Updated genome assembly of <i>Ginkgo biloba</i>

Ginkgo biloba is one of the worlds most ancient plants, a living fossil that has remained essentially unchanged in terms of gross morphology for more than 200 million years. Representing one of the four extant gymnosperm lineages and having no living relatives, it possesses a suite of fascinating characteristics including including a large genome, outstanding resistance/tolerance to abiotic and biotic stresses, and dioecious reproduction, making it an ideal model species for biological studies.
Here we present an updated chromosome-level genome assembly using HiC technology as a major improvement of the ginkgo draft assembly. A chromosome-level reference represents a valuable resource to facilitate of studies of biologic diversity, evolutionary history, and population genetics. With technological advances, we constructed to update the existing draft assembly to the chromosome-level using Hi-C, which has been proven to be a fast, inexpensive, and accurate technology that can be applied to many species. The fresh plant leaves of two-years seedling (TM301S) were crosslinked with 1% formaldehyde. To destroy the cell wall, formaldehyde fixed powder was added to Buffer solution. The restriction endonuclease MboI was used to digest DNA, followed by biotinylated residue labeling. The Hi-C library was then sequenced on BGISEQ-500 platform with 50 bp pair-end sequencing. HiC-Pro pipeline (v2.11.1) was implemented in quality control. Of all 653,202,535 raw pair-end reads, there are 32% (207,324,555) paired Hi-C reads are valid and suitable for following analysis. Basing on these valid Hi-C reads, we used Juicer (v1.6.2) and Aiden labs Hi-C assembly pipeline (v180922) to assemble the genome with the main parameter "-m haploid -s 4 -c 12", generating 12 chromosomes spanning 9.03 Gb (~94% of the whole genome).