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United States Department of Agriculture

Agricultural Research Service

Research Project: IDENTIFYING AND MANIPULATING DETERMINANTS OF PHOTOSYNTHATE PRODUCTION AND PARTITIONING

Location: Global Change and Photosynthesis Research Unit

Title: Greater antioxidant and respiratory metabolism in field-grown soybean exposed to elevated O3 under both ambient and elevated CO2 concentrations

Authors
item Gillespie, K -
item Xu, F -
item Richter, Katherine -
item Mcgrath, Justin -
item Markelz, R J Cody -
item ORT, DONALD
item Leakey, Andrew D B -
item AINSWORTH, ELIZABETH

Submitted to: Plant Cell and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 12, 2011
Publication Date: January 1, 2012
Citation: Gillespie, K.M., Xu, F., Richter, K.T., McGrath, J.M., Markelz, R., Ort, D.R., Leakey, A., Ainsworth, E.A. 2012. Greater antioxidant and respiratory metabolism in field-grown soybean exposed to elevated O3 under both ambient and elevated CO2 concentrations. Plant Cell and Environment. 35(1):169-184.

Interpretive Summary: Tropospheric O3 concentration ([O3]) has approximately doubled since the Industrial Revolution and is expected to increase further as ozone precursor emissions rise over this century. Atmospheric CO2 concentration ([CO2]) is also increasing at an unprecedented rate and will surpass 550 ppm by 2050. This study investigated molecular, biochemical and physiological changes in antioxidant metabolism in soybean exposed to elevated [O3] in a background of both ambient and elevated [CO2] in an open field environment. Using statistical analyses that effectively separated variability in ozone from variability in other environmental conditions including light, temperature and relative humidity, it was determined that antioxidant metabolism increased with increasing ozone. The energetically expensive increase in antioxidant metabolism was supported by increased respiratory metabolism in both ambient and elevated carbon dioxide.

Technical Abstract: Antioxidant metabolism is responsive to oxidative signals associated with fluctuating environmental conditions, and is proposed to be a key component of ozone (O3) tolerance in plants. Tropospheric O3 concentration ([O3]) has approximately doubled since the Industrial Revolution and is expected to increase further as precursor emissions rise over this century. Additionally, atmospheric CO2 concentration ([CO2]) is increasing at an unprecedented rate and will surpass 550 ppm by 2050. This study investigated molecular, biochemical and physiological changes in antioxidant metabolism in soybean exposed to elevated [O3] in a background of both ambient and elevated [CO2] in an open field environment. Principle components analysis was used to separate variability in [O3] from variability in other environmental conditions (temperature, light and relative humidity) into two orthogonal axes that accounted for 76% of the total variation. Subsequent analysis of covariance determined that soybean antioxidant metabolism increased with increasing [O3], in both ambient and elevated [CO2]. The transcriptional response was dampened at elevated [CO2], which was consistent with lower stomatal conductance and therefore lower O3 flux into leaves. There was transcriptional evidence for increased tetrapyrrole synthesis at elevated [O3], which was apparent in both ambient and elevated [CO2]. Energetically expensive increases in antioxidant metabolism and tetrapyrrole synthesis at elevated [O3] were supported by higher transcript levels of enzymes involved in respiratory metabolism. This work demonstrated that soybean antioxidant metabolism is up regulated at elevated [O3], requiring increased respiratory metabolism to fuel higher energy demands, and that elevated [CO2] dampens the biochemical and transcriptional response to elevated [O3].

Last Modified: 7/25/2014
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