Cytomixis in Pollen Mother Cells of Spearmint (Mentha spicata L.).

Tyagi, B. R.

doi:10.1508/cytologia.68.67

Cited by 16 publications

(10 citation statements)

References 52 publications

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“…The products of such PMCs result into the formation of sterile and variable sized pollen grains. Similar observations related to heterogeneity in the size of pollen grains and pollen sterility as a consequence of chromatin transfer and associated meiotic irregularities have been reported in Hordeum vulgare (Haroun 1996), Vicia faba (Haroun et al 2004), Brachiaria humidicola (Boldrini et al 2006), Mentha spicata (Tyagi 2003), Caltha palustris , Clematis flammula , Withania somnifera . Meconopsis aculeata , Hippophae rhamnoides , Lychnis indica var.…”

Section: Cytomixissupporting

confidence: 81%

Persistent occurrence of meiotic abnormalities in a new hexaploid cytotype of Thalictrum foetidum from Indian cold deserts

et al. 2011

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Thalictrum foetidum L. (Ranunculaceae), a morphologically variable and widely distributed species of temperate and alpine Himalayas is worked out cytologically for the first time from India. Earlier studies from outside India were restricted to chromosome counts and karyotypic analysis. We studied the male meiosis, microsporogenesis and pollen viability in the wild accessions from the cold deserts of Lahaul-Spiti, Kinnaur and Pangi Valley of Himachal Pradesh. Present cytomorphological surveys in the species record the existence of two distinct morphotypes involving plant size; colour and size of leaf/leaflet; dentation of leaflet lobes; and degree of leaf pubescence. All the accessions in the two morphovariants share the same meiotic chromosome number (n = 21) and adds a new intraspecific hexaploid cytotype. The accessions show the phenomenon of cytomixis involving transfer of chromatin material among proximate pollen mother cells (PMCs) and associated meiotic abnormalities like, out of plate bivalents, interchromosomal connections, and laggards, bridges and micronuclei at anaphases/telophases. Microsporogenesis results into abnormal sporads (tetrads with micronuclei, dyads, triads and polyads). The products of such sporads resulted into some pollen sterility and pollen grains of heterogeneous sizes. The persistent occurrence of phenomenon of cytomixis and associated meiotic abnormalities and consequently pollen sterility and pollen grains of heterogeneous sizes in the hexaploid cytotype of T. foetidum seems to be under some genetic factors associated with the genome.

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Section: Cytomixissupporting

confidence: 81%

Persistent occurrence of meiotic abnormalities in a new hexaploid cytotype of Thalictrum foetidum from Indian cold deserts

et al. 2011

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“…In plants, unreduced-gamete formation, complement fractionation (Thompson, 1962) and cytomixis (Tyagi, 2003) are mechanisms that overcome reproductive obstacles caused by reduced meiotic chromosome paring. Matzk et al (2001) suggested that formation of unreduced embryo sacs and normal reduced microsporogenesis might be possible in some hexaploid H. perforatum plants, based upon the observation of a 15Cx peak in the FCSS of bulked H. perforatum seeds.…”

Section: Discussionmentioning

confidence: 99%

“…However, these embryo types were not observed in previous FCSS studies (reviewed by Barcaccia et al, 2007) nor in our investigation. It is perhaps rather unlikely, but still possible, that hexaploids could produce a range of unbalanced male and female gametes with relatively complete chromosome complements through processes analogous to complement fractionation in Rubus (Thompson, 1962) or cytomixis in Mentha (Tyagi, 2003), leading to seeds with unusual embryo:endosperm ratios. We are now investigating this topic in more detail by following pollen and seed production in hexaploid seedlings.…”

Section: Discussionmentioning

confidence: 99%

Analysis of breeding systems, ploidy, and the role of hexaploids in three Hypericum perforatum L. populations

