Identification and characterisation of a novel 1-Cys thioredoxin peroxidase gene (AccTpx5) from Apis cerana cerana.

Thioredoxin peroxidases (Tpxs), members of the antioxidant protein family, play critical roles in resisting oxidative stress. In this work, a novel 1-Cys thioredoxin peroxidase gene was isolated from Apis cerana cerana and was named AccTpx5. The open reading frame (ORF) of AccTpx5 is 663bp in length and encodes a 220-amino acid protein with a predicted molecular mass and isoelectric point of 24,921kDa and 5.45, respectively. Promoter sequence analysis of AccTpx5 revealed the presence of putative transcription factor binding sites related to early development and stress responses. Additionally, real-time quantitative PCR (Q-PCR) analysis indicated that AccTpx5 was primarily present in some developmental stages, with the highest expression levels in the first-instar larvae. The expression level of AccTpx5 was up-regulated under various abiotic stresses, including 4°C, 42°C, HgCl2, H2O2, phoxim and acaricide treatments. Conversely, it was down-regulated by UV and pyriproxyfen treatments. Moreover, H2O2 concentration dramatically increased under a variety of stressful conditions. Finally, the purified recombinant AccTpx5 protein protected the supercoiled form of plasmid DNA from damage in the thiol-dependent mixed-function oxidation (MFO) system. These results suggest that AccTpx5 most likely plays an essential role in antioxidant defence.