Responses to drought stress of the biosynthetic and recycling metabolism of glutathione and ascorbate in Agropyron cristatum leaves on the Loess Plateau of China

doi:10.3724/SP.J.1258.2011.00653

Abstract

Abstract:

Aims Our objective was to clarify the mechanism of drought tolerance for Agropyron cristatum on the Loess Plateau of China through investigation of drought stress on the biosynthetic and recycling metabolism of glutathione and ascorbate in leaves.

Methods We investigated the levels and redox status of glutathione and ascorbate and the activities of galactonolactone dehydrogenase (GalLDH), gamma glutamyl cysteine synthetase (γ-ECS), ascorbate peroxidase glutathione reductase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR) in the leaves of A. cristatum under different levels of artificial drought stress using pot experiments.

Important findings Levels of glutathione and ascorbate and their redox status were maintained under drought stress by increasing activities of GalLDH, γ-ECS, APX, GR, DHAR and MDHAR involved in the metabolism of glutathione and ascorbate. This protected A. cristatum from oxidative damage induced by drought stress. However, there were differences in the responses of the metabolism of glutathione and ascorbate related to different drought stress levels with prolonged stress. With 24 or fewer days of stress treatment, the metabolism of glutathione and ascorbate was enhanced under severe drought stress. After 24 days of stress treatment, the activities of GalLDH, γ-ECS, APX, GR, DHAR and MDHAR decreased significantly under severe drought stress, because A. cristatum suffered more severe oxidative damage. However, the activities of these enzymes were maintained throughout the whole period of stress under moderate drought stress. This suggested that A. cristatum could effectively protect itself from oxidative damage induced by moderate drought stress for long time periods. However, A. cristatum could only effectively protect itself from oxidative damage induced by severe drought stress for limited time, and its antioxidant capacity decreased significantly with prolonged stress. Our results also suggested that ascorbate and glutathione had important roles in protecting against oxidative damage under drought stress.

Key words: Agropyron cristatum, ascorbate, drought stress, glutathione, Loess Plateau

SHAN Chang-Juan, HAN Rui-Lian, LIANG Zong-Suo. Responses to drought stress of the biosynthetic and recycling metabolism of glutathione and ascorbate in Agropyron cristatum leaves on the Loess Plateau of China[J]. Chin J Plant Ecol, 2011, 35(6): 653-662.

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URL: https://www.plant-ecology.com/EN/10.3724/SP.J.1258.2011.00653

https://www.plant-ecology.com/EN/Y2011/V35/I6/653

Figures/Tables 7

Fig. 1 Effects of drought stress on the activities of ascorbate peroxidase (APX) (A), glutathione reductase (GR) (B), dehydroascorbate reductase (DHAR) (C) and monodehydroascorbate reductase (MDHAR) (D) in the leaves of Agropyron cristatum (mean ± SE). N, M, S stand for normal water treatment, moderate drought treatment and serious drought treatment, respectively. Small letters stand for the significant difference at p = 0.05 level.

Fig. 2 Effects of drought stress on the activities of galactonolactone dehydrogenase (GalLDH) (A) and gamma glutamyl cysteine synthetase (γ-ECS) (B) in the leaves of Agropyron cristatum (mean ± SE). N, M, S stand for normal water treatment, moderate drought treatment and serious drought treatment, respectively. Small letters stand for the significant difference at p = 0.05 level.

Fig. 3 Effects of drought stress on the contents of reduced ascorbate (AsA) (A), total ascorbate (B), reduced glutathione (GSH) (C) and total glutathione (D) in the leaves of Agropyron cristatum (mean ± SE). N, M, S stand for normal water treatment, moderate drought treatment and serious drought treatment, respectively. Small letters stand for the significant difference at p = 0.05 level.

Fig. 4 Effects of drought stress on reduced ascorbate/dehydroascorbate acid (AsA/DHA) (A) and reduced glutathione/oxidized glutathione (GSH/GSSG) (B) in the leaves of Agropyron cristatum (mean ± SE). N, M, S stand for normal water treatment, moderate drought treatment and serious drought treatment, respectively. Small letters stand for the significant difference at p = 0.05 level.

Fig. 5 Effects of drought stress on the contents of H2O2 (A) and malondialdehyde (MDA) (B) in the leaves of Agropyron cristatum (mean ± SE). N, M, S stand for normal water treatment, moderate drought treatment and serious drought treatment, respectively. Small letters stand for the significant difference at p = 0.05 level.

Table 1 Effects of biosynthetic inhibitors for ascorbate and glutathione on the contents of H2O2 and MDA in leaves of Agropyron cristatum of under drought stress (mean ± SE)

测定指标 Parameters	N	M	M + A	M + BSO	S	S + A	S + BSO
H₂O₂(μmol·g^-1 DW)	9.5 ± 0.88^e	20.5 ± 1.59^d	27.0 ± 1.99^c	29.3 ± 2.17^c	39.2 ± 3.06^b	47.7 ± 4.29^a	52.0 ± 4.75^a
MDA (nmol·g^-1 DW)	35.0 ± 2.65^e	64.5 ± 5.41^d	73.0 ± 6.13^c	77.1 ± 6.43^c	106.0 ± 8.55^b	120.0 ± 9.36^a	128.0 ± 9.02^a

Fig. 6 Effects of drought stress on the plant height (A) and total biomass (B) per plant of Agropyron cristatum (mean ± SE). N, M, S stand for normal water treatment, moderate drought treatment and serious drought treatment, respectively. Small letters stand for the significant difference at p = 0.05 level.

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