Abstract Detail

Phylogenomics

Bentz, Philip [1], Carey, Sarah [2], Harkess, Alex [3], Leebens-Mack, Jim [4].

Evolution of Asparagus: multiple origins of dioecy and sex chromosomes.

Dioecy (separate sexes) and sex chromosomes have recently evolved independently in many angiosperm lineages. However, dioecy is a relatively rare phenotype amongst angiosperms, as the vast majority of lineages are hermaphroditic. Previous phylogenetic analysis of the genus Asparagus (Asparagaceae) indicates that dioecy may have independently evolved twice within the genus. However, due to limited taxa and loci sampling, statistical support for the number of dioecy origins in Asparagus is lacking. Here we elucidate the origin(s) of dioecy within Asparagus by integrating comparative genomics and phylogenomic methods. First, we reconstructed a plastid phylogenetic tree using nearly complete plastome sequences, and then separately used a multispecies coalescent summary approach with 254 single copy nuclear loci to estimate species relationships. Both analyses suggest either two origins (one in a clade containing A. horridus and another in the A. officinalis clade), or one origin (in the most recent common ancestor of A. horridus and A. officinalis) and a loss in a hermaphroditic clade occurred. We also report genomic comparisons, between the published genome assembly of a male A. officinalis and whole genome sequencing reads for multiple male and female genotypes of A. horridus. In our comparative analyses, we found no evidence of shared homologous sequence between the known sex-determining sequences in A. officinalis and any of the A. horridus genotypes. This suggests that two different sex-determination genetic pathways separately evolved between these dioecious lineages. Altogether our results leave open the possibility that dioecy evolved independently twice within Asparagus and, as a result, two novel sex chromosome systems may have evolved between closely related lineages.

1 - University Of Georgia, Department Of Plant Biology, 120 Carlton Street, Athens, GA, 30602, United States
2 - HudsonAlpha Institute For Biotechnology, Harkess Lab, 601 Genome Way NW , Huntsville, AL, 35806, United States
3 - Auburn University, HudsonAlpha Institute For Biotechnology, Harkess Lab, HudsonAlpha Institute For Biotechnology, 601 Genome Way, Huntsville, AL, 35806, United States
4 - University Of Georgia, Plant Biology, 2101 Miller Plant Sciences, Athens, GA, 30602, United States

Keywords:
comparative genomics
asparagus
asparagaceae
Monocots
Evolution
Dioecy
sex chromosomes
sex-determination.

Presentation Type: Oral Paper
Number: PHYLO I012
Abstract ID:212
Candidate for Awards:None