Transcriptomic Analysis of Cadmium Hyperaccumulation and Hypertolerance in Sedum plumbizincicola

Sedum plumbizincicola is a novel cadmium (Cd) hyperaccumulator with fast growth and relative large biomass, discovered in ancient mining areas in China. Cd contents in S. plumbizincicola shoots reaches 6000mg/kg DW without any visual symptom, indicating the possibility to be used for efficient phytoextraction of heavy metal pollutants, or as a model plant to investigate the underlying mechanisms of hyper-tolerance to and accumulation of Cd. We examined in detail the transcriptomes of S. plumbizincicola and the non-hyperaccumulation ecotype S. alfredii, using next-generation sequencing. Interestingly, less genes show altered expression in S. plumbizincicola compared to S. alfredii when exposed Cd treatments, though the most significant change in both species was observed in genes involved in metal homeostasis. In addition to some key transporter genes, such as ZIP family, HMA2/4 and YSL family, heat shock proteins-related and cell wall-related genes were also highly expressed in S. plumbizincicola. Moreover, genes involved in hormone signaling pathways expressed at higher levels in S. plumbizincicola than in S. alfredii, while these pathways are more inducible by Cd in S. alfredii. Together, our study provides a genome-wide transcriptomic profiling of S. plumbizincicola and S. alfredii, and revealed that in addition to some key transporters, heat shock proteins, cell wall and hormone signaling may also contribute to modulating Cd accumulation and tolerance in S. plumbizincicola.