scholarly journals Maternally-regulated gastrulation as a source of variation contributing to cavefish forebrain evolution

2018 ◽  
Author(s):  
Jorge Torres-Paz ◽  
Julien Leclercq ◽  
Sylvie Rétaux
Keyword(s):  
Neural Development ◽  
Brain Evolution ◽  
F1 Hybrids ◽  
Maternal Factors ◽  
Phenotypic Differences ◽  
Astyanax Mexicanus ◽  
Maternal Effect Genes ◽  
Blind Cave ◽  
The Moment ◽  
Brain Change

AbstractSequential developmental events, starting from the moment of fertilization, are crucial for the acquisition of animal body plan. Subtle modifications in such early events are likely to have a major impact in later morphogenesis, bringing along morphological diversification. Here, comparing the blind cave and the surface morphotypes of Astyanax mexicanus fish, we found heterochronies during gastrulation, producing organizer and axial mesoderm tissues with different properties, including differences in expression of dkk1b, that may have contributed to cavefish brain evolution. These variations observed during gastrulation depend fully on maternal factors, whereas later phenotypic differences in neural development became progressively hidden when zygotic genes take the control over development. Transcriptomic analysis of fertilized eggs from both morphotypes and reciprocal F1 hybrids showed a strong and specific maternal signature. Our work strongly suggests that maternal effect genes and developmental heterochronies occurring during gastrulation have impacted morphological brain change during cavefish evolution.

scholarly journals Maternally regulated gastrulation as a source of variation contributing to cavefish forebrain evolution

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Jorge Torres-Paz ◽  
Julien Leclercq ◽  
Sylvie Rétaux
Keyword(s):  
Brain Evolution ◽  
F1 Hybrids ◽  
Maternal Factors ◽  
Astyanax Mexicanus ◽  
Developmental Evolution ◽  
Larval Stages ◽  
Maternal Effect Genes ◽  
Blind Cave ◽  
The Moment ◽  
Brain Change

Sequential developmental events, starting from the moment of fertilization, are crucial for the acquisition of animal body plan. Subtle modifications in such early events are likely to have major impacts in later morphogenesis, bringing along morphological diversification. Here, comparing the blind cave and the surface morphotypes of Astyanax mexicanus fish, we found heterochronies during gastrulation that produce organizer and axial mesoderm tissues with different properties (including differences in the expression of dkk1b) that may have contributed to cavefish brain evolution. These variations observed during gastrulation depend fully on maternal factors. The developmental evolution of retinal morphogenesis and hypothalamic patterning are among those traits that retained significant maternal influence at larval stages. Transcriptomic analysis of fertilized eggs from both morphotypes and reciprocal F1 hybrids showed a strong and specific maternal signature. Our work strongly suggests that maternal effect genes and developmental heterochronies that occur during gastrulation have impacted morphological brain change during cavefish evolution.

Mid-parent advantage and heterosis in F1 hybrids of wheat from crosses among old and modern varieties

1998 ◽  
Vol 130 (3) ◽  
pp. 287-295 ◽  
Author(s):  
C. L. MORGAN
Keyword(s):  
Grain Yield ◽  
Yield Components ◽  
Field Trials ◽  
Yield Component ◽  
Grain Weight ◽  
F1 Hybrids ◽  
Phenotypic Differences ◽  
Beneficial Effects ◽  
Positive Heterosis ◽  
Modern Varieties

Twenty-eight F1 hybrids of wheat and their parents were grown in field trials at Trumpington, Cambridge during 1986/87 and 1987/88. They were derived from crosses between seven ‘modern’ varieties, used as female parents, and either two ‘old’ (Squareheads Master and Partridge) or two ‘modern’ varieties (Bert and Motto), which were used as male parents. Grain yield, yield components, biomass and height were determined. The male parents were chosen to provide contrasting phenotypes and genetic backgrounds for the F1 hybrids. Mid-parent advantage, the increase of a hybrid for a given character above the mean of its parents, and heterosis, the increase of a hybrid above the ‘better’ parent for that character, were calculated. Most F1 hybrids showed mid-parent advantage for the characters studied. This tended to be greatest for hybrids derived from parents with the largest phenotypic differences in that character. In contrast, where heterosis occurred it tended to be greatest where the phenotypic difference between the parents was least. This suggests that the beneficial effects of hybridization, resulting from the dispersion of dominant genes between the parents, was insufficient to overcome the detrimental effects of other genes present where the ‘less good’ parent was substantially lower than the ‘better’ parent. Hybrids derived from the ‘modern’ male parents had greater heterosis for grain yield and mean grain weight than those from the ‘old’ parents. Of the yield components, positive heterosis for mean grain weight resulted in heavier seeds and was the most important yield component in determining heterosis in grain yield. Heterosis for the number of grains/ear was small or did not differ significantly from zero while number of ears/m2 showed negative heterosis resulting in fewer ears/m2 in the hybrids.

