Characterization of a large sex determination region in Salix purpurea L. (Salicaceae)
Dioecy has evolved numerous times in plants, but heteromorphic sex chromosomes are apparently rare. Sex determination has been studied in multiple Salix and Populus (Salicaceae) species, and P. trichocarpa has an XY sex determination system on chromosome 19, while S. suchowensis and S. viminalis have a ZW system on chromosome 15. Here we use whole genome sequencing coupled with quantitative trait locus mapping and a genome-wide association study to characterize the genomic composition of the non-recombining portion of the sex determination region. We demonstrate that Salix purpurea also has a ZW system on chromosome 15. The sex determination region has reduced recombination, high structural polymorphism, an abundance of transposable elements, and contains genes that are involved in sex expression in other plants. We also show that chromosome 19 contains sex-associated markers in this S. purpurea assembly, along with other autosomes. This raises the intriguing possibility of a translocation of the sex determination region within the Salicaceae lineage, suggesting a common evolutionary origin of the Populus and Salix sex determination loci.
KeywordsSex Salix Genome Suppressed recombination Dioecy
We are grateful to Matt Olson for helpful comments on the manuscript.
This work was supported by grants from the USDA-NIFA CAP program (4705-WVU-USDA-9703), the DOE JGI Community Sequencing Program, and the NSF Dimensions of Biodiversity Program (DEB-1542509). Sequencing was conducted by the U.S. Department of Energy Joint Genome Institute, a DOE Office of Science User Facility, was supported by the Office of Science of the U.S. Department of Energy under Contract no. DE-AC02-05CH11231.
Compliance with ethical standards
Conflict of interest
All the authors declare that they have no conflicts of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
All raw sequencing data are available from the NCBI Sequence Read Archive (accessions SRP003908, SRP086434, and SRP086435) and the genome assembly and annotation are available from Phytozome (https://phytozome.jgi.doe.gov).
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