Evidence for degeneration of the Y chromosome in the dioecious plant Silene latifolia.
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 [6], more insertions of transposable elements [5, 7], and lower levels of expression [8] 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 [9], and strong pollen selection may oppose the degeneration of plant Y chromosomes [10]. 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
Gabriel A B
GA
Université de Lyon, Université Lyon 1, Centre National de la Recherche Scientifique, UMR 5558, Laboratoire de Biométrie et Biologie Evolutive, 69622 Villeurbanne Cedex, France. marais@biomserv.univ-lyon1.fr
Nicolas
Michael
M
Bergero
Roberta
R
Chambrier
Pierre
P
Kejnovsky
Eduard
E
Monéger
Françoise
F
Hobza
Roman
R
Widmer
Alex
A
Charlesworth
Deborah
D
D000818:Animals; D032461:Chromosomes, Plant; D004251:DNA Transposable Elements; D019143:Evolution, Molecular; D015870:Gene Expression; D017343:Genes, Plant; D007438:Introns; D029751:Silene / Q000235:genetics*; D014998:Y Chromosome
D004251:DNA Transposable Elements