Proteome analysis of proteins responsive to ambient and elevated ozone in rice seedlings

Ozone is a major gaseous pollutant that induces crop loss. Although the physiological and morphological responses of crops to ambient ozone have been well characterized, little is known about the protein responses. We firstly investigated the protein responses in rice seedlings under ambient and elevated ozone stress by a proteome approach. Twenty proteins were differentially expressed. Expression of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) large subunit (LSU) and their 17–18 kDa fragments and RuBisCO activase were reduced by both ambient and elevated ozone. RuBisCO small subunit (SSU), large subunit fragment (37 kDa), and oxygen-evolving enhancer proteins 1 and 2 increase in expression with ambient ozone, and decreased with elevated ozone. Ambient ozone induced a slight reduction, and elevated ozone induced a significant reduction in the expression of energy metabolism proteins. Expression of the antioxidant proteins glutathione S-transferase and Mn superoxide dismutase increased upon ozone exposure, but thioredoxin peroxidase expression decreased. Three defense/stress-related proteins, pathogenesis-related (PR) class 5 protein (PR5) and two PR10 proteins OsPR10/PBZ1 and RSOsPR10, were significantly induced after 2 days exposure to elevated ozone and gradually increased during exposure period. The results not only indicate the difference in protein responses between leaves exposed to ambient and elevated ozone, but also demonstrated the highly damaging effect of elevated ozone on rice seedlings at the proteome level.