Uncovering the key lncRNAs in regulating cadmium accumulation and translocation in sweet sorghum.

Abstract

Main conclusion: 1988 lncRNAs were identified in sweet sorghum roots under cadmium treatment; lncRNA 15962 and lncRNA 11558 were validated to be the key lncRNAs involved in regulating cadmium accumulation and translocation. Cadmium (Cd) has become one of the most harmful and widespread pollutants with industry development. Sweet sorghum is an ideal plant for phytoremediation of Cd-contaminated soil. However, little is known about the regulatory role of long non-coding RNAs (lncRNAs) associated with Cd stress response in sweet sorghum. Here, lncRNA-seq was carried out in the roots of two contrasting sweet sorghum genotypes (high-Cd accumulation genotype 'H18', and low-Cd accumulation genotype 'L69'). A total of 1988 lncRNAs were characterized, including 52 and 69 differentially expressed lncRNAs in 'H18' and 'L69' in response to Cd stress, respectively. Furthermore, the trans- or cis-target genes of lncRNAs were investigated. Then, 65 lncRNAs were characterized as the probable target of 117 miRNAs and 1888 genes were identified as putative cis-target genes of Cd-responsive lncRNAs. The dual-luciferase reporter assay indicated lncRNA 15962 may serve as the endogenous target mimics of sbi-miR5565e, which targeted two genes (Sobic.005G212900 and Sobic.009G144700) involved in cell wall metabolism. Four cis-target genes including SbYS1 which encoding a Cd chelate transporter, were up-regulated by overexpression of their corresponding lncRNAs in sweet sorghum protoplasts, suggesting the positive regulatory role of lncRNAs to these cis-target genes. Moreover, the expression of SbYS1 decreased when lncRNA 11558 was inhibited by exogenous miRNA application in 'H18' seedlings, further demonstrating the positive regulatory role of lncRNA 11558 to SbYS1. Altogether, our findings shed light on the regulatory role of lncRNAs associated with Cd accumulation and translocation in sweet sorghum.