The maize zsS3a gene codes for starch synthase. Transcriptional analysis revealed that it is mainly expressed in endosperm and is induced by abscisic acid (ABA). The 5'-flanking region of zsS3a was isolated, and a 1772 bp zsS3a promoter (PzsS3a) was fused to a Luc reporter gene with a maize Adh1 intron. Transient expression assay by bombardment transformation showed that, although the addition of the Adh1 intron enhanced the promoter activity approx. 52-fold, it did not alter the promoter specificity. PzsS3a with the Adh1 intron drove the Luc gene preferentially and it was highly expressed in the endosperm relative to the embryo but not in the leaf or root. Furthermore, the promoter activity in the endosperm was enhanced four fold by 100 mM ABA.