Fig. 1.

Overview of 7-DHC biosynthesis pathway and the engineering strategies applied in this study. a Overview of 7-DHC biosynthesis pathway in yeast. The MVA pathway is highlighted in blue and boxed, while the post-squalene pathway is highlighted in red and boxed. The blocked endogenous ergosterol synthesis pathway from zymosterol is illustrated in gray. An upward pointing arrow is used to indicate protein overexpression, and an “X” on a particular enzyme suggests that it is deleted. b Schematic representation of the engineering strategies to enhance 7-DHC production in S. cerevisiae. The host cell (blue) is engineered in combination with the only heterologous enzyme DHCR24 (orange). c The genetic modification for overexpressing endogenous MVA pathway genes. d The genetic modification for introducing DHCR24 expression modules along with disruption of GAL80, GAL7,10,1 or ERG6