Differential responses of G-protein Arabidopsis thaliana mutants to ozone.

•  Ground-level ozone (O ) curtails agricultural production in many regions worldwide. However, the etiology of O 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 O sensitivity of Arabidopsis mutants altered in the heterotrimeric G-protein pathway. •  Eight genotypes were treated with a range of O concentrations (0, 100, 175 and 250 nmol mol ) for 13 d in controlled environment chambers. •  After treatment with O , the epinasty typically observed for wild type leaves did not occur in mutant plants lacking the alpha subunit of the G-protein complex (gpa1). O -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 O flux. •  There was a positive correlation between the lack of a G-protein alpha subunit and decreased O sensitivity. Our results suggest that a heterotrimeric G-protein is critically involved in the expression of O effects in plants.