title: Greater antioxidant and respiratory metabolism in field-grown soybean exposed to elevated O3 under both ambient and elevated CO2.
abstract: Antioxidant metabolism is responsive to environmental conditions, and is proposed to be a key component of ozone (O(3)) tolerance in plants. Tropospheric O(3) concentration ([O(3)]) has doubled since the Industrial Revolution and will increase further if precursor emissions rise as expected over this century. Additionally, atmospheric CO(2) concentration ([CO(2)]) is increasing at an unprecedented rate and will surpass 550 ppm by 2050. This study investigated the molecular, biochemical and physiological changes in soybean exposed to elevated [O(3) ] in a background of ambient [CO(2)] and elevated [CO(2)] in the field. Previously, it has been difficult to demonstrate any link between antioxidant defences and O(3) stress under field conditions. However, this study used principle components analysis to separate variability in [O(3)] from variability in other environmental conditions (temperature, light and relative humidity). Subsequent analysis of covariance determined that soybean antioxidant metabolism increased with increasing [O(3)], in both ambient and elevated [CO(2)]. The transcriptional response was dampened at elevated [CO(2)], consistent with lower stomatal conductance and lower O(3) flux into leaves. Energetically expensive increases in antioxidant metabolism and tetrapyrrole synthesis at elevated [O(3)] were associated with greater transcript levels of enzymes involved in respiratory metabolism.
authors.affiliation: Department of Plant Biology and Institute for Genomic Biology, University of Illinois, Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Kelly M
authors.initials: KM
authors.lastname: Gillespie
authors.forename: Fangxiu
authors.initials: F
authors.lastname: Xu
authors.forename: Katherine T
authors.initials: KT
authors.lastname: Richter
authors.forename: Justin M
authors.initials: JM
authors.lastname: McGrath
authors.forename: R J Cody
authors.initials: RJ
authors.lastname: Markelz
authors.forename: Donald R
authors.initials: DR
authors.lastname: Ort
authors.forename: Andrew D B
authors.initials: AD
authors.lastname: Leakey
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Ainsworth
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D002241:Carbohydrates / Q000096:biosynthesis; D002245:Carbon Dioxide / Q000494:pharmacology*; D019069:Cell Respiration / Q000187:drug effects; D002734:Chlorophyll / Q000378:metabolism; D004777:Environment; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D020411:Oligonucleotide Array Sequence Analysis; D010126:Ozone / Q000494:pharmacology*; D010788:Photosynthesis / Q000187:drug effects; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D054046:Plant Stomata / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D018526:Plant Transpiration / Q000187:drug effects; D025341:Principal Component Analysis / Q000379:methods; D018749:RNA, Plant / Q000235:genetics; D013025:Glycine max / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D045725:Tetrapyrroles / Q000096:biosynthesis
chemical_list: D000975:Antioxidants; D002241:Carbohydrates; D018749:RNA, Plant; D045725:Tetrapyrroles; D002734:Chlorophyll; D002245:Carbon Dioxide; D010126:Ozone