Evolution of sex chromosomes in plants

Sex is arguably the largest source of variance within species. Consequently, sex chromosomes are key elements of the biology and evolution in species with genetic sex determination. Sex chromosomes follow a fascinating evolutionary trajectory, involving the accumulation of sex-antagonistic genes followed by the suppression of recombination — often by chromosome inversions. The lack of recombination leads to high levels of divergence between the homologous pair and the degeneration of one of the chromosomes (e.g., the Y chromosome of mammals).

However, many questions about this trajectory remain open, for example regarding the mode and tempo of sexual antagonism or the evolutionary forces that interact to favor or prevent the spread of chromosome inversions. We have contributed to some of these issues, specifically by generating models that predict levels of sequence divergence in sex chromosomes, describing the expected signatures of sex-antagonistic selection, and developing methods to estimate extremely low levels of recombination.

Currently, we are working towards the application of these models to the study of recently evolved sex chromosome systems in plants. “Young” sex chromosomes offer a unique perspective on the origin of sex and the dynamics of sex-linked genomic regions, and can tell us about the conditions that affect the evolution of recombination suppression, subsequent sex-chromosome divergence and potential degeneration.