Cadmium (Cd) contamination in arable soils presents a serious threat to agricultural crops and public health. Cd pollution-safe cultivars (Cd-PSCs) can effectively restrict human intake of Cd through food chain. However, not much is known on the genetic basis of low-Cd-accumulating trait. Here, we aim to investigate the microRNA (miRNA)-mediated post-transcriptional regulation underlying different capacities of Cd accumulation in Brassica parachinensis L.

Using small RNA sequencing, miRNAs were identified and characterized in two previously identified cultivars, a low- (SJ19) and a high-Cd-accumulating cultivar (CX4) of B. parachinensis.

18 known and 148 novel miRNAs were identified to be differentially expressed in response to Cd (Cd-responsive miRNAs) in the two cultivars. Distinct Cd responsive pathways were employed by the two cultivars. In CX4, the overexpression of miR395 was indicated to engage in Cd tolerance by regulating sulfur assimilation and associated with its high Cd accumulation. In SJ19, miRNA-mediated oxidative resistance was enhanced in response to Cd exposure. Furthermore, miR397, miR393 and miR160 were involved in the Cd-induced growth improvement in both roots and shoots of the low-Cd-accumulating cultivar.

Our findings provide new insights into miRNAs-mediated Cd response in B. parachinensis, and shed light on molecular-assisted Cd-PSC screening and breeding for agricultural crops and vegetables.

Graphical abstract