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    cơ chế xác định giới tính ở thực vật ?

    Các cơ chế (di truyền, sinh lý, hoá sinh,...) trong hiện tượng sau đây: trên cùng một cây tại sao có thể ra hoa đực, hoa cái và thậm chí cả hoa lưỡng tính (ví dụ: bầu bí, đu đủ,...). Đây là chủ đề seminar sắp đến, các bạn cố gắng giúp mình nhé.
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    Lâu nay không lên đây vì quá bận và sẽ còn lâu mới lên tiếp vì ngoài lý do công tác còn lý do khác là ở đây bà con...sính ''công nghệ'' quá. Hì ! Cũng vì lâu lâu mới ló mặt ra nên nhân đây tôi muốn có vài lời cùng các bạn: Các bạn yêu thích sinh học nói chung, công nghệ sinh học nói riêng và quyết tâm tiếp cận bằng được lĩnh vực công nghệ ? Đó là điều đáng quý nhưng đáng quý hơn là các bạn ''học sinh cấp 4'' hãy tự rèn luyện mình có một background vững chắc về ''sinh học'' rồi mới nói đến ''công nghệ''. Không phải tôi chê bai gì nhưng các bạn có khi nào đặt câu hỏi rằng khả năng của phòng thí nghiệm hoặc trung tâm nghiên cứu ''chất lượng cao'' tại trường hoặc viện nghiên cứu mà các bạn đang học tập nghiên cứu cho phép các bạn làm được những gì về ''công nghệ''. Sinh học là khoa học thực nghiệm, công nghệ sinh học đòi hỏi ở mức độ nào các bạn đã rõ, không biết các bạn có trăn trở không. Trong khi lý thuyết của sinh học cơ bản (mặc dù trong khung chương trình chiếm một khối lượng không nhỏ) nhưng bản thân tôi có cảm nhận sinh viên công nghệ sinh học quan tâm không nhiều đến điều đó và đem ''công nghệ'' để doạ dân sinh học cơ cản và cũng chính vì điều đó nên quy trình thì vanh vách nhưng giải thích bằng các nguyên lý cơ bản thì không thông nên có không ít cuộc khẩu chiến bất phân thắng bại giữa các ''phái'' với nhau và không hiếm khi rất...tào lao mà nguyên nhân chính như tôi đã nói cộng với sự máy móc, phụ thuộc trong học tập. Các bạn nghĩ sao ? Tôi nói nhăng cuội các bạn nghe không lọt và cho là ấu trĩ thì xin bỏ qua cho.
    Quay lại chủ đề, tôi thiết nghĩ đây không đơn thuần là một câu hỏi theo kiễu "1 vạn câu hỏi vì sao-phần thực vật" mà chuẩn bị tài liệu cho seminar. Bài báo sau đây hy vọng bổ sung thêm nguồn tài liệu tham khảo cho bạn vậy, lấy làm tiếc vì không giúp được gì nhiều.
    Oryza sativa L.
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    Research Article
    Plant *** determination and *** chromosomes
    D Charlesworth

    Institute of Cell, Animal and Population Biology, University of Edinburgh, Scotland, UK

    Correspondence to: D Charlesworth, Institute of Cell, Animal and Population Biology, University of Edinburgh, Ashworth Laboratory King's Buildings, West Mains Road., Edinburgh EH9 3JT, UK E-mail: Deborah.Charlesworth@ed.ac.uk


    Abstract

    *** determination systems in plants have evolved many times from hermaphro***ic ancestors (including monoecious plants with separate male and female flowers on the same individual), and *** chromosome systems have arisen several times in flowering plant evolution. Consistent with theoretical models for the evolutionary transition from hermaphro***ism to monoecy, multiple *** determining genes are involved, including male-sterility and female-sterility factors. The requirement that recombination should be rare between these different loci is probably the chief reason for the genetic degeneration of Y chromosomes. Theories for Y chromosome degeneration are reviewed in the light of recent results from genes on plant *** chromosomes.
    Here***y (2002) 88, 94-101. DOI: 10.1038/sj/hdy/6800016


