scholarly journals The relation of meiotic behaviour to hybridity, polyploidy and apomixis in the Ranunculus auricomus complex (Ranunculaceae)

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Birthe H. Barke ◽  
Kevin Karbstein ◽  
Mareike Daubert ◽  
Elvira Hörandl
Keyword(s):  
Parental Species ◽  
Hybrid Sterility ◽  
Male Meiosis ◽  
Developmental Changes ◽  
Female Meiosis ◽  
Developmental Abnormalities ◽  
Selective Pressures ◽  
Hybrid Plants ◽  
Homoploid Hybrid ◽  
Chromatin Bridges

Abstract Background Hybridization and polyploidization are powerful evolutionary factors that are associated with manifold developmental changes in plants such as irregular progression of meiosis and sporogenesis. The emergence of apomixis, which is asexual reproduction via seeds, is supposed to be connected to these factors and was often regarded as an escape from hybrid sterility. However, the functional trigger of apomixis is still unclear. Recently formed di- and polyploid Ranunculus hybrids, as well as their parental species were analysed for their modes of mega- and microsporogenesis by microscopy. Chromosomal configurations during male meiosis were screened for abnormalities. Meiotic and developmental abnormalities were documented qualitatively and collected quantitatively for statistical evaluations. Results Allopolyploids showed significantly higher frequencies of erroneous microsporogenesis than homoploid hybrid plants. Among diploids, F2 hybrids had significantly more disturbed meiosis than F1 hybrids and parental plants. Chromosomal aberrations included laggard chromosomes, chromatin bridges and disoriented spindle activities. Failure of megasporogenesis appeared to be much more frequent in than of microsporogenesis is correlated to apomixis onset. Conclusions Results suggest diverging selective pressures on female and male sporogenesis, with only minor effects of hybridity on microsporogenesis, but fatal effects on the course of megasporogenesis. Hence, pollen development continues without major alterations, while selection will favour apomixis as alternative to the female meiotic pathway. Relation of investigated errors of megasporogenesis with the observed occurrence of apospory in Ranunculus hybrids identifies disturbed female meiosis as potential elicitor of apomixis in order to rescue these plants from hybrid sterility. Male meiotic disturbance appears to be stronger in neopolyploids than in homoploid hybrids, while disturbances of megasporogenesis were not ploidy-dependent.

scholarly journals The relation of meiotic behaviour to hybridity, polyploidy and apomixis in the Ranunculus auricomus complex (Ranunculaceae)

2019 ◽  
Author(s):  
Birthe Hilkka Barke ◽  
Kevin Karbstein ◽  
Mareike Daubert ◽  
Elvira Hörandl
Keyword(s):  
Parental Species ◽  
Hybrid Sterility ◽  
Male Meiosis ◽  
Female Meiosis ◽  
Developmental Abnormalities ◽  
Selective Pressures ◽  
Male Development ◽  
Hybrid Plants ◽  
Homoploid Hybrid ◽  
Chromatin Bridges

Abstract Background Hybridization and polyploidization are powerful evolutionary factors that are associated with manifold developmental changes in plants such as irregular progression of meiosis and sporogenesis. The emergence of apomixis, which is asexual reproduction via seeds, is supposed to be connected to these factors and was often regarded as an escape from hybrid sterility. However, the functional trigger of apomixis is still unclear. Recently formed di- and polyploid Ranunculus hybrids as well as their parental species were analysed for their modes of mega- and microsporogenesis by microscopy. Chromosomal configurations during male meiosis were screened for abnormalities. Developmental abnormalities were documented qualitatively and collected quantitatively for statistical evaluations. Results Allopolyploids showed significantly higher frequencies of erroneous microsporogenesis than homoploid hybrid plants. Among diploids, F 2 hybrids had significantly more disturbed meiosis than F 1 hybrids and parental plants. Chromosomal aberrations included laggard chromosomes, chromatin bridges and disoriented spindle activities. Meiotic failure appeared to be much more frequent in female compared to male development. Conclusions Results suggest diverging selective pressures on female and male meiosis, with only minor effects of hybridity on male development, but fatal effects on the course of megasporogenesis. Hence, pollen development continues without major alterations, while selection will favour alternatives to the female meiotic pathway. Relation of investigated meiotic errors with the observed occurrence of apospory in Ranunculus hybrids identifies disturbed female meiosis as potential elicitor of apomixis in order to rescue these plants from hybrid sterility. Meiotic disturbance appears to be stronger in neopolyploids than in homoploid hybrids, which may contribute to the prevalence of apomixis in polyploid plants.

