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Anthocyanins are the most common class of floral pigments. They are responsible for most of the blue, purple, pink, and red colors we see in flowering plants. The basic structure of flavonoid pathway that produces anthocyanins is deeply conserved across all flowering plants, yet flower pigmentation is tremendously evolutionarily labile. One explanation for this paradox is that differences in pigmentation across species can arise through changes in gene expression, and indeed, regulatory differences have been implicated in many flower color transitions (e.g., Smith and Rausher, 2011). However, we have found that coding sequence mutations in structural genes (enzymes) can also contribute to the evolution of new flower colors (Smith et al. 2013).  By examining the evolution of pathway genes (both regulatory and structural) and their expression patterns across species, we aim to gain a general understanding of how changes in pathway function lead to color differences on a broad phylogenetic scale. We have also recently begun a parallel track of research, modeling the evolution of the pathway in silico. This computational approach allows us to explore how the structure of the pathway affects the range of mutations that contribute to flower color evolution.

Relevant publications:

Wheeler, L. C.+ & S. D. Smith. 2019. Computational modeling of anthocyanin pathway evolution: biases, hotspots and trade-offs. Integrative and Comparative Biology 59: 585-598. , 

Ng, J., L. B. Freitas & S. D. Smith. 2018. Stepwise evolution of floral pigmentation predicted by biochemical pathway structure. Evolution 72: 2792-2802. , Reprint Request

Gates, D. J, S. R. Strickler, L. A. Mueller, B. J. S. C. Olson, and S. D. Smith. 2016. Diversification of R2R3 MYB transcription factors in the tomato family Solanaceae. Journal of Molecular Evolution 83: 26-37.

Coburn, R. C., R. H. Griffin, and S. D. Smith. 2015. Genetic basis of a rare floral mutant in an Andean species of Solanaceae. American Journal of Botany 102: 1-9.

Smith, S. D., S. Wang, and M. D. Rausher. 2013. Functional evolution of an anthocyanin pathway enzyme during a flower color transition.  Molecular Biology and Evolution 30: 602-612.  

Smith, S. D., and M. D. Rausher. 2011. Gene loss and parallel evolution contribute to species difference in flower color.  Molecular Biology and Evolution 28: 2799-2810.