Artículos de revistas: "Transition to asexuality"

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Dedukh, Dmitrij, Anatolie Marta y Karel Janko. "Challenges and Costs of Asexuality: Variation in Premeiotic Genome Duplication in Gynogenetic Hybrids from Cobitis taenia Complex". International Journal of Molecular Sciences 22, n.º 22 (9 de noviembre de 2021): 12117. http://dx.doi.org/10.3390/ijms222212117.

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The transition from sexual reproduction to asexuality is often triggered by hybridization. The gametogenesis of many hybrid asexuals involves premeiotic genome endoreplication leading to bypass hybrid sterility and forming clonal gametes. However, it is still not clear when endoreplication occurs, how many gonial cells it affects and whether its rate differs among clonal lineages. Here, we investigated meiotic and premeiotic cells of diploid and triploid hybrids of spined loaches (Cypriniformes: Cobitis) that reproduce by gynogenesis. We found that in naturally and experimentally produced F1 hybrids asexuality is achieved by genome endoreplication, which occurs in gonocytes just before entering meiosis or, rarely, one or a few divisions before meiosis. However, genome endoreplication was observed only in a minor fraction of the hybrid’s gonocytes, while the vast majority of gonocytes were unable to duplicate their genomes and consequently could not proceed beyond pachytene due to defects in bivalent formation. We also noted that the rate of endoreplication was significantly higher among gonocytes of hybrids from natural clones than of experimentally produced F1 hybrids. Thus, asexuality and hybrid sterility are intimately related phenomena and the transition from sexual reproduction to asexuality must overcome significant problems with genome incompatibilities with a possible impact on reproductive potential.

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Beck, James B., Patrick J. Alexander, Loreen Allphin, Ihsan A. Al-Shehbaz, Catherine Rushworth, C. Donovan Bailey y Michael D. Windham. "DOES HYBRIDIZATION DRIVE THE TRANSITION TO ASEXUALITY IN DIPLOID BOECHERA?" Evolution 66, n.º 4 (8 de diciembre de 2011): 985–95. http://dx.doi.org/10.1111/j.1558-5646.2011.01507.x.

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3

Huylmans, Ann Kathrin, Ariana Macon, Francisco Hontoria y Beatriz Vicoso. "Transitions to asexuality and evolution of gene expression in Artemia brine shrimp". Proceedings of the Royal Society B: Biological Sciences 288, n.º 1959 (22 de septiembre de 2021): 20211720. http://dx.doi.org/10.1098/rspb.2021.1720.

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While sexual reproduction is widespread among many taxa, asexual lineages have repeatedly evolved from sexual ancestors. Despite extensive research on the evolution of sex, it is still unclear whether this switch represents a major transition requiring major molecular reorganization, and how convergent the changes involved are. In this study, we investigated the phylogenetic relationship and patterns of gene expression of sexual and asexual lineages of Eurasian Artemia brine shrimp, to assess how gene expression patterns are affected by the transition to asexuality. We find only a few genes that are consistently associated with the evolution of asexuality, suggesting that this shift may not require an extensive overhauling of the meiotic machinery. While genes with sex-biased expression have high rates of expression divergence within Eurasian Artemia , neither female- nor male-biased genes appear to show unusual evolutionary patterns after sexuality is lost, contrary to theoretical expectations.

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Kampfraath, Andries Augustus, Tjeerd Pieter Dudink, Ken Kraaijeveld, Jacintha Ellers y Zaira Valentina Zizzari. "Male Sexual Trait Decay in Two Asexual Springtail Populations Follows Neutral Mutation Accumulation Theory". Evolutionary Biology 47, n.º 4 (20 de agosto de 2020): 285–92. http://dx.doi.org/10.1007/s11692-020-09511-z.

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Abstract The transition to asexual reproduction is frequent and widespread across the tree of life and constitutes a major life history change. Without sexual reproduction, selection on sexually selected traits is expected to be weaker or absent, allowing the decay and ultimately loss of sexual traits. In this study, we applied an experimental approach to investigate the decay of reproductive traits under asexuality in two asexual populations of the springtail Folsomia candida. Specifically, we compared several key male sexual traits of a sexual population and two distinct parthenogenetic lines. To allow direct comparisons between sexual and asexual individuals we first determined a suite of life history characteristics in the sexual F. candida population, which performs an indirect transfer of sperm packages (spermatophores).To investigate the decay of male sexual traits under asexuality we measured the size of spermatophores, quantified the amount of sperm DNA material, and tested spermatophore attractiveness to females in all three populations. The amount of sperm DNA material in the sperm droplets and the attractiveness of spermatophores were lower in the asexual lines compared to the sexual population. However, the two asexual lines differed in the extent of decay of these traits. Our results are consistent with predictions from neutral mutation accumulation theory, and thus suggest this to be the main evolutionary process underlying the decay of male traits in F. candida.

