Developmental and Hormonal Regulation of Rice [alpha]-Amylase(RAmy1A)-gusA Fusion Genes in Transgenic Rice Seeds

Transgenic seeds of rice (Oryza sativa L.) were used to investigate temporal, spatial, and hormonal regulation of a rice [alpha]-amylase gene, RAmy1A. Two overlapping segments of the RAmy1A promoter were fused to the coding region of the bacterial reporter gene, gusA. The resulting promoter-gusA fusions, pE4/GUS (-232 to +31) and pH4/GUS (-748 to +31), were used separately to transform rice protoplasts. [beta]-Glucuronidase (GUS) activity was detected in germinated transgenic seeds, although the two constructs showed no significant difference in timing or location of GUS expression. Both constructs first expressed GUS in the scutellar epithelium and then in the aleurone layer. Aleurone expression of GUS activity was strongly induced when embryoless half-seeds were treated with gibberellic acid. GUS expression in the aleurone layer was also suppressed by abscisic acid. These results indicate that the 5[prime] regulatory region from -232 to +31 is sufficient for temporal, spatial, and hormonal regulation of RAmy1A gene expression.