Chromosome-scale and haplotype-resolved genome assembly of Populus trichocarpa

Abstract Populus trichocarpa, a pivotal model organism for woody transgenic research, not only garners substantial scientific interest but plays an integral role in forestry economics. Previous genomic assemblies of P. trichocarpa predominantly treated its heterozygous genome as homozygous, thereby neglecting crucial haplotypic diversity. Leveraging the high-fidelity (HiFi) sequencing capabilities of PacBio sequencing and the chromosome conformation capture insights provided by Illumina's Hi-C technique, this study is the first to achieve a near telomere-to-telomere assembly of both paternal and maternal haplotypes in P. trichocarpa. Comparative genomic analysis between these haplotypes has uncovered several allelic variants and pathways critical for trait determination through allele-specific expression. Furthermore, utilizing RNA-seq data from multiple tissues, this investigation has detailed the tissue-specific expression patterns of the leucine-rich repeat gene family, which are essential in mediating plant signal transduction and developmental regulation. Our results not only illuminate the functional genomics landscape of P. trichocarpa but also provide invaluable theoretical underpinnings for the genetic improvement of woody plants and a robust framework for exploring genetic variability and allelic expression disparities in arboreal species.