Sex determination and sex chromosome evolution in willows

Last changed: 02 September 2022

We identify ecological and genetic processes that lead to switches in sex determination systems among closely related willow species. Our studies will bring insights in the genetic regulation of the development of females and males, and in processes that are driving the evolution of new sex determination systems. These are fundamental processes and of relevance to all organisms with separate sexes.

Finding the chemicals and biofuels of the future

We collaborate on several projects where we are characterizing the genetic background to complex traits such as biomass and phenology related traits. These projects are aiming at exploring and identifying suitable plant material and breeding methods for using willows as a biomass source for bioenergy, chemicals and biofuels. 

Willows as a study system

In our research, we are working with willows in the Salix genus. Willows have several life history characteristics that make them ideal for various evolutionary genetics and genomics studies. They are for example easy to artificially cross, they have rather short generation times (appr. 3 years) and they have convenient genome sizes (appr. 450 Mbp). Furthermore, different species differ greatly in their ecology, which permits studies of links between ecological, genetic and genomic factors.

Selected publications

Pucholt, P. Wright, A. E., Liu Conze, L., Mank, J. E. and Berlin S. Early stages of sex chromosome evolution in the ancient dioecious willow Salix viminalis. (Under review).

Pucholt, P., Hallingbäck, H. R. Berlin, S. Allelic incompatibility can explain female biased sex ratios in dioecious plants. (Under review).

Hallingbäck, H. R. Fogelqvist, J., Powers, S.J. Turrion-Gomez, J., Rossiter, R., Amey, J., Martin, T., Weih, M., Gyllenstrand, N. Karp, A., Lagercrantz, U. Hanley, S. J., Berlin S. and Rönnberg-Wästljung, A-C. 2016. Association mapping in Salix viminalis L. (Salicaceae)–identification of candidate genes associated with growth and phenology. GCB Bioenergy 8:670-685.

Harikrishnan, S. L.*, Pucholt, P.* and Berlin, S. (2015). Sequence and gene expression evolution of paralogous genes in willows. Scientific Reports 5. (*Equal contribution)

Pucholt, P.*, Rönnberg-Wästljung. A-C.*, Berlin, S. (2015). Single locus sex determination and female heterogamety in the basket willow (Salix viminalis L.). Heredity 114:575-583. (*Equal contribution).

Berlin, S., Trybush, S. T., Fogelqvist, J., Gyllenstrand, N., Hallingbäck, H., Åhman, I., Nordh, N-E., Larsson S., Shield, I., Powers, S., Weih, M., Lagercrantz, U., Rönnberg-Wästljung, A-C., Karp, A and Hanley, S. J. (2014). Genetic diversity, population structure and phenotypic variation in European Salix viminalis L. (Salicaceae). Tree Genetics & Genomes 10:1595-1610.

Berlin, S., Lagercrantz, U., von Arnold S., Öst, T. and Rönnberg-Wästljung, A-C. (2010). High-density linkage mapping and evolution of paralogs and orthologs in Salix and Populus. BMC Genomics 11:129.

Mank, J., Vicoso, B., Berlin, S. and Charlesworth, B. (2010). Effective population size and the faster-X effect: empirical results and their interpretation. Evolution 64:663-674.

Berlin, S., Tomaras, D. and Charlesworth, B. (2007). Low mitochondrial variability in birds may indicate Hill-Robertson effects on the W chromosome. Heredity 99:389-396.

Berlin, S. and Ellegren, H. (2006) Fast accumulation of nonsynonymous mutations on the female-specific W chromosome in birds. Journal of Molecular Evolution 62:66-72.

Berlin S, Ellegren H. (2004). Chicken W: a genetically uniform chromosome in a highly variable genome. Proceedings of the National Academy of Sciences USA 101:15967-15969.

Cutting edge genome and trancriptome studies

We are using various sequencing technologies for exploring the willow genomes and transcriptomes. We have for example assembled a Salix viminalis female genome using the PacBio RSII technology and we are about to explore the sex chromosomes in this species using the new Chromium 10X technology. We are also studying sex-biased gene expression using RNA-seq data from multiple individuals and tissues. We have furthermore used the genotyping-by-sequencing technology in a bi-parental pedigree population and in a population consisting of more or less unrelated S. viminalis accessions and in that way obtained numerous markers across the genomes. These were used to construct a dense linkage map and for genome-wide association studies.   

People involved

  • Sofia Berlin Kolm, docent
  • Pascal Pucholt, PhD student

Important collaborators

  • Anki Rönnberg-Wästljung, Dept of Plant Biology, SLU.
  • Henrik Hallingbäck, Dept of Forest Genetics and Plant Physiology, SLU.
  • Judith Mank, Department of Genetics, Evolution and Environment, University College London.
  • Estelle Proux-Wéra, Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University.
  • Allison Churcher, Science for Life Laboratory, Department of Molecular Biology, Umeå University.
  • Björn Nystedt, Science for Life Laboratory, Department of Molecular Evolution, Cell and Molecular Biology, Biomedical Centre, Uppsala University.

Funding agencies

  • The Swedish Research Council, VR.
  • Carl-Tryggers Stiftelse.
  • The Swedish Research Council Formas.
  • SciLifeLab Bioinformatics Long-term Support (WABI)

Contact

Sofia Berlin Kolm

Researcher at the Department of Plant Biology
sofia.berlin@slu.se, 018-673375