Engineering Terpenoid Indole Alkaloids Biosynthetic Pathway in Catharanthus roseus Hairy Root Cultures by Overexpressing the Geraniol 10-hydroxylase Gene

Catharanthus roseus contains important anti-tumor terpenoid indole alkaloids (TIAs) such as vinblastine and vincristine. Cytochrome P450 enzyme geraniol 10-hydroxylase (G10H) is a putative rate-limiting enzyme involved in the TIAs biosynthetic pathway in C. roseus. In this study the g10h gene driven by the cauliflower mosaic virus 35S (CaMV 35S) promoter was introduced into C. roseus through Agrobacterium-mediated transformation. The integration and overexpression of the target gene (g10h) in hairy root lines were confirmed by polymerase chain reaction and RT-QPCR analysis respectively. Overexpression of g10h in transgenic hairy root lines significantly enhanced the accumulations of monomeric alkaloid ajmalicine and dimeric alkaloids, vincristine and vinblastine. Total TIAs production in hairy roots reached (9.51) mg/g DW, over 3-fold higher than that in the untransformed root lines. This is the first report that engineering of g10h into TIAs-producing plant species results in significant enhancement of TIAs accumulation in cultured hairy roots. This study demonstrates that the putative rate-limiting step catalyzed by G10H is indeed the real rate-limiting step involved in the TIAs biosynthetic pathway in C. roseus, which is one of the key targets for promoting TIAs production by genetic engineering.