An Improved Chromosome-Level Genome Assembly of the Firefly Pyrocoelia pectoralis

The endemic and endangered Chinese firefly Pyrocoelia pectoralis is a sexually dimorphic, nocturnal species. A previous attempt by this team to assemble a draft genome of P. pectoralis using PacBio and Illumina HiSeq X Ten platforms was limited in its usefulness by high redundancy and contamination. This prompted us to conduct an improved chromosome-level genome assembly of P. pectoralis. Ten chromosomes were further assembled based on Hi-C data to a 532.25 Mb final size with a 52.87 Mb scaffold N50. The total repeat lengths in the genome of P. pectoralis amount to 227.69 Mb; 42.78%. In total, 12,789 genes could be functionally annotated using at least one public database. Phylogenetic inference indicated that P. pectoralis and P. pyralis diverged ~51.41 million years ago. Gene family expansion and contraction analysis of 12 species were performed, and 546 expanded and 2660 contracted gene families were identified in P. pectoralis. We generated a high-quality draft of the P. pectoralis genome. This genome assembly should help promote research on the species' sexual dimorphism and its unique courtship behavior, which involves a combination of pheromonal and bioluminescent signals. It also can serve as a resource for accelerating genome-assisted improvements in the conservation of this species.