|Ainsworth, Elizabeth - Lisa|
Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2010
Publication Date: 5/1/2011
Citation: Gillespie, K.M., Rogers, A., Ainsworth, E.A. 2011. Growth at elevated ozone or elevated carbon dioxide concentration alters antioxidant capacity and response to acute oxidative stress in soybean (Glycine max). Journal of Experimental Botany. 62(8):2667-2678. Interpretive Summary: In the future, plants will be exposed to higher concentrations of carbon dioxide and ozone in the atmosphere. Both of these changes have been shown to alter antioxidant metabolism in plants, although the reports in the literature are inconsisent. In this study, we tested how long-term growth at elevated carbon dioxide or elevated ozone concentrations altered the antioxidant metabolism of soybean, and discovered that elevated ozone increased total antioxidant capacity, while elevated carbon dioxide decreased total antioxidant capacity. Changes in initial antioxidant capacity also affected the manner by which plants responded to an acute ozone stress. The results demonstrate the future elevated concentrations of carbon dioxide and ozone will differentially affect the antioxidant system in plants, which may have important implications as plants are increasingly exposed to environmental stress with global climate change.
Technical Abstract: In order to test the hypothesis that atmospheric environment alters total antioxidant capacity of plants and their capacity to respond to acute oxidative stress, soybeans were grown under at elevated carbon dioxide concentration ([CO2]) or elevated ozone concentration ([O3]), and then exposed to an acute O3 stress (200 ppb for 4 hrs). Total antioxidant metabolism, antioxidant enzyme activity and antioxidant transcript abundance were characterized before, immediately after, and during recovery from the acute O3 treatment. The elevated [O3] environment increased the total antioxidant capacity of plants, while chronic elevated [CO2] decreased total antioxidant capacity. Changes in total antioxidant capacity were matched by changes in ascorbate content, but not in total phenolic content of the plants. The growth environment significantly altered the pattern of antioxidant transcript and enzyme response to the acute O3 stress. Long-term growth at elevated [O3] appeared to “prime” the antioxidant system, and following the acute oxidative stress, there was an immediate transcriptional reprogramming that allowed for maintained or increased antioxidant enzyme activities. Growth at high [CO2] decreased the total antioxidant capacity, appeared to increase the response of the existing antioxidant enzymes, but dampened and delayed the transcriptional response. These results confirmed the hypothesis that growth environment alters the antioxidant system, the immediate response to an acute oxidative stress and the timing over which plants return to initial antioxidant levels. The results also indicate the future elevated concentrations of CO2 and O3 will differentially affect the antioxidant system.