    Keywords

    dioecy; *** linkage; Y chromosomes; Silene latifolia
    Oryza sativa L.
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    Introduction: why are plant *** chromosomes of particular interest?
    The genetic control of *** determination is becoming well understood in several animal systems, particularly Drosophila melanogaster, Caenorhab***is elegans and mammals. In plants, understanding the *** determination system is closely connected with understanding how separate ***es evolved, and current theoretical ideas about this also illuminate the evolution of *** chromosomes. Angiosperms are also of particular interest for empirical studies of *** chromosome evolution, because they probably evolved separate ***es repeatedly and relatively recently. Other plants, particularly Bryophytes (see Okada et al, 2001), also have interesting independently evolved *** chromosomes.
    In many ***ually reproducing plant species (and some animals) all individuals are essentially alike in their gender con***ion. Many such '***ually monomorphic' species are hermaphro***ic. The term 'co***ual' (Lloyd, 1984) is used when individual plants have both *** functions, whether present within each flower (hermaphro***e), or in separate male and female flowers (monoecious). A minority of plant species are '***ually polymorphic', including dioecious species, with separate males and females (Table 1). Many dioecious species with hermaphro***e relatives have evident rudiments of opposite *** structures in flowers of plants of each ***, suggesting recent evolution of uni***ual flowers (Darwin, 1877). The low frequency and scattered taxonomic distribution of dioecy and *** chromosomes suggest that co***uality is the ancestral angiosperm state (Figure 1) (Charlesworth, 1985; Renner and Ricklefs, 1995. *** chromosomes therefore probably evolved repeatedly and quite recently.
    In some plant taxa, it is possible to estimate how many times dioecy has evolved, and how long ago. Dioecy probably evolved twice in the Hawaiian genus Schiedia (Weller et al, 1995). The best studied case at present is the large genus Silene, in the same family (Caryophyllaceae). Many Silene species are gynodioecious and others are hermaphro***ic. A phylogeny constructed from internal transcribed spacer (ITS) sequences of nuclear ribosomal RNA genes of Silene species suggests two origins of dioecy in this genus also (Desfeux et al, 1996). Using a molecular clock, these data suggest an age of probably less than 20 million years for the heteromorphic *** chromosomes of the close relatives Silene latifolia and S. dioica. Comparative analysis suggests that dioecious lineages often have short evolutionary lives (Heilbuth, 2000). Thus separate ***es may have evolved more than 100 times in the flowering plants, given that 160 families have dioecious members.


    The genetics of *** determination in plants, and plant *** chromosomes
    *** inheritance and *** chromosomes in plants are strikingly similar to those in animals. The majority of plants studied have heterozygous males, or, when the chromosomes are visibly different (perhaps half of plants that have separate ***es, see Westergaard, 1958), male heterogamety (XY males, XX females). In many dioecious plants, males are 'inconstant', ie produce occasional fruits (Lloyd, 1975b; Lloyd and Bawa, 1984). Self fertilisation of such plants in several species has provided genetic evidence that males are heterozygous. As will be explained below, the male genotype must include a dominant suppressor of femaleness (SuF). On selfing, a 3:1 ratio of males to females is expected if SuF/SuF is viable, or 2:1 if the Y chromosome is genetically degenerated and this genotype is inviable. Each of these ratios has been found (Westergaard, 1958; Testolin et al, 1995). Some plant Y chromosomes are therefore at least partially genetically degenerate.
    Several kinds of evidence suggest the involvement of two loci in *** determination. Some data come from crosses between dioecious plants and related monoecious or hermaphro***e species (Westergaard, 1958). In Silene dioica and latifolia, there is direct evidence from cytological studies of Y chromosome deletions. There are three functionally different Y chromosome regions (see Figure 2), the SuF region, and two regions containing factors controlling early and late anther development (Westergaard, 1958; Grant et al, 1994; Farbos et al, 1999; Lardon et al, 1999). In these species, X and Y pairing in male meiosis is confined to the tips (Westergaard, 1958; Parker, 1990; Lardon et al, 1999), and recombination is absent for most of the Y chromosome.


