Lipocalin-mediated organophosphate esters (OPEs) active uptake and accumulation in rice (Oryza sativa L.)

To understand uptake and accumulation process of organophosphate esters (OPEs), growth, concentrations of OPEs, and transcript regulation of lipid transporters in rice seedlings were investigated under six OPE congeners exposures. The increase of seedlings' growth and accumulation of OPEs in plants were observed. Root concentration factors (RCFs) of aryl-OPEs were the highest in consistent with their strong hydrophobicity, indicating that they were more liable to be accumulated in roots. Meanwhile, shoot/root concentration factors (SRCFs) of halogenated alkyl-OPEs were the highest in accordance with their low hydrophobicity, implying that they were easily translocated to shoots. Lipid transporters involved in uptake and accumulation of OPEs, evidence from the transcript responses of their lipid transporters. Moreover, the only positive relationship between OsTIL expressions and accumulation of OPEs demonstrated the dominant role of OsTIL among the investigated transporters. In addition, although all of OPE congeners could be docked into active cavities of OsTIL with varied markedly binding affinities, hydrophobicity OPEs performed stronger binding energy with OsTIL after homology modeling and molecular docking analysis. Therefore, uptake and accumulation of OPEs were corporately charged by OPEs' physicochemical properties and lipid carrier transports in coincidence with the experimental observation about accumulation of OPEs in roots and shoots.