Poster: Oxidative stress

Abs # 82: Differential responses of G-protein Arabidopsis thaliana mutants to ozone

Presenter:	Booker, Fitzgerald L, fbooker@mindspring.com
Authors	Booker, Fitzgerald L (A) (B)  Burkey, Kent O (A) (B)  Overmyer, Kirk  (C)   Jones, Alan M (C)
Affiliations:	(A): USDA-ARS Air Quality-Plant Growth and Development Unit (B): Department of Crop Science, NC State University (C): Department of Biology, University of North Carolina at Chapel Hill

Current ground-level ozone (O₃) concentrations curtail agricultural production by 5 to 15% in many regions worldwide. Furthermore, tropospheric O₃ concentration is expected to increase in the 21^st century as emissions of its precursors continue to grow. 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. After treatment with 100 nmol O₃ mol^-1 7 h daily for 6 d, the epinasty typically observed for wild type leaves did not occur in mutant plants lacking the alpha subunit of the heterotrimeric 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.