    Why are *** determining loci linked?
    The evidence for multiple *** determining genes suggests that non-recombination between the X and Y chromosomes evolved to prevent recombination between these loci, since recombination would produce maladaptive phenotypes, particularly neuter individuals (Figure 3b; Lewis, 1942). It is widely assumed that the linkage evolved after establishment of unlinked male and female sterility genes, ie that these loci have been brought into proximity by inversions and/or translocations (Lewis, 1942). A genetic model of the evolutionary transition from co***uality to dioecy suggests, however, that linkage may often be necessary from the outset (Charlesworth and Charlesworth, 1978a). Starting from co***uality, the evolution of two ***es must generally require at least two genetic changes, one (male-sterility) creating females and the other (female-sterility) producing males (Figure 3a, Charlesworth and Charlesworth, 1978a). The process may sometimes have been more gradual, with partial sterility mutations (Lloyd, 1975a; Charlesworth and Charlesworth, 1978b). Plants and animals with a single ***-determining determining locus are probably often derived from systems with male-determining chromosomes (Bull, 1983; Traut and Willhoeft, 1990), as separate ***es cannot evolve in a single mutational step from an initial hermaphro***ic or monoecious state (except under the extremely improbable assumption that a mutation arises in a co*** whose heterozygotes have one ***, and homozygotes the other ***, eg Aa male and aa female).
    The existence of inconstant males (but not females) in many dioecious species (eg Galli et al, 1993; Testolin et al, 1995) supports this scenario of a major recessive mutation leading to females, followed by selection for modifiers making the co***es more male, as in Figure 3. Once females have been established in a population, the availability of their ovules favours higher investment in pollen output, so there is a selective pressure on the co***ual morph to evolve a greater male bias (Charlesworth and Charlesworth, 1978a). Modifier genes that make co***es more male-like should, however, also reduce female fertility (Figure 3b), unless they are ***-limited in their expression. This counter-selects against such factors, so partial female-sterility factors are generally most likely to spread in a gynodioecious population if they are linked to the male-sterility gene (Charlesworth and Charlesworth, 1978a; Nordborg, 1994). The spread of alleles beneficial in one *** but not in the other (antagonistic pleiotropy) similarly depends on linkage (Charlesworth and Charlesworth, 1980; Rice, 1997). There will also be selection for tighter linkage between the male-sterility locus and modifier loci (Charlesworth and Charlesworth, 1978a). Thus a cluster of linked loci in a particular chromosomal region, with suppressed recombination, and containing the *** determining loci and loci affecting male functions, will probably evolve.
    ***-linked markers should permit tests of whether the region involved in *** determination in dioecious species is also a single chromosomal location in co***ual relatives, or whether the *** determining genes were initially on different chromosomes, and only later came into proximity. All diploid Silene species have the same chromosome number (n = 12), suggesting that translocations of whole chromosomes have not contributed to the enlarged X and Y, though movements of lesser genome regions are possible.
    Oryza sativa L.
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    Evolution of *** chromosomes
    The theory outlined here explains the evolution of a rarely recombining chromosome region containing the *** determining genes, an incipient *** chromosome system. The female haplotype carries a recessive male-sterility allele, while the dominant male-determining chromosome would carry female-sterility alleles (and the wild-type allele at the male-sterility locus; Figure 3). *** chromosome evolution is intimately connected with Y chromosome degeneration. Most current understanding of how the distinctive properties of Y chromosomes evolved comes from theoretical work on the evolution of genomic regions with low recombination. Such regions are subject to several processes, given a sufficiently high rate of deleterious mutations (Charlesworth and Charlesworth, 2000).
    One process is mutation accumulation by Muller's ratchet (Muller, 1964; Haigh, 1978), leading to an increasing number of mutations, which become fixed as the process continues (Charlesworth and Charlesworth, 2000). Drosophila population sizes may be too high for this stochastic process to explain neo-Y chromosome degeneration (Charlesworth, 1996), and most plants have more chromosomes, and therefore fewer genes on a proto-Y chromosome than on a Drosophila chromosome, so in plants the mutation rate to deleterious alleles may be too low. Another possibility is hitch-hiking: favourable mutant alleles arise on the proto-Y and rise in frequency to fixation, concomitantly fixing deleterious alleles on the same chromosome (Rice, 1987). A third suggestion relies on accelerated fixation of deleterious mutations on a non-recombining chromosome (because selection against deleterious alleles leads to reduced effective population size; Charlesworth, 1996). All these processes involve reduced effective population size, and should therefore lead to low Y-chromosomal genetic diversity (Charlesworth and Charlesworth, 2000).
    The relatively recent origin of plant Y chromosomes, compared with those of most animals, make dioecious plants particularly suitable for studying the early stages of the degeneration process. The availability of closely related species, probably with chromosomes having gene content similar to that of the ancestral *** chromosomes, should show how genes have evolved since becoming ***-linked, offering a system to test between the different hypotheses. Most animal Y chromosomes degenerated long ago, making the processes responsible inaccessible to study, except in species with translocations between the *** chromosomes and autosomes. In species with X-autosome translocations, the neo-Y is not physically attached to the pre-existing Y chromosome, so its degeneration may result largely from the same kind of processes as in the initial evolution of Y chromosomes, but this is not certain. In plants, however, a there is de novo evolution of Y chromosomes. If plant, as well as animal Y chromosomes have degenerated, this would be evidence that the process is very general.