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Paland, S. "Transitions to Asexuality Result in Excess Amino Acid Substitutions". Science 311, n.º 5763 (17 de febrero de 2006): 990–92. http://dx.doi.org/10.1126/science.1118152.

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6

Larose, Chloé, Darren J. Parker y Tanja Schwander. "Fundamental and realized feeding niche breadths of sexual and asexual stick insects". Proceedings of the Royal Society B: Biological Sciences 285, n.º 1892 (28 de noviembre de 2018): 20181805. http://dx.doi.org/10.1098/rspb.2018.1805.

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The factors contributing to the maintenance of sex over asexuality in natural populations remain unclear. Ecological divergences between sexual and asexual lineages could help to maintain reproductive polymorphisms, at least transiently, but the consequences of asexuality for the evolution of ecological niches are unknown. Here, we investigated how niche breadths change in transitions from sexual reproduction to asexuality. We used host plant ranges as a proxy to compare the realized feeding niche breadths of five independently derived asexual Timema stick insect species and their sexual relatives at both the species and population levels. Asexual species had systematically narrower realized niches than sexual species, though this pattern was not apparent at the population level. To investigate how the narrower realized niches of asexual species arise, we performed feeding experiments to estimate fundamental niche breadths but found no systematic differences between reproductive modes. The narrow realized niches found in asexual species are therefore probably a consequence of biotic interactions such as predation or competition, that constrain realized niche size in asexuals more strongly than in sexuals.

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Butlin, R. "Comment on "Transitions to Asexuality Result in Excess Amino Acid Substitutions"". Science 313, n.º 5792 (8 de septiembre de 2006): 1389. http://dx.doi.org/10.1126/science.1128655.

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8

Tilquin, Anaïs y Hanna Kokko. "What does the geography of parthenogenesis teach us about sex?" Philosophical Transactions of the Royal Society B: Biological Sciences 371, n.º 1706 (19 de octubre de 2016): 20150538. http://dx.doi.org/10.1098/rstb.2015.0538.

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Theory predicts that sexual reproduction is difficult to maintain if asexuality is an option, yet sex is very common. To understand why, it is important to pay attention to repeatably occurring conditions that favour transitions to, or persistence of, asexuality. Geographic parthenogenesis is a term that has been applied to describe a large variety of patterns where sexual and related asexual forms differ in their geographic distribution. Often asexuality is stated to occur in a habitat that is, in some sense, marginal, but the interpretation differs across studies: parthenogens might not only predominate near the margin of the sexuals' distribution, but might also extend far beyond the sexual range; they may be disproportionately found in newly colonizable areas (e.g. areas previously glaciated), or in habitats where abiotic selection pressures are relatively stronger than biotic ones (e.g. cold, dry). Here, we review the various patterns proposed in the literature, the hypotheses put forward to explain them, and the assumptions they rely on. Surprisingly, few mathematical models consider geographic parthenogenesis as their focal question, but all models for the evolution of sex could be evaluated in this framework if the (often ecological) causal factors vary predictably with geography. We also recommend broadening the taxa studied beyond the traditional favourites. This article is part of the themed issue ‘Weird sex: the underappreciated diversity of sexual reproduction’.

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Neiman, M., T. F. Sharbel y T. Schwander. "Genetic causes of transitions from sexual reproduction to asexuality in plants and animals". Journal of Evolutionary Biology 27, n.º 7 (26 de marzo de 2014): 1346–59. http://dx.doi.org/10.1111/jeb.12357.

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Paland, S. y M. Lynch. "Response to Comment on "Transitions to Asexuality Result in Excess Amino Acid Substitutions"". Science 313, n.º 5792 (8 de septiembre de 2006): 1389. http://dx.doi.org/10.1126/science.1128745.

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11

Haag, K. L., E. Sheikh-Jabbari, F. Ben-Ami y D. Ebert. "Microsatellite and single-nucleotide polymorphisms indicate recurrent transitions to asexuality in a microsporidian parasite". Journal of Evolutionary Biology 26, n.º 5 (27 de marzo de 2013): 1117–28. http://dx.doi.org/10.1111/jeb.12125.

