The chromosome-level genome assembly of Astragalus sinicus and comparative genomic analyses provide new resources and insights for understanding legume-rhizobial interactions

第一作者：Danna Chang

第一单位：中国农科院农业资源与农业区划研究所

通讯作者：Weidong Cao

 Abstarct 

背景回顾：The legume species Astragalus sinicus (Chinese milk vetch [CMV]) has been widely cultivated for centuries in southern China as one of the most important green manures/cover crops for improving rice productivity and preventing soil degeneration. 

豆科植物紫云英（Astragalus sinicus）作为提高水稻产量和防止土壤退化的最重要绿肥/覆盖作物之一，在我国南方地区已有了数个世纪的广泛种植历史。

主要研究： In this study, we generated the first chromosome-scale reference genome of CMV by combining PacBio and Illumina sequencing with high-throughput chromatin conformation capture (Hi-C) technology. 

本文中，作者结合三代PacBio测序、二代Illumina测序和高通量染色质构象捕获（Hi-C）技术，首次报道了紫云英的染色体级别参考基因组。

结果1-基因组组装：The CMV genome was 595.52 Mb in length, with a contig N50 size of 1.50 Mb. 

紫云英基因组大小为595.52Mb，contig N50长度为1.5Mb。

结果2-基因组演化：Long terminal repeats (LTRs) had been amplified and contributed to genome size expansion in CMV. CMV has undergone two whole-genome duplication (WGD) events, and the genes retained after the WGD shared by Papilionoideae species shaped the rhizobial symbiosis and the hormonal regulation of nodulation. 

紫云英基因组中的长末端重复（LTRs）发生了扩张，导致了紫云英基因组的扩张。紫云英经历了两次全基因组复制事件，并且基因组复制事件后由蝶形花亚科物种所共享的保留基因塑造了根瘤菌共生系统以及激素对根瘤的调控。

结果3-根与根瘤：The chalcone synthase (CHS) gene family was expanded and was expressed primarily in the roots of CMV. Intriguingly, we found that resistance genes were more highly expressed in roots than in nodules of legume species, suggesting that their expression may be increased to bolster plant immunity in roots to cope with pathogen infection in legumes. 

查尔酮合酶（CHS）基因家族发生了扩张，且主要在紫云英的根组织中表达。有趣的是，作者发现豆科植物抗性基因在根组织中的表达要比在根瘤中的表达更高，表明豆科植物可能通过激活这些抗性基因在根中的表达来增强根组织的免疫以应付病原菌的侵染。

结论：Our work sheds light on the genetic basis of nodulation and symbiosis in CMV and provides a benchmark for accelerating genetic research and molecular breeding in the future.

本文的工作为紫云英中根结瘤和共生的遗传基础提供了新的视野，同时也为未来加速紫云英的遗传研究和分子育种提供了一个基准。

** 曹卫东 **

doi: https://doi.org/10.1016/j.xplc.2021.100263

Journal: Plant Communications

Published date:  Novemebr 07, 2021