Genome Assembly of the Cold-Tolerant Leaf Beetle Gonioctena quinquepunctata, an Important Resource for Studying Its Evolution and Reproductive Barriers between Species.

ABSTRACT

Coleoptera is the most species-rich insect order, yet is currently underrepresented in genomic databases. An assembly was generated for ca. 1.7-Gb genome of the leaf beetle Gonioctena quinquepunctata by first assembling long-sequence reads (Oxford Nanopore; ± 27-fold coverage) and subsequently polishing the resulting assembly with short sequence reads (Illumina; ± 85-fold coverage). The unusually large size (most Coleoptera species are associated with a reported size below 1 Gb) was at least partially attributed to the presence of a large fraction of repeated elements (73.8%). The final assembly was characterized by an N50 length of 432 kb and a BUSCO score of 95.5%. The heterozygosity rate was ±0.6%. Automated genome annotation informed by RNA-Seq resulted in 40,568 predicted proteins, which is much larger than the typical range 17,000-23,000 predicted for other Coleoptera. However, no evidence of a genome duplication was detected. This new reference genome will contribute to our understanding of genetic variation in the Coleoptera. Among others, it will also allow exploring reproductive barriers between species, investigating introgression in the nuclear genome, and identifying genes involved in resistance to extreme climate conditions.