Changes in composition and concentration of differential metabolites in root exudates are associated with aluminum-tolerance of Ricinus communis under a high CO2 environment

• Published in: Plant physiology and biochemistry 2024-12, Vol.217, p.109231, Article 109231
• Main Authors: Li, Yueming, Yang, Fan, Liu, Xin, Deng, Xiaoxia, Han, Peilin, Dai, Shang, Lin, Jixiang
• Format: Article
• Language: English
• Subjects: Aluminum stress; Metabolomics; Ricinus communis; Root exudates; Root physiology
• ISSN: 0981-9428; 1873-2690; 1873-2690
• DOI: 10.1016/j.plaphy.2024.109231

Root exudates are the most direct performance for plants responding to adverse environments, and are also important media for materials exchange, energy transmission and information communication between the roots and rhizosphere. However, how plant roots and exudates respond to aluminum (Al) stress under elevated CO2 concentration (eCO2) is still unclear. Ricinus communis is a famous oilseed crop throughout the world, which has strong tolerance to metal contaminated soil. In the present study, root physiological changes and the exudates of this species under aluminum stress and eCO2 based on metabolomic were investigated. The results showed that high Al concentration stress significantly increased aluminum, MDA, proline, and soluble sugar contents, and decreased the dry weights and soluble protein concentration. Furthermore, eCO2 alleviated the inhibition of root growth under high Al stress by increasing the dry weights, antioxidant enzyme activities and decreasing the MDA content. Collectively, a total of 511 metabolites were detected in the castor exudates of which lipids, organic acids, and organic oxygen compounds occupied 40.82%, 17.78% and 12.54%, respectively. There were 83, 15, and 100 differential metabolites for high Al stress, eCO2 and the interaction of the two factors compared with the control. 12 differential metabolites were found under eCO2 and Al stress compared with Al stress alone. Under Al stress, TCA cycle, organic acids, and lipids metabolisms were inhibited; coumarins and carbohydrates conjugates were significantly up-regulated, which may help castor adapt to aluminum-contaminated conditions. Moreover, eCO2 increased the secretion of organic acids, fatty acyls, and carbohydrates to enhance the antioxidant capacity and root growth of castor under Al stress; eCO2 enhanced the TCA cycle, organic acids accumulation, lipids metabolism, biosynthesis of amino acids, pentose and glucuronate interconversions, and inhibited DNA oxidative stress of castor roots under Al stress. The present study provides new insights into the crucial role of root exudates in improving Al-tolerance of castor under eCO2. Graphical abstract A model of the roots and exudates in castor in response to Al stress and eCO2. Up-regulated items under Al stress and eCO2 are marked with upward red arrows and down-regulated items under Al stress are marked with downward blue arrow. The red and blue boxes indicate that compared with CK0 or CK1, the differential metabolites c