The objective of this study was to investigate the role of the Pap1 transcription factor in response to long-term Cd2+ stress. The Schizosaccharomyces pombe wild-type strain and the Δpap1 mutant, treated with 0.5 mM CdSO4, were used in antioxidant enzyme and gene expression experiments. The Δpap1 mutant proved to be sensitive to Cd 2+ in the spot test assay, suggesting that the Pap1 transcription factor plays an important role in the response to Cd2+ stress. The Cd2+ uptake was the same in both strains. Determination of the superoxide level in the wild-type strain proved that superoxide was generated, suggesting that long-term Cd2+ treatment could trigger oxidative stress. Furthermore, the Δpap1 mutant displayed higher amounts of superoxide. These results were supported by the significantly lower amount of peroxide generated in the reaction catalyzed by superoxide dismutase (SOD). The Δpap1 mutant had a significantly lower glutathione S-transferase specific activity than that of the wild-type strain during long-term Cd2+ stress, caused by the lower GSH and sulfide assimilation. We have demonstrated that GST III activity was not induced by Cd2+ stress in the Δpap1 mutant. The overall low GST activity was not sufficient for the cell to eliminate Cd2+ caused damage and could result in a Cd 2+-sensitive phenotype of the Δpap1 mutant. The RT-PCR and Northern blot experiments proved that gst2 was not induced either by short-term or by long-term Cd2+ treatment. The SPCC965.06 (a putative K + ion channel subunit) gene expression increased, while the hmt1 (an ABC-type vacuolar transporter protein) expression decreased in both strains. No detectable alteration in the mRNA levels of, gpx1, hmt2, sod1, sod, and trx1 was observed. SOD enzyme analyses revealed that the absence of Pap1 protein could result in a lower SODs activity and affect the sulfate assimilation. This is the first report on the fact that the Pap1 transcription factor could play an important role in the cellular post-transcriptional/post-translational enzyme activity induction processes of SODs that occur in response to Cd2+.
ASJC Scopus subject areas
- Applied Microbiology and Biotechnology