LAUSR

Distyly is a floral polymorphism whereby plants in a population display two floral morphs (referred to as the longand short-styled morphs) that differ reciprocally in style length, anther height, and pollen size, etc., which together with a self-incompatibility (SI) system (Barrett et al., 2000; Barrett, 2002). The development of the two different morphs of flower is controlled by a single diallelic locus designated the “S locus” that is a multigene complex (Barrett, 1992). Although, progresses have been made to isolate and characterize the S locus in a number of distylous plant species (Barrett and Shore, 2008; Li et al., 2011; Nowak et al., 2015), the number of S locus genes and the molecular mechanism by which it operates still remain to be uncovered. Heterostylous plants, including distylous or tristylous plants, have been used as a model for genetics and evolutionary biology (Barrett, 1992). Heterostyly is one of the most effective mechanisms to avoid selfing and promote outcrossing in flowering plant (Barrett et al., 2000; Nowak et al., 2015). Heterostyly represent remarkable example of convergent evolution via natural selection and have been found in a wide range of species belonged to at least 28 families (Barrett and Shore, 2008). However, little is known of the nature of evolutionary changes in genes determined by natural selection during the origin and evolution of the heterostyly in flowering plants. Nymphoides peltata (Gmel.) O. Kuntze (Menyanthaceae) is a floating-leaf perennial aquatic plant. This species is a typical distylous plant with dimorphic herkogamy and intramorphand self-incompatibility (Wang, 2005). N. peltata can produce a number of relatively large flowers, and these yellow and showy flowers are produced over a long period of time. This developmental pattern makes it easy to get rich flower organ materials and manipulate in subsequent experiments. Based on above-mentioned features, this species is very suitable for studying the molecular mechanism of heterostyly and has a potential to be a new study system. In this study, we sequenced two floral transcriptomes from longand short-styled flowered plants of this distylous species using the RNA-Seq technique. We also idenfied the divergent orthologous genes between longand short-styled flowers. Our aims were to provide genetic resources for screening genes involved in the development of distyly and for revealing the role of natural selection in driving the floral morph diversity in the evolution of distylous plant.