Does Phenotypic Color Intensity Correlate with Expression of the Anthocyanidin Synthase Gene in Saponaria officinalis?

Indianapolis, IN

Saponaria officinalis is a perennial flowering plant that has been introduced to the United States. This plant can be considered invasive, and is known as “bouncing bet”, “soapwort”, or “sweet betty”. Saponaria officinalis produces protandrous flowers, meaning they transition from a male to female reproductive phase as they mature. In addition, each flower of S. officinalis develops pink pigmentation in its petals that can vary in intensity as it switches to the female phase. Anthocyanidin synthase (ANS) is an enzyme that has been shown to contribute to the production of red and purple pigments that determine the pink coloration of the flowers of many species. We hypothesized that expression of the gene coding for the ANS enzyme (ANS) should show a positive correlation with pink color intensity of the flower petals. To test this hypothesis, 53 flowers were collected from an experimental garden. A reflectometer was used on one petal of each flower to generate a pinkness index value to quantify the intensity of coloration. RNA was extracted from the remaining petals of each of the same 53 flowers. ANS expression was then measured by determining the concentration of mRNA transcribed from the ANS gene by reverse transcribing the RNA into cDNA and using qPCR. A regression analysis was performed to compare the ANS expression values to the pinkness index measured earlier. A positive correlation of ANS expression and color expression of petals indicates that the anthocyanidin synthase gene is important for the color development of the Saponaria officinalis flower.