Pretreatment with H2O2 alleviates aluminum-induced oxidative stress in wheat seedlings

Fang Jie Xu1, Chong Wei Jin1, Wen Jing Liu2, Yong Song Zhang2, Xian Yong Lin1,2*

1Ministry of Education Key Laboratory of Environmental Remediation and Ecosystem Health, 2Zhejiang Key Laboratory of Subtropical Soil Science and Plant Nutrition,

College of Environmental & Resources Science, Zhejiang University, Hangzhou 310029, China

Hydrogen peroxide (H2O2) is a normal reactive oxygen species (ROS) molecule which not only acts as a main cause of oxidative stress, but also involved in signal transduction pathways leading to activation of plant defense against biotic and abiotic stresses.

There is growing evidence showed that pretreatment of H2O2 could alleviated the deleterious effects of various stress conditions on plant growth and triggering higher stress tolerance in many plant species. However, to the best of our knowledge, it is still little information about the role of pre-application of H2O2 in activating Al acclimation and its relation to Al tolerant acquisition is still unclear.

The present study was aimed at elucidating the effect of H2O2 pretreatment on Al-induced antioxidant responses, including IRE, ROS overproduction, lipid peroxidation, cell death and antioxidant activity increases in two wheat genotypes differing in Al tolerance.

This research was financially supported by the National Basic Research Program of China (973 Program, No. 2007CB109305), National Natural Science Foundation of China (grant Nos. 30771292, 30900920, 30270784), the Foundation for University Ph. D. Granting Discipline of the Ministry of Education (grant No. 20060335014) and IPNI. *Corresponding author: xylin@zju.edu.cn

The pretreatment of H2O2 at appropriate time and concentration led to a pronounced alleviation of Al-induced deleterious effects in both wheat genotype during the subsequent Al exposure. Al sensitivity is an important factor affecting the function of H2O2 pretreatment in improving Al acclimation. The H2O2-pretreated increase in Al tolerance is greater in the Al-sensitive wheat genotype (Yangmai-5) as compared to the Al-tolerant wheat genotype (Jian-864). The pre-application of H2O2 may induce a stronger antioxidant capacity involving higher levels of enzymatic and non-enzymatic antioxidants in root tips of wheat seedlings during subsequent Al exposure, thereby reducing endogenous ROS accumulation and improving Al acclimation of the wheat plants. Therefore, it could be demonstrated that the increased antioxidant defense system level induced by exogenously applied H2O2 acts as the primary factor regulating Al acclimation process in wheat plants.

INTRODUCTION

RESULTS

CONCLUSIONS

Acknowledgement

Figure 1. Relative root Figure 1. Relative root elongation of Yangmai-5 elongation of Yangmai-5 and Jian-864 exposed to and Jian-864 exposed to various concentrations of various concentrations of AlClAlCl33 for 24 h (A) or for 24 h (A) or

exposed to 0 or 30 exposed to 0 or 30 M M AlClAlCl33 for 24 h, with or for 24 h, with or

without 2 h of 0.6 mM without 2 h of 0.6 mM HH22OO22 pretreatment (B). * pretreatment (B). *

indicates significant indicates significant difference at P < 0.05 and difference at P < 0.05 and ** indicates a significant ** indicates a significant difference at P<0.01 difference at P<0.01 between two treatments between two treatments at each Al concentration. at each Al concentration. Bars (i.e. means) with Bars (i.e. means) with different letters are different letters are significantly different significantly different within different within different genotypes and different genotypes and different treatments (P<0.05, n=20). treatments (P<0.05, n=20).