    Have plant Y chromosomes degenerated?
    Before using plants to study genetic degeneration, we need to know if their Y chromosomes are indeed degenerating. The evidence from the best studied species suggests some degeneration. Rumex acetosa Y chromosomes are heterochromatic (Clark et al, 1993; Réjon et al, 1994; Lengerova and Vyskot, 2001). On the other hand, DNAse digestion experiments suggest transcriptional activity of this Y chromosome (Clark et al, 1993), though this could be due to the presence of dispersed repetitive sequences that are transcribed, such as transposable elements. The high frequency of chromosome rearrangements in this species (Wilby and Parker, 1988), and variability of its Y chromosome morphology (Wilby and Parker, 1986), are consistent with such a possibility, but it has not yet been tested. Some X-linked mutations are not masked by the Rumex Y chromosome (Smith, 1963), ie males are hemizygous for this region, like classical ***-linked loci in many animals.
    In Silence latifolia, the two X chromosomes differ in the time of replication, as might be expected if one of them is transcriptionally silenced, and they appear to be differentially methylated, possibly indicating that dosage compensation is occurring by X inactivation in females (Vyskot et al, 1999). Gene expression from Y chromosomes is suggested by estimates of methylation levels (Vyskot et al, 1993), which may imply that many Y-linked genes have not degenerated greatly, if at all (though again the possibility of transposons cannot be excluded). The large size of the Y chromosomes in S. latifolia and dioica (Costich et al, 1991) and many other dioecious plants (Parker, 1990), also suggests that plant Y chromosomes have accumulated repetitive sequences, which have been found on Y chromosomes of S. latifolia (Donnison et al, 1996; Zhang et al, 1998; Lardon et al, 1999) and R. acetosa (Réjon et al, 1994). So far, however, abundances are mostly similar on the X and autosomes (Clark et al, 1993; Donnison et al, 1996; Scutt and Gilmartin, 1997). Thus the evidence is inconclusive, and the nature and range of kinds of such sequences is currently almost totally unknown.
    In most studied species with heteromorphic *** chromosomes YY genotypes are inviable (see above), as are androgenic haploid plants of S. latifolia, with only a Y chromosome (Ye et al, 1990), while X-haploid plants are viable. 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 *** 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. This suggests that plant Y chromosomes have reduced gene functions (Smith, 1963; Lloyd, 1974), though segregation distortion has not been ruled out (Taylor, 1994).


