Gametophytic Apomixis

Nogler, Gian A.

doi:10.1007/978-3-642-69302-1_10

Cited by 492 publications

(622 citation statements)

References 114 publications

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“…Gametophytic apomixis in higher plants refers to several mechanisms of asexual reproduction through seeds (Stebbins, 1950;Nogler, 1984b). In all cases, the apomictic process bypasses both meiosis and egg cell fertilization, producing offspring which are exact genetic replicas of the mother plant.…”

Section: Introductionmentioning

confidence: 99%

“…Typically, apomixis is a facultative phenomenon in which an apomictic plant usually produces a few meiotic embryos beside a majority of ameiotic (apomeiotic, after Renner, 1916) embryos. Furthermore, apomicts are usually restricted to polyploids (Nogler, 1984b).…”

Section: Introductionmentioning

confidence: 99%

“…Apomixis is a genetically controlled character (Nogler, 1984b). Despite decades of research, this control remains poorly understood and only two propositions have received a broad acceptance.…”

Section: Introductionmentioning

confidence: 99%

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Mapping diplosporous apomixis in tetraploid Tripsacum: one gene or several genes?

Grimanelli

Leblanc²,

Espinosa³

et al. 1998

Heredity

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Polyploids in Tripsacum, a wild relative of maize, reproduce through the diplosporous type of apomixis, an asexual mode of reproduction through seeds. Diplosporous apomixis involves both the failure of meiosis and the parthenogenetic development of the unreduced gametes, resulting in progenies that are exact genetic copies of the mother plant. Apomixis is believed to be controlled by one single dominant allele, responsible for the whole developmental process. Construction of a linkage map for the chromosome controlling diplosporous apomixis in Tripsacum was carried out in both tetraploid-apomictic and diploid-sexual Tripsacum species using maize restriction fragment length polymorphism (RFLP) probes. A high level of collinearity was observed between the Tripsacum chromosome carrying the control of apomixis and a duplicated segment in the maize genome. In the apomictic tetraploid, there was a strong restriction to recombination, as compared to the corresponding genomic segment in sexual plants and maize. This suggests that apomixis, although inherited as a single Mendelian allele, might really be controlled by a cluster of linked loci. The analysis also revealed the tetrasomic nature of the inheritance of the chromosomal segment controlling apomixis, which contradicts the usually accepted hypothesis of an allopolyploid origin of apomictic species. The implications of these data for the transfer of apomixis into cultivated crops are discussed, and a new approach to studying the genetics of apomixis, based on comparative mapping, is proposed.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mapping diplosporous apomixis in tetraploid Tripsacum: one gene or several genes?

Grimanelli

Leblanc²,

Espinosa³

et al. 1998

Heredity

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show abstract

“…In the latter case, the female gametophyte can be formed from direct differentiation of somatic cells in the ovule (apospory) or from an aberrant cell division cycle that prevents reduction and recombination, sometimes completely bypassing meiosis (diplospory). In most cases, the formation of the endosperm is still dependent on fertilization of the central cell ( pseudogamy), although rare cases of autonomous development of the endosperm have also been reported (Nogler 1984).…”

Section: Reproductive Versatility In Flowering Plantsmentioning

confidence: 99%

Reproductive Versatility and the Epigenetic Control of Female Gametogenesis

Vielle‐Calzada

Hernandez-Lagana

Rodríguez-Leal

et al. 2012

Cold Spring Harbor Symposia on Quantitative Biology

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Each year, plants and animals perform the task of repopulating the planet through patterns of courtship and mating that have a unifying and compelling logic: the production of offspring. Although life of nearly all organisms is organized around sex and breeding, Darwinian thinking focused more on the struggle for existence than on evolutionary significance of this frantic race to reproduce. In Darwin's own words, "We do not know the final cause of sexuality; why new beings should be produced by the union of the two sexual elements. The whole subject is hidden in darkness. . ." (Darwin 1862). In plants, a major consequence of this search for survival is the evolution of a multitude of reproductive alternatives that have intrigued botanists, geneticists, and evolutionary biologists for more than 100 years. Because sexually derived genetic diversity is interpreted as essential for adaptation, it is often thought that sex is necessary for the perpetuation of a species; however, many organismsincluding several hundred families of flowering plants-are going efficiently about propagating their kind without bothering with meiosis and mating. Whereas many plants can undergo vegetative propagation, through the production of stolons, bulbs, or rhizomes, for example, many others have developed methods to produce an embryo from a single cell whose nucleus is not formed by the fusion of two gametes, offering a direct developmental and evolutionary challenge to sexual reproduction. Recent evidence suggests that epigenetic mechanisms that control transcriptional silencing of DNA repetitive elements and heterochromatin are crucial for the acquisition of cell identity in the ovule, opening the possibility that the developmental distinction between sexual development and apomixis might have evolved as an adaptive response to evolutionary forces that modulate structural variation and reproductive versatility in flowering plants.The emergence of all plants is derived from a common ancestor that endosymbiotically acquired a photosynthetic bacterium capable of transforming light into energy, an evolutionary event that changed the surface of the planet by progressively transforming an environment dominated by cyanobacteria (blue-green bacteria) into a habitat predominantly occupied by photosynthetic multicellular organisms. Although fossilized spores suggest that land plants appeared more than 450 million years ago, the establishment of their life cycle through the alternation of haploid and diploid generations remains an unsolved mystery. In contrast to green algae and mosses, in which the gametophytic (haploid) phase is free-living and temporally dominant, flowering plants have a reduced and ephemeral gametophyte that forms male and female gametes and is necessary to ensure sexual reproduction.Plants have evolved a characteristic life strategy with alternating diploid and haploid phases (or generations), continuous postembryonic development that derives in the formation of aerial and underground meristems, and the absence of a germli...

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“…The autonomous division of aposporous egg cells generates viable embryos without fertilization. However, the majority of aposporous species is pseudogamous and requires fertilization of the polar nuclei for endosperm development (Nogler 1984).…”

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confidence: 99%

Ultrastructural Studies of Gametophytic Apomicts in Guinea Grass (Panicum maximum) I. Differentiation of Aposporous Initial Cell

2006

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SummaryThe ultrastructural features of the developing megasporocyte, especially the timing of degeneration of sexual cells during megosporogenesis, and differentiation of aposporous initial cell (AIC) in facultative apomictic guinea grass (Panicum maximum) has been studied. The first degeneration was observed in dyad stage. Accompanying the degeneration of sexual cell, the cell adjacent to the dyad in chalazal side, derived from nucellus began to increase its size of cell and change its organelles and shape, and thus, the cell become to the first AIC usually located in micropylar side. The AIC appeared in order continently adjacent to the first AIC in the chalazal side. However, all of the AICs could become to the mature embryo sac with 4-nucleates. The interdependent patterns of the nucellar cell and AIC, and their relationship are also discussed at subcellular level.

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Gametophytic Apomixis

Cited by 492 publications

References 114 publications

Mapping diplosporous apomixis in tetraploid Tripsacum: one gene or several genes?

Mapping diplosporous apomixis in tetraploid Tripsacum: one gene or several genes?

Reproductive Versatility and the Epigenetic Control of Female Gametogenesis

Ultrastructural Studies of Gametophytic Apomicts in Guinea Grass (Panicum maximum) I. Differentiation of Aposporous Initial Cell

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