Induction of glucosyltransferase transcription and activity during superoxide-dependent cell death in Arabidopsis plants

Expression of the UDP-glucosyltransferase (UGT73B5) gene is induced in Arabidopsis thaliana leaves during programmed cell death (PCD) stimulated by superoxide (O2.–) in the presence of cycloheximide (CHX) or salicylic acid (SA). Treatment with O2.–, CHX or SA alone did not result in PCD, and induced the UGT73B5 gene less strongly. Increased UDP-glucose:SA UGT activity was found in protein extracts from leaves treated with a combination of O2.– and SA. Genomic analysis showed that UGT73B5 is arranged in tandem with a similar UGT gene (UGT73B4) on chromosome 2. UGT73B5 promoter contains a G-box and several positive and negative SA-responsive elements. UGT73B5 transcription was also induced by mechanical cell crushing and by infection with an avirulent strain of Pseudomonas syringae or by treatment with intercellular fluid from Arabidopsis cell culture infected with a necrotrophic fungus, Botrytis cinerea. A possible role of UGT73B5 in the hypersensitive response is discussed.