Change in O2 Evolution Rate and Protein Property in the Leaf Blade of Oryza officinalis Wall ex Watt in Response to Salinity

We investigated the change in O2 evolution rate and proteins property in the leaf blade of wild species Oryza officinalis, in response to salinity (NaCl) and compared the response with those in salt-sensitive wild O. rufiopgon, salt-tolerant wild O. latifolia, and salt-tolerant variety O. sativa L. cv. Pokkali. Chlorophyll (Chl) content and Chl-based O2 evolution rate in the upper leaves of O. officinalis subjected to salinity stress tended to be higher than those of the control plant. Wild Oryza species had a higher leaf Na+ content than Pokkali, and the Na+ accumulation pattern in O. officinalis and O. latifolia was different from that in O. rufipogon and Pokkali. O. officinalis and O. latifolia accumulated more Na+ in the lower leaves. In all tested plants, there was no correlation between the Chl based O2 evolution rate and Na+ content of upper leaves. We analyzed the leaf blade protein by two-dimensional electrophoresis, and found 53 spots that were over-expressed by salinity stress in O. officinalis compared to that in the control, in which 24 spots were estimated to be localized in the chloroplast, and related to Chl synthesis, photosystem and water-water cycle. These results showed that the O2 evolution rate in the upper leaves of O. officinalis was increased by salinity stress, regardless of the accumulation of Na+. It is suggested that the increased O2 evolution rate per leaf area in the upper leaves is related to over-expression of proteins related to Chl synthesis, photosystem and scavengers of reactive oxygen species.