Genome-wide transcriptome and physiological analyses provide new insights into cadmium tolerance of tomato seedlings

Abstract

Abstract In China, cadmium (Cd) contamination has turned into a primary environmental concerns in agricultural soils. This research surveyed the molecular mechanism of biochemical and physiological in response to Cd stress in tomato plants. Cadmium treatment prominently restrained tomato root growth (by 43.46%), and stimulated their antioxidant enzyme activities (POD and CAT). Cadmium treatment reduced their dry weight of shoot and root at day 7, by 40.42% and 60.40%, respectively. During the entire processing period, total chlorophyll contents were decreased and the malondialdehyde (MDA) content increased. A comparative transcriptome (RNA-Seq) was assembled de novo and differentially expressed genes (DEGs) were surveyed among 7-day-old tomato plants with or without cadmium ion treatment for 24 h. 18,883 unigenes in total were grouped into 51 Gene Ontology (GO) categories and 89 Kyoto Encyclopedia of Genes and Genomes terms (KEGG). There were 1,716 differentially expressed genes (DEGs), 559 down- and 1157 up-regulated genes. Go term enrichment analysis revealed that multiple phytohormone-related signaling pathway were significantly enriched in DEGs. Most genes involved in lignin biosynthesis pathway were up-regulated, for instance, COMT and CCOMT. Cd2+ is absorbed into tomato root cells to generate ROS and gives rise to oxidative stress. The essential hormones biosynthesis such as ethylene, IAA and JA should be stimulated to induce the activation of signal proteins. Our results provide the basis for further understanding of Cd tolerance mechanisms in plants.