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12

Xie, Jing, Han Du, Guobo Guan, Yaojun Tong, Themistoklis K. Kourkoumpetis, Lixin Zhang, Feng-yan Bai y Guanghua Huang. "N-Acetylglucosamine Induces White-to-Opaque Switching and Mating in Candida tropicalis, Providing New Insights into Adaptation and Fungal Sexual Evolution". Eukaryotic Cell 11, n.º 6 (27 de abril de 2012): 773–82. http://dx.doi.org/10.1128/ec.00047-12.

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ABSTRACTPathogenic fungi are capable of switching between different phenotypes, each of which has a different biological advantage. In the most prevalent human fungal pathogen,Candida albicans, phenotypic transitions not only improve its adaptation to a continuously changing host microenvironment but also regulate sexual mating. In this report, we show thatCandida tropicalis, another important human opportunistic pathogen, undergoes reversible and heritable phenotypic switching, referred to as the “white-opaque” transition. Here we show thatN-acetylglucosamine (GlcNAc), an inducer of white-to-opaque switching inC. albicans, promotes opaque-cell formation and mating and also inhibits filamentation in a number of naturalC. tropicalisstrains. Our results suggest that host chemical signals may facilitate this phenotypic switching and mating ofC. tropicalis, which had been previously thought to reproduce asexually. Overexpression of theC. tropicalis WOR1gene inC. albicansinduces opaque-cell formation. Additionally, an intermediate phase between white and opaque was observed inC. tropicalis, indicating that the switching could be tristable.

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McElroy, Kyle E., Stefan Müller, Dunja K. Lamatsch, Laura Bankers, Peter D. Fields, Joseph R. Jalinsky, Joel Sharbrough, Jeffrey L. Boore, John M. Logsdon y Maurine Neiman. "Asexuality Associated with Marked Genomic Expansion of Tandemly Repeated rRNA and Histone Genes". Molecular Biology and Evolution 38, n.º 9 (22 de abril de 2021): 3581–92. http://dx.doi.org/10.1093/molbev/msab121.

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Abstract How does asexual reproduction influence genome evolution? Although is it clear that genomic structural variation is common and important in natural populations, we know very little about how one of the most fundamental of eukaryotic traits—mode of genomic inheritance—influences genome structure. We address this question with the New Zealand freshwater snail Potamopyrgus antipodarum, which features multiple separately derived obligately asexual lineages that coexist and compete with otherwise similar sexual lineages. We used whole-genome sequencing reads from a diverse set of sexual and asexual individuals to analyze genomic abundance of a critically important gene family, rDNA (the genes encoding rRNAs), that is notable for dynamic and variable copy number. Our genomic survey of rDNA in P. antipodarum revealed two striking results. First, the core histone and 5S rRNA genes occur between tandem copies of the 18S–5.8S–28S gene cluster, a unique architecture for these crucial gene families. Second, asexual P. antipodarum harbor dramatically more rDNA–histone copies than sexuals, which we validated through molecular and cytogenetic analysis. The repeated expansion of this genomic region in asexual P. antipodarum lineages following distinct transitions to asexuality represents a dramatic genome structural change associated with asexual reproduction—with potential functional consequences related to the loss of sexual reproduction.

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Burke, Nathan W. y Russell Bonduriansky. "The paradox of obligate sex: The roles of sexual conflict and mate scarcity in transitions to facultative and obligate asexuality". Journal of Evolutionary Biology 32, n.º 11 (10 de septiembre de 2019): 1230–41. http://dx.doi.org/10.1111/jeb.13523.

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Tvedte, Eric S., Kimberly K. O. Walden, Kyle E. McElroy, John H. Werren, Andrew A. Forbes, Glen R. Hood, John M. Logsdon, Jeffrey L. Feder y Hugh M. Robertson. "Genome of the Parasitoid Wasp Diachasma alloeum, an Emerging Model for Ecological Speciation and Transitions to Asexual Reproduction". Genome Biology and Evolution 11, n.º 10 (25 de septiembre de 2019): 2767–73. http://dx.doi.org/10.1093/gbe/evz205.

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Abstract Parasitoid wasps are among the most speciose animals, yet have relatively few available genomic resources. We report a draft genome assembly of the wasp Diachasma alloeum (Hymenoptera: Braconidae), a host-specific parasitoid of the apple maggot fly Rhagoletis pomonella (Diptera: Tephritidae), and a developing model for understanding how ecological speciation can “cascade” across trophic levels. Identification of gene content confirmed the overall quality of the draft genome, and we manually annotated ∼400 genes as part of this study, including those involved in oxidative phosphorylation, chemosensation, and reproduction. Through comparisons to model hymenopterans such as the European honeybee Apis mellifera and parasitoid wasp Nasonia vitripennis, as well as a more closely related braconid parasitoid Microplitis demolitor, we identified a proliferation of transposable elements in the genome, an expansion of chemosensory genes in parasitoid wasps, and the maintenance of several key genes with known roles in sexual reproduction and sex determination. The D. alloeum genome will provide a valuable resource for comparative genomics studies in Hymenoptera as well as specific investigations into the genomic changes associated with ecological speciation and transitions to asexuality.

