Gene organization of the liverwort Y chromosome reveals distinct sex chromosome evolution in a haploid system

Step-by-step evolution of neo-sex chromosomes in geographical populations of wild silkmoths, Samia cynthia ssp.

“…Hence, organisms carrying a primitive Y chromosome or an evolutionarily young neo-Y chromosome represent valuable models for the study of sex chromosome differentiation. Recent studies using genomic approaches provided supporting evidence for the hypothesis on early steps of sex chromosome evolution in several plants and animals with the XY system (Liu et al, 2004;Yamato et al, 2007;Bachtrog et al, 2008;Zhou et al, 2008). However, similar approaches have not been applied yet in the W chromosome of Lepidoptera.…”

Synthetic Botany

“…The sequences of the Y-chromosome, mitochondrial, and plastid genomes are available (Ohyama et al 1986;Oda et al 1992;Yamato et al 2007), whereas an assembled nuclear genome sequence is expected to be published shortly, and can be found in draft form online (marchantia.info). The size of the nuclear genome has been estimated at 280 Mb by flow cytometry, and 20,000 protein-coding genes have been predicted.…”

Junk DNA promotes sex chromosome evolution

“…However, plant sex chromosomes have been found from moss to flowering plants, including familiar crop species, such as asparagus, hop, kiwi fruit, papaya and spinach (Matsunaga and Kawano, 2001). The ancient Y chromosome in the liverwort Marchantia polymorpha is small and largely heterochromatic (Yamato et al, 2007), whereas most Y chromosomes in flowering plants are the largest chromosomes in male genomes and many plant sex chromosomes are morphologically indistinguishable (Matsunaga, 2006;Jamilena et al, 2008). Why do sex chromosomes in flowering plants seem to retain their primitive characteristics similar to a pair of autosomes?…”