The role of repetitive DNA in structure and evolution of sex chromosomes in plants

Abstract

Eukaryotic genomes contain a large proportion of repetitive DNA sequences, mostly transposable elements (TEs) and tandem repeats. These repetitive sequences often colonize specific chromosomal (Y or W chromosomes, B chromosomes) or subchromosomal (telomeres, centromeres) niches. Sex chromosomes, especially non-recombining regions of the Y chromosome, are subject to different evolutionary forces compared with autosomes. In nonrecombining regions of the Y chromosome repetitive DNA sequences are accumulated, representing a dominant and early process forming the Y chromosome, probably before genes start to degenerate. Here we review the occurrence and role of repetitive DNA in Y chromosome evolution in various species with a focus on dioecious plants. We also discuss the potential link between recombination and transposition in shaping genomes.

Highly conserved Z and molecularly diverged W chromosomes in the fish genus Triportheus (Characiformes, Triportheidae)

“…In a diversity of organisms, heterochromatinization, accompanied by amplification of tandem repeats, represents an important step in the morphological differentiation of simple sex chromosome systems, especially in the ZW ones (Nanda et al, 2000;Kondo et al, 2004;Marchal et al, 2004;Peichel et al, 2004;Charlesworth et al, 2005;Ezaz et al, 2009;Kejnovský et al, 2009). Same type of studies provided evidence that rDNA cistrons can also occur on the sex chromosomes of distinct organisms (see, for example, Goodpasture and Bloom, 1975;Schmid et al, 1983;Yonenaga-Yassuda et al, 1983;Morielle and Varella-Garcia, 1988;Cioffi et al, 2010).…”

Junk DNA promotes sex chromosome evolution

“…Accumulation of these junk DNA sequences also contributes to the production of the gene deserts found in the Y chromosome. Kejnovskỳ et al (2008) have recently discussed the potential for junk DNA accumulation to start at an early stage in the evolution of sex chromosomes. Both past cytogenetic analyses and recent genome projects have revealed that many animal Y chromosomes have more abundant heterochromatin derived from repetitive sequences compared with X chromosomes and autosomes.…”

“…For example, it will give us the opportunity to study the problem of whether junk DNA accumulation occurs before or after gene degeneration on Y chromosomes (Marais et al, 2008). Kejnovskỳ et al (2008) reported that the accumulation of repetitive sequences was generally found in the evolutionarily young plant Y chromosomes. The papaya Y chromosome is the youngest in plants, having diverged from the X chromosome only 2-3 m.y.a.…”

Sex chromosome composition revealed in Characidium fishes (Characiformes: Crenuchidae) by molecular cytogenetic methods

“…clear correlation between these sequences and sex chromosomes has been established by numerous studies (e.g., Nanda et al 1990Nanda et al , 2000Matsubara et al 2006;Kejnovsky et al 2009) including several Neotropical fish groups (e.g., Parise-Maltempi et al 2007;Cioffi et al 2011Cioffi et al , 2012Machado et al 2011), suggesting that the differentiation of sex chromosomes' mechanism is often associated with the accumulation of repetitive DNA. Accordingly, repetitive sequences represent a powerful tool to elucidate both the processes of morphological differentiation of sex chromosomes in fishes and to possibly understand some of the diversity of the differentiation systems observed in this group of vertebrates (Cioffi et al 2011).…”