The Mytilus genome reveals molecular adaptations of mussel to sessile life, biomineralised armour, and microbial
Mytilus are characterized by the sessile life via byssus, the shell armour via biomineralization, and the adaptation to the living water with abundant microbial. Therefore, Mytilus is a good model for studying bioadhesion, biomineralization, and immune adaptation to microbial. Individuals of M. coruscus were collected from East China Sea and the adductor muscle of an individual male mussel was dissected for DNA extraction. A total of 3 microgram genomic DNA were used for library preparation and genome sequencing, genome size estimation, assembly, and annotations. Deep sequencing of M. coruscus from East China Sea produced a total of 470.41 Gb of clean sequences, including 296.73 Gb (171.52 x) from BGI platform and 173.68Gb (100.39 x) from Pacbio Sequel. The genome size of M. coruscus was estimated as 1,733.26 Mb, and the heterozygosity of M. coruscus genome was estimated to be 1.53%, based on the 17 mer analysis with 646,739,670 used reads. To assemble the highly polymorphic Mytilus genome, a SOAP de novo approach was used to resolve the complex bubble structures resulting from high genome heterozygosity. With the assistances of Falcon, Arrow, and Pilon, and based on the Hi-C sequencing results, an initial 1,743.53 Mb genome assembly was obtained with 12,449 Scaffolds (N50: 28.67Mb) and 2,789 contigs (N50:1.08Mb). The integrity and high quality of the assembly is estimated by BUSCO, and demonstrated by the mapping of 91.3 % of BUSCO genes (893 of 978 total BUSCO groups searched against metazoa_odb9), including complete and single-copy BUSCOs (87.9%) and complete and duplicated BUSCOs (3.4%). This percentage is much higher than that in most of existing molluscan genomes. The M. coruscus genome contains 35,704 predicted protein-coding genes. Functional analysis via comparison with various public protein databases annotated 31,940 genes, accounting for 89.46% of all the predicted genes. Using OthoMCL 2.0, the gene family of M. coruscus was analyzed and compared with other mollusks genome. M. coruscus has the most abundant total genes (35,704) and gene families (13,375). Of which, 1,089 families were identified as unique to M. Coruscus. The abundant novel gene families of M. Coruscus appears to be in accordance with the expectation that evolutionary novelties are associated with novel genes.