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Annaliese S. Mason - One of the best experts on this subject based on the ideXlab platform.
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Unreduced Gamete formation in wheat × Aegilops spp. hybrids is genotype specific and prevented by shared homologous subgenomes
Plant Cell Reports, 2016Co-Authors: Zhaleh Fakhri, Ghader Mirzaghaderi, Samira Ahmadian, Annaliese S. MasonAbstract:Key message The presence of homologous subgenomes inhibited Unreduced Gamete formation in wheat × Aegilops interspecific hybrids. Unreduced Gamete rates were under the control of the wheat nuclear genome. Abstract Production of Unreduced Gametes is common among interspecific hybrids, and may be affected by parental genotypes and genomic similarity. In the present study, five cultivars of Triticum aestivum and two tetraploid Aegilops species (i.e. Ae. triuncialis and Ae. cylindrica ) were reciprocally crossed to produce 20 interspecific hybrid combinations. These hybrids comprised two different types: T. aestivum × Aegilops triuncialis ; 2 n = ABDU^tC^t (which lack a common subgenome) and T. aestivum × Ae. cylindrica ; 2 n = ABDD^cC^c (which share a common subgenome). The frequency of Unreduced Gametes in F_1 hybrids was estimated in sporads from the frequency of dyads, and the frequency of viable pollen, germinated pollen and seed set were recorded. Different meiotic abnormalities recorded in the hybrids included precocious chromosome migration to the poles at metaphase I and II, laggards in anaphase I and II, micronuclei and chromosome stickiness, failure in cell wall formation, premature cytokinesis and microspore fusion. The mean frequency of restitution meiosis was 10.1 %, and the mean frequency of Unreduced viable pollen was 4.84 % in T. aestivum × Ae. triuncialis hybrids. By contrast, in T. aestivum × Ae. cylindrica hybrids no meiotic restitution was observed, and a low rate of viable Gametes (0.3 %) was recorded. This study present evidence that high levels of homologous pairing between the D and D^c subgenomes may interfere with meiotic restitution and the formation of Unreduced Gametes. Variation in Unreduced Gamete production was also observed between T. aestivum × Ae. triuncialis hybrid plants, suggesting genetic control of this trait.
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Unreduced Gamete formation in wheat × Aegilops spp. hybrids is genotype specific and prevented by shared homologous subgenomes.
Plant cell reports, 2016Co-Authors: Zhaleh Fakhri, Ghader Mirzaghaderi, Samira Ahmadian, Annaliese S. MasonAbstract:The presence of homologous subgenomes inhibited Unreduced Gamete formation in wheat × Aegilops interspecific hybrids. Unreduced Gamete rates were under the control of the wheat nuclear genome. Production of Unreduced Gametes is common among interspecific hybrids, and may be affected by parental genotypes and genomic similarity. In the present study, five cultivars of Triticum aestivum and two tetraploid Aegilops species (i.e. Ae. triuncialis and Ae. cylindrica) were reciprocally crossed to produce 20 interspecific hybrid combinations. These hybrids comprised two different types: T. aestivum × Aegilops triuncialis; 2n = ABDUtCt (which lack a common subgenome) and T. aestivum × Ae. cylindrica; 2n = ABDDcCc (which share a common subgenome). The frequency of Unreduced Gametes in F1 hybrids was estimated in sporads from the frequency of dyads, and the frequency of viable pollen, germinated pollen and seed set were recorded. Different meiotic abnormalities recorded in the hybrids included precocious chromosome migration to the poles at metaphase I and II, laggards in anaphase I and II, micronuclei and chromosome stickiness, failure in cell wall formation, premature cytokinesis and microspore fusion. The mean frequency of restitution meiosis was 10.1 %, and the mean frequency of Unreduced viable pollen was 4.84 % in T. aestivum × Ae. triuncialis hybrids. By contrast, in T. aestivum × Ae. cylindrica hybrids no meiotic restitution was observed, and a low rate of viable Gametes (0.3 %) was recorded. This study present evidence that high levels of homologous pairing between the D and Dc subgenomes may interfere with meiotic restitution and the formation of Unreduced Gametes. Variation in Unreduced Gamete production was also observed between T. aestivum × Ae. triuncialis hybrid plants, suggesting genetic control of this trait.