Figure 2.Figure 2. MDA MDA concentration (A) and concentration (A) and Evan blue uptake (B) Evan blue uptake (B) in root tips of in root tips of Yangmai-5 and Jian-Yangmai-5 and Jian-864 exposed to 0 or 864 exposed to 0 or 30 30 M AlClM AlCl33 for 24 h, for 24 h,

with or without 2 h of with or without 2 h of 0.6 mM H0.6 mM H22OO22

pretreatment. Bars pretreatment. Bars (i.e. means) with (i.e. means) with different letters are different letters are significantly different significantly different within different within different genotypes and genotypes and different treatments different treatments (P<0.05, n=3). (P<0.05, n=3).

Figure 3. Figure 3. Concentrations of Concentrations of OO22

.-.- (A) and H (A) and H22OO22 (B) (B)

in root tips of in root tips of Yangmai-5 and Jian-Yangmai-5 and Jian-864 exposed to 0 or 864 exposed to 0 or 30 30 M AlClM AlCl33 for 24 h, for 24 h,

with or without 2 h with or without 2 h of 0.6 mM Hof 0.6 mM H22OO22

pretreatment. Bars pretreatment. Bars (i.e. means) with (i.e. means) with different letters are different letters are significantly significantly different within different within different genotypes different genotypes and different and different treatments (P<0.05, treatments (P<0.05, n=3).n=3).

Figure 6. DPPH-radical Figure 6. DPPH-radical scavenging activity (A) scavenging activity (A) and FRAP assayed total and FRAP assayed total antioxidant capacities antioxidant capacities (B) in root tips of (B) in root tips of Yangmai-5 and Jian-864 Yangmai-5 and Jian-864 exposed to 0 or 30 exposed to 0 or 30 M M AlClAlCl33 for 24 h, with or for 24 h, with or

without 2 h of 0.6 mM without 2 h of 0.6 mM HH22OO22 pretreatment. Bars pretreatment. Bars

(i.e. means) with (i.e. means) with different letters are different letters are significantly different significantly different within different within different genotypes and different genotypes and different treatments (P<0.05, treatments (P<0.05, n=3). n=3).

Figure 4. Activities of SOD (A), CAT (B), POD (C), APX (D), MDHAR (E), DHAR (F), GR (G) and Figure 4. Activities of SOD (A), CAT (B), POD (C), APX (D), MDHAR (E), DHAR (F), GR (G) and GPX (H) in root tips of Yangmai-5 and Jian-864 exposed to 0 or 30 GPX (H) in root tips of Yangmai-5 and Jian-864 exposed to 0 or 30 M AlClM AlCl33 for 24 h, with or for 24 h, with or

without 2 h of 0.6 mM Hwithout 2 h of 0.6 mM H22OO22 pretreatment. Bars (i.e. means) with different letters are pretreatment. Bars (i.e. means) with different letters are

significantly different within different genotypes and different treatments (P<0.05, n=3). significantly different within different genotypes and different treatments (P<0.05, n=3).

Figure 5. Concentrations of AsA (A), GSH (B), ratios of AsA/ (AsA+DHA) (C) and GSH/GSSG Figure 5. Concentrations of AsA (A), GSH (B), ratios of AsA/ (AsA+DHA) (C) and GSH/GSSG (D) in root tips of Yangmai-5 and Jian-864 exposed to 0 or 30 (D) in root tips of Yangmai-5 and Jian-864 exposed to 0 or 30 M AlClM AlCl33 for 24 h, with or without for 24 h, with or without

2 h of 0.6 mM H2 h of 0.6 mM H22OO22 pretreatment. Bars (i.e. means) with different letters are significantly pretreatment. Bars (i.e. means) with different letters are significantly

different within different genotypes and different treatments (P<0.05, n=3).different within different genotypes and different treatments (P<0.05, n=3).

0 10 20 30 40 5015

30

45

60

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90

105

120

RR

E (

%)

A

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RR

E (

%)

Al concentration (mol L-1)

Yangmai-5 Jian-864

*

0

20

40

60

80

100

120

B

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Jian-864

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2(+)Al(-) H

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Yangmai-5 Jian-8640

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60

80

100

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)

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(m

mol

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