Comparison of Gene Loss and Adaptation Between Two Independent Return to the Sea Events in Seagrasses

Seagrasses are angiosperms which live fully submerged in the marine environment. They evolved from a terrestrial ancestor to re-colonize the sea during the early evolution of monocotyledonous plants. Genes involved in multiple pathways, such as hormone biosynthesis, stomatal development and cell wall modification, have been previously shown to be lost or modified in Zostera species when compared to terrestrial plants. Here we report the comparison between seagrass species of two families which evolved at 60 million years apart, Zosteraceae and Hydrocharitaceae. There is evidence that Hydrocharitaceae shared the same group of lost or modified genes with Zosteraceae. The results highlighted the response of two independent return to the sea events towards selection pressures posed by the marine environment and presented an example of parallel evolution in plants.