PREDICTABILITY AND IRREVERSIBILITY OF GENETIC CHANGES ASSOCIATED WITH FLOWER COLOR EVOLUTION INPENSTEMON BARBATUS

Abstract

Two outstanding questions in evolutionary biology are whether, and how often, the genetic basis of phenotypic evolution is predictable; and whether genetic change constrains evolutionary reversibility. We address these questions by studying the genetic basis of red flower color in Penstemon barbatus. The production of red flowers often involves the inactivation of one or both of two anthocyanin pathway genes, Flavonoid 3 ,5 -hydroxylase (F3 5 h) and Flavonoid 3 -hydroxylase (F3 h). We used gene expression and enzyme function assays to determine that redundant inactivating mutations to F3 5 h underlie the evolution of red flowers in P. barbatus. Comparison of our results to previously characterized shifts from blue to red flowers suggests that the genetic change associated with the evolution of red flowers is predictable: when it involves elimination of F3 5 H activity, functional inactivation or deletion of this gene tends to occur; however, when it involves elimination of F3 H activity, tissue-specific regulatory substitutions occur and the gene is not functionally inactivated. This pattern is consistent with emerging data from physiological experiments indicating that F3 h may have pleiotropic effects and is thus subject to purifying selection. The multiple, redundant inactivating mutations to F3 5 h suggest that reversal to blue-purple flowers in this group would be unlikely.

Evolutionary correlations in flavonoid production across flowers and leaves in the Iochrominae (Solanaceae)

“…Evolutionary studies of flavonoid production have largely focused on changes in floral anthocyanins, which are key contributors to floral hue (Hopkins and Rausher, 2011;Rausher, 2008;Smith and Rausher, 2011;Wessinger and Rausher, 2014;Whittall et al, 2006). This study shows that these shifts in floral anthocyanins can result in correlated changes in floral flavonols, particularly those at the same hydroxylation level.…”

Identification of major quantitative trait loci underlying floral pollination syndrome divergence in Penstemon

“…This QTL corresponds to F3 0 5 0 h, which resides directly under the peak LOD (figure 4). We have previously shown that this gene is responsible for the difference in colour between the two species [13]. For each of the remaining traits, there were three significant QTLs, explaining a total of 45-65% of the total proportion of trait variation.…”

“…Yet, some empirical evidence from quantitative trait locus (QTL) studies on pollination syndrome divergence suggests that there may be common patterns at the genetic level. For example, previous QTL studies have suggested that traits such as flower colour and nectar volume often involve few substitutions of medium to large effect [9][10][11][12][13], while changes in morphological characters tend to involve more loci with smaller effects [12,14,15]. In addition, these studies have revealed that QTLs for different traits sometimes co-localize (e.g.…”

Identification of aR2R3-MYBgene regulating anthocyanin biosynthesis and relationships between its variation and flower color difference in lotus (NelumboAdans.)

“…Anthocyanin are the major water-soluble pigments, produced by the flavonoid biosynthesis pathway, widely distributed in flowering plants and responsible for pink, purple, red, and blue of many flowers and fruits (Chandler & Tanaka, 2007; Wessinger & Rausher, 2014). Currently, all structural genes involved in the anthocyanin synthesis have been well characterized in many species (Schwinn & Davies, 2004; Grotewold, 2006; Guo et al, 2014).…”