Dataset Information

Reconstruction of ancient homeobox gene linkages inferred from a new high-quality assembly of the Hong Kong oyster (Magallana hongkongensis) genome.

ABSTRACT:

Background

Homeobox-containing genes encode crucial transcription factors involved in animal, plant and fungal development, and changes to homeobox genes have been linked to the evolution of novel body plans and morphologies. In animals, some homeobox genes are clustered together in the genome, either as remnants from ancestral genomic arrangements, or due to coordinated gene regulation. Consequently, analyses of homeobox gene organization across animal phylogeny provide important insights into the evolution of genome organization and developmental gene control, and their interaction. However, homeobox gene organization remains to be fully elucidated in several key animal ancestors, including those of molluscs, lophotrochozoans and bilaterians.

Results

Here, we present a high-quality chromosome-level genome assembly of the Hong Kong oyster, Magallana hongkongensis (2n = 20), for which 93.2% of the genomic sequences are contained on 10 pseudomolecules (~ 758 Mb, scaffold N50 = 72.3 Mb). Our genome assembly was scaffolded using Hi-C reads, facilitating a larger scaffold size compared to the recently published M. hongkongensis genome of Peng et al. (Mol Ecol Resources, 2020), which was scaffolded using the Crassostrea gigas assembly. A total of 46,963 predicted gene models (45,308 protein coding genes) were incorporated in our genome, and genome completeness estimated by BUSCO was 94.6%. Homeobox gene linkages were analysed in detail relative to available data for other mollusc lineages.

Conclusions

The analyses performed in this study and the accompanying genome sequence provide important genetic resources for this economically and culturally valuable oyster species, and offer a platform to improve understanding of animal biology and evolution more generally. Transposable element content is comparable to that found in other mollusc species, contrary to the conclusion of another recent analysis. Also, our chromosome-level assembly allows the inference of ancient gene linkages (synteny) for the homeobox-containing genes, even though a number of the homeobox gene clusters, like the Hox/ParaHox clusters, are undergoing dispersal in molluscs such as this oyster.

SUBMITTER: Li Y

PROVIDER: S-EPMC7566022 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Four bacterial isolates were recovered from the blood cultures of four patients, two of whom were from Hong Kong and two of whom were from Canada. The two Hong Kong strains were isolated from a 48-year-old man with intestinal obstruction and secondary sepsis (strain HKU16T) and from a 39-year-old man with acute appendicitis (strain HKU17), while the two Canadian strains were isolated from a 74-year-old man with biliary sepsis (strain CA1) and from a 66-year-old woman with metastatic carcinoma and sepsis (strain CA2). While the first three patients survived, the last patient died 2 weeks after the episode of bacteremia. All four isolates are strictly anaerobic, nonsporulating, gram-positive coccobacilli that were unidentified by conventional phenotypic tests and commercial identification systems. They grow on sheep blood agar as nonhemolytic pinpoint colonies after 48 h of incubation at 37 degrees C in an anaerobic environment. All are catalase positive and motile, with flagella. They produce acid from arabinose, glucose, mannose, and xylose. They do not produce indole or reduce nitrate. They are sensitive to penicillin, vancomycin, and metronidazole but resistant to cefotaxime. 16S rRNA gene sequence analysis showed 16.0%, 16.8%, and 21.0% base differences from Clostridium propionicum, Clostridium neopropionicum, and Atopobium minutum, respectively. The G+C content of strain HKU16T is 40.2% +/- 2.2%. Based on their phylogenetic affiliation, unique G+C content, and phenotypic characteristics, we propose a new genus and species, Catabacter hongkongensis gen. nov., sp. nov., to describe the bacterium, for which HKU16 is the type strain, and suggest that it be assigned to a new family, Catabacteriaceae. The gastrointestinal tract was probably the source of the bacterium for at least three of the four patients. The isolation of a catalase-positive, motile, nonsporulating, anaerobic gram-positive bacillus in clinical laboratories should raise the possibility of C. hongkongensis. Further studies should be performed to ascertain the epidemiology and other disease associations of this bacterium.