Selenite reduced uptake/translocation of cadmium via regulation of assembles and interactions of pectins, hemicelluloses, lignins, callose and Casparian strips in rice roots.

Selenium (Se) can reduce cadmium (Cd) uptake/translocation via regulating pectins, hemicelluloses and lignins of plant root cell walls, but the detailed molecular mechanisms are not clear. In this study, six hydroponic experiments were set up to explore the relationships of uptake/translocation inhibition of Cd by selenite (Se(IV)) with cell wall component (CWC) synthesis and/or interactions. Cd and Se was supplied (alone or combinedly) at 1.0 mg L–1 and 0.5 mg L–1, respectively, with the treatment without Cd and Se as the control. When compared to the Cd1 treatment, the Se0.5Cd1 treatment 1) significantly increased total sugar concentrations in pectins, hemicelluloses and callose, suggesting an enhanced capacity of binding Cd or blocking Cd translocation; 2) stimulated the deposition of Casparian strips (CS) in root endodermis and exodermis to block Cd translocation; 3) stimulated the release of C–O–C (–OH– or –O–) and C O (carboxyl, carbonyl, or amide) to combine Cd; 4) regulated differential expression genes (DEGs) and metabolites (DMs) correlated with synthesis and/or interactions of CWSs to affect cell wall net structure to affect root cell division, subsequent root morphology and finally elemental uptake; and 5) stimulated de–methylesterification of pectins via reducing expression abundances of many DMs and DEGs in the Yang Cycle to reduce supply of methyls to homogalacturonan, and regulated gene expressions of pectin methylesterase to release carboxyls to combine Cd; and 6) down–regulated gene expressions associated with Cd uptake/translocation. [Display omitted] • Se increased total sugar concentration in pectins, hemicelluloses and callose under Cd exposure. • Se promoted deposit of Casparian strips via upregulating DEGs and DMs correlated with their synthesis. • Se demethylated pectins via regulation of DEGs correlated with PME and DMs in Yang Cycle. • Se inhibited expression of DEGs correlated with xylan degradation and possibly facilitated arabinoxylan formation. • Se stimulated release of functional groups including C–O–C (–OH– or –O–) and C O to combine Cd. [ABSTRACT FROM AUTHOR]