Figure 3.

An example of a gain in floral anthocyanin via co-option of an R2R3-MYB in Mimulus aurantiacus. (A) The yellow flowers of M. australis contain no detectable anthocyanin in floral tissue. (B) A cis-regulatory mutation in MaMyb2 causes the derived red-flowered phenotype observed in M. puniceus, and strong divergent selection on flower color by pollinators has driven the fixation of the red and yellow alleles in nature (Streisfeld et al., 2013). (C) Although anthocyanins are present in vegetative tissue in M. australis, they are typically found at low concentrations. (D) In contrast, vegetative anthocyanins are often induced to high levels in M. puniceus, consistent with the possibility that negative pleiotropic effects of the co-option event have been overcome by strong selection by pollinators. The genetics of the relationship between floral and vegetative anthocyanins is currently under investigation.