Li, Fay-WeiBrouwer, PaulCarretero-Paulet, LorenzoCheng, ShifengDe Vries, JanDelaux, Pierre-MarcEily, ArianaKoppers, NilsKuo, Li-YaungLi, ZhengSimenc, MathewSmall, IanWafula, EricAngarita, StephanyBarker, Michael S.Brautigam, AndreaDePamphilis, ClaudeGould, SvenHosmani, Prashant S.Huang, Yao-MoanHuettel, BrunoKato, YoichiroLiu, XinMaere, StevenMcDowell, RoseMueller, Lukas A.Nierop, Klaas G.J.Rensing, Stefan A.Robison, TannerRothfels, Carl J.Sigel, Erin M.Song, YueTimilsena, Prakash R.Van de Peer, YvesWang, HongliWilhelmsson, Per K.I.Wolf, Paul G.Xu, XunDer, Joshua P.Schluepmann, HenrietteWong, Gane K.-S.Pryer, Kathleen M.2018-10-122018-10-122018-07-02Li, F.-W., Brouwer, P., Carretero-Paulet, L. et al 2018, 'Fern genomes elucidate land plant evolution and cyanobacterial symbioses', Nature Plant, vol. 4, no. 7, pp.460-472.2055-026X (print)2055-0278 (online)10.1038/s41477-018-0188-8http://hdl.handle.net/2263/66862Ferns are the closest sister group to all seed plants, yet little is known about their genomes other than that they are generally colossal. Here, we report on the genomes of Azolla filiculoides and Salvinia cucullata (Salviniales) and present evidence for episodic whole-genome duplication in ferns—one at the base of ‘core leptosporangiates’ and one specific to Azolla. One fernspecific gene that we identified, recently shown to confer high insect resistance, seems to have been derived from bacteria through horizontal gene transfer. Azolla coexists in a unique symbiosis with N2-fixing cyanobacteria, and we demonstrate a clear pattern of cospeciation between the two partners. Furthermore, the Azolla genome lacks genes that are common to arbuscular mycorrhizal and root nodule symbioses, and we identify several putative transporter genes specific to Azolla–cyanobacterial symbiosis. These genomic resources will help in exploring the biotechnological potential of Azolla and address fundamental questions in the evolution of plant life.en© Open Access. This article is licensed under a Creative Commons Attribution 4.0 International License.FernsSeed plantsInsect resistanceGenomesAzolla filiculoidesSalvinia cucullataEpisodic whole-genome duplicationCore leptosporangiateAzollaArticle