The relationship between pyridine nucleotides and seed dormancy.
To investigate the proposed role for NAD metabolism in regulating seed dormancy, NAD metabolites and associated enzyme activities were analysed in seed of Arabidopsis thaliana ecotypes ranging from Col-0, which has low seed dormancy, to Cvi, which is highly dormant. Seed poly(ADP-ribosyl)ation levels did not correlate well with the depth of seed dormancy but did correlate with the sensitivity of germination to the DNA damaging agent MMS. Cvi seed had relatively high NAD and low NADP levels compared with the less dormant ecotypes and the NAD : NADP ratios correlated well with dormancy. The activity of NAD kinase was relatively low, and NADP phosphatase was relatively high in dormant Cvi seed, indicating that these enzymes may be involved in controlling the NAD : NADP ratio. Dormant fresh Cvi and nondormant after-ripened Cvi seeds were used to investigate further. Measurement of reduced and oxidised pyridine nucleotides indicated that breaking of dormancy was associated with a reduction in NAD levels but not with an increase in NADP levels. It is proposed that poly(ADP-ribose) polymerase is involved in protecting the seed from genotoxic stress, whereas the level of NAD affects the depth of dormancy, perhaps by enhancing abscisic acid (ABA) synthesis.
Hunt
Lee
L
University of Sheffield, Department of Molecular Biology and Biotechnology, Firth Court, Western Bank, Sheffield S10 2TN, UK.
Gray
Julie E
JE
University of Sheffield, Department of Molecular Biology and Biotechnology, Firth Court, Western Bank, Sheffield S10 2TN, UK.
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D055726:Cabo Verde; D004259:DNA-Directed DNA Polymerase; D015870:Gene Expression; D018525:Germination / Q000235:genetics / Q000502:physiology*; D009243:NAD / Q000378:metabolism*; D009249:NADP / Q000378:metabolism*; D009536:Niacinamide / Q000378:metabolism; D009535:Nicotinamidase / Q000378:metabolism; D009708:Nucleotidases / Q000378:metabolism; D009711:Nucleotides / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000378:metabolism*
D009711:Nucleotides; D009243:NAD; D009536:Niacinamide; D009249:NADP; D011065:Poly(ADP-ribose) Polymerases; D017853:Phosphotransferases (Alcohol Group Acceptor); C021844:NAD kinase; D004259:DNA-Directed DNA Polymerase; C045660:NADP phosphatase; D009708:Nucleotidases; D009535:Nicotinamidase