How animals evolved from a single-celled ancestor, transitioning from a unicellular lifestyle to a coordinated multicellular entity, remains a fascinating question. Key events in this transition ...involved the emergence of processes related to cell adhesion, cell-cell communication and gene regulation. To understand how these capacities evolved, we need to reconstruct the features of both the last common multicellular ancestor of animals and the last unicellular ancestor of animals. In this review, we summarize recent advances in the characterization of these ancestors, inferred by comparative genomic analyses between the earliest branching animals and those radiating later, and between animals and their closest unicellular relatives. We also provide an updated hypothesis regarding the transition to animal multicellularity, which was likely gradual and involved the use of gene regulatory mechanisms in the emergence of early developmental and morphogenetic plans. Finally, we discuss some new avenues of research that will complement these studies in the coming years.
Many annelids can regenerate missing body parts or reproduce asexually, generating all cell types in adult stages. However, the putative adult stem cell populations involved in these processes, and ...the diversity of cell types generated by them, are still unknown. To address this, we recover 75,218 single cell transcriptomes of the highly regenerative and asexually-reproducing annelid Pristina leidyi. Our results uncover a rich cell type diversity including annelid specific types as well as novel types. Moreover, we characterise transcription factors and gene networks that are expressed specifically in these populations. Finally, we uncover a broadly abundant cluster of putative stem cells with a pluripotent signature. This population expresses well-known stem cell markers such as vasa, piwi and nanos homologues, but also shows heterogeneous expression of differentiated cell markers and their transcription factors. We find conserved expression of pluripotency regulators, including multiple chromatin remodelling and epigenetic factors, in piwi+ cells. Finally, lineage reconstruction analyses reveal computational differentiation trajectories from piwi+ cells to diverse adult types. Our data reveal the cell type diversity of adult annelids by single cell transcriptomics and suggest that a piwi+ cell population with a pluripotent stem cell signature is associated with adult cell type differentiation.
Progression through the cell cycle in eukaryotes is regulated on multiple levels. The main driver of the cell cycle progression is the periodic activity of cyclin-dependent kinase (CDK) complexes. In ...parallel, transcription during the cell cycle is regulated by a transcriptional program that ensures the just-in-time gene expression. Many core cell cycle regulators are widely conserved in eukaryotes, among them cyclins and CDKs; however, periodic transcriptional programs are divergent between distantly related species. In addition, many otherwise conserved cell cycle regulators have been lost and independently evolved in yeast, a widely used model organism for cell cycle research. For a better understanding of the evolution of the cell cycle regulation in opisthokonts, we investigated the transcriptional program during the cell cycle of the filasterean Capsaspora owczarzaki, a unicellular species closely related to animals. We developed a protocol for cell cycle synchronization in Capsaspora cultures and assessed gene expression over time across the entire cell cycle. We identified a set of 801 periodic genes that grouped into five clusters of expression over time. Comparison with datasets from other eukaryotes revealed that the periodic transcriptional program of Capsaspora is most similar to that of animal cells. We found that orthologues of cyclin A, B and E are expressed at the same cell cycle stages as in human cells and in the same temporal order. However, in contrast to human cells where these cyclins interact with multiple CDKs, Capsaspora cyclins likely interact with a single ancestral CDK1-3. Thus, the Capsaspora cyclin-CDK system could represent an intermediate state in the evolution of animal-like cyclin-CDK regulation. Overall, our results demonstrate that Capsaspora could be a useful unicellular model system for animal cell cycle regulation.
SignificanceIn this manuscript, we address an essential question in developmental and evolutionary biology: How have changes in gene regulatory networks contributed to the invertebrate-to-vertebrate ...transition? To address this issue, we perturbed four signaling pathways critical for body plan formation in the cephalochordate amphioxus and in zebrafish and compared the effects of such perturbations on gene expression and gene regulation in both species. Our data reveal that many developmental genes have gained response to these signaling pathways in the vertebrate lineage. Moreover, we show that the interconnectivity between these pathways is much higher in zebrafish than in amphioxus. We conclude that this increased signaling pathway complexity likely contributed to vertebrate morphological novelties during evolution.
Deuterostomes are a monophyletic group of animals that includes Hemichordata, Echinodermata (together called Ambulacraria), and Chordata. The diversity of deuterostome body plans has made it ...challenging to reconstruct their ancestral condition and to decipher the genetic changes that drove the diversification of deuterostome lineages. Here, we generate chromosome-level genome assemblies of 2 hemichordate species, Ptychodera flava and Schizocardium californicum , and use comparative genomic approaches to infer the chromosomal architecture of the deuterostome common ancestor and delineate lineage-specific chromosomal modifications. We show that hemichordate chromosomes (1 N = 23) exhibit remarkable chromosome-scale macrosynteny when compared to other deuterostomes and can be derived from 24 deuterostome ancestral linkage groups (ALGs). These deuterostome ALGs in turn match previously inferred bilaterian ALGs, consistent with a relatively short transition from the last common bilaterian ancestor to the origin of deuterostomes. Based on this deuterostome ALG complement, we deduced chromosomal rearrangement events that occurred in different lineages. For example, a fusion-with-mixing event produced an Ambulacraria-specific ALG that subsequently split into 2 chromosomes in extant hemichordates, while this homologous ALG further fused with another chromosome in sea urchins. Orthologous genes distributed in these rearranged chromosomes are enriched for functions in various developmental processes. We found that the deeply conserved Hox clusters are located in highly rearranged chromosomes and that maintenance of the clusters are likely due to lower densities of transposable elements within the clusters. We also provide evidence that the deuterostome-specific pharyngeal gene cluster was established via the combination of 3 pre-assembled microsyntenic blocks. We suggest that since chromosomal rearrangement events and formation of new gene clusters may change the regulatory controls of developmental genes, these events may have contributed to the evolution of diverse body plans among deuterostomes.