Widrlechner

Rigby

2010

Industrial Crops and Products

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Hexaploid seeds are produced by predominantly tetraploid populations of Hypericum perforatum, but the fate of hexaploid seedlings and their reproductive behavior have not been closely examined. We used flow cytometry to analyze single seeds and individual plant samples of three accessions of H. perforatum to determine ploidy levels and reproductive pathways. Seed samples of all three accessions were facultative apomicts, with tetraploid cytotype predominant (85-91%) and a lower frequency of hexaploids (9-14%), with diploids (5%) detected in only one population. Seedling populations consisted of tetraploids (87-97%) and hexaploids (3-13%). Hexaploid embryos are most likely generated by a 2n gamete of the tetraploid and fertilized by a normal, reduced tetraploid male gamete. These hexaploids are expected to produce unbalanced gametes because they possess chromosome complements that include two triploid sets originally derived from two different species. The observation that some tetraploid seeds had endosperm with high cellular DNA content indicates that some unbalanced male gametes produced by hexaploids were evidently viable and could effect fertilization. Whether this mechanism is also true for egg cells or whether the hexaploids are capable of producing unreduced embryo sacs is uncertain. Because of severe reproductive difficulties, hexaploid seedlings may play a very minor role in gene flow and the further evolution of H. perforatum. The likelihood that hexaploids will evolve to types with an increased frequency of bivalent paring in meiosis is relatively low. However, hexaploids may include novel chemotypes, which could be vegetatively propagated if valuable, medicinal types can be identified among them. We used flow cytometry to analyze single seeds and individual plant samples of three accessions of H. perforatum to determine ploidy levels and reproductive pathways. Seed samples of all three accessions were facultative apomicts, with tetraploid cytotype predominant (85-91%) and a lower frequency of hexaploids (9-14%), with diploids (5%) detected in only one population. Seedling populations consisted of tetraploids (87-97%) and hexaploids (3-13%). Hexaploid embryos are most likely generated by a 2n gamete of the tetraploid and fertilized by a normal, reduced tetraploid male gamete. These hexaploids are expected to produce unbalanced gametes because they possess chromosome complements that include two triploid sets originally derived from two different species. The observation that some tetraploid seeds had endosperm with high cellular DNA content indicates that some unbalanced male gametes produced by hexaploids were evidently viable and could effect fertilization. Whether this mechanism is also true for egg cells or whether the hexaploids are capable of producing unreduced embryo sacs is uncertain. Because of severe reproductive difficulties, hexaploid seedlings may play a very minor role in gene flow and the further evolution of H. perforatum. The likelihood that hexaploids will evolve to types wi...

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“…Additionally, 2n gametes may be formed by cytomixis or syncyte formation. Cytomixis involves the migration of chromatins or chromosomes from one cell (donor) to another (recipient) through a cytoplasmic connection during meiosis (Gates 1911), so that the recipient cell produces 2n gametes after meiosis (Bahl and Tyagi 1988;Falistocco et al 1995;Tyagi 2003;Ghaffari 2006). Syncyte formation, broadly defined by Levan (1941), involves the fusion of two or more pollen mother cells (PMCs, or nuclei), generally in early prophase of the first meiotic division, so that the syncyte produces 2n gametes after meiosis (Levan 1941;Sarbhoy 1980).…”

Section: Introductionmentioning

confidence: 99%

Syncyte formation in the microsporangium of Chrysanthemum (Asteraceae): a pathway to infraspecific polyploidy

2009

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Polyploidy, which is thought to have played an important role in plant evolution and speciation, is prevalent in Chrysanthemum (x = 9). In fact, polyploid series are known in C. zawadskii (2x, 4x, 6x, 8x, and 10x) and C. indicum (2x, 4x, and 6x), but the mechanism by which polyploidization occurs is unknown. Here we show that in diploid individuals of both C. zawadskii and C. indicum, the fusion between two adjacent pollen mother cells (PMCs) occurs at a frequency of 1.1-1.3% early in the first meiotic division. While possessing the chromosomes of both PMCs, the fused cell or syncyte undertakes subsequent meiotic division processes as a single large PMC, producing four 2n pollen grains that are able to germinate. Despite their low frequency, syncyte formation may have played a major role in the production of infraspecific polyploids in Chrysanthemum.

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Cytomixis in Pollen Mother Cells of Spearmint (Mentha spicata L.).

Cited by 16 publications

References 52 publications

Persistent occurrence of meiotic abnormalities in a new hexaploid cytotype of Thalictrum foetidum from Indian cold deserts

Persistent occurrence of meiotic abnormalities in a new hexaploid cytotype of Thalictrum foetidum from Indian cold deserts

Analysis of breeding systems, ploidy, and the role of hexaploids in three Hypericum perforatum L. populations

Syncyte formation in the microsporangium of Chrysanthemum (Asteraceae): a pathway to infraspecific polyploidy

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