Fig. 1.

β-carotene biosynthesis is accomplished by orthologous enzymes across taxa. (A) Generalized flow-chart of the isoprenoid, sterol, and carotenoid biosynthesis pathways. Enzymatic coloration corresponds to orthologs outlined in (B). (B) Orthologous carotenoid biosynthesis genes in nonphotosynthetic and photosynthetic organisms (expanded from Alcaíno et al. 2016 and Sandmann 2001). Genes that are orthologous are shaded similarly; fusion genes are indicated by concatenation (e.g., crtIBY is a fusion gene of crtI, crtB, and crtYc/d).