Transcript expression profiles of Arabidopsis thaliana grown under controlled conditions and open-air elevated concentrations of CO ₂ and of O ₃

Microarrays have significantly enhanced our ability to track transcripts and changes in gene expression under different conditions and environments. In order to find determinants of plant performance influenced by atmospheric changes, we tracked transcript profiles in Arabidopsis thaliana (L.) Heynh. grown in a field within SoyFACE. This facility (http://www.soyface.uiuc.edu/ index.htm) consists of a series of open-air rings within which either [CO ₂] or [O ₃] are elevated above current atmospheric concentrations by 1.5× and 1.2×, respectively. A microarray platform including ∼26,000 DNA elements was used to monitor transcript abundance and changes due to exposure to elevated [CO ₂] and [O ₃]. Transcripts from plants in growth chambers were further compared with material from plants grown in Free Air Concentration Enrichment (FACE) rings under ambient conditions. Most changes in gene expression were observed between growth chamber and ambient field conditions. Two to four times the number of transcripts were either up- or down-regulated between controlled versus field ambient conditions compared with high versus low [CO ₂] or [O ₃] contrasts. The differences showed a preponderance of regulated transcripts in categories such as chaperones and general defense reactions, altered (secondary) metabolic functions, redox control, energy provision, protein turnover, signaling and transcription. We discuss the results obtained in a model non-crop plant for their possible relevance in studies with crop species.