Exogenous spermidine alleviates the adverse effects of aluminum toxicity on photosystem II through improved antioxidant system and endogenous polyamine contents

• Published in: Ecotoxicology and environmental safety 2021-01, Vol.207, p.111265, Article 111265
• Main Authors: Jiang, Dexing, Hou, Junjie, Gao, Wenwen, Tong, Xi, Li, Meng, Chu, Xiao, Chen, Guoxiang
• Format: Article
• Language: English
• Subjects: Aluminum; Aluminum - metabolism; Aluminum - toxicity; Antioxidants - metabolism; Chlorophyll - metabolism; Chloroplast; Chloroplasts - drug effects; Hydrogen Peroxide - metabolism; Malondialdehyde - metabolism; Nutrient elements; Oxidative stress; Photosynthesis - drug effects; Photosystem II Protein Complex - drug effects; Photosystem II Protein Complex - metabolism; Polyamines - metabolism; Protective Agents - pharmacology; Spermidine; Spermidine - metabolism; Spermidine - pharmacology
• ISSN: 0147-6513; 1090-2414
• DOI: 10.1016/j.ecoenv.2020.111265

Aluminum (Al) toxicity is a major yield-limiting factor for crops in acidic soils. In this work, we have investigated the potential role of spermidine (Spd) on Al toxicity in rice chloroplasts. Exogenous Spd markedly reduced Al concentration and elevated other nutrient elements such as Mn, Mg, Fe, K, Ca, and Mo in chloroplasts of Al-treated plants. Meanwhile, Spd further activated arginine decarboxylase (ADC) activity of key enzyme in polyamine (PA) synthesis, and enhanced PA contents in chloroplasts. Spd application dramatically addressed Al-induced chlorophyll (Chl) losses, inhibited thylakoid membrane protein complexes degradation, especially photosystem II (PSII), and significantly depressed the accumulations of superoxide radical (O2·-), hydrogen peroxide (H2O2), and malondialdehyde (MDA) in chloroplasts. Spd addition activated antioxidant enzyme activities and decreased soluble sugar content in chloroplasts compared with Al treatment alone. Spd not only reversed the inhibition of photosynthesis-related gene transcript levels induced by Al toxicity, but diminished the increased expression of Chl catabolism-related genes. Furthermore, Chl fluorescence analysis showed that Spd protected PSII reaction centers and photosynthetic electron transport chain under Al stress, thus improving photosynthetic performance. These results suggest that PAs are involved in Al tolerance in rice chloroplasts and can effectively protect the integrity and function of photosynthetic apparatus, especially PSII, by mitigating oxidative damage induced by Al toxicity. •Spermidine application reduced Al accumulation and elevated uptake of nutrient elements in chloroplasts.•Spermidine application mitigated Al-induced oxidative damage in chloroplasts.•Spermidine application markedly increased ADC activity and polyamine contents under Al stress.•Spermidine application delayed the degradation of Chl-protein complexes in Al-stressed plants.•Spermidine application enhanced photosynthetic performance in Al-stressed plants.