Florida Museum of Natural History, University of Florida, Gainesville, FL, USA.
Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN, 37996-1610, USA.
Nat Commun. 2024 May 27;15(1):4262. doi: 10.1038/s41467-024-48036-3.
Root nodule symbiosis (RNS) is a complex trait that enables plants to access atmospheric nitrogen converted into usable forms through a mutualistic relationship with soil bacteria. Pinpointing the evolutionary origins of RNS is critical for understanding its genetic basis, but building this evolutionary context is complicated by data limitations and the intermittent presence of RNS in a single clade of ca. 30,000 species of flowering plants, i.e., the nitrogen-fixing clade (NFC). We developed the most extensive de novo phylogeny for the NFC and an RNS trait database to reconstruct the evolution of RNS. Our analysis identifies evolutionary rate heterogeneity associated with a two-step process: An ancestral precursor state transitioned to a more labile state from which RNS was rapidly gained at multiple points in the NFC. We illustrate how a two-step process could explain multiple independent gains and losses of RNS, contrary to recent hypotheses suggesting one gain and numerous losses, and suggest a broader phylogenetic and genetic scope may be required for genome-phenome mapping.
根瘤共生（RNS）是一种复杂的特性，它使植物能够通过与土壤细菌的互利关系将大气中的氮转化为可用的形式。确定 RNS 的进化起源对于了解其遗传基础至关重要，但由于数据限制以及 RNS 在约 30,000 种开花植物的单一分支（即固氮分支（NFC））中的间歇性存在，构建这种进化背景变得复杂。我们为 NFC 开发了最广泛的从头进化树和 RNS 性状数据库，以重建 RNS 的进化。我们的分析确定了与两步过程相关的进化率异质性：从祖先前体状态转变为更不稳定的状态，然后在 NFC 的多个点迅速获得 RNS。我们说明了两步过程如何可以解释 RNS 的多次独立获得和丧失，这与最近的假说相反，后者表明只有一次获得和多次丧失，并且表明可能需要更广泛的系统发育和遗传范围进行基因组-表型映射。
