Selenium reduces cadmium uptake into rice suspension cells by regulating the expression of lignin synthesis and cadmium-related genes.

Although previous studies have indicated that selenium (Se) can reduce cadmium (Cd) uptake into rice, the mechanism at the cellular level has not been reported. Here, rice suspension cells exposed to Cd treatment in the presence or absence of Se were characterized. Compared with treatment with alone, pretreatment with Se increased the proportion of live cells by 83.1%. The levels of reactive oxygen species and mitochondrial membrane potential in the Se-pretreated rice cells were decreased by 86.6% and 76.0%, respectively. In addition, non-invasive micro-test technology suggested that the mean values of Cd2+ influx decreased significantly in the Se-pretreated rice cells in a concentration-dependent manner. The results of inductively coupled plasma-mass spectrometry (ICP-MS) showed that 67.4%-78.8% Cd accumulated onto the cell walls of the pretreated-Se rice cells. The addition of Se increased the lignin content and thickness of the cell walls, leading to an improved mechanical force of the cell walls, as determined by atomic force microscopy (AFM). Furthermore, Se pretreatment decreased the expression of genes involved in Cd uptake (OsNramp5) and transport (OsLCT1) but activated the expression of genes involved in Cd transport into vacuoles (OsHMA3) and lignin synthesis (OsPAL, OsCoMT and Os4CL3). These results indicated that supplying Se alleviates Cd toxicity by regulating the express of lignin synthesis and Cd-related genes. The present findings provide new insights on a plausible explanation of the Se-reduced Cd uptake into rice.