The wheel tree (Trochodendron aralioides) genome

The wheel tree (Trochodendron aralioides) is one of only two species in the basal eudicot order Trochodendrales. Together with Tetracentron sinense, it is unique in having secondary xylem without vessel elements which was long considered to be a primitive character. Both Trochodendron and its sister species are widespread in cultivation and popular for use in gardens and parks. Despite the extreme diversity in flower morphology in the basal eudicots grade, only two genomes (the columbine, Aquilegia coerulea, and the sacred lotus, Nelumbo nucifera) are available in the entire grade, strongly limiting our ability to reconstruct and understand the history and drivers of floral diversification. Herein, we assembled and analyzed the genome of the wheel tree using a combination of short- and long- read sequencing with Hi-C data to generate chromosome-length scaffolds and a highly contiguous genome assembly. Here, we constructed a high-quality chromosome-level reference genome assembly for T. aralioides using long reads from the PacBio DNA sequencing platform and a genome assembly strategy taking advantage of the Canu assembler. This assembly of T. aralioides genome is the first chromosome-level reference genome constructed for the Trochodendrales order, and the closest relative to core eudicots sequenced to date. The completeness and continuity of the genome will provide high quality genomic resources for studies on floral evolution and the rapid divergence of eudicots.