Integrated physiological, transcriptomic and metabolomic analysis revealed key genes related to cadmium-stress...

Cadmium (Cd) contamination poses severe threats to ecosystems and human health, necessitating effective phytoremediation strategies. Although substantial progress has been made in understanding the molecular mechanisms of Cd tolerance in poplar species, the integrated physiological, transcriptomic and metabolomic analyses of poplar response to cadmium-induced stress has not been reported, and more genes associated with cadmium tolerance are needed to be explored. This study investigated the phenotypic, biochemical, transcriptomic and metabolomic responses under Cd stress in poplar. Results revealed that Shanxin poplar showed significantly inhibited plant growth, reduced biomass, and oxidative damage under 20 μM Cd treatment, evidenced by elevated malondialdehyde (MDA) and reactive oxygen species (ROS) levels. Antioxidant enzymes exhibited dose-dependent activation, with pronounced ROS scavenging under 20 μM Cd treatment. Metabolomic analysis revealed predominant alterations in carbohydrate metabolism, phenylpropanoid biosynthesis, and organic acid synthesis pathways under 20 μM Cd treatment. Transcriptome sequencing identified 4255 differentially expressed genes, which were enriched in biosynthesis of secondary metabolites, plant hormone signal transduction and phenylpropanoid biosynthesis. Key transporter families (ABC, ZIP, MATE) and transcription factors (WRKY, NAC) were significantly induced, highlighting their roles in Cd detoxification. Among them, two candidate genes, WRKY49 and NAC1, had been demonstrated that their heterologous expression in yeast enhanced Cd tolerance. This study elucidated the physiological and molecular adaptations of poplar to Cd stress, providing insights for breeding Cd-tolerant tree species to enhance phytoremediation efficacy.