Impact of tropospheric ozone on root proteomes of two soybean genotypes with contrasting sensitivity to ozone

Tropospheric ozone (O3), a critically harmful greenhouse gas, has steadily increased over the last several decades, leading to significant soybean (Glycine max) yield loses worldwide. However, substantial efforts have focused on the effect of elevated O3 concentration (eOZ) on shoots rather than the roots that support plant fitness and directly interact with soil ecosystems. To better assess the impact of eOZ on roots, this study investigated morphological and proteomic profiles of two soybean genotypes from the same genetic background, but with contrasting O3 resilience, Fiskeby III (O3-tolerant) and Fiskeby 840–7–3 (O3-sensitive). Plants were treated either with sub-ambient O3 or eOZ in a field-based air exclusion system (AES) and harvested at flowering and pod-filling stages. Our results established that the effect of eOZ on decreasing root biomass initiated at the flowering stage, while above-ground biomass was not altered. However, O3-caused biomass reduction was observed in both, roots and shoots, at the pod-filling stage. Season-long eOZ ultimately caused a 29 % seed yield reduction in Fiskeby III, and 50 % in Fiskeby 840–7–3. Root proteome analysis showed that the effect of O3 in roots is complex, and distinct between flowering and pod-filling stages. Changes in the abundance of proteins correspond to glycolysis, TCA cycle, nitrogen metabolism, secondary metabolites, antioxidant, and stress response pathway, and differed between genotypes. Some of these changes may be in response to eOZ as an attempt to mitigate the effects of a challenging environment, and others are likely due to genetic differences that confer an adaptative advantage to the O3 resilient genotype. These findings provide further knowledge of proteins and pathways that may confer O3-tolerance, which can be applied to develop O3-resistant, high-yielding soybean.