Evolution of a symbiotic receptor through gene duplications in the legume-rhizobium mutualism
Evolution of a symbiotic receptor through gene duplications in the legume-rhizobium mutualism
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DOI：
10.1111/nph.12549
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发表时间：
2014-02-01
期刊：
影响因子：
9.4
通讯作者：
Geurts, Rene
中科院分区：
文献类型：
--
作者：
De Mita, Stephane;Streng, Arend;Geurts, Rene
豆科植物和固氮根瘤菌之间的共生选择了预先存在的菌根末端特征。特别是，两种共生体都释放脂壳低聚糖（LCO），这些脂壳寡糖可被 LysM 型受体激酶识别。我们研究了根瘤菌 LCO 受体基因 MtLYK3-LjNFR1 的进化史，以深入了解根瘤菌共生的进化起源。我们进行了系统发育分析，整合了非豆科植物和豆科植物的基因拷贝，包括非结瘤的、系统发育基础豆科植物紫荆 (Cercis chinensis)。通过分子进化模式研究了拷贝之间分化的特征。我们表明，在豆科植物根瘤菌共生进化之前存在两轮复制。分子进化模式表明，由此产生的三个旁系同源基因拷贝经历了不同的选择性限制。特别是，一个副本保留了祖先的功能，另一个副本专门负责根瘤菌 LCO 的感知。有人提出，豆科植物 LCO 受体是通过获得两个激酶基序从假定的祖先防御相关几丁质受体进化而来的。然而，系统发育分析表明这些结构域实际上是祖先的，这表明这种情况不太可能发生。我们的研究强调了 MtLYK3-LjNFR1 基因中基因复制和随后的新功能化的进化意义。我们假设它们的祖先更有可能是菌根 LCO 受体，而不是防御相关受体激酶。
The symbiosis between legumes and nitrogen-fixing rhizobia co-opted pre-existing end-omycorrhizal features. In particular, both symbionts release lipo-chitooligosaccharides (LCOs) that are recognized by LysM-type receptor kinases. We investigated the evolutionary history of rhizobial LCO receptor genes MtLYK3-LjNFR1 to gain insight into the evolutionary origin of the rhizobial symbiosis.We performed a phylogenetic analysis integrating gene copies from nonlegumes and legumes, including the non-nodulating, phylogenetically basal legume Cercis chinensis. Signatures of differentiation between copies were investigated through patterns of molecular evolution.We show that two rounds of duplication preceded the evolution of the rhizobial symbiosis in legumes. Molecular evolution patterns indicate that the resulting three paralogous gene copies experienced different selective constraints. In particular, one copy maintained the ancestral function, and another specialized into perception of rhizobial LCOs. It has been suggested that legume LCO receptors evolved from a putative ancestral defense-related chitin receptor through the acquisition of two kinase motifs. However, the phylogenetic analysis shows that these domains are actually ancestral, suggesting that this scenario is unlikely.Our study underlines the evolutionary significance of gene duplication and subsequent neo-functionalization in MtLYK3-LjNFR1 genes. We hypothesize that their ancestor was more likely a mycorrhizal LCO receptor, than a defense-related receptor kinase.