scholarly journals Unleashing meiotic crossovers in hybrid plants

2017 ◽  
Vol 115 (10) ◽  
pp. 2431-2436 ◽  
Author(s):  
Joiselle Blanche Fernandes ◽  
Mathilde Séguéla-Arnaud ◽  
Cécile Larchevêque ◽  
Andrew H. Lloyd ◽  
Raphael Mercier
Keyword(s):  
Fold Increase ◽  
Pure Line ◽  
Male Meiosis ◽  
Wild Type ◽  
Female Meiosis ◽  
Male Recombination ◽  
Upper Limit ◽  
Hybrid Plants ◽  
Wild Type Female ◽  
Breeding Efficiency

Meiotic crossovers shuffle parental genetic information, providing novel combinations of alleles on which natural or artificial selection can act. However, crossover events are relatively rare, typically one to three exchange points per chromosome pair. Recent work has identified three pathways limiting meiotic crossovers in Arabidopsis thaliana that rely on the activity of FANCM [Crismani W, et al. (2012) Science 336:1588–1590], RECQ4 [Séguéla-Arnaud M, et al. (2015) Proc Natl Acad Sci USA 112:4713–4718], and FIGL1 [Girard C, et al. (2015) PLoS Genet 11:e1005369]. Here we analyzed recombination in plants in which one, two, or all three of these pathways were disrupted in both pure line and hybrid contexts. The greatest effect was observed when combining recq4 and figl1 mutations, which increased the hybrid genetic map length from 389 to 3,037 cM. This corresponds to an unprecedented 7.8-fold increase in crossover frequency. Disrupting the three pathways did not further increase recombination, suggesting that some upper limit had been reached. The increase in crossovers is not uniform along chromosomes and rises from centromere to telomere. Finally, although in wild type recombination is much higher in male meiosis than in female meiosis (490 cM vs. 290 cM), female recombination is higher than male recombination in recq4 figl1 (3,200 cM vs. 2,720 cM), suggesting that the factors that make wild-type female meiosis less recombinogenic than male wild-type meiosis do not apply in the mutant context. The massive increase in recombination observed in recq4 figl1 hybrids opens the possibility of manipulating recombination to enhance plant breeding efficiency.

scholarly journals Male meiosis and pollen morphology in diploid Indonesian wild bananas and cultivars

The Nucleus ◽  
2021 ◽  
Author(s):  
Fajarudin Ahmad ◽  
Yuyu S. Poerba ◽  
Gert H. J. Kema ◽  
Hans de Jong
Keyword(s):  
Hybrid Sterility ◽  
Pollen Grains ◽  
Chromosome Analysis ◽  
Male Meiosis ◽  
Enzyme Treatment ◽  
Unreduced Gamete ◽  
Ploidy Levels ◽  
Scientific Disciplines ◽  
Sterile Pollen ◽  
Mother Cells

AbstractBreeding of banana is hampered by its genetic complexity, structural chromosome rearrangements and different ploidy levels. Various scientific disciplines, including cytogenetics, linkage mapping, and bioinformatics, are helpful tools in characterising cultivars and wild relatives used in crossing programs. Chromosome analysis still plays a pivotal role in studying hybrid sterility and structural and numerical variants. In this study, we describe the optimisation of the chromosome spreading protocol of pollen mother cells focusing on the effects of standard fixation methods, duration of the pectolytic enzyme treatment and advantages of fluorescence microscopy of DAPI stained cell spreads. We demonstrate the benefits of this protocol on meiotic features of five wild diploid Musa acuminata bananas and a diploid (AA) cultivar banana “Rejang”, with particular attention on pairing configurations and chromosome transmission that may be indicative for translocations and inversions. Pollen slides demonstrate regular-shaped spores except “Rejang”, which shows fertile pollen grains of different size and sterile pollen grains, suggesting partial sterility and unreduced gamete formation that likely resulted from restitutional meiotic divisions.

