Cadmium pollution leads to selectivity loss of glutamate receptor channels for permeation of Ca2+/Mn2+/Fe2+/Zn2+ over Cd2+ in rice plant

Abstract

The selective permeation of glutamate receptor channels (GLRs) for essential and toxic elements in plant cells is poorly understood. The present study found that the ratios between cadmium (Cd) and 7 essential elements (i.e., K, Mg, Ca, Mn, Fe, Zn and Cu) in grains and vegetative organs increased significantly with the increase of soil Cd levels. Accumulation of Cd resulted in the significant increase of Ca, Mn, Fe and Zn content and the expression levels of Ca channel genes (OsCNGC1,2 and OsOSCA1.1,2.4), while remarkable reduction of glutamate content and expression levels of GLR3.1–3.4 in rice. When planted in the same Cd-polluted soil, mutant fc8 displayed significantly higher content of Ca, Fe, Zn and expression levels of GLR3.1–3.4 than its wild type NPB. On the contrary, the ratios between Cd and essential elements in fc8 were significantly lower than that in NPB. These results indicate that Cd pollution may damage the structural integrity of GLRs by inhibiting glutamate synthesis and expression levels of GLR3.1–3.4, which leads to the increase of ion influx but the decrease of preferential selectivity for Ca2+/ Mn2+/ Fe2+/ Zn2+ over Cd2+ through GLRs in rice cells.