The Development of Male and Female Regenerants by In Vitro Androgenesis in Dioecious Plant Melandrium album

Vagera, J.; Paulı́ková, D.; Doležel, Jaroslav

doi:10.1006/anbo.1994.1056

Cited by 32 publications

(27 citation statements)

References 13 publications

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“…Table 2 lists the PAR genes, plus three genes that map close to PAR genes and were initial candidate PAR genes, but are now assigned to the fully sex-linked region of the X chromosome (see below). The cytological length of the X, relative to the set of autosomes in females, is known to be 14% of the genome (Vagera et al 1994). On this basis, our mapping results yield large estimated physical sizes per centimorgan for both the X and autosomes (4.65 and 3.4 Mb, respectively).…”

Section: Genetic Map Of S Latifoliamentioning

confidence: 60%

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Expansion of the Pseudo-autosomal Region and Ongoing Recombination Suppression in the Silene latifolia Sex Chromosomes

Bergero

Qiu

Forrest³

et al. 2013

Genetics

122

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There are two very interesting aspects to the evolution of sex chromosomes: what happens after recombination between these chromosome pairs stops and why suppressed recombination evolves. The former question has been intensively studied in a diversity of organisms, but the latter has been studied largely theoretically. To obtain empirical data, we used codominant genic markers in genetic mapping of the dioecious plant Silene latifolia, together with comparative mapping of S. latifolia sex-linked genes in S. vulgaris (a related hermaphrodite species without sex chromosomes). We mapped 29 S. latifolia fully sex-linked genes (including 21 newly discovered from transcriptome sequencing), plus 6 genes in a recombining pseudo-autosomal region (PAR) whose genetic map length is 25 cM in both male and female meiosis, suggesting that the PAR may contain many genes. Our comparative mapping shows that most fully sex-linked genes in S. latifolia are located on a single S. vulgaris linkage group and were probably inherited from a single autosome of an ancestor. However, unexpectedly, our maps suggest that the S. latifolia PAR region expanded through translocation events. Some genes in these regions still recombine in S. latifolia, but some genes from both addition events are now fully sex-linked. Recombination suppression is therefore still ongoing in S. latifolia, and multiple recombination suppression events have occurred in a timescale of few million years, much shorter than the timescale of formation of the most recent evolutionary strata of mammal and bird sex chromosomes. It is now understood that the large nonrecombining regions of sex chromosomes in mammals have expanded over evolutionary time, forming "evolutionary strata" with differing levels of sequence divergence between X-and Y-gene pairs, from ancient highly diverged regions, to regions in which the genes started diverging much more recently, which are located closest to the pseudo-autosomal region (PAR) on the X chromosome genetic and physical maps (Lahn and Page 1999;Skaletsky et al. 2003;Marais et al. 2008). The more recent evolutionary strata were formed by recombination suppression in regions formed by an addition of autosomal genetic material to the sex chromosomes (Waters et al. 2001), demonstrating that suppressed recombination spread from the ancestral sex chromosomal region into initially recombining regions. The PAR is shared across Eutherian mammals (despite differences in its boundary and the recent addition of a second PAR, PAR2, in humans), which is a physically small remnant of the added region, which is still autosomal in marsupials (Waters et al. 2001).The major current explanation for the evolution of expanded nonrecombining regions of sex chromosomes is

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Section: Genetic Map Of S Latifoliamentioning

confidence: 60%

“…To estimate the physical size (in megabases) of a centimorgan in S. latifolia, we used the estimated genome size of 2879 Mb (Vagera et al 1994) and assumed that 14% of the female genome is represented by the X chromosome of 350 Mb and that 86% is autosomal, representing 2076 Mb (Matsunaga et al 1994).…”

Section: Linkage Analysismentioning

confidence: 99%

Expansion of the Pseudo-autosomal Region and Ongoing Recombination Suppression in the Silene latifolia Sex Chromosomes

Bergero

Qiu

Forrest³

et al. 2013

Genetics

122

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“…The large inversion that has been detected in the Y of S. latifolia , covering a region of at least 23.9 cM in the X, does not seem to be the cause for the lack of recombination, but seems to have taken place after suppression of recombination (Zluvova et al, 2005). The lethality of YY seedlings and the non-viability of haploid Y plants indicates that the Y of this species has lost essential genes and is therefore degenerate (Ye et al, 1990;Veuskens et al, 1992), although Vagera et al (1994) reported the development of dihaploid fertile male plants (2n = 22 + YY) obtained by in vitro androgenesis.…”

Section: Sex Chromosome Structure In Different Plant Systems Covers Dmentioning

confidence: 99%

Plant sex chromosomes: molecular structure and function

Jamilena

Mariotti

Manzano³

2008

Cytogenet Genome Res

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Recent molecular and genomic studies carried out in a number of model dioecious plant species, including Asparagus officinalis, Carica papaya, Silene latifolia, Rumex acetosa and Marchantia polymorpha, have shed light on the molecular structure of both homomorphic and heteromorphic sex chromosomes, and also on the gene functions they have maintained since their evolution from a pair of autosomes. The molecular structure of sex chromosomes in species from different plant families represents the evolutionary pathway followed by sex chromosomes during their evolution. The degree of Y chromosome degeneration that accompanies the suppression of recombination between the Xs and Ys differs among species. The primitive Ys of A. officinalis and C. papaya have only diverged from their homomorphic Xs in a short male-specific and non-recombining region (MSY), while the heteromorphic Ys of S. latifolia, R. acetosa and M. polymorpha have diverged from their respective Xs. As in the Y chromosomes of mammals and Drosophila, the accumulation of repetitive DNA, including both transposable elements and satellite DNA, has played an important role in the divergence and size enlargement of plant Ys, and consequently in reducing gene density. Nevertheless, the degeneration process in plants does not appear to have reached the Y-linked genes. Although a low gene density has been found in the sequenced Y chromosome of M. polymorpha, most of its genes are essential and are expressed in the vegetative and reproductive organs in both male and females. Similarly, most of the Y-linked genes that have been isolated and characterized up to now in S. latifolia are housekeeping genes that have X-linked homologues, and are therefore expressed in both males and females. Only one of them seems to be degenerate with respect to its homologous region in the X. Sequence analysis of larger regions in the homomorphic X and Y chromosomes of papaya and asparagus, and also in the heteromorphic sex chromosomes of S. latifolia and R. acetosa, will reveal the degenerative changes that the Y-linked gene functions have experienced during sex chromosome evolution.

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“…However, the viability and fertility of occasional YY dihaploids (Vagera et al, 1994) argues against complete loss or inactivation of genes, presumably because increased gene dosage permits survival. Finally, female biased sex ratios in both S. latifolia (see Correns, 1928, but also Carroll, 1990) and Rumex acetosa (Smith, 1963;Wilby and Parker, 1988) as well as other dioecious species suggest that pollen grains with Y chromosomes grow more slowly than X-bearing pollen.…”

Section: Have Plant Y Chromosomes Degenerated?mentioning

confidence: 99%