scholarly journals An abundance of developmental anomalies and abnormalities in Pleistocene people

2018 ◽  
Vol 115 (47) ◽  
pp. 11941-11946 ◽  
Author(s):  
Erik Trinkaus
Keyword(s):  
Fossil Record ◽  
Elevated Level ◽  
Developmental Disorders ◽  
Upper Paleolithic ◽  
Developmental Changes ◽  
Single Factor ◽  
Developmental Abnormalities ◽  
Low Probability ◽  
Developmental Variants

Diverse developmental abnormalities and anomalous features are evident in the PleistoceneHomofossil record, varying from minor but rare dental, vertebral, and carpal variants to exceptional systemic disorders. There are currently 75 documented anomalies or abnormalities from 66 individuals, spanning the Pleistocene but primarily from the Late Pleistocene Middle and Upper Paleolithic with their more complete skeletal remains. The expected probabilities of finding these variants or developmental disorders vary from <5% to <0.0001%, based on either recent human incidences or relevant Pleistocene sample distributions. Given the modest sample sizes available for the skeletal or dental elements in question, especially if the samples are appropriately limited in time and geography, the cumulative multiplicative probability of finding these developmental changes is vanishingly small. These data raise questions regarding social survival abilities, differing mortuary treatments of the biologically unusual, the role of ubiquitous stress among these Pleistocene foragers, and their levels of consanguinity. No single factor sufficiently accounts for the elevated level of these developmental variants or the low probability of finding them in the available paleontological record.

Volatile oils and the study of natural hybridization between Correa aemula and C. reflexa (Rutaceae)

1977 ◽  
Vol 25 (3) ◽  
pp. 291 ◽  
Author(s):  
T Whiffin
Keyword(s):  
Numerical Analysis ◽  
Parental Species ◽  
Volatile Oil ◽  
Natural Hybridization ◽  
Volatile Oils ◽  
Hybrid Swarm ◽  
Hybrid Plants ◽  
Complex Variation

A small hybrid swarm between Correa aemula and C. reflexa was located and examined morphologically and chemically, with an emphasis on volatile oils. The hybrid plants were intermediate morphologically between the two parental species. The volatile oil data were subjected to multivariate numerical analysis, the results of which confirmed the general intermediacy of the hybrid plants. In general it was found that ordination is a more useful technique for the study of hybridization than is classification. It would appear that numerical analysis of volatile oil data will prove a useful technique in the study of the complex variation found within the genus Correa.

scholarly journals Hybridization History and Repetitive Element Content in the Genome of a Homoploid Hybrid, Yucca gloriosa (Asparagaceae)

2021 ◽  
Vol 11 ◽  
Author(s):  
Karolina Heyduk ◽  
Edward V. McAssey ◽  
Jane Grimwood ◽  
Shengqiang Shu ◽  
Jeremy Schmutz ◽  
...  
Keyword(s):  
Parental Species ◽  
Expression Patterns ◽  
Hybrid Plant ◽  
Sequencing Data ◽  
Hybrid Species ◽  
Chloroplast Genomes ◽  
Important Trait ◽  
Homoploid Hybrid ◽  
Whole Genome Resequencing ◽  
Expression Evidence