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Mackay-Smith, Ava, Mary Kate Dornon, Rosalind Lucier, Anna Okimoto, Flavia Mendonca de Sousa, Marcela Rodriguero, Viviana Confalonieri, Analia A. Lanteri y Andrea S. Sequeira. "Host-specific gene expression as a tool for introduction success in Naupactus parthenogenetic weevils". PLOS ONE 16, n.º 7 (30 de julio de 2021): e0248202. http://dx.doi.org/10.1371/journal.pone.0248202.

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Food resource access can mediate establishment success in invasive species, and generalist herbivorous insects are thought to rely on mechanisms of transcriptional plasticity to respond to dietary variation. While asexually reproducing invasives typically have low genetic variation, the twofold reproductive capacity of asexual organisms is a marked advantage for colonization. We studied host-related transcriptional acclimation in parthenogenetic, invasive, and polyphagous weevils: Naupactus cervinus and N. leucoloma. We analyzed patterns of gene expression in three gene categories that can mediate weevil-host plant interactions through identification of suitable host plants, short-term acclimation to host plant defenses, and long-term adaptation to host plant defenses and their pathogens. This approach employed comparative transcriptomic methods to investigate differentially expressed host detection, detoxification, immune defense genes, and pathway-level gene set enrichment. Our results show that weevil gene expression responses can be host plant-specific, and that elements of that response can be maintained in the offspring. Some host plant groups, such as legumes, appear to be more taxing as they elicit a complex gene expression response which is both strong in intensity and specific in identity. However, the weevil response to taxing host plants shares many differentially expressed genes with other stressful situations, such as host plant cultivation conditions and transition to novel host, suggesting that there is an evolutionarily favorable shared gene expression regime for responding to different types of stressful situations. Modulating gene expression in the absence of other avenues for phenotypic adaptation may be an important mechanism of successful colonization for these introduced insects.

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Ji, Xiaoxiao, Xiaolong Li, Lin Wang, Suning Liu, Xinyu Jiang y Yufeng Pan. "Asexuality in Drosophila juvenile males is organizational and independent of juvenile hormone". EMBO reports, 2 de agosto de 2023. http://dx.doi.org/10.15252/embr.202356898.

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AbstractSexuality is generally prevented in newborns and arises with organizational rewiring of neural circuitry and optimization of fitness for reproduction competition. Recent studies reported that sex circuitry in Drosophila melanogaster is developed in juvenile males but functionally inhibited by juvenile hormone (JH). Here, we find that the fly sex circuitry, mainly expressing the male‐specific fruitless (fruM) and/or doublesex (dsx), is organizationally undeveloped and functionally inoperative in juvenile males. Artificially activating all fruM neurons induces substantial courtship in solitary adult males but not in juvenile males. Synaptic transmissions between major courtship regulators and all dsx neurons are strong in adult males but either weak or undetectable in juvenile males. We further find that JH does not inhibit male courtship in juvenile males but instead promotes courtship robustness in adult males. Our results indicate that the transition to sexuality from juvenile to adult flies requires organizational rewiring of neural circuitry.

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Ye, Zhiqiang, Xiaoqian Jiang, Michael E. Pfrender y Michael Lynch. "Genome-Wide Allele-Specific Expression in Obligately Asexual Daphnia pulex and the Implications for the Genetic Basis of Asexuality". Genome Biology and Evolution 13, n.º 11 (1 de noviembre de 2021). http://dx.doi.org/10.1093/gbe/evab243.

