A role for ferritin in the antioxidant system in coffee cell cultures.
Iron (Fe) is an essential nutrient for plants, but it can generate oxidative stress at high concentrations. In this study, Coffea arabica L. cell suspension cultures were exposed to excess Fe (60 and 240 μM) to investigate changes in the gene expression of ferritin and antioxidant enzymes. Iron content accumulated during cell growth, and Western blot analysis showed an increase of ferritin in cells treated with Fe. The expression of two ferritin genes retrieved from the Brazilian coffee EST database was studied. CaFER1, but not CaFER2, transcripts were induced by Fe exposure. Phylogenetic analysis revealed that CaFER1 is not similar to CaFER2 or to any ferritin that has been characterised in detail. The increase in ferritin gene expression was accompanied by an increase in the activity of antioxidant enzymes. Superoxide dismutase, guaiacol peroxidase, catalase, and glutathione reductase activities increased in cells grown in the presence of excess Fe, especially at 60 μM, while the activity of glutathione S-transferase decreased. These data suggest that Fe induces oxidative stress in coffee cell suspension cultures and that ferritin participates in the antioxidant system to protect cells against oxidative damage. Thus, cellular Fe concentrations must be finely regulated to avoid cellular damage most likely caused by increased oxidative stress induced by Fe. However, transcriptional analyses indicate that ferritin genes are differentially controlled, as only CaFER1 expression was responsive to Fe treatment.
Departamento de Biologia Vegetal, Instituto de Biologia, CP 6109, Universidade Estadual de Campinas, Campinas, SP, 13083-970, Brazil.
Alexandra
A
Bottcher
Paula Macedo
PM
Nobile
Paula Fabiane
PF
Martins
Fábio Frangiotti
FF
Conte
Ricardo Antunes
RA
Azevedo
Paulo
P
Mazzafera
D000595:Amino Acid Sequence; D000975:Antioxidants / Q000378:metabolism*; D001483:Base Sequence; D015153:Blotting, Western; D002374:Catalase / Q000235:genetics / Q000378:metabolism; D003069:Coffee / Q000187:drug effects / Q000378:metabolism*; D020224:Expressed Sequence Tags; D005293:Ferritins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D005980:Glutathione Reductase / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D018384:Oxidative Stress / Q000187:drug effects; D009195:Peroxidase / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D016415:Sequence Alignment; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism
D000975:Antioxidants; D003069:Coffee; D010940:Plant Proteins; D005293:Ferritins; C121048:guaiacol peroxidase; D002374:Catalase; D009195:Peroxidase; D013482:Superoxide Dismutase; D005980:Glutathione Reductase