Genomics / Proteomics
Harkess, Alex , Leebens-Mack, Jim .
Retrotransposon amplification and sex chromosome evolution in Asparagus.
The recent evolution of sex chromosomes in the genus Asparagus provides a foundation for examining changes in genomic content during the transition from hermaphroditism to dioecy. Recent phylogenetic analyses are increasingly supporting the hypothesis that all dioecious species form a single clade, implying that dioecy evolved once in the genus. The origin of dioecy in Asparagus was accompanied by a range expansion from Africa to Europe and Asia and an increase in genome size. The diploid genome sizes of dioecious species are nearly double those of hermaphrodites. Analyses of transcribed paralog pairs, mapping populations and gene trees fail to reveal evidence of ancient polyploidy in dioecious Asparagus species. We hypothesize that the increased genome size is associated with transposon activity. To identify trends in transposon density across the genus, we conducted low-pass 454 Whole Genome Shotgun (WGS) sequencing of five hermaphrodite and four dioecious species. Reads representing the repetitive portion of each genome were identified through hierarchical clustering, then subsequently assembled and annotated. Results indicate that while Ty3-Gypsy retroelements are the most frequent repetitive portion in all sampled genomes, there is an average 2.5x increase of Ty1-Copia retroelements in the dioecious species compared to the hermaphrodites. We are currently employing phylogenetic analyses of retrotransposon protein coding domains to verify this amplification. We predict that increased transposon activity can explain a large portion of genome expansion in dioecious Asparagus species.
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1 - University of Georgia, 2502 Miller Plant Sciences, Athens, GA, 30602, USA
Presentation Type: Poster:Posters for Topics
Location: Battelle South/Convention Center
Date: Monday, July 9th, 2012
Time: 5:30 PM