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Unreduced Gamete formation in wheat aegilops spp hybrids is genotype specific and prevented by shared homologous subgenomes
Plant Cell Reports, 2016Co-Authors: Zhaleh Fakhri, Ghader Mirzaghaderi, Samira Ahmadian, Annaliese S. MasonAbstract:The presence of homologous subgenomes inhibited Unreduced Gamete formation in wheat × Aegilops interspecific hybrids. Unreduced Gamete rates were under the control of the wheat nuclear genome. Production of Unreduced Gametes is common among interspecific hybrids, and may be affected by parental genotypes and genomic similarity. In the present study, five cultivars of Triticum aestivum and two tetraploid Aegilops species (i.e. Ae. triuncialis and Ae. cylindrica) were reciprocally crossed to produce 20 interspecific hybrid combinations. These hybrids comprised two different types: T. aestivum × Aegilops triuncialis; 2n = ABDUtCt (which lack a common subgenome) and T. aestivum × Ae. cylindrica; 2n = ABDDcCc (which share a common subgenome). The frequency of Unreduced Gametes in F1 hybrids was estimated in sporads from the frequency of dyads, and the frequency of viable pollen, germinated pollen and seed set were recorded. Different meiotic abnormalities recorded in the hybrids included precocious chromosome migration to the poles at metaphase I and II, laggards in anaphase I and II, micronuclei and chromosome stickiness, failure in cell wall formation, premature cytokinesis and microspore fusion. The mean frequency of restitution meiosis was 10.1 %, and the mean frequency of Unreduced viable pollen was 4.84 % in T. aestivum × Ae. triuncialis hybrids. By contrast, in T. aestivum × Ae. cylindrica hybrids no meiotic restitution was observed, and a low rate of viable Gametes (0.3 %) was recorded. This study present evidence that high levels of homologous pairing between the D and Dc subgenomes may interfere with meiotic restitution and the formation of Unreduced Gametes. Variation in Unreduced Gamete production was also observed between T. aestivum × Ae. triuncialis hybrid plants, suggesting genetic control of this trait.
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Unreduced Gametes: meiotic mishap or evolutionary mechanism?
Trends in Genetics, 2014Co-Authors: Annaliese S. Mason, J. Chris PiresAbstract:Unreduced Gametes (Gametes with the somatic chromosome number) are known to facilitate polyploid formation. Unreduced Gametes result from a plethora of different mechanisms across different taxa, suggesting that the ability to produce Unreduced Gametes has evolutionary utility. Heritable genetic variation for Unreduced Gamete production has been observed, thereby providing an evolutionary substrate. Unreduced Gametes are also frequently involved in interspecific hybridisation events as well as being produced by interspecific hybrids, facilitating allopolyploidisation. Environmental stress often triggers Unreduced Gamete production, suggesting that Unreduced Gametes may facilitate polyploid speciation in response to changing environments. Thus, although Unreduced Gamete formation may be a meiotic mishap, we suggest that Unreduced Gametes can be more explicitly considered as a mechanism for evolutionary speciation that should be measured and tested across and within lineages for exaptive evolution (a feature with evolutionary utility that has not arisen under conventional selective pressure) and evolvability (the capacity to generate adaptive genetic variation).
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A new method for producing allohexaploid Brassica through Unreduced Gametes
Euphytica, 2012Co-Authors: Annaliese S. Mason, Guijun Yan, Wallace A. Cowling, Matthew N. NelsonAbstract:We trialled a two-step method of producing allohexaploid Brassica with three genomes (A, B, and C) derived from pair-wise crossing among three allotetraploid Brassica species. In the first step, the three allotetraploid Brassica species ( Brassica juncea , A^jA^jB^jB^j; Brassica napus , A^nA^nC^nC^n; and Brassica carinata , B^cB^cC^cC^c) were intercrossed in pairs to produce unbalanced trigenomic hybrids: A^jA^nB^jC^n, B^jB^cA^jC^c and C^nC^cA^nB^c. In the second step, these hybrids were crossed with the complementary allotetraploid parent, that is, A^jA^nB^jC^n × B^cB^cC^cC^c ( B. carinata ), B^jB^cA^jC^c × A^nA^nC^nC^n ( B. napus ) and C^nC^cA^nB^c × A^jA^jB^jB^j ( B. juncea ). We hypothesised that the unbalanced trigenomic hybrids would produce high levels of Unreduced Gametes with the same genome composition as the hybrid. These Unreduced Gametes would unite with reduced Gametes from the complementary allotetraploids to form allohexaploid Brassica progeny (A^jA^nB^cB^jC^cC^n). From 112 s generation interspecific progeny, two progeny were shown by locus-specific simple sequence repeat markers to be near-allohexaploids derived from an Unreduced Gamete from C^nC^cA^nB^c and a reduced Gamete from B. juncea (A^jB^j). One of these plants was highly self-fertile, had 50 chromosomes, and inherited patterns of marker alleles (A^jA^nB^cB^jC^cC^n) that were predicted from first division restitution at meiosis in the C^nC^cA^nB^c parent. The second near-allohexaploid had 60 chromosomes, was sterile, and inherited patterns of marker alleles that indicated second division restitution in the C^nC^cA^nB^c parent. Trigenomic hybrid Brassica produced by these methods will be valuable bridges to move alleles between allotetraploid species, and may contribute useful meiotic stability alleles to a future allohexaploid species.
