Differential responses of G-protein Arabidopsis thaliana mutants to ozone

•  Ground-level ozone (O₃ ) curtails agricultural production in many regions worldwide. However, the etiology of O₃ toxicity remains unclear. Activated oxygen species appear to inflict biochemical lesions and propagate defense responses that compound plant injury. Because some plant defense responses involve membrane-delimited GTPases (G proteins), we evaluated the O₃ sensitivity of Arabidopsis mutants altered in the heterotrimeric G-protein pathway. •  Eight genotypes were treated with a range of O₃ concentrations (0, 100, 175 and 250 nmol mol^-1 ) for 13 d in controlled environment chambers. •  After treatment with O₃ , the epinasty typically observed for wild type leaves did not occur in mutant plants lacking the alpha subunit of the G-protein complex (gpa1). O₃ -induced suppression of leaf chlorophyll levels and leaf mass per unit leaf area were less for gpa1 mutants and were not due to differences in O₃ flux. •  There was a positive correlation between the lack of a G-protein alpha subunit and decreased O₃ sensitivity. Our results suggest that a heterotrimeric G-protein is critically involved in the expression of O₃ effects in plants.