Abstract

cDNA encoding Mn-superoxide dismutase (MnSOD) and 18S rRNA of Phascolosoma esculenta were cloned in this study. The partial MnSOD cDNA obtained consisted of 411 bp, encoded a protein of 137 amino acids and contained a MnSOD signature (DVWEHAYY). Physiological activity responses and expression of MnSOD mRNA inP. Esculenta exposed to benzo(a)pyrene (BaP) for 4, 24, 48 , 96, 168 and 336 h were also studied, and results indicate that P. Esculenta showed a strong ability to resist BaP stress. The expression levels of MnSOD mRNA were highest at 4 h of exposure, while the physiological activity levels of MnSOD were highest at 96 h, but then returned to baseline levels. The different response rates indicated that there was a very intricate regulating mechanism that prevents the damaging effects of the oxidative stress imposed by BaP. This result suggests that the expression of MnSOD mRNA in P. Esculenta in a short time can be used as a sensitive biomarker to alarm an early acute BaP contamination.

Key words: Phascolosoma esculenta, benzo(a)pyrene (BaP), Mn-superoxide dismutase (MnSOD), gene expression, physiological activity.