C. N. Stewart - One of the best experts on this subject based on the ideXlab platform.
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Hybridization between transgenic Brassica napus L. and its wild relatives: Brassica rapa L., Raphanus raphanistrum L., Sinapis arvensis L., and Erucastrum gallicum (Willd.) O.E. Schulz
Theoretical and Applied Genetics, 2003Co-Authors: Suzanne I Warwick, Peter G. Mason, Marie-josée Simard, Hugh J Beckie, G. Seguin-swartz, Anne Legere, L Braun, C. N. StewartAbstract:The frequency of gene flow from Brassica napus L. (canola) to four wild relatives, Brassica rapa L., Raphanus raphanistrum L., Sinapis arvensis L. and Erucastrum gallicum (Willd.) O.E. Schulz, was assessed in greenhouse and/or field experiments, and actual rates measured in commercial fields in Canada. Various marker systems were used to detect hybrid individuals: herbicide resistance traits (HR), green fluorescent protein marker (GFP), species-specific amplified fragment length polymorphisms (AFLPs) and ploidy level. Hybridization between B. rapa and B. napus occurred in two field experiments (frequency approximately 7%) and in wild populations in commercial fields (approximately 13.6%). The higher frequency in commercial fields was most likely due to greater distance between B. rapa plants. All F1 hybrids were morphologically similar to B. rapa, had B. napus- and B. rapa-specific AFLP markers and were triploid (AAC, 2n = 29 chromosomes). They had reduced pollen viability (about 55%) and segregated for both self-incompatible and self-compatible individuals (the latter being a B. napus trait). In contrast, gene flow between R. raphanistrum and B. napus was very rare. A single R. raphanistrum × B. napus F1 hybrid was detected in 32,821 seedlings from the HR B. napus field experiment. The hybrid was morphologically similar to R. raphanistrum except for the presence of valves, a B. napus trait, in the distorted seed pods. It had a genomic structure consistent with the fusion of an Unreduced Gamete of R. raphanistrum and a reduced Gamete of B. napus (RrRrAC, 2n = 37), both B. napus- and R. raphanistrum-specific AFLP markers, and had
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hybridization between transgenic brassica napus l and its wild relatives brassica rapa l raphanus raphanistrum l sinapis arvensis l and erucastrum gallicum willd o e schulz
Theoretical and Applied Genetics, 2003Co-Authors: Suzanne I Warwick, Peter G. Mason, Marie-josée Simard, Hugh J Beckie, Anne Legere, L Braun, Ginette Seguinswartz, C. N. StewartAbstract:The frequency of gene flow from Brassica napus L. (canola) to four wild relatives, Brassica rapa L., Raphanus raphanistrum L., Sinapis arvensis L. and Erucastrum gallicum (Willd.) O.E. Schulz, was assessed in greenhouse and/or field experiments, and actual rates measured in commercial fields in Canada. Various marker systems were used to detect hybrid individuals: herbicide resistance traits (HR), green fluorescent protein marker (GFP), species-specific amplified fragment length polymorphisms (AFLPs) and ploidy level. Hybridization between B. rapa and B. napus occurred in two field experiments (frequency approximately 7%) and in wild populations in commercial fields (approximately 13.6%). The higher frequency in commercial fields was most likely due to greater distance between B. rapa plants. All F1 hybrids were morphologically similar to B. rapa, had B. napus- and B. rapa-specific AFLP markers and were triploid (AAC, 2n = 29 chromosomes). They had reduced pollen viability (about 55%) and segregated for both self-incompatible and self-compatible individuals (the latter being a B. napus trait). In contrast, gene flow between R. raphanistrum and B. napus was very rare. A single R. raphanistrum × B. napus F1 hybrid was detected in 32,821 seedlings from the HR B. napus field experiment. The hybrid was morphologically similar to R. raphanistrum except for the presence of valves, a B. napus trait, in the distorted seed pods. It had a genomic structure consistent with the fusion of an Unreduced Gamete of R. raphanistrum and a reduced Gamete of B. napus (RrRrAC, 2n = 37), both B. napus- and R. raphanistrum-specific AFLP markers, and had <1% pollen viability. No hybrids were detected in the greenhouse experiments (1,534 seedlings), the GFP field experiment (4,059 seedlings) or in commercial fields in Quebec and Alberta (22,114 seedlings). No S. arvensis or E. gallicum × B. napus hybrids were detected (42,828 and 21,841 seedlings, respectively) from commercial fields in Saskatchewan. These findings suggest that the probability of gene flow from transgenic B. napus to R. raphanistrum, S. arvensis or E. gallicum is very low (<2–5 × 10–5). However, transgenes can disperse in the environment via wild B. rapa in eastern Canada and possibly via commercial B. rapa volunteers in western Canada.
