Ferritin gene expression and antioxidant response of two Coffea arabica cultivars exposed to iron and aluminium / Expressão de genes da ferritina e resposta antioxidante em duas cultivares de Coffea arabica expostas a ferro e aluminio

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Ferritin is a protein capable to store iron (Fe) atoms in a nontoxic form, controlling the level of this metal in the cells. In humans, ferritin is able to accommodate aluminium (Al) atoms, avoiding its toxicity. Considering that Coffea arabica plants are able to grow well in acidic soils with high Al and suspension cells treated with this same metal showed high ferritin gene expression, it is possible that this protein is also able to complex Al atoms in planta. The induction of ferritin synthesis in suspension cells of C. arabica cv. Mundo Novo with 300 and 1.200 µmol/L of ferrous sulphate revealed an increase of 8,9 and 18,2 times, respectively, of transcripts of ferritin gene CaFer1, as compared with the control. The treatment with 5 mmol/L of aluminium-potassium sulphate resulted in the reduction of 4,57 times the expression of this gene, as compared with the control. In cells from the Icatu cultivar all treatments resulted in reduction of the expression of CaFer1. This decrease was about 29,0 and 6,3 times in cells treated with 300 and 1.200 µmol/L of ferrous sulphate, respectively, and 98,02 times in the treatment with 5 mmol/L of aluminium-potassium sulphate, as compared with the control. For both varieties, these same treatments did not result in significant differential expression of the other ferritin gene analyzed, CaFer2. Western Blots data were in agreement with this observation. Therefore, ferritin expression in suspension cells of Coffea plants responds to Fe, as shown for other plants, however, on account of the no accumulation of ferritin in both cultivars treated with 5 mmol/L of aluminium-potassium sulphate, possibly this protein is not involved with Al complexation in C. arabica plants or the level of Al used was sufficiently high to provoke damages in the nucleic acids or to impair the normal transcription of the genes. An in silico analysis carried out with CaFer1 and CaFer2 from C. arabica and with ferritin genes of the Coffea canephora and Coffea racemosa revealed high similarity between CaFer1 and C. canephora ferritin, and CaFer2 with C. racemosa ferritin. Finally, assays of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), glutathione reductase (GR), and guaiacol peroxidase (GPOX) revealed that cell cultures of the Mundo Novo variety are more responsive to the treatments with the metals, except for GST, wich was the only enzyme with higher activity in cells from the Icatu cultivar. Furthermore, it was observed that enzymatic response was dose dependent and that Mundo Novo and Icatu used distinct mechanisms to protect cells against reactive oxygen species.

ASSUNTO(S)

ferritin coffea arabica ferritina aluminio aluminium

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