Evolutionary Study On The Genetic Variants Of Genes On Anthocyanin Pathway And Flower Color Variation In Ipomoea Purpurea

How is genotypic variation related to the phenotypic variation has remained one of the fundamental questions in biology. One effective way of addressing this issue is to explore the relationship between molecular evolution of functional genes and their phenotypic effects. Here we utilized anthocyanin pathway (which determines what pigment is to be produced in flower) in the common morning glory (Ipomoea purpurea) to study two questions: 1) what is the biological significance of allelic polymorphism? and 2) what is the effect of phenotypic selection on the molecular evolution?For the first question, we investigated allelic polymorphism at several loci of the structural and regulatory genes affecting the anthocyanin pathway, including those encoding the first enzyme on the pathway chalcone synthase D (CHS-D), down stream enzymes anthocyanidin synthase (ANS) and UDP-glucose flavonoid 3-glucosyltransferase (UF3GT), and myb genes at the regulatory W locus. We then conducted self-pollination in the greenhouse to obtain homozygote individuals. For the second question, we investigated the pollinators and flower-visiting frequencies of the pollinators on Ipomoea purpurea in the field. We then compared the genetic variations between white-flowered and color-flowered individuals. The current data show that there are at least three alleles of CHS-D among the Chinese populations, one of them is newly found, in addition to the known 7 alleles. Five alleles were discovered at the ANS locus and three of them firstly observed in China. Two known alleles were found at the UF3GT locus. The functional allele at the W locus is Ipmyb2, which was newly found in Chinese populations, and it differs mainly in the intron regions from those of the reported allele Ipmyb1; in comparison to Ipmyb2, the newly found second allele ipmyb2 has eight substitutions in the exons, a 6-bp deletion, and a 19-bp deletion, causing ORF shifting, and exists mostly in white-flowered individuals. The field observations on the pollinators show that white-flowered plants get fewer visits than color-flowered individuals. The pollinators on Chinese Ipomoea purpurea are mostly moths (Macroglossum stellatarum L.) rather than bumblebees as found in America, and the moths appeared to pollinate more efficiently than bees. The field data suggested that pollinators...