Co-exposure to Organophosphate esters (OPEs) and Cadmium alleviated their accumulation in rice (Oryza sativa L.) by inhibiting transports' transcription

Combined contamination of Organophosphate esters (OPEs) and heavy metal has been concerning on their potential threaten to human health through food chain. In order to estimate effects of OPEs and heavy metal's combined contamination on crop, the growth of rice seedlings, pollutant accumulations and their involved in transcript regulation pathway under OPEs and Cd contamination were investigated. In results, only single OPEs pollution improved the biomass of rice, while single Cd pollution inhibited the growth of plants. Although the combined contaminations of OPEs and Cd also showed negative effect for plant growth, OPEs could alleviate the negative effect of Cd on rice. The Octanol-water partition coefficients (log K ow ) of OPEs were positively correlated with root concentration factor (RCF) values in the trend line and negatively correlated with shoot concentration factor (SCRF) and translocation factor (TF). OPEs and Cd inferred with each other's accumulations in plants through reducing RCF, SCRF and TF. After addition of Cd, the expressions of OsTIL, OsLTP4, OsLTPL1 , and OsMLP423 genes involved in OPEs accumulation were downregulated. Moreover, the presence of Cd also affected the binding sites and binding energy of the four proteins with OPEs. Meanwhile, the expression of OsNramp1, OsNramp5, OsHMA2, OsGS1 , and OsPCS1 genes involved in Cd accumulation and toleration were also downregulated after addition of OPEs. These results suggested that OPEs and Cd directly repressed each other gene transcript involved in accumulation and toleration process.