Carey S.B. auteur aut IRD Aközbek L. auteur aut IRD Lovell J.T. auteur aut IRD Jenkins J. auteur aut IRD Healey A.L. auteur aut IRD Shu S. auteur aut IRD Grabowski P. auteur aut IRD Yocca A. auteur aut IRD Stewart A. auteur aut IRD Jones T. auteur aut IRD Barry K. auteur aut IRD Rajasekar S. auteur aut IRD Talag J. auteur aut IRD Scutt C. auteur aut IRD Lowry P.P. auteur aut IRD Munzinger Jérôme auteur aut IRD Knox E.B. auteur aut IRD Soltis D.E. auteur aut IRD Soltis P.S. auteur aut IRD Grimwood J. auteur aut IRD Schmutz J. auteur aut IRD Leebens-Mack J. auteur aut IRD Harkess A. auteur aut IRD text journalArticle eng text/pdf reformatted digital access Sex chromosomes have evolved hundreds of times across the flowering plant tree of life; their recent origins in some members of this clade can shed light on the early consequences of suppressed recombination, a crucial step in sex chromosome evolution. Amborella trichopoda, the sole species of a lineage that is sister to all other extant flowering plants, is dioecious with a young ZW sex determination system. Here we present a haplotype-resolved genome assembly, including highly contiguous assemblies of the Z and W chromosomes. We identify a ~3-megabase sex-determination region (SDR) captured in two strata that includes a ~300-kilobase inversion that is enriched with repetitive sequences and contains a homologue of the Arabidopsis METHYLTHIOADENOSINE NUCLEOSIDASE (MTN1-2) genes, which are known to be involved in fertility. However, the remainder of the SDR does not show patterns typically found in non-recombining SDRs, such as repeat accumulation and gene loss. These findings are consistent with the hypothesis that dioecy is derived in Amborella and the sex chromosome pair has not significantly degenerated. specialized 076PHYBIO06 10 12 1944-1954 2024 2055-0278 https://www.documentation.ird.fr/hor/fdi:010092515 10.1038/s41477-024-01858-x 2055-0278 [F B010092515] https://www.documentation.ird.fr/hor/fdi:010092515 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2025-01/010092515.pdf IRD - Base Horizon / Pleins textes 2025-01-08 2025-11-06 fdi:010092515 fre