The human Y--probably because of its nonrecombining nature--has lost 97% of its genes since X and Y chromosomes started to diverge [1, 2]. There are clear signs of degeneration in the Drosophila miranda neoY chromosome (an autosome fused to the Y chromosome), with neoY genes showing faster protein evolution [3-6], accumulation of unpreferred codons , more insertions of transposable elements [5, 7], and lower levels of expression  than neoX genes. In the many other taxa with sex chromosomes, Y degeneration has hardly been studied. In plants, many genes are expressed in pollen , and strong pollen selection may oppose the degeneration of plant Y chromosomes . Silene latifolia is a dioecious plant with young heteromorphic sex chromosomes [11, 12]. Here we test whether the S. latifolia Y chromosome is undergoing genetic degeneration by analyzing seven sex-linked genes. S. latifolia Y-linked genes tend to evolve faster at the protein level than their X-linked homologs, and they have lower expression levels. Several Y gene introns have increased in length, with evidence for transposable-element accumulation. We detect signs of degeneration in most of the Y-linked gene sequences analyzed, similar to those of animal Y-linked and neo-Y chromosome genes.
Marais, G., Nicolas, M., Bergero, R., Chambrier, P., Kejnovsky, E., Moneger, F., Hobza, R., Widmer, A., & Charlesworth, D. (2008). Evidence for degeneration of the Y chromosome in the dioecious plant Silene latifolia. Current Biology, 18(7), 545-549. https://doi.org/10.1016/j.cub.2008.03.023