    Molecular genetics of plant Y chromosomes
    Our understanding of the evolution of plant *** chromosomes and *** determination should be advanced by the use of molecular markers, so several groups are searching for these. The region containing the *** determining loci must initially have been fully homologous between the two alternative chromosomes. One goal of studies of plant *** chromosomes is therefore to test for homology. Both X- and Y-linked markers are now being discovered in plants with and without heteromorphic *** chromosomes (eg Testolin et al, 1995; Harvey et al, 1997; Polley et al, 1997; Zhang et al, 1998; Mandolino et al, 1999). Most markers are, however, anonymous, and cannot tell us which X-linked loci have homologues on the Y chromosomes and which do not.
    Isolation of male-specific cDNAs from developing flower buds or reproductive organs has not yet led to discovery of *** determining genes (Matsunaga et al, 1996; Barbacar et al, 1997), probably because ***-determination happens very early in flower development (Grant et al, 1994), so the genes identified are controlled in response to ***, rather than the controlling loci. Genes known to be important in floral development, including the homoeotic MADS-box genes also appear not to have direct roles in *** determination (Hardenack et al, 1994; Ainsworth et al, 1995). This is not surprising, as these mutations change floral organ identities, whereas in uni***ual flowers apparently normal reproductive organs merely stop developing, as predicted by the genetic model above.
    Both X- and Y-linked expressed loci have now been identified in S. latifolia. One approach is to directly search for ***-linked genes (Guttman and Charlesworth, 1998). This has identified the X-linked MROS-X (male reproductive organ specific) gene and its Y-linked homologue, MROS3-Y, which appears to have degenerated. MROS3-Y contains only a short region of homology to the MROS3-X sequence. This region has been evolving in a neutral manner, with a ratio of silent to replacement substitutions, Ka/Ks, of 0.974, close to unity, as expected for a sequence evolving without selective constraints (Nei, 1987).
    Another approach has isolated Y-linked genes present in mRNA populations from S. latifolia male flower buds. Two gene pairs have so far been characterised. Based on sequence similarity to other genes, the SlX/Y1 pair appears to encode a WD-repeats protein (Delichère et al, 1999) and SlX/Y4 a fructose-2, 6-bisphosphatase (Atanassov et al, 2001), and neither is likely to be involved in *** determination. The recombination fraction between SlX1 and SlX4 (Figure 2) suggests that they are far apart on the X, and potentially also on the Y chromosome, unless this has been rearranged. Comparisons of the coding sequences of these X-and Y-linked genes, including outgroup sequences in non-dioecious Silene species, yield Ka/Ks < 0.2 (Atanassov et al, 2001). The protein sequences of both the Y- and X-linked genes have therefore been maintained for at least most of their evolutionary history since the X and Y ceased recombining, ie these Y-linked genes have not degenerated. Silent site divergence between SlX4 and SlY4 is similar to that between the X- and Y-chromosome copies of MROS3, and both suggest an age estimate of the *** chromosome system similar to that based on the ITS sequences (Desfeux et al, 1996). The SlX1 and SlY1 genes are considerably less diverged. It will be very interesting to study more X/Y-linked gene pairs to test whether the Y chromosome seems to have been built up in a stepwise manner, as seems to be true of the human Y (Lahn and Page, 1999; Waters et al, 2001).
    If the Y chromosomes of dioecious Silenes are actively degenerating, Y-linked genes are predicted to have reduced diversity, and we can use patterns of diversity at non-degenerated loci (such as those just described) to test for selective sweeps. In samples from several S. latifolia and S. dioica populations, SlY1 diversity is indeed lower than that of SlX1, after correcting for the smaller number of Y than X chromosomes in populations (Caballero, 1995). Analysis using outgroup sequences shows that this is not due to a higher mutation rate of the Y-linked genes (Filatov et al, 2001). Tests such as Tajima's test do not suggest selective sweeps (Filatov et al, 2000, 2001). However, these tests are affected by subdivision (Schierup et al, 2000), for which there is evidence in these species (McCauley, 1994; Giles et al, 1998; Ingvarsson and Giles, 1999; Richards et al, 1999), which probably affects the Y chromosome more than other chromosomes, because of its smaller effective size (Wang, 1999). Larger samples from within single populations are therefore needed. It is also difficult to test for diversity differences in the presence of introgression between the two Silene species. Y-chromosome variants differ between the two species, whereas some X-linked variants are shared between them (Filatov et al, 2001). A final difficulty is that autosomal loci are also needed in order to know whether Y-chromosomal variation is reduced, or X-linked diversity elevated. The one autosomal locus so far studied has low diversity, but this does not point to increased X-linked diversity, because this gene appears to have experienced a selective sweep (Filatov et al, 2001), so more autosomal genes are needed. Comparisons are also needed with species whose Y-chromosome is fully degenerated. If low diversity is also found in these, it would point to causes such as mutation rate differences, rather than effects of the selective processes during genetic degeneration.
    Oryza sativa L.
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    Discussion
    With the availability of molecular techniques, we may now hope to understand more about how *** chromosomes evolve. Mapping data, even with anonymous markers, should give estimates of the fraction of X-linked loci that are located in the pairing and differential regions. In the absence of useful chromosome banding patterns that identify regions, single-copy anonymous markers can also be useful for mapping in combination with Y-chromosome deletions (Donnison et al, 1996). Deletion mapping of the Y chromosome does not precisely pinpoint the ***-determination loci, but it should be possible to define the regions in which these genes are located Figure 2 summarises current information about the S. latifolia Y.
    Once genes have been identified and sequenced, we will be able to estimate how long *** chromosome evolution takes. This should help us evaluate the plausibility of the proposed mechanisms for the process. The results of such studies may, in turn, contribute to our knowledge of mutation rates to deleterious mutations, and to a growing body of understanding of evolution in the absence of recombination. Studies of the early stages of *** chromosome degeneration offer the potential to have a eukaryote version of the interesting results on genome degradation in a***ual prokaryotes (Wernergreen and Moran, 1999). If, as appears likely, plant *** chromosomes are found to be only partially genetically degenerated, they may offer opportunities to help understand the relationship between the evolution of genetic degeneration and of dosage compensation.


    Acknowledgements
    I think V Laporte and DA Filatov for many discussions during our work on sequences of S. latiofolia ***-linked genes. These genes were initially characterised in the lab of I Negrutiu and F Monéger, to whom thanks are due for providing sequence information without which our evolutionary studies could not have been done. DA Filatov was supported by a grant to D Charlesworth from the Leverhulme Trust, V Laporte by a grant from the BBSRC, and D Charlesworth by a NERC Senior Research fellowship.


