Assessing Anthocyanin Biosynthesis in Solanaceae as a Model Pathway for Secondary Metabolism

Solanaceaehave played an important role in elucidating how flower color is specified by the flavonoid biosynthesispathway (FBP), which produces anthocyaninsand other secondary metabolites. With well-established reverse geneticstools and rich genomic resources, Solanaceaeprovide a robust framework to examine the diversification of this well-studied pathway over short evolutionary timescales and to evaluate the predictability of genetic perturbation on pathway flux. Genomes of eight Solanaceaespecies, nine related asterids, and four rosids were mined to evaluate variation in copy number of the suite of FBP enzymes involved in anthocyanin biosynthesis. Comparison of annotation sources indicated that the NCBI annotation pipeline generated more and longer FBP annotations on average than genome-specific annotation pipelines. The pattern of diversification of each enzyme among asteridswas assessed by phylogenetic analysis, showing that the CHS superfamily encompasses a large paralogous family of ancient and recent duplicates, whereas other FBP enzymes have diversified via recent duplications in particular lineages. Heterologous expressionof a pansy F3′5′H gene in tobacco changed flower color from pink to dark purple, demonstrating that anthocyaninproduction can be predictably modified using reverse genetics. These results suggest that the SolanaceaeFBP could be an ideal system to model genotype-to-phenotype interactions for secondary metabolism.