Hybridization in plants results in phenotypic and genotypic perturbations that can have dramatic effects on hybrid physiology, ecology, and overall fitness. Hybridization can also perturb epigenetic control of transposable elements, resulting in their proliferation. Understanding the mechanisms that maintain genomic integrity after hybridization is often confounded by changes in ploidy that occur in hybrid plant species. Homoploid hybrid species, which have no change in chromosome number relative to their parents, offer an opportunity to study the genomic consequences of hybridization in the absence of change in ploidy. Yucca gloriosa (Asparagaceae) is a young homoploid hybrid species, resulting from a cross between Yucca aloifolia and Yucca filamentosa. Previous analyses of ∼11 kb of the chloroplast genome and nuclear-encoded microsatellites implicated a single Y. aloifolia genotype as the maternal parent of Y. gloriosa. Using whole genome resequencing, we assembled chloroplast genomes from 41 accessions of all three species to re-assess the hybrid origins of Y. gloriosa. We further used re-sequencing data to annotate transposon abundance in the three species and mRNA-seq to analyze transcription of transposons. The chloroplast phylogeny and haplotype analysis suggest multiple hybridization events contributing to the origin of Y. gloriosa, with both parental species acting as the maternal donor. Transposon abundance at the superfamily level was significantly different between the three species; the hybrid was frequently intermediate to the parental species in TE superfamily abundance or appeared more similar to one or the other parent. In only one case—Copia LTR transposons—did Y. gloriosa have a significantly higher abundance relative to either parent. Expression patterns across the three species showed little increased transcriptional activity of transposons, suggesting that either no transposon release occurred in Y. gloriosa upon hybridization, or that any transposons that were activated via hybridization were rapidly silenced. The identification and quantification of transposon families paired with expression evidence paves the way for additional work seeking to link epigenetics with the important trait variation seen in this homoploid hybrid system.

scholarly journals Homeotic transformations and number changes in the vertebral column of Triturus newts

2015 ◽  
Author(s):  
Maja Slijepčević ◽  
Frietson F Galis ◽  
Jan W Arntzen ◽  
Ana Ivanović
Keyword(s):  
Intraspecific Variation ◽  
Selection Pressure ◽  
Parental Species ◽  
Aquatic Environments ◽  
Thoracic Vertebrae ◽  
Modal Number ◽  
Selective Pressures ◽  
Selection For ◽  
Species Hybridization ◽  
Range Of Variation

We explored intraspecific variation in vertebral formulae, more specifically the variation in the number of thoracic vertebrae and frequencies of transitional sacral vertebrae in Triturus newts (Caudata: Salamandridae). Within salamandrid salamanders this monophyletic group shows the highest disparity in the number of thoracic vertebrae and considerable intraspecific variation in the number of thoracic vertebrae. Triturus species also differ in their ecological preferences, from predominantly terrestrial to largely aquatic. Following Geoffroy St. Hilaire’s and Darwin’s rule which states that structures with a large number of serially homologous repetitive elements are more variable than structures with smaller numbers, we hypothesized that the variation in vertebral formulae increases in more elongated species with a larger number of thoracic vertebrae. We furthermore hypothesized that the frequency of transitional vertebrae will be correlated with the variation in the number of thoracic vertebrae within the species. We also investigated potential effects of species hybridization on the vertebral formula. The proportion of individuals with a number of thoracic vertebrae different from the modal number and the range of variation in number of vertebrae significantly increased in species with a larger number of thoracic vertebrae. Contrary to our expectation, the frequencies of transitional vertebrae were not correlated with frequencies of change in the complete vertebrae number. The frequency of transitional sacral vertebra in hybrids did not significantly differ from that of the parental species. Such a pattern could be a result of selection pressure against transitional vertebrae and/or a bias towards the development of full vertebrae numbers. Although our data indicate relaxed selection for vertebral count changes in more elongated, aquatic species, more data on different selective pressures in species with different numbers of vertebrae in the two contrasting, terrestrial and aquatic environments are needed to test for causality.