scholarly journals Theoretical justification of the possibility of selection perspective individuals in variety populations of self-pollinators on the example of soybean

2021 ◽  
Vol 186 (2) ◽  
pp. 31-40
Author(s):  
V.M. Lukomets ◽  
◽  
S.V. Zelentsov ◽  
E.V. Moshnenko ◽  
◽  
...  
Keyword(s):  
F1 Hybrids ◽  
Individual Selection ◽  
Breeding Methods ◽  
Morphometric Traits ◽  
Phenotypic Differences ◽  
Soybean Cultivars ◽  
Oil Crops ◽  
Experimental Base ◽  
Modified Formula ◽  
Selection Of

Breeding practice shows that soybean cultivars developed by synthetic breeding methods are submitted for the state variety testing in the F10–F11 generation. But the newly bred cultivars are not completely homozygous. The studies were related to the determination of the frequencies of formation of atypical and suitable for selection promising individuals in soybean cultivars developed by synthetic breeding methods. The studies were carried out in 2019–2020 at the central experimental base of V.S. Pustovoit All-Russian Research Institute of Oil Crops, Krasnodar. In the experiments, we used cultivars of our own breeding: Selena, Puma, Vita, Irbis, Bars, Barguzin and Sayana with a total age of 11–15 years from the year F1 hybrids were obtained. To confirm the practical possibility of isolating individuals differing from the phenotypic varietal norm in varietal populations, a complete examination of the crops of all studied soybean cultivars was carried out. In the fields of all cultivars, individuals were identified that differed from the varietal norm phenotypically. Mostly, the isolated individuals were distinguished by an increased plant height, a more powerful habit, an increased number of beans per plant, and resistance to lodging. The facts of the detection of atypical individuals with improved morphological traits in soybean cultivars of different ages confirm the possibility of individual selection of plants in varietal populations based on morphometric traits. The statistical dynamics of a decrease in heterozygous individuals in increasing generations in a hybrid self-pollinating population in terms of the number of paired genes, by which the parental forms can hypothetically differ, were calculated using the modified formula of S. Borojević (1984). It was found that the frequency of formation of phenotypically different individuals in varietal populations of soybeans depends on the total age of the cultivar. The frequency of the formation of morphologically different individuals decreases with an increase in the number of generations of the cultivar. Individual selection of individuals with positive phenotypic differences from the varietal norm can be recommended as an additional source of promising and practically homozygous starting material for accelerated analytical breeding of soybean.

scholarly journals A hypomorphic cystathionine ß-synthase gene contributes to cavefish eye loss by disrupting optic vasculature

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Li Ma ◽  
Aniket V. Gore ◽  
Daniel Castranova ◽  
Janet Shi ◽  
Mandy Ng ◽  
...  
Keyword(s):  
Circulatory System ◽  
Astyanax Mexicanus ◽  
Transsulfuration Pathway ◽  
Key Enzyme ◽  
Surface Dwelling ◽  
Blind Cave ◽  
Vestigial Structures ◽  
Key Indicators ◽  
Evolutionary Descent ◽  
Eye Formation

Abstract Vestigial structures are key indicators of evolutionary descent, but the mechanisms underlying their development are poorly understood. This study examines vestigial eye formation in the teleost Astyanax mexicanus, which consists of a sighted surface-dwelling morph and multiple populations of blind cave morphs. Cavefish embryos initially develop eyes, but they subsequently degenerate and become vestigial structures embedded in the head. The mutated genes involved in cavefish vestigial eye formation have not been characterized. Here we identify cystathionine ß-synthase a (cbsa), which encodes the key enzyme of the transsulfuration pathway, as one of the mutated genes responsible for eye degeneration in multiple cavefish populations. The inactivation of cbsa affects eye development by increasing the transsulfuration intermediate homocysteine and inducing defects in optic vasculature, which result in aneurysms and eye hemorrhages. Our findings suggest that localized modifications in the circulatory system may have contributed to the evolution of vestigial eyes in cavefish.

