Submitted to: Plant and Cell Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/18/2000
Publication Date: N/A
Interpretive Summary: Low temperatures at and following planting often reduce seedling growth. These early-season growth reductions ultimately reduce yield at the end of the season that result in decreased profits for producers. Plants have mechanisms that protect them against low temperature damage, but they are not capable of completely preventing damage. In this study, one of the protective mechanisms was artificially enhanced. This enhancement improved seedling growth and vigor at low temperatures when compared to plants with normal levels of protection. This study demonstrates that enhancement of a single part of the protective system can improve overall plant per- formance and suggests that such modifications may provide a means for reducing plant losses due to low temperatures.
Technical Abstract: Overexpression of a tobacco glutathione S-transferase with glutathione peroxidase activity (GST/GPX)in transgenic tobacco (Nicotiana tabacum L.) has been shown to enhance seed germination and seedling growth under stressful conditions. To gain a better understanding of the mechanisms that underlie this effect, comparative analysis of the metabolic activity of transgenic and control seedlings were performed. Exposure to stressful conditions, including low and elevated temperatures and salinity, resulted in concomitant decreases in both seedling growth and metabolic activity in control seedlings, while GST/GPX-expressing seedlings maintained higher growth rates and increased metabolic activity. The apparent protection of metabolic activity in GST/GPX-expressing seedlings corresponded with decreased lipid peroxidation and maintenance of the ascorbate pool in a more reduced state. In addition, levels of ascorbate peroxidase activity increased slightly and levels of monodehydroascorbate reductase were elevated by about three-fold in GST/GPX-expressing plants. These results indicate that overexpression of GST/GPX in transgenic tobacco seedlings provides increased glutathione-dependent peroxide scavenging and alterations in ascorbate metabolism which lead to reduced oxidative stress. This protection could be, at least in part, responsible for the increased stress tolerance of GST/GPX-expressing seedlings.