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Submitted to: Physiologia Plantarum
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/16/2003 Publication Date: 3/4/2004 Citation: Anderson, J.V., Davis, D.G. 2004. Abiotic stress alters transcript profiles and activity of glutathione S-transferase, glutathione peroxidase, and glutathione reductase in Euphorbia esula. Physiologia Plantarum. 120:421-433. Interpretive Summary: Leafy spurge is a serious invasive perennial weed of range and recreational lands of North American plains and prairies. Leafy spurge exhibits remarkable resistance to many abiotic and biotic stressors. Acquiring new knowledge about stress-induced defense mechanisms and signaling pathways associated with survival of leafy spurge during periods of stress could lead to new and improved biologically-based strategies that could be incorporated into current integrated pest management systems. Antioxidants, such as glutathione, play important roles in plant defense mechanisms. We monitored the expression and activity of several glutathione-metabolizing enzymes in leafy spurge plants exposed to xenobiotic- and environmental-stress. Both xenobiotic- and environmental-stress caused increased expression and activity of glutathione-metabolizing enzymes in leafy spurge. The expression pattern of a stress-inducible, mitogen activated protein kinase (MAPK) in stressed leafy spurge suggests that altered glutathione metabolism could be linked to induction of stress-signaling cascades. However, our data indicates that the induction of MAPK is well down stress, or secondary to the initial signaling mechanisms leading to increased expression and activity of glutathione metabolizing enzymes. Technical Abstract: Leafy spurge (Euphorbia esula L.) is an invasive perennial weed in North American plains and prairies which exhibits remarkable tolerance towards abiotic and biotic stress. Glutathione plays an important role in plant defense mechanisms and varying degrees of glutathione S-transferase (GST), glutathione reductase (GR), and glutathione peroxidase (GPX) activity have been observed in leafy spurge tissue exposed to xenobiotic- and environmental-stress. Tissue treated with a xenobiotic [Diclofop-methyl (DM)] had increased GST, GR, and GPX activity. Six different EeGST cDNAs (including a phi, tau, theta, and zeta class GST), one EeGPX cDNA, and one EeGR cDNA isolated from leafy spurge were used monitor differential expression patterns in leafy spurge plants exposed to DM-, cold-, and drought-stress. Changes in GST, GPX, and GR activities in DM-treated tissue were, in part, attributed to both induced gene expression and decreased total protein content. The reduction in protein content was attributed mainly to the degradation of Rubisco. None of the GPX activity in leafy spurge protein extracts were affinity-bound to either S-hexylglutathione- or glutathione-agarose columns. Increased GST activity in DM-treated tissue has attributed to phi- and tau-type GSTs. Up-regulation of a leafy spurge stress-inducible, MAP kinase observed in DM- and drought-treated tissue indicate that signal transduction cascades involved in defense signaling may be responsive to stress-induced changes in glutathione concentrations. |
