The genome of medicinal plant Sophora flavescens has undergone significant expansion of both transposons and genes.

Abstract

PurposeSophora flavescens is a medicinal plant in the genus Sophora of the Fabaceae family. The root of S. flavescens is known in China as Kushen and has a long history of wide use in multiple formulations of Traditional Chinese Medicine (TCM). However, there is little genomic information available for S. flavescens. MethodsIn this study, we used third-generation Nanopore long-read sequencing technology combined with Hi-C scaffolding technology to de novo assemble the S. flavescens genome. ResultsWe obtained a chromosomal level high-quality S. flavescens draft genome. The draft genome size is approximately 2.08 Gb, with more than 80% annotated as Transposable Elements (TEs), which have recently and rapidly proliferated. This genome size is [~]5x larger than its closest sequenced relative Lupinus albus l.. We annotated 60,485 genes and examined their expression profiles in leaf, stem and root tissues, and also characterised the genes and pathways involved in the biosynthesis of major bioactive compounds, including alkaloids, flavonoids and isoflavonoids. ConclusionThe assembled genome highlights the very different evolutionary trajectories that have occurred in recently diverged Fabaceae, leading to smaller duplicated genomes vs larger genomes resulting from TE expansion. Our assembly provides valuable resources for conservation, genetic research and breeding of S. flavescens.