A Topographical Method for the Development of Neural Networks for Artificial Brain Evolution

2005 ◽  
Vol 11 (3) ◽  
pp. 293-316 ◽  
Author(s):  
Sung Young Jung
Keyword(s):  
Gene Expression ◽  
Neural Networks ◽  
Neural Development ◽  
Evolutionary Process ◽  
Brain Evolution ◽  
Development Method ◽  
Neural Connections ◽  
Modular Networks ◽  
Long Duration ◽  
Artificial Brain

Developmental neural networks, which are constructed according to developmental rules (i.e., genes), have the potential to be differentiated into heteromorphic neural structures capable of performing various kinds of activities. The fact that the biological neural architectures are found to be highly repetitive, layered, and topographically organized has important consequences for neural development methods. The purpose of this article is to propose a neural development method that can construct topographical neural connections, that is, a topographical development method, to facilitate fast and efficient development. This is achieved by arborizing neural connections on a developmental tree that rarely produces dead connections. Modular gene expression and corresponding modular networks have an important role in a gradual evolutionary process. Gene expression for modular networks is also proposed here as a way to reduce the probability of fatal mutants created through gene alteration. The corresponding evolutionary experiment shows that various neural structures—layered, repetitive, modular, and complex ones like those in the biological brain—can be constructed and easily observed. It also demonstrates that due to the efficiency of the proposed method, large neural networks can be easily managed, thereby making it suitable for long duration evolutionary experiments.

scholarly journals An epigenetic mechanism for cavefish eye degeneration

2017 ◽  
Author(s):  
Aniket V. Gore ◽  
Kelly A. Tomins ◽  
James Iben ◽  
Li Ma ◽  
Daniel Castranova ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Eye Development ◽  
Phenotypic Diversity ◽  
Phenotypic Variability ◽  
Epigenetic Mechanism ◽  
Gene Repression ◽  
Specific Gene ◽  
Astyanax Mexicanus ◽  
Eye Disorders ◽  
Blind Cave

Coding and non-coding mutations in DNA contribute significantly to phenotypic variability during evolution. However, less is known about the role of epigenetics in this process. Although previous studies have identified eye development genes associated with the loss of eyes phenotype in the Pachón blind cave morph of the Mexican tetra Astyanax mexicanus1-6, no inactivating mutations have been found in any of these genes2,3,7-10. Here we show that excess DNA methylation-based epigenetic silencing promotes eye degeneration in blind cave Astyanax mexicanus. By performing parallel analyses in Astyanax mexicanus cave and surface morphs and in the zebrafish Danio rerio, we have discovered that DNA methylation mediates eye-specific gene repression and globally regulates early eye development. The most significantly hypermethylated and down-regulated genes in the cave morph are also linked to human eye disorders, suggesting the function of these genes is conserved across the vertebrates. Our results show that changes in DNA methylation-based gene repression can serve as an important molecular mechanism generating phenotypic diversity during development and evolution.

scholarly journals Identification of maternal-effect genes in zebrafish using maternal crispants

Development ◽  
2021 ◽  
Author(s):  
Cara E. Moravec ◽  
Gabriella C. Voit ◽  
Jarred Otterlee ◽  
Francisco Pelegri
Keyword(s):  
Maternal Effect ◽  
Reverse Genetics ◽  
Germ Line ◽  
Maternal Factors ◽  
Single Generation ◽  
Maternal Effect Genes ◽  
Biallelic Mutations ◽  
Genome Activation

In animals, early development is dependent on a pool of maternal factors, both RNA and proteins, which are required for basic cellular process and cell differentiation until zygotic genome activation. The role of a majority of these maternally expressed factors is not fully understood. By exploiting the biallelic editing ability of CRISPR-Cas9, we identify and characterize maternal-effect genes in a single generation, using a maternal crispant technique. We validated the ability to generate biallelic mutations in the germline by creating maternal crispants that phenocopied previously characterized maternal-effect genes: motley/birc5b, tmi/prc1l, and aura/mid1ip1. Additionally, by targeting maternally expressed genes of unknown function in zebrafish, we identified two new maternal-effect zebrafish genes, kpna7 and fhdc3. The genetic identity of these maternal crispants was confirmed by sequencing haploid progeny from F0 females, which allowed the analysis of newly induced lesions in the maternal germ line. Our studies show that maternal crispants allow for the effective identification and primary characterization of maternal-effect genes in a single generation, facilitating the reverse genetics analysis of maternal factors that drive embryonic development.

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