Abstract

Thioredoxin plays an important role in inhibiting apoptosis and protecting cells from oxidative stress. This study was aimed to clarify how the expression of Trx from Cristaria plicata is regulated by Nrf2/ARE pathway. The expression of Cp Trx mRNA was significantly up-regulated in gill and kidney tissues under microcystin stress. The Nrf2 gene of Cristaria plicata was identified to possess an auto active domain bit. While Cp Nrf2 was knocked down by specific small RNA, Cp Trx mRNA expression was significantly down-regulated. The promoter of Cp Trx gene had high transcriptional activity, and this basic transcriptional activity persisted after ARE element mutation. The region of promoter −206 to +217 bp was a core promoter region and had forward regulatory elements. Gel shift Assay exhibited that the Cp Trx promoter could bind to the purified proteins Cp Nrf2 and Cp MafK in vitro. The binding phenomenon disappeared after the ARE element mutation in promoter region. Subcellular localization experiments displayed that fluorescence overlap between Cp Nrf2 and Trx promoter increased under microcystin toxin stress. These results suggested that Trx expression was regulated by Nrf2/ARE pathway under oxidative stress.