Department of Crop Sciences, University of Illinois, Urbana.
Max Planck Institute for Developmental Biology, Tübingen, Germany.
Genome Biol Evol. 2020 Nov 3;12(11):1988-1993. doi: 10.1093/gbe/evaa177.
Amaranthus tuberculatus, Amaranthus hybridus, and Amaranthus palmeri are agronomically important weed species. Here, we present the most contiguous draft assemblies of these three species to date. We utilized a combination of Pacific Biosciences long-read sequencing and chromatin contact mapping information to assemble and order sequences of A. palmeri to near-chromosome-level resolution, with scaffold N50 of 20.1 Mb. To resolve the issues of heterozygosity and coassembly of alleles in diploid species, we adapted the trio binning approach to produce haplotype assemblies of A. tuberculatus and A. hybridus. This approach resulted in an improved assembly of A. tuberculatus, and the first genome assembly for A. hybridus, with contig N50s of 2.58 and 2.26 Mb, respectively. Species-specific transcriptomes and information from related species were used to predict transcripts within each assembly. Syntenic comparisons of these species and Amaranthus hypochondriacus identified sites of genomic rearrangement, including duplication and translocation, whereas genetic map construction within A. tuberculatus highlighted the need for further ordering of the A. hybridus and A. tuberculatus contigs. These multiple reference genomes will accelerate genomic studies in these species to further our understanding of weedy evolution within Amaranthus.
反枝苋、刺苋和野苋菜是具有重要农艺价值的杂草物种。本文提供了这三种物种迄今为止最连续的草图组装。我们综合利用了 PacBio 长读测序和染色质接触图谱信息,以近乎染色体水平的分辨率组装和排序野苋菜的序列,支架 N50 为 20.1Mb。为了解决二倍体物种杂合性和等位基因共组装的问题,我们采用了 trio binning 方法,生成了反枝苋和刺苋的单倍型组装。这种方法提高了反枝苋的组装质量,并首次组装了刺苋的基因组,其 contig N50 分别为 2.58Mb 和 2.26Mb。我们利用各物种的特异转录组和相关物种的信息来预测每个组装中的转录本。这些物种与安菜苋的共线性比较确定了基因组重排的位点,包括重复和易位,而在反枝苋中构建遗传图谱则突出了需要进一步对刺苋和反枝苋的 contig 进行排序。这些多个参考基因组将加速这些物种的基因组研究,进一步加深我们对苋属杂草进化的理解。