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Abstract Although obligately asexual lineages are thought to experience selective disadvantages associated with reduced efficiency of fixing beneficial mutations and purging deleterious mutations, such lineages are phylogenetically and geographically widespread. However, despite several genome-wide association studies, little is known about the genetic elements underlying the origin of obligate asexuality and how they spread. Because many obligately asexual lineages have hybrid origins, it has been suggested that asexuality is caused by the unbalanced expression of alleles from the hybridizing species. Here, we investigate this idea by identifying genes with allele-specific expression (ASE) in a Daphnia pulex population, in which obligate parthenogens (OP) and cyclical parthenogens (CP) coexist, with the OP clones having been originally derived from hybridization between CP D. pulex and its sister species, Daphnia pulicaria. OP D. pulex have significantly more ASE genes (ASEGs) than do CP D. pulex. Whole-genomic comparison of OP and CP clones revealed ∼15,000 OP-specific markers and 42 consistent ASEGs enriched in marker-defined regions. Ten of the 42 ASEGs have alleles coding for different protein sequences, suggesting functional differences between the products of the two parental alleles. At least three of these ten genes appear to be directly involved in meiosis-related processes, for example, RanBP2 can cause abnormal chromosome segregation in anaphase I, and the presence of Wee1 in immature oocytes leads to failure to enter meiosis II. These results provide a guide for future molecular resolution of the genetic basis of the transition to ameiotic parthenogenesis.

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Molinier, Cécile, Thomas Lenormand y Christoph R. Haag. "No recombination suppression in asexually produced males of Daphnia pulex". Evolution, 22 de junio de 2023. http://dx.doi.org/10.1093/evolut/qpad114.

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Abstract Obligate parthenogenesis (OP) is often thought to evolve by disruption of reductional meiosis and suppression of crossover recombination. In the crustacean Daphnia pulex, OP lineages, which have evolved from cyclical parthenogenetic (CP) ancestors, occasionally produce males that are capable of reductional meiosis. Here, by constructing high-density linkage maps, we find that these males show only slightly and non-significantly reduced recombination rates compared to CP males and females. Both meiosis disruption and recombination suppression are therefore sex-limited (or partly so), which speaks against the evolution of OP by disruption of a gene that is essential for meiosis or recombination in both sexes. The findings may be explained by female-limited action of genes that suppress recombination, but previously identified candidate genes are known to be expressed in both sexes. Alternatively, and equally consistent with the data, OP might have evolved through a re-use of the parthenogenesis pathways already present in CP and through their extension to all events of oogenesis. The causal mutations for the CP to OP transition may therefore include mutations in genes involved in oogenesis regulation and may not necessarily be restricted to genes of the “meiosis toolkit”. More generally, our study emphasizes that there are many ways to achieve asexuality, and elucidating the possible mechanisms is key to ultimately identify the genes and traits involved.

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Mau, Martin, Terezie M. Mandáková, Xingliang Ma, Jana Ebersbach, Lifang Zou, Martin A. Lysak y Timothy F. Sharbel. "Evolution of an Apomixis-Specific Allele Class in Supernumerary Chromatin of Apomictic Boechera". Frontiers in Plant Science 13 (1 de junio de 2022). http://dx.doi.org/10.3389/fpls.2022.890038.

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Asexual reproduction through seeds in plants (i.e., apomixis) is a heritable trait, and apomixis- linked loci have been identified in multiple species. However, direct identification of genomic elements is typically hindered as apomixis-linked loci and are commonly found in recombination-suppressed and repetitive regions. Heterochromatinized elements, such as B chromosomes and other supernumerary chromosomal DNA fragments have long been known to be associated with asexuality in both plants and animals and are prime candidate regions for the evolution of multiple apomixis factors controlling the individual elements of apomixis. Here, we examined molecular evolution, gene regulation, and chromosomal location of a male apomeiosis factor (UPG2), a long noncoding RNA gene, in sexual and apomictic Boechera with and without male apomeiosis (i.e., balanced and unbalanced apomicts). We revealed the origin of the gene in the apomixis genome on an apomixis-specific, supernumerary heterochromatic Boechera chromosome (Boe1). The UPG2 is active in the tapetum at male meiosis. We found allele classes specific to apomictic and sexual Boechera accessions and a third class that shares the features of both and points to a convergent transition state. Sex alleles are found only in some of the sexual accessions and have higher nucleotide divergence and lower transcriptional activity compared to apo alleles. These data demonstrate selective pressure to maintain the function of UPG2 for unreduced pollen formation in apomicts as the occasional transmission of the allele from unbalanced apomicts into sexual organisms that lead to pseudogenization and functional decay of copies in sexual organisms.

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Tichopád, Tomáš, Roman Franěk, Marie Doležálková-Kaštánková, Dmitrij Dedukh, Anatolie Marta, Karel Halačka, Christoph Steinbach, Karel Janko y Martin Pšenička. "Clonal gametogenesis is triggered by intrinsic stimuli in the hybrid’s germ cells but is dependent on sex differentiation". Biology of Reproduction, 13 de abril de 2022. http://dx.doi.org/10.1093/biolre/ioac074.

