Physiological and transcriptome analyses reveal copper toxicity responses in tomato plants

Abstract

Copper (Cu) is an essential trace element, but excess Cu is toxic to plants, animals and humans. Tomatoes are widely cultivated vegetables worldwide. Due to the excessive use of pesticides and fertilizers, Cu toxicity often occurs during tomato cultivation. However, the physiological and molecular mechanisms underlying Cu toxicity responses in tomato plants have not been fully elucidated. In this study, using physiological and transcriptomic analyses, we investigated the effects of excess Cu on tomato plant growth. The results showed that Cu toxicity inhibits photosynthesis and induces oxidative damage in tomato plants. Excess Cu decreases the concentrations of cytokinin and indoleacetic acid and interferes with cytokinin and auxin signaling pathways, thus slowing plant growth. Furthermore, increased abscisic acid concentrations are beneficial for improving the tolerance of tomato plants to Cu toxicity. Excess Cu disrupts mineral element accumulation in tomato plants. Cu toxicity also reprograms carbon/nitrogen metabolism pathways and represses lignin catabolic processes in roots, thus altering the material flow and energy flow in plants and disrupting the cell wall structure, ultimately inhibiting the growth and development of tomato plants. In addition, molecular regulatory network analysis identified 17 transcription factors as hub genes in the roots of excess Cu-treated tomato plants. These findings provide insights into the adaptation of tomato plants to Cu toxicity, contributing to the development of tomato varieties with high tolerance to Cu toxicity.