A 45-bp proximal region containing AACA and GCN4 motif is sufficient to confer endosperm-specific expression of the rice storage protein glutelin gene, GluA-3.

A 45-bp proximal region of the rice glutelin promoter (-104/-60) containing two putative cis-elements, the AACA motif and GCN4 motifs, was fused to a truncated CaMV 35S promoter (-90/+9; -90 delta 35S)/GUS. The 45-bp fragment specifically enhanced the promoter activity in endosperm tissue of transformed tobacco. A substitution mutation of the GCN4 motif reduced the promoter activity, whereas mutation of the AACA motif increased the activity in the embryo as well as in the endosperm. These results suggest that the GCN4 motif generally enhances the promoter activity but that the combination of the two motifs confers the endosperm specificity. Furthermore, the function of the two motifs was dependent on the orientation and/or distance from a G-box element in -90 delta 35S, suggesting that synergistic interaction between the factors that recognize those motifs and the G-box element is important for transcriptional regulation.