An Electrophoretic Investigation of Intragametophytic Selfing in Equisetum Arvense

Soltis, Douglas E.; Soltis, Pamela S.; Noyes, Richard D.

doi:10.1002/j.1537-2197.1988.tb13434.x

Cited by 23 publications

(5 citation statements)

References 45 publications

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“…Variety protobillotii has higher levels of genetic diversity than var. obovatum, although they are also relatively low (A ϭ 1.3, p ϭ 28.6, H o ϭ 0.014, and H e ϭ 0.014) and are similar to the ones obtained for Botrychium virginianum (L.) Sw. (Soltis and Soltis, 1986), Blechnum spicant (L.) Roth , Equisetum arvense L. (Soltis, Soltis, and Noyes, 1988), and Hemionitis palmata L. (Ranker, 1992).…”

Section: Discussionmentioning

confidence: 99%

Isozyme variation and genetic relationships among taxa in the Asplenium obovatum group (Aspleniaceae, Pteridophyta)

Herrero

Pajarón

Prada

2001

American J of Botany

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The Asplenium obovatum group consists of diploid and tetraploid taxa; the origin of the tetraploid A. obovatum subsp. lanceolatum was previously considered to have occurred via autopolyploidy, involving one of the diploids of the group, either A. obovatum subsp. obovatum var. obovatum or var. protobillotii. To test this hypothesis, electrophoretic analyses of eight enzyme systems encoded by fourteen putative loci and cytological studies of the artificial hybrid between both diploid varieties were conducted. Alleles of the loci Lap-1, Mdh-2, Mdh-3, Pgm-1, Pgm-1', and 6Pgd-1 emerged as genetic markers for the diploids and were present in an additive pattern in most of the analyzed individuals of the tetraploid. Cytological results indicated a high degree of genomic homology between the diploids. These results indicated that the tetraploid behaves as a segmental allopolyploid. Our results showed that both diploids were involved in the origin of the tetraploid. We propose the new combination Asplenium obovatum subsp. protobillotii for one of the diploids.

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Section: Discussionmentioning

confidence: 99%

Isozyme variation and genetic relationships among taxa in the Asplenium obovatum group (Aspleniaceae, Pteridophyta)

Herrero

Pajarón

Prada

2001

American J of Botany

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“…Electrophoretic analysis of naturally occurring fern populations also revealed diploid gene expression of enzyme-encoding loci (Haufler and Soltis 1984;Gastony and Gottlieb 1985). These findings discrediting the paleopolyploid hypothesis in homosporous ferns were subsequently generalized for the homosporous vascular plants as a whole (Haufler and Soltis 1986;Soltis 1987, 1988a,b;Soltis et al 1988). Thus isozyme studies showed that despite their high chromosome numbers, homosporous ferns with the lowest chromosome number in their genus (n ¼ 27-52) have gene expression patterns typical of diploid angiosperms.…”

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confidence: 92%

Genetic Map-Based Analysis of Genome Structure in the Homosporous Fern Ceratopteris richardii

Nakazato¹,

Jung

Housworth

et al. 2006

Genetics

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Homosporous ferns have extremely high chromosome numbers relative to flowering plants, but the species with the lowest chromosome numbers show gene expression patterns typical of diploid organisms, suggesting that they may be diploidized ancient polyploids. To investigate the role of polyploidy in fern genome evolution, and to provide permanent genetic resources for this neglected group, we constructed a high-resolution genetic linkage map of the homosporous fern model species, Ceratopteris richardii (n ¼ 39). Linkage map construction employed 488 doubled haploid lines (DHLs) that were genotyped for 368 RFLP, 358 AFLP, and 3 isozyme markers. Forty-one linkage groups were recovered, with average spacing between markers of 3.18 cM. Most loci ($76%) are duplicated and most duplicates occur on different linkage groups, indicating that as in other eukaryotic genomes, gene duplication plays a prominent role in shaping the architecture of fern genomes. Although past polyploidization is a potential mechanism for the observed abundance of gene duplicates, a wide range in the number of gene duplicates as well as the absence of large syntenic regions consisting of duplicated gene copies implies that small-scale duplications may be the primary mode of gene duplication in C. richardii. Alternatively, evidence of past polyploidization(s) may be masked by extensive chromosomal rearrangements as well as smaller-scale duplications and deletions following polyploidization(s).

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“…Thus the hypothesized high level of self-fertilization in bisexual gametophytes was rejected, and the supposed need for polyploid homoeologous heterozygosity to counteract homologous homozygosity disappeared. These findings discrediting the paleopolyploid hypothesis were subsequently generalized for the homosporous pteridophytes as a whole (3,(14)(15)(16)(17)(18)(19).…”

Section: Resultsmentioning

confidence: 84%

Gene silencing in a polyploid homosporous fern: paleopolyploidy revisited.

Gastony

1991

Proc. Natl. Acad. Sci. U.S.A.

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Because of their high chromosome numbers, homosporous vascular plants were considered paleopolyploids until recent enzyme electrophoretic studies rejected this hypothesis by showing that they express only diploid numbers of isozymes. In polyploid sporophytes of the homosporous fern Pellaea rufa, however, progressive diminution of phosphoglucoisomerase activities encoded by one ancestral genome culminates in tetraploid plants exhibiting a completely diploidized electrophoretic phenotype for this enzyme. The demonstration that such gene silencing can make a polyploid fern look isozymically like a diploid questions the validity of isozyme evidence for testing the paleopolyploid hypothesis and supports the proposed role of polyploidization followed by genetic diploidization in the evolutionary history of homosporous pteridophytes.The homosporous ferns and other homosporous pteridophytes have long been regarded as the prime examples of polyploidy among the vascular plants because of their high chromosome numbers (mean n = 57.05) relative to those of heterosporous plants such as the angiosperms (mean n = 15.99) (1). The leading hypothesis to explain these high numbers attributes them to polyploidization in the ancestry of homosporous plants (paleopolyploidy) (2). Enzyme electrophoretic studies discussed below, however, have shown that the number of isozymes per enzyme in homosporous fern species with the lowest chromosome numbers in their genera is the same as in diploid angiosperms, implying that these ferns have a diploid number of gene loci encoding these enzymes. Because homosporous ferns do not express extra sets of genes as expected in polyploids, these results have discredited the hypothesis that their high chromosome numbers result from paleopolyploidy. A revised version of the paleopolyploid hypothesis (3) reconciles these data by proposing that fern phylogeny has involved repeated cycles of polyploidization followed by genetic diploidization involving gene silencing. This proposal accounts for the lack of isozyme evidence for paleopolyploid loci by asserting that the extra loci have been silenced, an assertion that is speculative inasmuch as no direct evidence of gene silencing in ferns has been published to date. This report provides direct evidence of diploidization of electrophoretic phenotypes in a polyploid homosporous fern and thus supports the view that polyploidization coupled with genetic diploidization could be an important evolutionary mechanism in this group.

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An Electrophoretic Investigation of Intragametophytic Selfing in Equisetum Arvense

Cited by 23 publications

References 45 publications

Isozyme variation and genetic relationships among taxa in the Asplenium obovatum group (Aspleniaceae, Pteridophyta)

Isozyme variation and genetic relationships among taxa in the Asplenium obovatum group (Aspleniaceae, Pteridophyta)

Genetic Map-Based Analysis of Genome Structure in the Homosporous Fern Ceratopteris richardii

Gene silencing in a polyploid homosporous fern: paleopolyploidy revisited.

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