tadashi
authors.initials: T
authors.lastname: Yoshimoto
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ito
authors.forename: Takahisa
authors.initials: T
authors.lastname: Ogawa
authors.forename: Masahiro
authors.initials: M
authors.lastname: Tamoi
authors.forename: Kazuya
authors.initials: K
authors.lastname: Yoshimura
authors.forename: Shigeru
authors.initials: S
authors.lastname: Shigeoka
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003624:Darkness; D004789:Enzyme Activation; D025461:Feedback, Physiological; D005486:Flavin Mononucleotide / Q000378:metabolism; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008027:Light; D059828:Plant Cells / Q000378:metabolism; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics / Q000528:radiation effects; D018087:Plastids / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D011755:Pyrophosphatases / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D000096964:Nudix Hydrolases
chemical_list: D029681:Arabidopsis Proteins; D005486:Flavin Mononucleotide; D005182:Flavin-Adenine Dinucleotide; D011755:Pyrophosphatases; D012333:RNA, Messenger; D000096964:Nudix Hydrolases; C411003:RIBA protein, Arabidopsis