    References

    Ainsworth CC, Crossley S, Buchanan-Wollaston V, Thangavelu M, Parker J. (1995). Male and female flowers of the dioecious plant sorrel show different patterns of MADS box gene expression. Pl Cell, 7: 1583-1598.
    Atanassov I, Delichère C, Filatov DA, Charlesworth D, Negrutiu I, Monéger F. (2001). A putative monofunctional fructose-2,6-bisphosphatase gene has functional copies located on the X and Y *** chromosomes in white campion (Silene latifolia). Mol Biol Evol, 18: 2162-2168. MEDLINE
    Barbacar N, Hinnisdaels S, Farbos I, Moneger F, Lardon A, Delichère C et al. (1997). Isolation of early genes expressed in reproductive organs of the dioecious white campion (Silene latifolia) by subtraction cloning using an a***ual mutant. Plant J, 12: 805-817. MEDLINE
    Bull JJ. (1983). Evolution of *** Determining Mechanisms. Benjamin/Cummings: Menlo Park, CA.
    Caballero A. (1995). On the effective size of populations with separate ***es, with particular reference to ***-linked genes. Genetics, 139: 1007-1011. MEDLINE
    Carroll SB, Mulcahy DL. (1990). Progeny *** ratios in dioecious Silene latifolia. Am J Bot, 80: 551-556.
    Charlesworth D. (1984). Androdioecy and the evolution of dioecy. Biol J Linn Soc, 23: 333-348.
    Charlesworth D. (1985). Distribution of dioecy and self-incompatibility in angiosperms. In: Greenwood PJ, Slatkin M (eds), Evolution - Essays in Honour of John Maynard Smith. Cambridge University Press: Cambridge, pp 237-268..
    Charlesworth B. (1996). The evolution of chromosomal *** determination and dosage compensation. Curr Biol, 6: 149-162. MEDLINE
    Charlesworth B, Charlesworth D. (1978a). A model for the evolution of dioecy and gynodioecy. Am Nat, 112: 975-997.
    Charlesworth D, Charlesworth B. (1978b). Population genetics of partial male-sterility and the evolution of monoecy and dioecy. Here***y, 41: 137-153.
    Charlesworth D, Charlesworth B. (1980). *** differences in fitness and selection for centric fusions between ***-chromosomes and autosomes. Gent Res, 35: 205-214.
    Charlesworth B, Charlesworth D. (2000). The degeneration of Y chromosomes. Phil Trans Roy Soc Lond B, 355: 1563-1572.
    Charlesworth D, Guttman DS. (1999). The evolution of dioecy and plant *** chromosome systems. In: Ainsworth CC (ed), *** Determination in Plants. BIOS, Oxford, pp 25-49..
    Clark MS, Parker JS, Ainsworth CC. (1993). Repeated DNA and heterochromatin structure in Rumex acetosa. Here***y, 70: 527-536.
    Correns C. (1928). Bestimmung, Vererbung and Verteilung des Geschlechtes bei den höheren Pflanzen. Handb. Vererbungswissenschaft, 2: 1-138.
    Costich DE, Meagher TR, Yurkow EJ. (1991). A rapid means of *** identification in Silene latifolia by use of flow cytometry. Plant Mol Biol Reporter, 9: 359-370.
    Darwin CR. (1877). The Different Forms of Flowers on Plants of the Same Species. John Murray: London.
    Delichère C, Veuskens J, Hernould M, Barbacar N, Mouras A, Negrutiu I et al. (1999). SlY1, the first active gene cloned from a plant Y chromosome, encodes a WD-repeat protein. EMBO J, 18: 4169-4179. Article MEDLINE
    Desfeux C, Maurice S, Henry JP, Lejeune B, Gouyon PH. (1996). Evolution of reproductive systems in the genus Silene. Proc R Soc B, 263: 409-414.
    Donnison IS, Siroky J, Vyskot B, Saedler H, Grant SR. (1996). Isolation of Y chromosome-specific sequences from Silene latifolia and mapping of male *** determining genes using representational difference analysis. Genetics, 144: 1893-1901. MEDLINE
    Farbos I, Veuskens J, Vyskot B, Oliveira M, Hinnisdaels S, Aghmir A et al. (1999). ***ual dimorphism in white campion: complex deletion on the Y chromosome results in a floral a***ual type. Genetics, 151: 1187-1196. MEDLINE
    Filatov DA, Laporte V, Vitte C, Charlesworth D. (2001). DNA diversity in *** linked and autosomal genes of the plant species Silene latifolia and S. dioica. Molec Biol Evol, 18: 1442-1454. MEDLINE
