XVI International Botanical Congess

Transcription of the C4-pyruvate, Pi dikinase (ppdk) gene in maize is subject to metabolic repression by sugars. However, sugar repression elements in the C4-ppdk gene promoter have not been identified. In this study, we examined sugar-repressible expression of the C4-ppdk gene promoter-GUS fusions by the maize protoplasts transient expression system. Promoter activity of the -620 to -1 region which did not contain the 5' UTR was repressed by sugar. On the other hand, the 3' deleted promoter which contained the -620 to -330 region showed much lower rates of sugar-repressible expression. These results indicate that the -330 to -1 region is responsible for high levels of sugar-repressible expression. Further assays of promoter deletions will be reported.