RT Journal Article SR Electronic T1 Retrotransposon Proliferation Coincident with the Evolution of Dioecy in Asparagus JF G3: Genes|Genomes|Genetics FD Genetics Society of America SP 2679 OP 2685 DO 10.1534/g3.116.030239 VO 6 IS 9 A1 Harkess, Alex A1 Mercati, Francesco A1 Abbate, Loredana A1 McKain, Michael A1 Pires, J. Chris A1 Sala, Tea A1 Sunseri, Francesco A1 Falavigna, Agostino A1 Leebens-Mack, Jim YR 2016 UL http://www.g3journal.org/content/6/9/2679.abstract AB Current phylogenetic sampling reveals that dioecy and an XY sex chromosome pair evolved once, or possibly twice, in the genus Asparagus. Although there appear to be some lineage-specific polyploidization events, the base chromosome number of 2n = 2× = 20 is relatively conserved across the Asparagus genus. Regardless, dioecious species tend to have larger genomes than hermaphroditic species. Here, we test whether this genome size expansion in dioecious species is related to a polyploidization and subsequent chromosome fusion, or to retrotransposon proliferation in dioecious species. We first estimate genome sizes, or use published values, for four hermaphrodites and four dioecious species distributed across the phylogeny, and show that dioecious species typically have larger genomes than hermaphroditic species. Utilizing a phylogenomic approach, we find no evidence for ancient polyploidization contributing to increased genome sizes of sampled dioecious species. We do find support for an ancient whole genome duplication (WGD) event predating the diversification of the Asparagus genus. Repetitive DNA content of the four hermaphroditic and four dioecious species was characterized based on randomly sampled whole genome shotgun sequencing, and common elements were annotated. Across our broad phylogenetic sampling, Ty-1 Copia retroelements, in particular, have undergone a marked proliferation in dioecious species. In the absence of a detectable WGD event, retrotransposon proliferation is the most likely explanation for the precipitous increase in genome size in dioecious Asparagus species.