Two Genes Responsible for Remarkable Difference in Flower Color of Nearby Snapdragons Identified; Islands of Divergence Established by Gene Flow & Multiple Selective Sweeps; Bee Pollination a Key Factor

Snapdragons are charming tall plants that flower in a range of bright colors. In Spain, where snapdragons grow wild, these flower colors show a remarkable pattern: When driving up a road from Barcelona to the Pyrenees, snapdragons of the species Antirrhinum majus bloom in magenta at the beginning of the road, before a population of yellow flowering snapdragons takes over - separated by just a two kilometer c long stretch in which flower colors mix. Such hybrid zones of snapdragons are quite infrequent; only a few others are known. But why don't the snapdragons mix, with yellow and magenta flowers growing together over a wide area? Dr. Nick Barton at the Institute of Science and Technology Austria (IST Austria), together with Dr. David Field, previously a postdoc in Dr. Barton's group and now Assistant Professor at the University of Vienna, collaborated with molecular geneticists at the John Innes Center in Norwich, UK, to investigate the causes of this pattern. In an article published online on October 8, 2018 in PNAS, the scientists report that they identified the genes responsible for flower color difference from DNA sequence data. The open-access article is titled “Selection and Gene Flow Shape Genomic Islands That Control Floral Guides.” "DNA sequencing is becoming cheaper and cheaper. But analyzing sequence data and interpreting the patterns seen is very hard,” Dr. Barton explains. “In this study, we used sequence data from Antirrhinum plants to locate the individual genes that are responsible for the difference in flower color across the hybrid zone." The researchers compared the genome sequences of 50 snapdragons of each color, and measured how much the sequences diverged between magenta and yellow snapdragon populations.
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