P. Ollitrault - One of the best experts on this subject based on the ideXlab platform.
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Male and female inheritance patterns in tetraploid ‘Moncada’ mandarin
Plant Cell Reports, 2020Co-Authors: Miguel Garavello, L. Navarro, J. Cuenca, Andrés Garcia-lor, Neus Ortega, P. OllitraultAbstract:Key message Tetraploid `Moncada´ mandarin, used as male and female in interploidy hybridizations, displays mainly tetrasomic inheritance for most LGs, with slight variations according to the direction of the crossing. Abstract Triploid-breeding programs in citrus are key tool to develop seedless cultivars. Obtaining triploid citrus hybrids may be achieved through different strategies, such as the exploitation of female Unreduced Gamete in crosses between diploid parents and diploid by tetraploid sexual hybridizations, in which tetraploid genotypes can be used as male or female parents. Genetic configuration of triploid populations from interploid crosses greatly depends on the chromosomic segregation mode of the tetraploid parent used. Here, we have analyzed the inheritance of the tetraploid ‘Moncada’ mandarin and compared the genetic structures of the resulting Gametes when used as male and as female parent. The preferential chromosome pairing rate is calculated from the parental heterozygosity restitution (PHR) of codominant molecular markers, indicating the proportion between disomic and tetrasomic segregation. Tetraploid ‘Moncada’ both as female and male parent largely exhibited tetrasomic segregation. However, as female parent, one linkage group (LG8) showed intermediate segregation with tendency towards tetrasomic inheritance, while another linkage group (LG4) evidenced a clear intermediate segregation. On the other hand, when used as male parent two linkage groups (LG5 and LG6) showed values that fit an intermediate inheritance model with tetrasomic tendency. Significant doubled reduction (DR) rates were observed in five linkage groups as female parent, and in six linkage groups as male parent. The new knowledge generated here will serve to define crossing strategies in citrus improvement programs to efficiently obtain new varieties of interest in the global fresh consumption market.
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Male and female inheritance patterns in tetraploid 'Moncada' mandarin.
Plant cell reports, 2019Co-Authors: Miguel Garavello, L. Navarro, J. Cuenca, Neus Ortega, Andrés Garcia-lor, P. OllitraultAbstract:Tetraploid `Moncada´ mandarin, used as male and female in interploidy hybridizations, displays mainly tetrasomic inheritance for most LGs, with slight variations according to the direction of the crossing. Triploid-breeding programs in citrus are key tool to develop seedless cultivars. Obtaining triploid citrus hybrids may be achieved through different strategies, such as the exploitation of female Unreduced Gamete in crosses between diploid parents and diploid by tetraploid sexual hybridizations, in which tetraploid genotypes can be used as male or female parents. Genetic configuration of triploid populations from interploid crosses greatly depends on the chromosomic segregation mode of the tetraploid parent used. Here, we have analyzed the inheritance of the tetraploid ‘Moncada’ mandarin and compared the genetic structures of the resulting Gametes when used as male and as female parent. The preferential chromosome pairing rate is calculated from the parental heterozygosity restitution (PHR) of codominant molecular markers, indicating the proportion between disomic and tetrasomic segregation. Tetraploid ‘Moncada’ both as female and male parent largely exhibited tetrasomic segregation. However, as female parent, one linkage group (LG8) showed intermediate segregation with tendency towards tetrasomic inheritance, while another linkage group (LG4) evidenced a clear intermediate segregation. On the other hand, when used as male parent two linkage groups (LG5 and LG6) showed values that fit an intermediate inheritance model with tetrasomic tendency. Significant doubled reduction (DR) rates were observed in five linkage groups as female parent, and in six linkage groups as male parent. The new knowledge generated here will serve to define crossing strategies in citrus improvement programs to efficiently obtain new varieties of interest in the global fresh consumption market.
