Suppression of highly efficient cadmium translocation by exogenous gibberellin provides insights into the molecular regulation mechanism of hyperaccumulation in Sedum plumbizincicola

Sedum plumbizincicola is a hyperaccumulating species with highly efficient uptake, translocation and distribution system for cadmium (Cd), a non-essential and toxic heavy metal. To understand the molecular regulation mechanisms of Cd transport and accumulation in this hyperaccumulator is still a challenge. In this study, we observed that exogenous gibberellin A3 (GA3) significantly reduced Cd loading efficiency from root to shoot and uploading efficiency from stem to leaves in S. plumbizincicola under Cd treatments, which provided us a remarkable opportunity to study the signaling mechanisms for regulation of highly efficient Cd transport and translocation in S. plumbizincicola. Here, we constructed a de novo full-length transcriptome database with the integration of full-length and next-generation transcriptome sequences for Cd-treated S. plumbizincicola with or without exogenous GA3 application. From this database, we identified 1461 differentially expressed genes (DEGs), which were related to solute transport, cell wall metabolism and signal transduction, and most of them were down-regulated by the exogenous application of gibberellin. In particularly, a substantial number of the downregulated genes belong to calmodulin-like (CML) proteins, calcium-dependent protein kinase, calcium-permeable channel, mitochondrial calcium uniporter (MCU) and Na+/Ca2+ exchanger-like proteins (NCL/EF-CAX). These results indicated that calcium homeostasis and signal transduction may play an important role in the regulation of highly efficient translocation of cadmium in hyperaccumulator S. pumbizincicola.