ATP-binding cassette transporter enhances tolerance to DDT in Tetrahymena.

Yingzhi Ning,Lifang Feng,Guanglong Liu,Jie Xiong,Huai Dang,Dongxia Yuan,Wei Miao

doi:10.1007/s11427-014-4743-x

Abstract

The reuse of dichlorodiphenyltrichloroethane (DDT) as an indoor residual spray was permitted by the World Health Organization in 2007, and approximately 14 countries still use DDT to control disease vectors. The extensive exposure of insects to DDT has resulted in the emergence of DDT resistance, especially in mosquitoes, and the mechanism for this resistance in mosquitoes has been widely reported. Spraying can also introduce DDT directly into surface water, and DDT can subsequently accumulate in microorganisms, but the mechanism for the resistance to DDT degradation in microorganisms is unclear. Using whole-genome microarray analysis, we detected an abcb15 gene that was up-regulated in a specific manner by DDT treatment in T. thermophile. The deduced ABCB15 peptide sequence had two transmembrane domains (TMDs) and two nucleotide-binding domains (NBDs) to form the structure TMD-NBD-TMD-NBD, and each NBD contained three conserved motifs: Walker-A, C-loop, and Walker-B, which indicated the T. thermophila abcb15 was a typical ABC transporter gene. The expression of ABCB15 fused with a C-terminal green fluorescent protein was found to be on the periphery of the cell, suggesting that ABCB15 was a membrane pump protein. In addition, cells with abcb15 partially knocked down (abcb15-KD) grew slower than wild-type cells in the presence of 256 mg L(-1) DDT, indicating the tolerance of abcb15-KD strain to DDT exposure was decreased. Thus, we suggest that in Tetrahymena, the membrane pump protein encoded by ABCT gene abcb15 can enhance the tolerance to DDT and protect cells from this exogenous toxin by efficiently pumping it to the extracellular space.

Highlights

Dichlorodiphenyltrichloroethane (DDT), an organochlorine pesticide, was used to control insects that carried diseases and destroyed agricultural crops worldwide from the 1940s to the 1960s
We recently identified genes that were differentially expressed in Tetrahymena thermophila after exposure to DDT, and we found that an ATP-binding cassette transporter (ABCT) gene belonging to the B family may be associated with the robust DDT resistance of T. thermophile [11]
Each nucleotide-binding domains (NBDs) contained three conserved motifs: Walker-A, C-loop, and Walker-B (Figure 3). All these results indicate that abcb15 in T. thermophila is a typical ABC transporter gene

Summary

Introduction

Dichlorodiphenyltrichloroethane (DDT), an organochlorine pesticide, was used to control insects that carried diseases (e.g., malaria and typhus) and destroyed agricultural crops worldwide from the 1940s to the 1960s. With high lipophilicity and a long half-life, DDT sprayed into the environment and accumulated in organisms, creates significant threats to wildlife and human health. Currently DDT remains to be a significant threat to the health of wildlife and humans for two reasons: first, the prevalence of malaria markedly in-. Since sprayed DDT can be released onto surface water directly or indirectly through dry and wet deposition from the atmosphere [5], microorganisms can adapt to the presence of DDT under its long-term exposure, allowing its accumulation and serial transfer to higher levels in the food chain [6]. We recently identified genes that were differentially expressed in Tetrahymena thermophila after exposure to DDT, and we found that an ATP-binding cassette transporter (ABCT) gene (abcb15) belonging to the B family may be associated with the robust DDT resistance of T. thermophile [11]. The function of abcb was analyzed to elucidate the mechanism of tolerance to DDT in T. thermophile

Methods

Results

Conclusion