Abstract Detail

Phytochemical Section

Stanton, Kimmy [1], Karoly, Keith [2].

The Genetic Basis of Flower Color Divergence in the PNW larkspurs, Delphinium leucophaeum and D. nuttallii.

Northwest species in the genus Delphinium (the larkspurs, Family Ranunculaceae) provide several interesting examples in which flower color evolution, involving pigments in the flavonoid pathway, has contributed to taxonomic divergence. We have investigated the genetic basis of a flower color polymorphism that distinguishes the blue-flowered Nuttall's larkspur (Delphinium nuttallii) from the white rock-larkspur (D. leucophaeum), its white-flowered, recently diverged sister-taxon. Analysis of floral phenotypes from controlled crosses that produced F1, F2, and back-crossed (BC) progeny showed that the flower color difference results from variation at a single locus. Surprisingly, the white-flowered phenotype was dominant to the blue phenotype. Analysis of the flavonoid pigments (anthocyanins and flavonols) in the sepals of each species showed the presence of anthocyanins in sepals of the blue-flowered species, while sepals of the white-flowered species lacked anthocyanins and, instead, had increased quantities of flavonols. To identify the underlying locus causing the divergence, we investigated several candidate structural and regulatory genes responsible for the enzymatic steps in the flavonoid pathway at the branch point leading to either the production of flavonols or the production of anthocyanins. Gene sequences were determined for our species for dihydroflavonol 4-reductase (DFR), flavonoid 3', 5'-hydroxylase (F3'5'H), flavonol synthase (FLS) and an R2R3-myb transcription factor (MYB12) that we believe is a regulator of FLS. We performed a co-segregation analysis in families involving F2 and first-generation BC progeny, looking for co-segregation between the flower color phenotype and genetic markers at each locus that identified the parental alleles contributed by the two species in the original F1 crosses. Parental alleles for the MYB12 transcription factor were the only alleles that showed a significant co-segregation with the flower color phenotype in F2 and BC progeny. These results suggest that the flower color divergence was caused by an evolutionary change in transcriptional regulation, leading to increased flavonol and decreased anthocyanin production in floral tissues of the derived D. leucophaeum.

1 - Whitman College, Biology, 345 Boyer Ave, Walla Walla, WA, 99362, USA
2 - Reed College, 3203 SE Woodstock Blvd., Portland, OR, 97202, USA

Keywords:
flower color
flavonol
Anthocyanin.

Presentation Type: Oral Paper:Papers for Sections
Session: 30
Location: Salon 13/The Shaw Conference Centre
Date: Wednesday, July 29th, 2015
Time: 10:30 AM
Number: 30010
Abstract ID:1105
Candidate for Awards:None