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Abstract Interspecific hybridization may trigger the transition from sexual reproduction to asexuality, but mechanistic reasons for such a change in a hybrid’s reproduction are poorly understood. Gametogenesis of many asexual hybrids involves a stage of premeiotic endoreduplication (PMER), when gonial cells duplicate chromosomes and subsequent meiotic divisions involve bivalents between identical copies, leading to production of clonal gametes. Here, we investigated the triggers of PMER and whether its induction is linked to intrinsic stimuli within a hybrid’s gonial cells or whether it is regulated by the surrounding gonadal tissue. We investigated gametogenesis in the Cobitis taenia hybrid complex, which involves sexually reproducing species (Cobitis elongatoides and C. taenia) as well as their hybrids, where females reproduce clonally via PMER while males are sterile. We transplanted spermatogonial stem cells (SSCs) from C. elongatoides and triploid hybrid males into embryos of sexual species and of asexual hybrid females, respectively, and observed their development in an allospecific gonadal environment. Sexual SSCs underwent regular meiosis and produced normally reduced gametes when transplanted into clonal females. On the other hand, the hybrid’s SSCs lead to sterility when transplanted into sexual males, but maintained their ability to undergo asexual development (PMER) and production of clonal eggs, when transplanted into sexual females. This suggests that asexual gametogenesis is under complex control when somatic gonadal tissue indirectly affects the execution of asexual development by determining the sexual differentiation of stem cells and once such cells develop to female phenotypes, hybrid germ cells trigger the PMER from their intrinsic signals.

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Fyon, Frédéric, Waldir Miron Berbel-Filho, Ingo Schlupp, Geoff Wild y Francisco Úbeda. "Why Do Hybrids Turn Down Sex?" Evolution, 17 de julio de 2023. http://dx.doi.org/10.1093/evolut/qpad129.

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Abstract Asexual reproduction is ancestral in prokaryotes; the switch to sexuality in eukaryotes is one of the major transitions in the history of life. The study of the maintenance of sex in eukaryotes has raised considerable interest for decades and is still one of evolutionary biology’s most prominent question. The observation that many asexual species are of hybrid origin have led some to propose that asexuality in hybrids results from sexual processes being disturbed because of incompatibilities between the two parental species’ genomes. However, in some cases, failure to produce asexual F1s in the lab may indicate that this mechanism is not the only road to asexuality in hybrid species. Here, we present a mathematical model and propose an alternative, adaptive route for the evolution of asexuality from previously sexual hybrids. Under some reproductive alterations, we show that asexuality can evolve to rescue hybrids’ reproduction. Importantly, we highlight that when incompatibilities only affect the fusion of sperm and egg’s genomes, the two traits that characterize asexuality, namely unreduced meiosis and the initiation of embryogenesis without the incorporation of the sperm’s pronucleus, can evolve separately, greatly facilitating the overall evolutionary route. Taken together, our results provide an alternative, potentially complementary explanation for the link between asexuality and hybridization.

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Larose, Chloé, Guillaume Lavanchy, Susana Freitas, Darren J. Parker y Tanja Schwander. "Facultative parthenogenesis: a transient state in transitions between sex and obligate asexuality in stick insects?" Peer Community Journal 3 (13 de julio de 2023). http://dx.doi.org/10.24072/pcjournal.283.

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Jaron, Kamil S., Jens Bast, Reuben W. Nowell, T. Rhyker Ranallo-Benavidez, Marc Robinson-Rechavi y Tanja Schwander. "Genomic Features of Parthenogenetic Animals". Journal of Heredity, 28 de septiembre de 2020. http://dx.doi.org/10.1093/jhered/esaa031.

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Abstract Evolution without sex is predicted to impact genomes in numerous ways. Case studies of individual parthenogenetic animals have reported peculiar genomic features that were suggested to be caused by their mode of reproduction, including high heterozygosity, a high abundance of horizontally acquired genes, a low transposable element load, or the presence of palindromes. We systematically characterized these genomic features in published genomes of 26 parthenogenetic animals representing at least 18 independent transitions to asexuality. Surprisingly, not a single feature was systematically replicated across a majority of these transitions, suggesting that previously reported patterns were lineage-specific rather than illustrating the general consequences of parthenogenesis. We found that only parthenogens of hybrid origin were characterized by high heterozygosity levels. Parthenogens that were not of hybrid origin appeared to be largely homozygous, independent of the cellular mechanism underlying parthenogenesis. Overall, despite the importance of recombination rate variation for the evolution of sexual animal genomes, the genome-wide absence of recombination does not appear to have had the dramatic effects which are expected from classical theoretical models. The reasons for this are probably a combination of lineage-specific patterns, the impact of the origin of parthenogenesis, and a survivorship bias of parthenogenetic lineages.

