Expression of the tomato peroxidase gene TPX1 in NaCl-adapted and unadapted suspension cells

The expression pattern of a peroxidase - (EC 1.11.1.7) encoding gene, TPX1, was studied in NaCl-adapted and unadapted tomato (Lycopersicon esculentum) cells growing in suspension culture. We followed the transcript level during the cell growth cycle and under different salt treatments. There was a cell-cycle-dependent TPX1 expression, the maximum level of transcripts coinciding with the period of cell enlargement in both salt-adapted and unadapted tomato cells. However, enzyme activity of the encoded isoperoxidase was only detected in the culture medium of the salt-adapted cells. NaCl treatment decreased TPX1 transcripts in both cell lines, but the threshold concentration for this down-regulation was higher in adapted cells. In conclusion, salt-adapted tomato cells show significant changes in comparison with unadapted cells in the expression of a gene encoding a cell-wall-targeted peroxidase.