Isolation of an ozone-sensitive and jasmonate-semi-insensitive Arabidopsis mutant (oji1).

A novel ozone-sensitive mutant was isolated from Arabidopsis T-DNA tagging lines. This mutant revealed severe foliar injury and higher ethylene emission than the wild type under ozone exposure. The ozone-induced injury and ethylene emission were suppressed by pretreatment with aminoethoxyvinyl glycine, an inhibitor of ethylene biosynthesis, both in this mutant and wild-type plants. Pretreatment with methyl-jasmonate (MeJA) at 10 micro M, however, suppressed the ozone-induced ethylene emission and foliar injury only in the wild-type plants. This mutant was less sensitive to jasmonate than the wild type, estimated by the MeJA-induced inhibition of root elongation and ozone-induced expression of AtVSP1, a jasmonate-inducible gene. Thus, this mutant was named oji1 (ozone-sensitive and jasmonate-insensitive 1). These results suggest that the ozone sensitivity of oji1 is caused by the increase in ozone-induced emission of ethylene as a result of low sensitivity to jasmonate, which plays defensive roles under stress conditions.