A requirement for the Abnormal Spindle protein to organise microtubules of the central spindle for cytokinesis inDrosophila

2002 ◽  
Vol 115 (5) ◽  
pp. 913-922 ◽  
Author(s):  
Maria Giovanna Riparbelli ◽  
Giuliano Callaini ◽  
David M. Glover ◽  
Maria do Carmo Avides
Keyword(s):  
Spindle Pole Body ◽  
Spindle Pole ◽  
Male Meiosis ◽  
Wild Type ◽  
Female Meiosis ◽  
Central Spindle ◽  
Spindle Poles ◽  
Late Anaphase ◽  
Mutant Cells ◽  
Sperm Aster

Drosophila abnormal spindle (asp) mutants exhibit a mitotic metaphase checkpoint arrest with abnormal spindle poles, which reflects a requirement for Asp for the integrity of microtubule organising centres (MTOCs). In male meiosis, the absence of a strong spindle integrity checkpoint enables asp mutant cells to proceed through anaphase and telophase. However, the central spindle region is not correctly organised and cells frequently fail to complete cytokinesis. This contrasts with meiosis in wild-type males where at late anaphase a dense array of microtubules forms in the central spindle region that has Asp localised at its border. We speculate that Asp is associated with the minus ends of microtubules that have been released from the spindle poles to form the central spindle. A parallel situation arises in female meiosis where Asp not only associates with the minus ends of microtubules at the acentriolar poles but also with the central spindle pole body that forms between the two tandem spindles of meiosis II. Upon fertilisation, Asp is also recruited to the MTOC that nucleates the sperm aster. Asp is required for growth of the microtubules of the sperm aster,which in asp mutants remains diminutive and so prevents migration of the pronuclei.

Recombination in male and female meiocytes contrasted

1977 ◽  
Vol 277 (955) ◽  
pp. 227-233 ◽  
Keyword(s):  
Chiasma Frequency ◽  
Male Meiosis ◽  
Comparative Data ◽  
Evolutionary Significance ◽  
Female Meiosis ◽  
Male And Female ◽  
Intrachromosomal Recombination ◽  
Male Side ◽  
Chromosomal Recombination

For technical reasons studies of chiasma frequency and distribution, and hence of intrachromosomal recombination, have mostly been confined to male meiosis. However, there is now sufficient comparative data on male and female meiosis, in both plants and animals, to show that the extent of intra-chromosomal recombination in some organisms may be much the same on the female as on the male side, whereas other organisms show extreme sexual divergence in this regard. The evolutionary significance of such diversity remains enigmatic

scholarly journals Genetic divergence and the number of hybridizing species affect the path to homoploid hybrid speciation

2018 ◽  
Vol 115 (39) ◽  
pp. 9761-9766 ◽  
Author(s):  
Aaron A. Comeault ◽  
Daniel R. Matute
Keyword(s):  
Genetic Diversity ◽  
Reproductive Isolation ◽  
Genetic Divergence ◽  
Adaptive Systems ◽  
Parental Species ◽  
Hybrid Speciation ◽  
Hybrid Species ◽  
Empirical Question ◽  
Homoploid Hybrid

Hybridization is often maladaptive and in some instances has led to the loss of biodiversity. However, hybridization can also promote speciation, such as during homoploid hybrid speciation, thereby generating biodiversity. Despite examples of homoploid hybrid species, the importance of hybridization as a speciation mechanism is still widely debated, and we lack a general understanding of the conditions most likely to generate homoploid hybrid species. Here we show that the level of genetic divergence between hybridizing species has a large effect on the probability that their hybrids evolve reproductive isolation. We find that populations of hybrids formed by parental species with intermediate levels of divergence were more likely to mate assortatively, and discriminate against their parental species, than those generated from weakly or strongly diverged parental species. Reproductive isolation was also found between hybrid populations, suggesting differential sorting of parental traits across populations. Finally, hybrid populations derived from three species were more likely to evolve reproductive isolation than those derived from two species, supporting arguments that hybridization-supplied genetic diversity can lead to the evolution of novel “adaptive systems” and promote speciation. Our results illustrate when we expect hybridization and admixture to promote hybrid speciation. Whether homoploid hybrid speciation is a common speciation mechanism in general remains an outstanding empirical question.

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