OZONE-INDUCED EXPRESSION OF STRESS-RELATED GENES IN ARABIDOPSIS-THALIANA

Ozone is a major gaseous pollutant that is known to have detrimental e ffects on plant growth and metabolism. We have investigated the effect s of ozone on Arabidopsis thaliana growth and the pattern of expressio n of several stress-related genes. A. thaliana plants treated with eit her 150 or 300 parts per billion (ppb) ozone daily for 6 h exhibited r educed growth and leaf curling. Fresh and dry weights of ozone-treated plants were reduced 30 to 48% compared to ambient air controls. RNA b lot analyses demonstrated that mRNA levels for glutathione S-transfera se (GST), phenylalanine ammonia-lyase (PAL), a neutral peroxidase, and a cytosolic Cu/Zn superoxide dismutase (SOD) were higher in plants tr eated with 300 ppb ozone than in ambient air-treated controls. The mRN A levels of lipoxygenase and a catalase were not affected by ozone tre atment. Of the transcripts examined, GST mRNA levels increased the mos t, showing a 26-fold induction 3 h after the initiation of ozone treat ment. PAL mRNA was also rapidly induced, reaching 3-fold higher levels than controls within 3 h of ozone treatment. The neutral peroxidase a nd SOD mRNA levels rose more slowly, with both reaching maximum levels corresponding to 5-fold and 3-fold induction, respectively, approxima tely 12 h after ozone treatment. These studies indicate that ozone-ind uced expression of stress-related genes in A. thaliana provides an exc ellent model system for investigating the molecular and genetic basis of ozone-induced responses in plants.