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Gigascience. 2018 Nov 27. doi: 10.1093/gigascience/giy141. [Epub ahead of print]

The genome of the tegu lizard Salvator merianae: combining Illumina, PacBio, and optical mapping data to generate a highly contiguous assembly.

Author information

1
Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
2
Max Planck Institute for the Physics of Complex Systems, Dresden, Germany.
3
Center for Systems Biology Dresden, Germany.
4
BioNano Genomics, San Diego, USA.
5
Center for Molecular and Cellular Bioengineering, Technische Universit├Ąt Dresden, Germany.

Abstract

Background:

Reptiles are a species-rich group with great phenotypic and life history diversity, but are highly underrepresented among the vertebrate species with sequenced genomes.

Results:

Here, we report a high-quality genome assembly of the tegu lizard Salvator merianae, the first lacertid with a sequenced genome. We combined 74X Illumina short read, 29.8X PacBio long read and optical mapping data to generate a high-quality assembly with a scaffold N50 value of 55.4 Mb. The contig N50 value of this assembly is 521 Kb, making it the most contiguous reptile assembly so far. We show that the tegu assembly has the highest completeness of coding genes and conserved non-exonic elements (CNEs) compared to other reptiles. Furthermore, the tegu assembly has the highest number of evolutionarily conserved CNE pairs, corroborating a high assembly contiguity in intergenic regions. Like in other reptiles, Long Interspersed Nuclear Elements (LINEs) comprise the most abundant transposon class. We used transcriptomic data, homology- and de novo gene predictions to annotate 22,413 coding genes, of which 16,995 (76%) likely have human orthologs as inferred by CESAR-derived gene mappings. Finally, we generated a multiple genome alignment comprising 10 squamates and 7 other amniote species and identified conserved regions that are under evolutionary constraint. Conserved non-exonic elements cover 38 Mb (1.8%) of the tegu genome, with 3.3 Mb in these elements being squamate-specific. In contrast to placental mammal-specific CNEs, very few of these squamate-specific CNEs (<20 Kb) overlap transposons, highlighting a difference in how lineage-specific CNEs originated in these two clades.

Conclusions:

The tegu lizard genome together with the multiple genome alignment and comprehensive conserved element datasets provide a valuable resource for comparative genomic studies of reptiles and other amniotes.

PMID:
30481296
DOI:
10.1093/gigascience/giy141

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