How animals emerged from their unicellular ancestor remains a major evolutionary question. New genome data from the closest unicellular relatives of animals have provided important insights into the ...evolution of animal multicellularity. We know that the unicellular ancestor of animals had an unexpectedly complex genetic repertoire, including many genes that are key to animal development and multicellularity. Thus, assessing the function of these genes among unicellular relatives of animals is key to understanding how they were co-opted at the onset of the Metazoa. However, such analyses have been hampered by the lack of genetic tools. Progress has been made in choanoflagellates and teretosporeans, two of the three lineages closely related to animals, whereas no tools are yet available for functional analysis in the third lineage: the filastereans. Importantly, filastereans have a striking repertoire of genes involved in transcriptional regulation and other developmental processes. Here, we describe a reliable transfection method for the filasterean
We also provide a set of constructs for visualising subcellular structures in live cells. These tools convert
into a unique experimentally tractable organism to use to investigate the origin and evolution of animal multicellularity.
Los depósitos tipo pórfido, son las fuentes minerales más grandes del mundo. Durante la exploración con extracción de núcleos de perforación, es posible obtener información geotécnica del macizo ...rocoso. Esta información, permite clasificar la calidad geomecánica del macizo rocoso por medio de sistemas de clasificación empíricos como “Rock Mass Rating” (RMR), Mining Rock Mass Rating (MRMR) y el “Q”. Teniendo en cuenta que en los depósitos tipo pórfido, el macizo se encuentra afectado por la presencia de alteraciones hidrotermales; esto implica, que la roca puede presentar variaciones en sus propiedades geomecánicas, dependiendo de la alteración presente. En esta investigación, se consideraron 6292 m de perforaciones con información geotécnica. Con esta información, se realizó una clasificación del macizo por los sistemas mencionados. Una vez clasificado el depósito, se realizó un comparativo entre los sistemas de clasificación mencionados. Basados en las litologías y alteraciones hidrotermales presentes en el depósito por medio de estadística descriptiva (valores medios, diagramas de cajas, regresiones lineales). El estudio de clasificación del macizo considerando las alteraciones, permitió observar diferencias en los resultados de la clasificación geomecánica del material, con respecto a la clasificación del macizo sin tenerlas en cuenta.
Emerging applications in the area of wireless sensor networks that include a wide variety of scenarios typically involve a significant number of nodes deployed in a wide area. To ensure proper ...communication between the network nodes to the base station, the messages are propagated by intermediate nodes, so a route with multiple links is established. In general, sensor nodes are characterized by limited resources; therefore it is essential to use protocols that ensure not only communication but also that save the most energy while providing scalability. Different routing protocols have been proposed for WSN s, but the reactive routing algorithms have shown be more energy efficient, which makes them suitable for wireless sensor networks. In this paper the performance of the reactive type protocol (Ad -Hoc On Demand Distance Vector) is evaluated under the simulation platform OMNeT ++ through different scenarios . The AODV protocol has been chosen by the performance superiority comparing with Emerging applications in the area of wireless sensor networks that include a wide variety of scenarios typically involve a significant number of nodes deployed in a wide area. To ensure proper communication between the network nodes to the base station, the messages are propagated by intermediate nodes, so a route with multiple links is established. In general, sensor nodes are characterized by limited resources; therefore it is essential to use protocols that ensure not only communication but also that save the most energy while providing calability. Different routing protocols have been proposed for WSN s, but the reactive routing algorithms have shown be more energy efficient, which makes them suitable for wireless sensor networks. In this paper the performance of the reactive type protocol (Ad -Hoc On Demand Distance Vector) is evaluated under the simulation platform OMNeT ++ through different scenarios . The AODV protocol has been chosen by the performance superiority comparing with
Las aplicaciones emergentes en el área de redes de sensores inalámbricos comprenden una amplia variedad de escenarios que involucran típicamente un número significativo de nodos desplegados en un ...área amplia. Para garantizar una correcta comunicación entre los nodos de la red con la estación base, los mensajes se propagan por nodos intermedios, de forma que se establece una ruta con múltiples enlaces. En general, los nodos de una red de sensores se caracterizan por sus recursos limitados, en consecuencia, es fundamental el uso de protocolos que garanticen no solo la comunicación sino también que permitan ahorrar la mayor cantidad de energía mientras proporcionan escalabilidad.
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