Abstract
Salicylic acid (SA) is synthesized in ozone-exposed Arabidopsis and plays a role of protection from leaf injury. However, despite its importance in plant defense against ozone exposure, the regulation of SA biosynthesis in ozone-exposed plant had not been revealed.
So far, we showed that SA was synthesized from chorismate via isochorismate by stimulating the expression of isochorismate synthase 1 (ICS1) in ozone-exposed Arabidopsis. To clarify the effect of SA signaling on SA biosynthesis, we analyzed the ability of SA biosynthesis in nonexpresser of PR genes 1 (npr1). The mutant of npr1 showed more increased ICS1 transcripts and SA level than wild-type during ozone exposure. Furthermore, the activation of ICS1 expression in ozone-exposed Arabidopsis was inhibited by SA treatment. These results suggest that SA level in ozone-exposed Arabidopsis is negatively regulated by SA signaling.
