Evolution of X and Y in Dioecious Plants
Although most flowering plants are hermaphroditic, having male and female function within a single flower, a few have shifted sexual function into separate male and female individuals, a condition known as dioecy. White campion (Silene latifolia) is a dioecious plant with XY chromosomes that determine the plant’s sex; however, whether they arose through a similar evolutionary process as the mammalian XY system is unclear. Muyle et al. sequenced the transcriptome of S. latifolia and found that genes on the Y chromosome show significantly less gene expression than those from the X. Examination of sex-linked transcripts from male and female plants indicated that S. latifolia is in the process of evolving dosage compensation for the X chromosome because of the degeneration of the Y, analogous to that of many animals, including humans. Furthermore, given the evolutionary youthfulness of this system (<10 million years compared to 150 million years for mammals), these findings suggest that dosage compensation is a relatively early process in the evolution of sex chromosomes.