Anthoceros genomes illuminate the origin of land plants and the unique biology of hornworts

Abstract

<p class="first" id="Par1">Hornworts comprise a bryophyte lineage that diverged from other extant land plants &gt;400 million years ago and bears unique biological features, including a distinct sporophyte architecture, cyanobacterial symbiosis and a pyrenoid-based carbon-concentrating mechanism (CCM). Here, we provide three high-quality genomes of <i>Anthoceros</i> hornworts. Phylogenomic analyses place hornworts as a sister clade to liverworts plus mosses with high support. The <i>Anthoceros</i> genomes lack repeat-dense centromeres as well as whole-genome duplication, and contain a limited transcription factor repertoire. Several genes involved in angiosperm meristem and stomatal function are conserved in <i>Anthoceros</i> and upregulated during sporophyte development, suggesting possible homologies at the genetic level. We identified candidate genes involved in cyanobacterial symbiosis and found that <i>LCIB</i>, a <i>Chlamydomonas</i> CCM gene, is present in hornworts but absent in other plant lineages, implying a possible conserved role in CCM function. We anticipate that these hornwort genomes will serve as essential references for future hornwort research and comparative studies across land plants. </p><p class="first" id="Par2">Analyses of three high-quality genomes of <i>Anthoceros</i> hornworts place hornworts as a sister clade to the lineage including liverworts and mosses, and provide insights into the unique biological features of hornworts. </p>