title: Paternal Genome Elimination inLiposcelisBooklice (Insecta: Psocodea).
abstract: How sex is determined in insects is diverse and dynamic, and includes male heterogamety, female heterogamety, and haplodiploidy. In many insect lineages, sex determination is either completely unknown or poorly studied. We studied sex determination in Psocodea-a species-rich order of insects that includes parasitic lice, barklice, and booklice. We focus on a recently discovered species ofLiposcelisbooklice (Psocodea: Troctomorpha), which are among the closest free-living relatives of parasitic lice. Using genetic, genomic, and immunohistochemical approaches, we show that this group exhibits paternal genome elimination (PGE), an unusual mode of sex determination that involves genomic imprinting. Controlled crosses, following a genetic marker over multiple generations, demonstrated that males only transmit to offspring genes they inherited from their mother. Immunofluorescence microscopy revealed densely packed chromocenters associated with H3K9me3-a conserved marker for heterochromatin-in males, but not in females, suggesting silencing of chromosomes in males. Genome assembly and comparison of read coverage in male and female libraries showed no evidence for differentiated sex chromosomes. We also found that females produce more sons early in life, consistent with facultative sex allocation. It is likely that PGE is widespread in Psocodea, including human lice. This order represents a promising model for studying this enigmatic mode of sex determination.
authors.affiliation: Department of Biology, University of Victoria, V8P 5C2, Canada hodson.christina@gmail.com stevep@uvic.ca.|Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, EH9 3JG, United Kingdom.
authors.forename: Christina N
authors.initials: CN
authors.lastname: Hodson
authors.affiliation: Department of Biology, University of Victoria, V8P 5C2, Canada.
authors.forename: Phineas T
authors.initials: PT
authors.lastname: Hamilton
authors.affiliation: Department of Biochemistry and Microbiology, University of Victoria, V8P 5C2, Canada.
authors.forename: Dave
authors.initials: D
authors.lastname: Dilworth
authors.affiliation: Department of Biochemistry and Microbiology, University of Victoria, V8P 5C2, Canada.
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Nelson
authors.affiliation: Department of Biology, University of Victoria, V8P 5C2, Canada.
authors.forename: Caitlin I
authors.initials: CI
authors.lastname: Curtis
authors.affiliation: Department of Biology, University of Victoria, V8P 5C2, Canada hodson.christina@gmail.com stevep@uvic.ca.|Integrated Microbial Biodiversity Program, Canadian Institute for Advanced Research, Toronto M5G 1Z8, Canada.
authors.forename: Steve J
authors.initials: SJ
authors.lastname: Perlman
mesh_terms: D000818:Animals; D005260:Female; D049750:Genome, Insect; D018392:Genomic Imprinting / Q000235:genetics*; D006570:Heterochromatin / Q000235:genetics*; D006801:Humans; D008297:Male; D008003:Phthiraptera / Q000235:genetics* / Q000254:growth & development; D019849:Sex Determination Processes
chemical_list: D006570:Heterochromatin
keywords: genome exclusion; genomic imprinting; segregation distortion; sex determination; sex ratio