# Conjoint analysis of physio-biochemical, transcriptomic, and metabolomic reveals the response characteristics of solanum nigrum L. to cadmium stress

## TL;DR

This study explores how Solanum nigrum plants respond to cadmium stress by analyzing their physiological, transcriptomic, and metabolomic changes.

## Contribution

The study identifies key molecular and metabolic pathways involved in cadmium tolerance in Solanum nigrum using a conjoint analysis approach.

## Key findings

- Cadmium stress significantly affects biomass, nutrient balance, and photosynthetic pigments in Solanum nigrum.
- Transcriptomic and metabolomic analyses reveal crucial genes and metabolites involved in Cd transport and detoxification.
- Common metabolic pathways like TCA cycle and glutathione metabolism are activated in response to Cd stress.

## Abstract

Cadmium (Cd) is a nonessential element in plants and has adverse effects on the growth and development of plants. However, the molecular mechanisms of Cd phytotoxicity, tolerance and accumulation in hyperaccumulators Solanum nigrum L. has not been well understood. Here, physiology, transcriptome, and metabolome analyses were conducted to investigate the influence on the S. nigrum under 0, 25, 50, 75 and 100 µM Cd concentrations for 7 days. Pot experiments demonstrated that compared with the control, Cd treatment significantly inhibited the biomass, promoted the Cd accumulation and translocation, and disturbed the balance of mineral nutrient metabolism in S. nigrum, particularly at 100 µM Cd level. Moreover, the photosynthetic pigments contents were severely decreased, while the content of total protein, proline, malondialdehyde (MDA), H2O2, and antioxidant enzyme activities generally increased first and then slightly declined with increasing Cd concentrations, in both leaves and roots. Furthermore, combined with the previous transcriptomic data, numerous crucial coding-genes related to mineral nutrients and Cd ion transport, and the antioxidant enzymes biosynthesis were identified, and their expression pattern was regulated under different Cd stress. Simultaneously, metabolomic analyses revealed that Cd treatment significantly changed the expression level of many metabolites related to amino acid, lipid, carbohydrate, and nucleotide metabolism. Metabolic pathway analysis also showed that S. nigrum roots activated some differentially expressed metabolites (DEMs) involved in energy metabolism, which may enhance the energy supply for detoxification. Importantly, central common metabolism pathways of DEGs and DEMs, including the “TCA cycle”, “glutathione metabolic pathway” and “glyoxylate and dicarboxylate metabolism” were screened using conjoint transcriptomics and metabolomics analysis. Our results provide some novel evidences on the physiological and molecular mechanisms of Cd tolerance in hyperaccumulator S. nigrum plants.

The online version contains supplementary material available at 10.1186/s12870-024-05278-z.