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.