A physiological and genetic study of the ozone-sensitive Arabidopsis thaliana mutant soz2 as an approach to elucidate photoprotective mechanisms in plants

Abstract

Photoinhibition of photosynthesis has been shown to be of physiological significance in many plant species. It is known that inhibition of both photosystem (PS)II and PSI involves reactive oxygen species (ROS).Under normal growth conditions, the recessive ozone-sensitive Arabidopsis thaliana mutant soz2 exhibits a pale phenotype compared to wild-type. This phenotype is more pronounced after exposure to ozone. Moreover, soz2 revealed a twofold increase in the content of the lipid peroxidation product malondialdehyde (MDA) compared to wildtype after ozone fumigation. The pale phenotype and the increase in MDA/g dry weight suggest that soz2 could suffer from oxidative stress due to a defect in protective pigments or chlorophyll biosynthesis. Therefore, the soz2 mutant has the potential to be a tool for identification of photoprotective mechanisms that plants use to cope with unfavorable environmental conditions. Wildtype and soz2 mutants were subjected to ROS generating conditions (e.g. high light in combination with low temperature). Effects on the photosynthetic apparatus were recorded by measuring potential PSI and PSII activities. Xanthophyll cycle activity was assessed by analyzing pigments by means of HPLC. SOZ2 has been mapped to chromosome 2. The position of SOZ2 was resolved in finer detail using polymorphic mapping populations.