Abstract Detail

Comparative Genomics/Transcriptomics

Akozbek, Laramie [1], Carey, Sarah [2], Hale, Haley [2], Leslie, Goertzen [2], Harkess, Alex [3].

The conservation of sexual systems and sex-determining regions in the dioecious species of Myricaceae.

Dioecy, where male and female flowers are found on different individuals, has evolved thousands of independent times in plants, yet this uncommon reproductive strategy is only found in ~5-6% of angiosperms. Almost entirely dioecious families like Myricaeceae are even rarer, accounting for less than 10% of all dioecious genera. Many of these species are paradoxical in their widespread distribution and continued evolutionary success despite the theoretical limits on their fitness–e.g. only half of the population producing offspring and reduced reproductive assurance compared to hermaphrodites. Their existence suggests that this reproductive strategy may not always limit radiation and thus be an evolutionary “dead end.” Yet, in such families, we do not know if the genomic basis of their sexual systems (e.g. XX/XY) is conserved across members or if multiple independent origins explain widespread dioecy with the family. Modern genomic technologies allow us to combine high-fidelity whole genome sequencing with classical phylogenetic techniques to both structurally and evolutionarily characterize the non-recombining regions of plant genomes. While high-quality genome references are ideal for identifying the precise locations of the non-recombining sex-determining regions (SDRs) in these species, k-mer based analyses of paired-end 150 bp Illumina data from multiple male and female accessions can be reliably harnessed to distinguish sex-specific sequences and putative sex-determining genes. Furthermore, approximate structural information can be inferred by mapping the sex-specific k-mers of a reference-less species to the genome of a closely related one. We took this approach to identify the SDR of Southern wax myrtle (Morella cerifera). Sex-specific reads were mapped to the Morella rubra genome. Female-specific k-mers from M. cerifera mapped densely to the same 59 kbp SDR in M. rubra, suggesting that these species share a ZZ/ZW system, but an additional 5 Mbp of sex-specific M. cerifera reads mapped to a nearby region of the same chromosome, which suggests that the M. cerifera SDR might be expanding in size, and potentially gene content, relative to M. rubra. We are currently building a comprehensive phylogeny for all members of Myricaceae based on target sequencing (Angiosperms353) of herbarium specimens and generating a chromosome-scale reference genome for M. cerifera with PacBio HiFi long-reads and Dovetail Omni-C scaffolding, which we will use to refine these analyses and to further characteristic the evolution of dioecy in this family as additional species in the family are sequenced. Such investigations across diverse dioecious species will reveal the stability of dioecy across diverging lineages and provide insights about genomic variation in families that share the same sexual system.

1 - HudsonAlpha Institute For Biotechnology, Alex Harkess Lab #4231, 601 Genome Way, Huntsville, AL, 35806, United States
2 - HudsonAlpha Institute For Biotechnology, Alex Harkess Lab #4231, 601 Genome Way, Huntsville, AL, 35806, USA
3 - Auburn University, HudsonAlpha Institute For Biotechnology, Harkess Lab, HudsonAlpha Institute For Biotechnology, 601 Genome Way, Huntsville, AL, 35806, United States

Sex chromosome
sex-determining region.

Presentation Type: Poster
Number: PGT002
Abstract ID:963
Candidate for Awards:None

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