Cloning and functional analysis of the promoter of a maize starch synthase III gene (ZmDULL1)

The ZmDULL1 gene encodes a starch synthase and is a determinant of the structure of endosperm starch in maize (Zea mays L.). However, little is known regarding the regulatory mechanism of the ZmDULL1 gene. In this study, we isolated and characterized the ZmDULL1 promoter (PDULL1), which is the 5' flanking region of ZmDULL1 in maize. Sequence analysis showed that several cis-acting elements important for endosperm expression (GCN4_motif and AACA-element) were located within the promoter. A series of PDULL1 deletion derivatives, PDULL1-1-PDULL1-4, from the translation start code (-1676, -1216, -740, and -343) were fused to the β-glucuronidase (GUS) reporter gene. Each deletion construct was transformed into rice using the Agrobacterium-mediated method, and then GUS activity was measured in transgenic plants. The results showed that PDULL1 was an endosperm-specific promoter. Further analysis showed that the promoter sequence (-343 to -1 base pairs) was sufficient for mediating GUS gene expression in endosperm. These results indicate that the region from -343 to -1 base pairs of PDULL1 is valuable for transgenic rice breeding and genetic engineering studies.