    Filatov DA, Monéger F, Negrutiu I, Charlesworth D. (2000). Evolution of a plant Y-chromosome: variability in a Y-linked gene of Silene latifolia. Nature, 404: 388-390. Article MEDLINE
    Galli MG, Bracale M, Falavigna A, Raffaldi F, Savini C, Vigo A. (1993). Different kinds of male flowers in the dioecious plant Asparagus officinalis L. *** Plant Reprod, 6: 16-21.
    Giles BE, Lundqvist E, Goudet J. (1998). Restricted gene flow and subpopulation differentiation in Silene dioica. Here***y, 80: 715-723.
    Grant S, Houben A, Vyskot B, Siroky J, Pan WH, Macas J et al. (1994). Genetics of *** determination in flowering plants. Devel Genet, 15: 214-230.
    Guttman DS, Charlesworth D. (1998). An X-linked gene has a degenerate Y-linked homologue in the dioecious plant Silene latifolia. Nature, 393: 263-266. Article MEDLINE
    Haigh J. (1978). The accumulation of deleterious genes in a population. Theor Pop Biol, 14: 251-267.
    Hardenack S, Saedler H, Ye D, Grant S. (1994). Comparison of MADS box gene expression in developing male and female flowers of the dioecious plants white campion. Plant Cell, 6: 1775-1787. MEDLINE
    Harvey CF, Gill CP, Fraser LG, McNeilage MA. (1997). *** determination in Actinidia. 1. ***-linked markers and progeny *** ratio in diploid A. chinensis. *** Plant Repro, 10: 149-154.
    Heilbuth JC. (2000). Lower species richness in dioecious clades. Am Nat, 156: 221-241.
    Ingvarsson PK, Giles BE. (1999). Kin-structured colonization and small-scale genetic differentiation in Silene dioica. Evolution, 53: 605-611.
    Lahn BT, Page DC. (1999). Four evolutionary strata on the human X chromosome. Science, 286: 964-967. Article MEDLINE
    Lardon A, Georgiev S, Aghmir A, Merrer GL, Negrutiu I. (1999). ***ual dimorphism in white campion: complex control of carpel number is revealed by Y chromosome deletions. Genetics, 151: 1173-1185. MEDLINE
    Lengerova M, Vyskot B. (2001). *** chromatin and nucleolar analyses in Rumex acetosa L. Protoplasma, 217: 147-153. MEDLINE
    Lewis D. (1942). The evolution of *** in flowering plants. Biolog Rev, 17: 46-67.
    Lloyd DG. (1974). Female-predominant *** ratios in angiosperms. Here***y, 32: 35-44.
    Lloyd DG. (1975a). Breeding systems in Cotula. III. Dioecious populations. New Phytol, 74: 109-123.
    Lloyd DG. (1975b). The transmission of genes via pollen and ovules in gynodioecy angiosperms. Theoret Pop Biol, 9: 299-316.
    Lloyd DG. (1984). Gender allocations in outcrossing co***ual plants. In: Dirzo R, Sarukhan J (eds), Perspectives on Plant Population Ecology. Sinauer: Sunderland, Mass, pp 277-300..
    Lloyd DG, Bawa KS. (1984). Modification of the gender of seed plants in varying con***ions. Evol Biol, 17: 255-338.
    Mandolino G, Carboni A, Forapani S, Faeti V, Ranalli P. (1999). Identification of DNA markers linked to the male *** in dioecious hemp (Cannabis sativa L.). Theoret Appl Genet, 98: 86-92.
    Matsunaga S, Kawano S, Takano H, Uchida H, Sakai A, Kuroiwa T. (1996). Isolation and developmental expression of male reproductive organ-specific genes in a dioecious campion, Melandrium album (Silene latifolia). Plant J, 10: 679-689. Article MEDLINE
    McCauley DE. (1994). Contrasting the distribution of chloroplast DNA and allozyme polymorphism among local populations of Silene alba: implications for studies of gene flow in plants. Proc Natl Acad Sci USA, 91: 8127-8131. MEDLINE
    Muller HJ. (1964). The relation of recombination to mutational advance. Mut Res, 1: 2-9.
    Nei M. (1987). Molecular Evolutionary Genetics. Columbia University Press: New York.
    Nordborg M. (1994). A model of genetic modification in gynodioecious plants. Proc Roy Soc Lond B, 257: 149-154.
    Okada S, Sone T, Fujisawa M, Nakayama S, Takenaka M, Ishizaki K et al. (2001). The Y chromosome in the liverwort Marchantia polymorpha has accumulated unique repeat sequences harboring a male-specific gene. Proc Natl Acad Sci USA, 98: 9454-9459. MEDLINE
    Parker JS. (1990). ***-chromosome and *** differentiation in flowering plants. Chromosomes Today, 10: 187-198.
