New mechanistic insights into PAHs transport across wheat root cell membrane: Evidence for ABC transporter mediation

Polycyclic aromatic hydrocarbons (PAHs) are a class of highly carcinogenic organic pollutants. Our previous results revealed that the active uptake of PAHs by plant roots is performed through H+/PAHs co-transport. However, the proteins and mechanisms of co-transport of PAHs remain unknown. We hypothesized that ABC transporters are involved in PAHs co-transport via the roots. We found a total of 47 ABC transporters with alkalinity and hydrophobicity which were up-regulated or newly expressed in the wheat roots after phenanthrene exposure. And the concentration of ABC transporters rose. There was a positive relationship between the concentration of phenanthrene and ABC transporter expression in the wheat roots. Additionally, the trend observed in the ABC transporters expression was also found in the gene expression. With energies below -6 kcal mol-1, a stable docking conformation formed between ABC transporters and PAHs. π-π stacking and van der Waals force bound PAHs to ABCB or ABCG. The binding strength of ABCB subfamily proteins with homodimers is stronger than that of ABCG subfamily proteins with single molecules. ABC transporters may transport PAHs by forming a dimer-shaped pocket, translocating it into cells, then opening it within the cells, to release the bound PAHs. These results contributed to our understanding of how ABC transporters aid plant root uptake of PAHs.