Transcriptional, physiological and cytological analysis validated the roles of some key genes linked Cd stress in Salix matsudana Koidz

Salix matsudana Koidz. is a fast-growing tree species with high cadmium (Cd) tolerance, making it potentially suitable for phytoremediation. To further explore the molecular mechanisms of Cd accumulation and tolerance in S. matsudana, genome-wide transcriptome sequencing of the roots of S. matsudana, along with detection of intracellular Cd, analyses of Cd-induced physiological response and cytological toxicity was investigated. The transcriptome analyses revealed that 342 and 583 genes in the roots of S. matsudana exposed to Cd for 7 days were up-regulated and down-regulated, respectively. These genes encode proteins involved in regulation and metabolism processes such as metal transport, antioxidant response, and Cd detoxification, as well as DNA replication and transcription, which suggest they play important roles under Cd stress. Physiological and cytological studies showed that low concentrations of Cd (10 μM) can not cause obvious changes, but high concentrations of Cd (100 μM) interfered with the accumulation of micronutrients, increased the activities of CAT, POD and SOD, reduced the contents of soluble protein and soluble carbohydrates significantly (p < 0.05) and decreased the mitotic index (MI) and induced chromosomal aberrations in the root tip cells. The transcriptome results were consistent with the observed physiological and cellular changes. The identified Cd-responsive genes provide insights for the characterization of molecular mechanisms underlying Cd tolerance in S. matsudana.