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Hirooka, Shunsuke, Takeshi Itabashi, Takako M. Ichinose, Ryo Onuma, Takayuki Fujiwara, Shota Yamashita, Lin Wei Jong, Reiko Tomita, Atsuko H. Iwane y Shin-ya Miyagishima. "Life cycle and functional genomics of the unicellular red alga Galdieria for elucidating algal and plant evolution and industrial use". Proceedings of the National Academy of Sciences 119, n.º 41 (4 de octubre de 2022). http://dx.doi.org/10.1073/pnas.2210665119.

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Sexual reproduction is widespread in eukaryotes; however, only asexual reproduction has been observed in unicellular red algae, including Galdieria , which branched early in Archaeplastida. Galdieria possesses a small genome; it is polyextremophile, grows either photoautotrophically, mixotrophically, or heterotrophically, and is being developed as an industrial source of vitamins and pigments because of its high biomass productivity. Here, we show that Galdieria exhibits a sexual life cycle, alternating between cell-walled diploid and cell wall–less haploid, and that both phases can proliferate asexually. The haploid can move over surfaces and undergo self-diploidization or generate heterozygous diploids through mating. Further, we prepared the whole genome and a comparative transcriptome dataset between the diploid and haploid and developed genetic tools for the stable gene expression, gene disruption, and selectable marker recycling system using the cell wall–less haploid. The BELL/KNOX and MADS-box transcription factors, which function in haploid-to-diploid transition and development in plants, are specifically expressed in the haploid and diploid, respectively, and are involved in the haploid-to-diploid transition in Galdieria , providing information on the missing link of the sexual life cycle evolution in Archaeplastida. Four actin genes are differently involved in motility of the haploid and cytokinesis in the diploid, both of which are myosin independent and likely reflect ancestral roles of actin. We have also generated photosynthesis-deficient mutants, such as blue-colored cells, which were depleted in chlorophyll and carotenoids, for industrial pigment production. These features of Galdieria facilitate the understanding of the evolution of algae and plants and the industrial use of microalgae.

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Artzy-Randrup, Yael, Tamir Epstein, Joel S. Brown, Ricardo L. B. Costa, Brian J. Czerniecki y Robert A. Gatenby. "Novel evolutionary dynamics of small populations in breast cancer adjuvant and neoadjuvant therapy". npj Breast Cancer 7, n.º 1 (11 de marzo de 2021). http://dx.doi.org/10.1038/s41523-021-00230-y.

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AbstractDisseminated cancer cells (DCCs) are detected in the circulation and bone marrow of up to 40% of breast cancer (BC) patients with clinically localized disease. The formation of metastases is governed by eco-evolutionary interactions of DCCs with the tissue during the transition from microscopic populations to macroscopic disease. Here, we view BC adjuvant and neoadjuvant treatments in the context of small population extinction dynamics observed in the Anthropocene era. Specifically, the unique eco-evolutionary dynamics of small asexually reproducing cancer populations render them highly vulnerable to: (1) environmental and demographic fluctuations, (2) Allee effects, (3) genetic drift and (4) population fragmentation. Furthermore, these typically interact, producing self-reinforcing, destructive dynamics—termed the Extinction Vortex—eradicating the population even when none of the perturbations is individually capable of causing extinction. We propose that developing BC adjuvant and neoadjuvant protocols may exploit these dynamics to prevent recovery and proliferation of small cancer populations during and after treatment—termed “Eco-evolutionary rescue” in natural extinctions. We hypothesize more strategic application of currently available agents based on the extinction vulnerabilities of small populations could improve clinical outcomes.

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Chen, Guanhan, Xinying Zhou, Mutalibjon Khasannov, Robert N. Spengler, Jian Ma, Tukhtash Annaev, Nasibillo Kambarov et al. "Morphotype broadening of the grapevine (Vitis vinifera L.) from Oxus civilization 4000 BP, Central Asia". Scientific Reports 12, n.º 1 (29 de septiembre de 2022). http://dx.doi.org/10.1038/s41598-022-19644-0.

