Qu-1: a transformation-and regeneration-amenable doubled haploid cell line with a reference genome sequence for...

Plant suspension homogeneous cells are invaluable materials for investigating molecular mechanisms underlying various biological processes. In this study, we established and characterized a doubled haploid cell line from Populus simonii × P. nigra, designated as Qu-1. This cell line exhibited high viability and dispersibility under suspension culture conditions and retained the ability to regenerate into whole plants. K-mer analysis confirmed the homozygous genome of Qu-1, and a chromosome-level genome assembly was subsequently achieved by using PacBio sequencing. Additionally, we established an efficient transient transformation protocol using PEG-mediated protoplasts and a stable Agrobacterium-mediated transformation system for Qu-1. To explore the mutagenesis potential of this cell line, we treated the cell line with ethyl methanesulfonate (EMS) and performed genome resequencing to identify mutation sites. Overall, Qu-1 represents the first poplar cell line with a homozygous genome and is as a powerful tool for molecular biology research in woody plants.