Metabolome Analysis of Response to Oxidative Stress in Rice Suspension Cells Overexpressing Cell Death Suppressor Bax Inhibitor-1

Abstract

Bax inhibitor-1 (BI-1) is a cell death suppression factor widely conserved in higher plants and animals. Overexpression of Arabidopsis BI-1 (AtBI-1) in plants confers tolerance to various cell death-inducible stresses. However, apart from the cell death-suppressing activity, little is known about the physiological roles of BI-1-overexpressing plants. In this study, we evaluated the effects of AtBI-1 overexpression on the rice metabolome in response to oxidative stress. AtBI-1-overexpressing rice cells in suspension displayed enhanced tolerance to menadione-induced oxidative stress compared with vector control cells, whereas AtBI-1 overexpression did not influence the increase of intracellular H(2)O(2) concentration or inhibition of oxidative stress-sensitive aconitase activity. Capillary electrophoresis-mass spectrometry (CE-MS)-based metabolome analysis revealed dynamic metabolic changes in oxidatively stressed rice cells, e.g. depletion of the central metabolic pathway, imbalance of the redox state and energy charge, and accumulation of amino acids. Furthermore, comparative metabolome analysis demonstrated that AtBI-1 overexpression did not affect primary metabolism in rice cells under normal growth conditions but significantly altered metabolite composition within several distinct pathways under cell death-inducible oxidative stress. The AtBI-1-mediated metabolic alteration included recovery of the redox state and energy charge, which are known as important factors for metabolic defense against oxidative stress. These observations suggest that although AtBI-1 does not affect rice metabolism directly, its cell death suppression activity leads to enhanced capacity to acclimate oxidative stress.

Overexpression of BAX INHIBITOR-1 Links Plasma Membrane Microdomain Proteins to Stress

“…Conversely, plants overexpressing BI-1 exhibit tolerance to cell death induced by various stresses (Kawai-Yamada et al, 2001Matsumura et al, 2003;Ihara-Ohori et al, 2007;Watanabe and Lam, 2008;Ishikawa et al, 2010). Moreover, BI-1 overexpression confers not only tolerance to oxidative stress-mediated cell death but also enhanced metabolic acclimation involved in energy and redox balance (Ishikawa et al, 2010). The results of these studies indicate that plant BI-1 is potentially useful for engineering stress-tolerant plants.…”

“…To investigate the effects of BI-1 on lipid metabolism and membrane microdomain components, we used a rice suspension culture line in which the overexpression of Arabidopsis BI-1 significantly enhances the tolerance to cell death induced by elicitors, salicylic acid (SA), and oxidative stress (Matsumura et al, 2003;Ishikawa et al, 2010). The suspension culture system allows harvesting the large number of homogenous samples required for the biochemical preparation of membrane microdomain components.…”

“…Although plants lack the homolog of animal BAX as an inducer of programmed cell death, loss of BI-1 expression results in a severe cell death phenotype under stress conditions, such as fumonisin B1-induced ER stress and disturbance of ion homeostasis (Watanabe and Lam, 2006;Ihara-Ohori et al, 2007). Conversely, plants overexpressing BI-1 exhibit tolerance to cell death induced by various stresses (Kawai-Yamada et al, 2001Matsumura et al, 2003;Ihara-Ohori et al, 2007;Watanabe and Lam, 2008;Ishikawa et al, 2010). Moreover, BI-1 overexpression confers not only tolerance to oxidative stress-mediated cell death but also enhanced metabolic acclimation involved in energy and redox balance (Ishikawa et al, 2010).…”

Plant Metabolomics: A Characterisation of Plant Responses to Abiotic Stresses

“…Moreover, the following variations in metabolites that can prevent oxidative damage were reported in menadione-treated roots: an increased abundance of proline (with a concomitant decrease in its precursor, glutamate), changes in polyamine metabolism with a decrease in putrescine, and accumulation of some methionine-derived aliphatic glucosinolates (Baxter et al, 2007;Lehmann et al, 2009). An enhanced tolerance to menadione-induced oxidative stress was displayed by rice cultured cells overexpressing the Arabidopsis Bax Inhibitor-1 (AtBI-1) gene (Ishikawa et al, 2010). Bax Inhibitor-1 is an endoplasmic reticulum membrane protein, acting as a cell death suppression factor, that is widely conserved in animals and higher plants.…”

Bax inhibitor-1: a highly conserved endoplasmic reticulum-resident cell death suppressor

“…In fact, BI-1 can apparently increase the capacity of cellular homeostasis, including primary metabolism, under oxidative stress conditions and thereby facilitate the repression of cell death, although AtBI-I overxpression does not trigger any obvious changes under normal growth conditions. 26 These metabolic changes under oxidative stress could be linked with alterations in Ca 2 þ signaling and sphingolipid metabolism (see below).…”