A transcriptomic view of cadmium retention in roots of cadmium-safe rice line (Oryza sativa L.)

A better understanding of the mechanisms controlling cadmium (Cd) accumulation in rice will benefit the development of strategies to minimize Cd accumulation in grains. A Cd-safe rice line designated D62B accumulated less than 0.2 mg Cd kg^-1 in brown rice due to its strong capacity for Cd retention in roots. Here transcriptomic was used to clarify the underlying mechanisms of Cd response in roots of D62B compared with a high Cd-accumulating line (Wujin4B). There were 777, 1058 differentially expressed genes (DEGs) in D62B and Wujin4B, respectively, when exposed to Cd. The functions of DEGs were clearly line-specific. Cell wall biosynthesis responded more intensively to Cd stress in D62B, facilitating Cd restriction. Meanwhile, more glutathione (GSH) and phytochelatins synthesized in D62B with the upregulation of sulphur and GSH metabolism. Besides, membrane proteins played critical roles in Cd response in D62B, whereas 18 terms involved in regulation were enriched in Wujin4B. Exogenous GSH further induced the expression of genes related to GSH metabolism and cell wall biosynthesis, leading to the retention of more Cd. Great responsiveness of cell wall biosynthesis and GSH metabolism could be considered the most important specific mechanisms for Cd retention in the roots of Cd-safe rice line.