Sugar response sequence in the promoter of a rice alpha-amylase gene serves as a transcriptional enhancer.
Expression of alpha-amylase genes in both rice suspension cells and germinating embryos is repressed by sugars and the mechanism involves transcriptional regulation. The promoter of a rice alpha-amylase gene alphaAmy3 was analyzed by both loss- and gain-of-function studies and the major sugar response sequence (SRS) was located between 186 and 82 base pairs upstream of the transcription start site. The SRS conferred sugar responsiveness to a minimal promoter in an orientation-independent manner. It also converted a sugar-insensitive rice actin gene promoter into a sugar-sensitive promoter in a dose-dependent manner. Linker-scan mutation studies identified three essential motifs: the GC box, the G box, and the TATCCA element, within the SRS. Sequences containing either the GC box plus G box or the TATCCA element each mediated sugar response, however, they acted synergistically to give a high level glucose starvation-induced expression. Nuclear proteins from rice suspension cells binding to the TATCCA element in a sequence-specific and sugar-dependent manner were identified. The TATCCA element is also an important component of the gibberellin response complex of the alpha-amylase genes in germinating cereal grains, suggesting that the regulation of alpha-amylase gene expression by sugar and hormone signals may share common regulatory machinery.
Lu
C A
CA
Graduate Institute of Life Sciences, National Defense Medical Center, and Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, Republic of China.
Lim
E K
EK
Yu
S M
SM
D001483:Base Sequence; D050260:Carbohydrate Metabolism; D002478:Cells, Cultured; D018744:DNA, Plant; D004742:Enhancer Elements, Genetic; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D012275:Oryza / Q000166:cytology / Q000201:enzymology*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D000516:alpha-Amylases / Q000235:genetics*
D018744:DNA, Plant; D009687:Nuclear Proteins; D000516:alpha-Amylases