Metabolome Analysis Revealed the Mechanism of Exogenous Glutathione to Alleviate Cadmium Stress in Maize (Zea mays L.) Seedlings

Abstract

Cadmium (Cd) is one of the major heavy metal pollutants in the environment and imposes severe limitations on crop growth and production. Glutathione (GSH) plays an important role in plant Cd tolerance which is able to scavenge stresses-induced reactive oxygen species (ROS) and is involved in the biosynthesis of phytochelatins (PCs). Our previous study revealed that Cd stress affects maize growth, and the GSH treatment could relieve Cd stress in maize seedlings. In this study, we attempted to characterize the metabolomics changes in maize leaves and roots under Cd stress and exogenous GSH conditions. We identified 145 and 133 metabolites in the leaves and roots, respectively. Cd stress decreased the tricarboxylic acid cycle (TCA cycle) metabolism and increased the amino acid contents in the leaves, while it decreased the amino acid contents, increased the TCA cycle metabolism, the sugar contents, and shikimic acid metabolism in the roots. On the other hand, exogenous GSH increased the GSH content, changed the production of metabolites related to antioxidant systems (such as ascorbic acid-related metabolites and flavonoid-related metabolites), and alleviated lipid peroxidation, thereby alleviating the toxic effect of Cd stress on maize. These findings support the idea that GSH alleviates Cd-induced stress in maize and may help to elucidate the mechanism governing Cd-induced stress and the GSH-driven alleviation effect.

Mitigation of Environmental Stress-Impacts in Plants: Role of Sole and Combinatory Exogenous Application of Glutathione

“…Besides increasing enzymatic activities and upregulation of GSH biosynthesis gene expressions, exogenous GSH plays a significant role in regulating photosynthetic activities ( Wang et al, 2011 ; Khan et al, 2016 ; Li et al, 2021 ). Wang et al (2021) carried out a greenhouse hydroponic experiment using two different barley genotypes, Cd-sensitive Dong 17 and Cd-tolerant Weisuobuzhi, to investigate the effects of exogenous GSH on their photosynthetic performances under Cd stress. It was revealed that the treatment of GSH significantly increased both genotypes, especially Cd-sensitive Dong 17, with a great increase in parameters such as the net photosynthetic rate, stomatal conductance, transpiration rate and photochemical efficiency (F v /F m ) by 130.2, 68.9, and 52.4%, respectively, when compared to the control plant ( Wang et al, 2011 ).…”

“…Apart from the uptake and distribution of HM, metabolomics, which is the study of the identification, quantification, and distribution of metabolites, such as sugars, alcohols, amino acids, organic acids, and polyamines, provides a better understanding of the plant’s responses to any interference, including HM stresses ( Ghatak et al, 2018 ). In the metabolome study of maize leaves under Cd stress, the tricarboxylic acid (TCA) cycle-related metabolites such as malic acid and maleic acid were found to be decreased in leaves, possibly due to the nature of its enzyme known as fumarate hydratase, that was reported to be particularly sensitive to ROS ( Lushchak, 2011 ; Wang et al, 2021 ). With the addition of GSH, the trend of the TCA cycle-related metabolites was reversed, where malic and maleic acid levels were detected to increase in leaves, implying that the exogenous GSH successfully alleviates the oxidative stress induced by Cd toxicity on the TCA cycle ( Wang et al, 2021 ).…”

“…In the metabolome study of maize leaves under Cd stress, the tricarboxylic acid (TCA) cycle-related metabolites such as malic acid and maleic acid were found to be decreased in leaves, possibly due to the nature of its enzyme known as fumarate hydratase, that was reported to be particularly sensitive to ROS ( Lushchak, 2011 ; Wang et al, 2021 ). With the addition of GSH, the trend of the TCA cycle-related metabolites was reversed, where malic and maleic acid levels were detected to increase in leaves, implying that the exogenous GSH successfully alleviates the oxidative stress induced by Cd toxicity on the TCA cycle ( Wang et al, 2021 ). Besides TCA cycle-related metabolites, sugar contents such as maltose, fructose, heptanose, sophorose and sucrose in plants under the treatment of GSH were significantly increased.…”

“…Therefore, studies have been focused on investigating the effects of exogenous application of GSH on plants via foliar spray or seed soaking method to compensate for the decreased level of endogenous GSH, which in an attempt to alter the redox state of GSH/GSSG. Positive results for the exogenous application of GSH were shown especially in mitigating abiotic stresses like drought, salinity, metal toxicity, and temperature extremities and further improving the growth and yield of major plant crops that include rice, wheat, maize, and chickpea ( Hussain et al, 2016 ; El-Beltagi et al, 2020 ; Li et al, 2021 ; Wang et al, 2021 ).…”

Ovary Abortion Induced by Combined Waterlogging and Shading Stress at the Flowering Stage Involves Amino Acids and Flavonoid Metabolism in Maize

“…Understanding the complexity of the mechanisms responsible for ovary and silk development and how waterlogging and shading stress cause ovary abortion is critically important to improve maize production. Metabolomic studies have unraveled some mechanisms underlying kernel development ( Wen et al, 2014 ; Yang et al, 2018 ; Bernardi et al, 2019 ; Gálvez Ranilla, 2020 ) and the responses of different crop varieties to various abiotic stress ( Obata et al, 2015 ; Sun et al, 2016 ; Xiong et al, 2019 ; Wang et al, 2021 ). The reasons for maize ovary/kernel abortion in response to abiotic stress are very complex.…”