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Maximum-likelihood method identifies meiotic restitution mechanism from heterozygosity transmission of centromeric loci: application in citrus
Scientific Reports, 2015Co-Authors: José Cuenca, Andrés Garcia-lor, Pablo Aleza, Jose Juarez, Yann Froelicher, Luis Navarro, P. OllitraultAbstract:Polyploidisation is a key source of diversification and speciation in plants. Most researchers consider sexual polyploidisation leading to Unreduced Gamete as its main origin. Unreduced Gametes are useful in several crop breeding schemes. Their formation mechanism, i.e., First-Division Restitution (FDR) or Second-Division Restitution (SDR), greatly impacts the gametic and population structures and, therefore, the breeding efficiency. Previous methods to identify the underlying mechanism required the analysis of a large set of markers over large progeny. This work develops a new maximum-likelihood method to identify the Unreduced Gamete formation mechanism both at the population and individual levels using independent centromeric markers. Knowledge of marker-centromere distances greatly improves the statistical power of the comparison between the SDR and FDR hypotheses. Simulating data demonstrated the importance of selecting markers very close to the centromere to obtain significant conclusions at individual level. This new method was used to identify the meiotic restitution mechanism in nineteen mandarin genotypes used as female parents in triploid citrus breeding. SDR was identified for 85.3% of 543 triploid hybrids and FDR for 0.6%. No significant conclusions were obtained for 14.1% of the hybrids. At population level SDR was the predominant mechanisms for the 19 parental mandarins.
Suzanne I Warwick - One of the best experts on this subject based on the ideXlab platform.
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Hybridization between transgenic Brassica napus L. and its wild relatives: Brassica rapa L., Raphanus raphanistrum L., Sinapis arvensis L., and Erucastrum gallicum (Willd.) O.E. Schulz
Theoretical and Applied Genetics, 2003Co-Authors: Suzanne I Warwick, Peter G. Mason, Marie-josée Simard, Hugh J Beckie, G. Seguin-swartz, Anne Legere, L Braun, C. N. StewartAbstract:The frequency of gene flow from Brassica napus L. (canola) to four wild relatives, Brassica rapa L., Raphanus raphanistrum L., Sinapis arvensis L. and Erucastrum gallicum (Willd.) O.E. Schulz, was assessed in greenhouse and/or field experiments, and actual rates measured in commercial fields in Canada. Various marker systems were used to detect hybrid individuals: herbicide resistance traits (HR), green fluorescent protein marker (GFP), species-specific amplified fragment length polymorphisms (AFLPs) and ploidy level. Hybridization between B. rapa and B. napus occurred in two field experiments (frequency approximately 7%) and in wild populations in commercial fields (approximately 13.6%). The higher frequency in commercial fields was most likely due to greater distance between B. rapa plants. All F1 hybrids were morphologically similar to B. rapa, had B. napus- and B. rapa-specific AFLP markers and were triploid (AAC, 2n = 29 chromosomes). They had reduced pollen viability (about 55%) and segregated for both self-incompatible and self-compatible individuals (the latter being a B. napus trait). In contrast, gene flow between R. raphanistrum and B. napus was very rare. A single R. raphanistrum × B. napus F1 hybrid was detected in 32,821 seedlings from the HR B. napus field experiment. The hybrid was morphologically similar to R. raphanistrum except for the presence of valves, a B. napus trait, in the distorted seed pods. It had a genomic structure consistent with the fusion of an Unreduced Gamete of R. raphanistrum and a reduced Gamete of B. napus (RrRrAC, 2n = 37), both B. napus- and R. raphanistrum-specific AFLP markers, and had
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hybridization between transgenic brassica napus l and its wild relatives brassica rapa l raphanus raphanistrum l sinapis arvensis l and erucastrum gallicum willd o e schulz