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AbstractThe region of Transoxiana underwent an early agricultural-demographic transition leading to the earliest proto-urban centers in Central Asia. The agronomic details of this cultural shift are still poorly studied, especially regarding the role that long-generation perennials, such as grapes, played in the cultivation system. In this paper, we present directly dated remains of grape pips from the early urban centers of Sapalli and Djarkutan, in south Uzbekistan. We also present linear morphometric data, which illustrate a considerable range of variation under cultivation that we divide into four distinct morphotypes according to pip shape. While some of the pips in these two assemblages morphologically fall within the range of wild forms, others more closely resemble modern domesticated populations. Most of the specimens measure along a gradient between the two poles, showing a mixed combination of domesticated and wild features. We also point out that the seeds recovered from the Djarkutan temple were, on average, larger and contained more affinity towards domesticated forms than those from domestic contexts. The potential preference of morphotypes seems to suggest that there were recognized different varieties that local cultivators might aware and possibly propagating asexually.

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Jia, Huixia, Qing Zhao, Jiangping Song, Xiaohui Zhang, Wenlong Yang, Zhenzhen Du, Yue Zhu y Haiping Wang. "Large-scale population structure and genetic architecture of agronomic traits of garlic". Horticulture Research, 22 de febrero de 2023. http://dx.doi.org/10.1093/hr/uhad034.

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Abstract Garlic, an asexually propagated crop, is the second important bulb crop after the onion and is used as a vegetable and medicinal plant. Abundant and diverse garlic resources have been formed over thousands of years of cultivation. However, genome variation, population structure and genetic architecture of garlic agronomic traits were still not well elucidated. Here, 1,100,258 single nucleotide polymorphisms (SNPs) were identified using genotyping-by-sequencing in 606 garlic accessions collected from 43 countries. Population structure, principal component and phylogenetic analysis showed that these accessions were divided into five subpopulations. Twenty agronomic traits, including above-ground growth traits, bulb-related and bolt-related traits in two consecutive years were implemented genome-wide association study. In total, 542 SNPs were associated with these agronomic traits, among which 188 SNPs were repeatedly associated with more than two traits. One SNP (chr6: 1896135972) was repeatedly associated with ten traits. These associated SNPs were located within or near 858 genes, 56 of which were transcription factors. Interestingly, one non-synonymous SNP (Chr4: 166524085) in ribosomal protein S5 was repeatedly associated with above-ground growth and bulb-related traits. Additionally, gene ontology enrichment analysis of candidate genes for genomic selection regions between complete-bolting and non-bolting accessions showed that these genes were significantly enriched in ‘vegetative to reproductive phase transition of meristem’, ‘shoot system development’, ‘reproductive process’, etc. These results provide valuable information for the reliable and efficient selection of candidate genes to achieve garlic genetic improvement and superior varieties.

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Amplatz, Klara, Elisabeth Zieger, Daniel Abed-Navandi, Anton Weissenbacher y Andreas Wanninger. "Neuromuscular development in the emerging scyphozoan model system, Cassiopea xamachana: implications for the evolution of cnidarian nervous systems". Frontiers in Neuroscience 17 (11 de enero de 2024). http://dx.doi.org/10.3389/fnins.2023.1324980.

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The scyphozoan Cassiopea xamachana is an emerging cnidarian model system for studying regeneration, animal-algae symbiotic relationships, and various aspects of evolutionary biology including the early emergence of animal nervous systems. Cassiopea has a life cycle similar to other scyphozoans, which includes the alternation between a sessile, asexual form (polyp) and a sexually reproducing stage, the medusa. The transition between the two forms is called strobilation, where the polyp releases a miniature medusa, the iconic ephyra, that subsequently develops into the adult medusa. In addition, Cassiopea polyps may reproduce asexually by budding off free-swimming so-called planuloid buds. While the development of planuloid buds and polyps has been studied in some detail, little is known about the ontogeny of the sexually produced planula larva. Using immunofluorescence labeling and confocal microscopy, we examined neuromuscular development during metamorphosis of the planula larva into the juvenile polyp in C. xamachana. For this purpose, we used tyrosinated α-tubulin-, FMRFamide- and serotonin-like immunoreactivity together with phalloidin labeling. Our results show a planula nervous system that consists of a basiectodermal neural plexus with mostly longitudinally oriented neurites. This neural meshwork is connected to sensory neurons in the superficial stratum of the ectoderm, which are exclusively localized in the aboral half of the larva. During settlement, this aborally concentrated nervous system of the planula is replaced completely by the orally concentrated nervous system of the polyp. Adult polyps show an extensive nerve net with a loose concentration around the oral disc. These findings are consistent with data from other scyphozoans and most likely constitute a conserved feature of scyphozoan discomedusae. Taken together, the data currently available suggest an aborally concentrated nervous system including sensory cells as part of the neural ground pattern of cnidarian planula larvae. The reorganization of the nervous system from anterior to posterior in planula-to-polyp metamorphosis most likely also constitutes an ancestral trait in cnidarian evolution.

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