Abstract: Ribosome-inactivating proteins(RIPs) represent a type of proteins that universally depurinate the conserved a-sarcin loop of ribosome 28S rRNA. A 0.6-kb fragment of the 5' flanking region preceding the curcin gene, encoding a type I RIP of Jatropha curcas, was cloned, and its expression pattern was studied by b-glucuronidase(GUS) assay in transgenic tobacco. The result showed that this fragment was sufficient to drive the reporter gene expression in seeds. Histochemical analysis revealed that the promoter was expressed specifically in endosperm in the dicotyledonous system of tobacco, starting from the embryo at the heart-shape stage.