Heterologous activation of the Hevea PEP16 promoter in the rubber-producing laticiferous tissues of Taraxacum kok-saghyz

Hevea brasiliensis, the most abundant rubber crop, is used widely for the commercial production of natural rubber. To reduce the risk of a shortage in the supply of natural rubber that may arise from a single major rubber crop, rubber dandelion (Taraxacum kok-saghyz) has been developed as an alternative rubber-producing crop by using a transgenic approach. However, it is necessary to identify a suitable promoter for the transfer of rubber biosynthesis-related genes to the species. In this study, the promoter region of H. brasiliensis PEP16, which was isolated as a potentially important component in rubber biosynthesis, was sequenced and a pPEP16::GUS fusion construct was introduced into T. kok-saghyz. Histological and fluorometric studies using transgenic T. kok-saghyz plants indicated that the HbPEP16 promoter was highly activated in a laticiferous tissue-specific manner under normal growth conditions and that promoter activation was tightly regulated by various hormones and external signals. These findings suggested that the HbPEP16 promoter may be a useful molecular tool for the manipulation of gene expression in the laticiferous tissues of T. kok-saghyz.