Theoretical and Applied Genetics, 2003Co-Authors: Suzanne I Warwick, Peter G. Mason, Marie-josée Simard, Hugh J Beckie, Anne Legere, L Braun, Ginette Seguinswartz, C. N. StewartAbstract:The frequency of gene flow from Brassica napus L. (canola) to four wild relatives, Brassica rapa L., Raphanus raphanistrum L., Sinapis arvensis L. and Erucastrum gallicum (Willd.) O.E. Schulz, was assessed in greenhouse and/or field experiments, and actual rates measured in commercial fields in Canada. Various marker systems were used to detect hybrid individuals: herbicide resistance traits (HR), green fluorescent protein marker (GFP), species-specific amplified fragment length polymorphisms (AFLPs) and ploidy level. Hybridization between B. rapa and B. napus occurred in two field experiments (frequency approximately 7%) and in wild populations in commercial fields (approximately 13.6%). The higher frequency in commercial fields was most likely due to greater distance between B. rapa plants. All F1 hybrids were morphologically similar to B. rapa, had B. napus- and B. rapa-specific AFLP markers and were triploid (AAC, 2n = 29 chromosomes). They had reduced pollen viability (about 55%) and segregated for both self-incompatible and self-compatible individuals (the latter being a B. napus trait). In contrast, gene flow between R. raphanistrum and B. napus was very rare. A single R. raphanistrum × B. napus F1 hybrid was detected in 32,821 seedlings from the HR B. napus field experiment. The hybrid was morphologically similar to R. raphanistrum except for the presence of valves, a B. napus trait, in the distorted seed pods. It had a genomic structure consistent with the fusion of an Unreduced Gamete of R. raphanistrum and a reduced Gamete of B. napus (RrRrAC, 2n = 37), both B. napus- and R. raphanistrum-specific AFLP markers, and had <1% pollen viability. No hybrids were detected in the greenhouse experiments (1,534 seedlings), the GFP field experiment (4,059 seedlings) or in commercial fields in Quebec and Alberta (22,114 seedlings). No S. arvensis or E. gallicum × B. napus hybrids were detected (42,828 and 21,841 seedlings, respectively) from commercial fields in Saskatchewan. These findings suggest that the probability of gene flow from transgenic B. napus to R. raphanistrum, S. arvensis or E. gallicum is very low (<2–5 × 10–5). However, transgenes can disperse in the environment via wild B. rapa in eastern Canada and possibly via commercial B. rapa volunteers in western Canada.
Claudia Köhler - One of the best experts on this subject based on the ideXlab platform.
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Unreduced Gamete formation in plants: mechanisms and prospects
Journal of Experimental Botany, 2010Co-Authors: Lynette Brownfield, Claudia KöhlerAbstract:Polyploids, organisms with more than two sets of chromosomes, are widespread in flowering plants, including many important crop species. Increases in ploidy level are believed to arise commonly through the production of Gametes that have not had their ploidy level reduced during meiosis. Although there have been cytological descriptions of Unreduced Gamete formation in a number of plants, until recently none of the underlying genes or molecular mechanisms involved in Unreduced Gamete production have been described. The recent discovery of several genes in which mutations give rise to a high frequency of Unreduced Gametes in the model plant Arabidopsis thaliana opens the door to the elucidation of this important event and its manipulation in crop species. Here this recent progress is reviewed and the identified genes and the mechanism by which the loss of protein function leads to the formation of Unreduced Gametes are discussed. The potential to use the knowledge gained from Arabidopsis mutants to design tools and develop techniques to engineer Unreduced Gamete production in important crop species for use in plant breeding is also discussed.
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the impact of the triploid block on the origin and evolution of polyploid plants
Trends in Genetics, 2010Co-Authors: Claudia Köhler, Ortrun Mittelsten Scheid, Aleksandra ErilovaAbstract:Polyploidization, a widespread phenomenon among plants, is considered a major speciation mechanism. Polyploid plants have a high degree of immediate post-zygotic reproductive isolation from their progenitors, as backcrossing to either parent will produce mainly nonviable progeny. This reproductive barrier is called triploid block and it is caused by malfunction of the endosperm. Nevertheless, the main route to polyploid formation is via Unreduced Gametes and unstable triploid progeny, suggesting that there are ways to overcome the triploid block. Until recently, the mechanistic basis for Unreduced Gamete formation and the triploid block were completely unknown. Recent developments have revealed genetic pathways leading to Unreduced Gamete formation as well as the underlying genetic basis for the triploid block in Arabidopsis. These novel findings will provide the basis for a genetic understanding of polyploid formation and subsequent speciation in plants.
