Fern genomes elucidate land plant evolution and cyanobacterial symbioses

First author: Fay-Wei Li; Affiliations: Boyce Thompson Institute (北京林业大学): Ithaca, USA

Corresponding author: Fay-Wei Li

Ferns are the closest sister group to all seed plants, yet little is known about their genomes other than that they are generally colossal (巨大的). Here, we report on the genomes of Azolla filiculoides (细叶满江红) and Salvinia cucullata 勺叶槐叶苹 (Salviniales 槐叶苹目) and present evidence for episodic whole-genome duplication in ferns-one at the base of ‘core leptosporangiates 核心薄囊蕨类’ and one specific to Azolla (满江红属). One fern-specific 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 (共生) with N2-fixing cyanobacteria (蓝藻), and we demonstrate a clear pattern of cospeciation (共物种形成) between the two partners. Furthermore, the Azolla genome lacks genes that are common to arbuscular mycorrhizal (丛枝菌根) and root nodule (根瘤) 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.

蕨类是所有种子植物最近缘的姊妹类群，然而除了知道它们基因组巨大之外，其它的基因组特性仍然了解很少。本文报道了槐叶苹目细叶满江红和勺叶槐叶苹两个蕨类植物，并且鉴定到了两次全基因组复制事件，一次发生在核心薄囊蕨类基部，一次是满江红属特有。作者鉴定到的蕨类特有基因之一，最近被证明赋予了蕨类植物更高的昆虫抗性，可能通过基因水平转移从细菌中获取该基因。满江红属与N2固定蓝藻以独特共生方式共存，作者揭示了这两个共生物种之间明显的共物种形成模式。此外，满江红属基因组缺少丛枝菌根和根瘤共生共有的基因，作者鉴定到了一些特异于满江红属-蓝藻共生的转运基因。本文所揭示的蕨类植物基因组信息将有助于进一步挖掘满江红属的生物技术潜力及解决植物物种演化的基本问题。

通讯：Fay-Wei Li (http://www.fernway.net/fayweili/)

个人简介：2005-2009年，国立台湾大学，学士；2010-2015年，杜克大学，博士；2015-2016年，加州大学伯克利分校与杜克大学，博士后；2016-2017年，苏黎世大学，博士后。

研究方向：蕨类植物基因组；植物-蓝细菌共生；植物光感受器演化。

doi: https://doi.org/10.1038/s41477-018-0188-8

Journal: Nature Plants

Published date: 02 July, 2018

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