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G3 (Bethesda). 2017 Oct 5;7(10):3281-3294. doi: 10.1534/g3.117.300187.

Neo-sex Chromosomes in the Monarch Butterfly, Danaus plexippus.

Author information

1
Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66046.
2
Faculty of Science, University of South Bohemia in České Budéjovice, 370 05 České Budějovice, Czech Republic.
3
Institute of Entomology, Biology Centre of the Czech Academy of Sciences, Czech Academy of Sciences, 370 05 České Budějovice, Czech Republic.
4
Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66046 jrwalters@ku.edu.

Abstract

We report the discovery of a neo-sex chromosome in the monarch butterfly, Danaus plexippus, and several of its close relatives. Z-linked scaffolds in the D. plexippus genome assembly were identified via sex-specific differences in Illumina sequencing coverage. Additionally, a majority of the D. plexippus genome assembly was assigned to chromosomes based on counts of one-to-one orthologs relative to the butterfly Melitaea cinxia (with replication using two other lepidopteran species), in which genome scaffolds have been mapped to linkage groups. Sequencing coverage-based assessments of Z linkage combined with homology-based chromosomal assignments provided strong evidence for a Z-autosome fusion in the Danaus lineage, involving the autosome homologous to chromosome 21 in M. cinxia Coverage analysis also identified three notable assembly errors resulting in chimeric Z-autosome scaffolds. Cytogenetic analysis further revealed a large W chromosome that is partially euchromatic, consistent with being a neo-W chromosome. The discovery of a neo-Z and the provisional assignment of chromosome linkage for >90% of D. plexippus genes lays the foundation for novel insights concerning sex chromosome evolution in this female-heterogametic model species for functional and evolutionary genomics.

KEYWORDS:

Lepidoptera; chromosomal fusion; evolution; genomics; sex chromosomes

PMID:
28839116
PMCID:
PMC5633379
DOI:
10.1534/g3.117.300187
[Indexed for MEDLINE]
Free PMC Article

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