Polyploid genome assembly of Cardamine chenopodiifolia.

Abstract

Cardamine chenopodiifolia is an amphicarpic plant in the Brassicaceae family. Plants develop two fruit types, one above and another below ground. This rare trait is associated with octoploidy in C. chenopodiifolia. The absence of genomic data for C. chenopodiifolia currently limits our understanding of the development and evolution of amphicarpy. Here, we produced a chromosome-scale assembly of the C. chenopodiifolia genome using high-fidelity long read sequencing with the Pacific Biosciences platform. We assembled 32 chromosomes and two organelle genomes with a total length of 597.2 Mb and an N50 of 18.8 Mb. Genome completeness was estimated at 99.8%. We observed structural variation among homeologous chromosomes, suggesting that C. chenopodiifolia originated via allopolyploidy, and phased the octoploid genome into four sub-genomes using orthogroup trees. This fully phased, chromosome-level genome assembly is an important resource to help investigate amphicarpy in C. chenopodiifolia and the origin of trait novelties by allopolyploidy.