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Abstract Detail

Comparative Genomics/Transcriptomics

Carey, Sarah [1], McDaniel, Stuart [2].

Genomic consequences of UV sex chromosomes.

Sex chromosomes have evolved several times across the tree of life, yet the evolutionary processes shaping their gene content remain enigmatic. Sex chromosomes are well-documented in bryophytes, providing an untapped resource for exploring factors shaping their evolution. Sex in dioecious bryophytes is determined by a haploid UV sex chromosomal system. In this system, each sex has a non-recombining chromosome (U for females and V for males). The U and V pair at meiosis in the monomorphic, diploid sporophyte and segregate to the haploid, male and female gametophytes. Much like in diploid XY and ZW systems, a key characteristic of UV sex chromosomes is suppressed recombination. However, unlike the XY/ZW systems, both the female U and the male V exhibit suppressed recombination, because there is no homogametic UU or VV sex where the sex chromosomes can freely recombine. Thus, the UV system allows us to tease apart the effects of suppressed recombination and sex-specific inheritance on the evolution of sex chromosome content and structure. Here we used a combination of Illumina, PacBio, and Hi-C data to generate chromosome-scale assemblies of the 360MB genomes of a male and a female isolate of the moss Ceratodon purpureus. We also generated RNAseq data of 8 male/female sibling pairs and 23 genome resequence isolates sampled from across the distribution of the species. We use these data to examine patterns of gene-capture and structure on the sex chromosomes. We find no evidence of strata remaining from the multiple gene-capture events, suggesting little selection to maintain gene order. However, we do find signs of degeneration including lower gene density, higher TEs, and decreased codon bias on both U and V sex chromosomes. Interestingly, we also find lower effective population sizes on both the U and V, with the V twice as low as the U, likely due to sexual selection. These analyses highlight the complex evolutionary history of moss UV sex chromosomes and provide an interesting comparison to diploid systems.

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1 - University of Florida, Biology Department, Gainesville, FL, 32611, USA
2 - Biology Department, University Of Florida, Gainesville, FL, 32611, United States

Sex Chromosomes
Ceratodon purpureus.

Presentation Type: Oral Paper
Session: CG2, Comparative Genetics/Genomics II
Location: Tucson I/Starr Pass
Date: Tuesday, July 30th, 2019
Time: 2:15 PM
Number: CG2003
Abstract ID:677
Candidate for Awards:Margaret Menzel Award

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