Investigating the impact of elevated levels of ozone on tropical wheat using integrated phenotypical, physiological, biochemical, and proteomics approaches.

Ozone (O3), a potent air pollutant and a significant greenhouse gas, has been recognized as a major component of global climate change. However, current increasing trends in its background level are projecting a more severe threat to natural and cultivated plants in the near future. The present study has been designed to evaluate the impact of elevated concentrations of O3 on phenotypical, physiological, and biochemical traits in two high-yielding cultivars of wheat, followed by analysis of the leaf proteome using one/two-dimensional gel electrophoresis (1-/2-DGE) coupled to immunoblotting and mass spectrometry analyses under near-natural conditions using open top chambers. Prominently, O3 exposure caused specific foliar injury in both the wheat cultivars. Results also showed that O3 stress significantly decreased photosynthetic rate, stomatal conductance, and chlorophyll fluorescence kinetics (Fv/Fm) in test cultivars. Biochemical evaluations further revealed a higher loss in photosynthetic pigments, whereas a significantly induced antioxidant system under elevated O3 concentrations pointed toward an ability of O3 to generate oxidative stress. 1-DGE analysis showed drastic reductions in the abundantly present ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) large and small subunits. Western blot analysis confirmed induced accumulation of antioxidative enzymes like superoxide dismutase and ascorbate peroxidase protein(s) and common defense/stress-related thaumatin-like protein(s). 2-DGE analysis revealed a total of 38 differentially expressed protein spots, common in both the wheat cultivars. Among those, some major leaf photosynthetic proteins (including RuBisCO and RuBisCO activase) and important energy metabolism proteins (including ATP synthase, aldolase, and phosphoglycerate kinase) were drastically reduced, whereas some stress/defense-related proteins (such as harpin-binding protein and germin-like protein) were induced. In all, the present study reveals an intimate molecular network provoked by O3 affecting photosynthesis and triggering antioxidative defense and stress-related proteins culminating in accelerated foliar injury in wheat plants.