    Polley A, Seigner E, Ganal MW. (1997). Identification of *** in hop (Humulus lupulus) using molecular markers. GENOME, 40: 357-361.
    Réjon CR, Jamilena M, Ramos MG, Parker JS, Rejon MR. (1994). Cytogenetic and molecular analysis of the multiple ***-chromosome system of Rumex acetosa. Here***y, 72: 209-215.
    Renner SS, Ricklefs RE. (1995). Dioecy and its correlates in the flowering plants. Am J Bot, 82: 596-606.
    Rice WR. (1987). Genetic hitch-hiking and the evolution of reduced genetic activity of the Y *** chromosome. Genetics, 116: 161-167. MEDLINE
    Rice WR. (1997). The accumulation of ***ually antagonistic genes as a selective agent promoting the evolution of reduced recombination between primitive ***-chromosomes. Evolution, 41: 911-914.
    Richards CM, Church S, McCauley DE. (1999). The influence of population size and isolation on gene flow by pollen in Silene alba. Evolution, 53: 63-73.
    Schierup MH, Vekemans X, Charlesworth D. (2000). The effect of hitchhiking on genes linked to a balanced polymorphism in a subdivided population. Genet Res, 76: 63-73. Article MEDLINE
    Scutt CP, Gilmartin PM. (1997). High-stringency subtraction for the identification of differentially regulated cDNA clones. Biotechniques, 23: 468. MEDLINE
    Smith BW. (1963). The mechanism of *** determination in Rumex hastatulus. Genetics, 48: 1265-1288.
    Soltis PS, Soltis DE, Wolf PG, Nickrent DL, Chaw S-M, Chapman RL. (1999). The phylogeny of land plants inferred from 18S rRNA sequences: pushing the limits of rDNA signal? Mol Biol Evol, 16: 1774-1784. MEDLINE
    Taylor DR. (1994). The genetic-basis of ***-ratio in Silene alba (=S. latifolia). Genetics, 136: 641-651. MEDLINE
    Testolin R, Cipriani G, Costa G. (1995). *** segregation ratio and gender expression in the genus Actinidia. *** Plant Repr, 8: 129-132.
    Traut W, Willhoeft U. (1990). A jumping *** determining factor in the fly Megaselia scalaris. Chromosoma (Berl.), 99: 407-412.
    Vagera J, Paulikova D, Dolezel J. (1994). The development of male and female regenerants by in-vitro androgenesis in dioecious plant Melandrium album. Ann Bot, 73: 455-459.
    Vyskot B, Araya A, Veuskens J, Negrutiu I, Mouras A. (1993). DNA methylation of *** chromosomes in a dioecious plant, Melandrium album. Mol Gen Genet, 239: 219-224. MEDLINE
    Vyskot B, Siroky J, Hladilova R, Belyaev ND, Turner BM. (1999). Euchromatic domains in plant chromosomes as revealed by H4 histone acetylation and early DNA replication. Genome, 42: 343-350. Article MEDLINE
    Wang J. (1999). Effective size and F-statistics of subdivided populations for ***-linked loc. Theoret Pop Biol, 55: 176-188.
    Waters PD, Duffy B, Frost CJ, Delbridge ML, Graves JAM. (2001). The human Y chromosome derives largely from a single autosomal region added to the *** chromosomes 80-130 million years ago. Cytogenet Cell Genet, 92: 74-79. MEDLINE
    Weller SG, Wagner WL, Sakai AK. (1995). A phylogenetic analysis of Schiedia and Alsinidendron (Caryophyllaceae: Alsinoideae): implications for the evolution of breeding systems. Syst Bot, 20: 315-337.
    Wernergreen JJ, Moran NA. (1999). Evidence for genetic drift in endosymbionts (Buchnera): analyses of protein-coding genes. Mol Biol Evol, 16: 83-97. MEDLINE
    Westergaard M. (1958). The mechanism of *** determination in dioecious plants. Adv Genet, 9: 217-281.
    Wilby AS, Parker JS. (1986). Continuous variation in Y-chromosome structure of Rumex acetosa. Here***y, 57: 247-254.
    Wilby AS, Parker JS. (1988). Mendelian and non-Mendelian inheritance of newly-arisen chromosome rearrangements. Here***y, 60: 263-268. MEDLINE
    Ye D, Installé P, Ciuperescu C, Veuskens J, Wu Y, Salesses G et al. (1990). *** determination in the dioecious Melandrium. I. First lessons from androgenic haploids. *** Plant Repr, 3: 179-186.
    Zhang YH, DiStilio VS, Rehman F, Avery A, Mulcahy DL, Kesseli R. (1998). Y chromosome specific markers and the evolution of dioecy in the genus Silene. Génome, 41: 141-147.

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