Differential accumulation of transcripts encoding sulfur assimilation enzymes upon sulfur and or nitrogen deprivation in Arabidopsis thaliana

Expression of nine genes encoding enzymes involved in the sulfur assimilati on pathway was examined by RNA blot hybridization. Significantly increased levels of transcripts encoding ATP sulfurylase and APS reductase were appar ent under sulfur deprivation. However, in the absence of nitrogen, their re sponsiveness to sulfur deprivation was markedly reduced. Results suggest th at the sulfur assimilation pathway is regulated at the transcriptional leve l by both nitrogen and sulfur sources.