Molecular convergence in the evolution of betalains

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• Hester Sheehan, Brockington group
• Thursday 24 October 2019, 13:00-13:30
• Department of Plant Sciences, Large Lecture Theatre.

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Betalains are pigments that produce a palette of pink, purple, yellow and orange colours. These specialised metabolites are fascinating from an evolutionary standpoint because betalains are mutually exclusive with the otherwise ubiquitous anthocyanin pigments and because they are found only in the plant order, Caryophyllales. Betalains have a homoplasic distribution in the Caryophyllales and until recently it was thought that this pattern was explained by betalains having evolved once, with multiple reversals occurring to anthocyanin pigmentation. However, our work on a key biosynthetic enzyme, DODA , shows that it is very likely that betalains evolved at least three times and thus that they represent an example of convergent evolution. I will present the work that led to this conclusion, which involved the functional characterization of DODA enzymes from a diverse range of betalain- and anthocyanin-pigmented Caryophyllales species. We also reconstructed functionally important amino acid sites across the DODA phylogeny and found evidence for convergence at the molecular level. Using molecular convergence models and protein modeling to come up with candidate residues, we plan to test these residues using a yeast heterologous assay to determine the extent of molecular convergence between the different origins. Ultimately, we hope to determine the critical mutations that allowed an enzyme to specialize on a different substrate and assist in producing a novel class of plant pigments.

This talk is part of the Plant Sciences Departmental Seminars series.

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