A High-Quality Genome Sequence of Model Legume Lotus japonicus (MG-20) Provides Insights into the Evolution of Root Nodule Symbiosis

Abstract

Lotus japonicus is an important model legume for studying symbiotic nitrogen fixation as well as plant development. A genomic sequence of L. japonicus (MG20) has been available for more than ten years. However, the low quality of the genome limits its application in functional genomic studies. Therefore, it is necessary to assemble high-quality chromosome sequences of L. japonicus using new sequencing technology to facilitate the study of functional genomics. In this report, we used the third-generation sequencing combined with the Illumina HiSeq platform to sequence the genome of L. japonicus (MG20). We obtained 544 Mb of genomic sequence using third-generation assembly. Based on sequence analysis, 357 Mb of repeats, 28,251 genes, 626 tRNAs, 1409 rRNAs, and 1233 pseudogenes were predicted in the genome. A total of 27,991 genes were annotated into databases. Compared to the previously published data, the new genome database contains complete L. japonicus sequences in the proper order and orientation with a contig N50 2.81Mb and an excellent genome coverage, which provides more accurate genome information and more precise assembly for functional genomic study.