Isolation and functional characterization of SUCROSE SYNTHASE 1 and SUCROSE TRANSPORTER 2 promoters from ramie (Boehmeria nivea L. Gaudich).

Sucrose synthase and sucrose transporter are involved in sucrose metabolism and partitioning of photosynthetic products, respectively. In this study, we cloned SUCROSE SYNTHASE 1 and SUCROSE TRANSPORTER 2 genes from ramie. Real-time quantitative PCR revealed that BnSUS1 and BnSUT2 were widely expressed in the analyzed tissues. Subsequently, the two promoters of BnSUS1 and BnSUT2 were isolated and truncated. The two promoters and their truncated fragments were fused GUS to transform into Arabidopsis. GUS staining showed that BnSUS1-1690 and BnSUS1-1420 had vascular specificity in cotyledons and mature leaves while BnSUT2-2239, BnSUT2-1681, BnSUT2-1199 and BnSUT2-618 had a constitutive function in seedlings and mature organs. Notably, the activity of BnSUT2-2239 and its fragments (except that of BnSUT2-231) are strongly induced by mechanical wounding. Moreover, BnSUS1-1051 and BnSUS1-485 are sensitive to CuSO treatment while BnSUT2-2239 and BnSUT2-1681 are sensitive to PEG and ABA treatments, respectively. Our findings will provide the foundation for deciphering the functions of BnSUS1 and BnSUT2, and also expand the promoter library to provide more options for plant genetic engineering.