biologia plantarum

Biologia plantarum 67:45-53, 2023 | DOI: 10.32615/bp.2023.002

The impact of cadmium stress on the ascorbate-glutathione pathway and ascorbate regeneration in tea plants

H.B. WANG¹, Y.Q. LIU¹, L.L. CHEN¹, X.Q. LI¹, N.H. HA^{1, 2}, T.X. HOANG², X.H. LI¹, X. CHEN^{1, *}

¹ Tea Research Institute, Nanjing Agricultural University, Nanjing 210095, P.R. China

² Northern Mountainous Agriculture and Forestry Science Institute, Phu Tho 35909, Vietnam

Ascorbic acid (AsA) and glutathione (GSH) contribute to defense responses under abiotic stresses. The present study explored the ascorbate-glutathione cycle and ascorbate regeneration under high concentration (30 mM) of cadmium in the tea plant (Camellia sinensis L.). The tea leaves showed speckles and necrosis from the third day of Cd treatment. The content of superoxide anion (O₂^.-) and hydrogen peroxide (H₂O₂) in the leaves were significantly higher until the seventh day after Cd treatment. The content of O₂^.- and H₂O₂ were the highest on the fifth day (212.7 and 153.6 % of the control, respectively). The AsA content increased (86.9 %) on the first day after Cd treatment and decreased significantly in the subsequent days, while GSH showed a reverse trend. The enzymatic activity assays showed that dehydroascorbate reductase (DHAR) and glutathione reductase (GR) involved in AsA regeneration were downregulated considerably after Cd foliar application. In contrast, the activities of ascorbate peroxidase (APX) and monodehydroascorbate reductase (MDHAR) increased on the first day and then declined. Reverse-transcription quantitative PCR showed upregulation of glutathione synthetase (CsGSHS), γ-glutamylcysteine synthetase (Csγ-ECS), and CsMDHAR of the AsA regeneration pathway and downregulation of CsDHAR and CsGR. The expressions of GDP-L-galactose phosphorylase (CsGGP), L-galactose-1-phosphate phosphatase (CsGPP), and L-galactono- 1,4-lactone dehydrogenase (CsGaILDH) of the L-galactose pathway were also downregulated. The results indicated that AsA, which can respond to Cd stress of plants by increasing antioxidant ability, was consumed to scavenge ROS; moreover, Cd stress inhibited AsA synthesis and regeneration, which made that tea plants suffering severe damage.

Keywords: AsA-GSH cycle, cadmium stress, Camellia sinensis, gene expression.

Received: September 9, 2022; Revised: February 21, 2023; Accepted: February 27, 2023; Published online: April 10, 2023  Show citation