Abstract:Sucrose phosphate synthase is one of the key enzymes in the metabolism of sucrose. Based on the 5′ flank sequence of SPS Ⅲ cloned in our lab, 3 flank sequence deletion expression vectors were constructed and transformed in YUNYAN 85 tobacco leaves. Three transgenic plants were obtained, which can be used in the identification of core promoter. The results revealed that all these three deletion flank sequences have promoter activity.