ABSTRACT
Multicellular organisms have evolved sophisticated mechanisms for responding to various developmental,environmental and physical stimuli by regulating transcription. The correlation of distribution of RNAPolymerase II (RNA Pol II) with transcription is well established in higher metazoans, however genome-wideinformation about its distribution in early metazoans, such as Hydra, is virtually absent. To gain insights intoRNA Pol II-mediated transcription and chromatin organization in Hydra, we performed chromatin immunoprecipitation (ChIP)-coupled high-throughput sequencing (ChIP-seq) for RNA Pol II and Histone H3. Strikingly, we found that Hydra RNA Pol II is uniformly distributed across the entire gene body, as opposed to itscounterparts in bilaterians such as human and mouse. Furthermore, correlation with transcriptome datarevealed that the levels of RNA Pol II correlate with the magnitude of gene expression. Strikingly, thecharacteristic peak of RNA Pol II pause typically observed in bilaterians at the transcription start sites (TSSs)was not observed in Hydra. The RNA Pol II traversing ratio in Hydra was found to be intermediate to yeastand bilaterians. The search for factors involved in RNA Pol II pause revealed that RNA Pol II pausingmachinery was most likely acquired first in Cnidaria. However, only a small subset of genes exhibited thepromoter proximal RNP Pol II pause. Interestingly, the nucleosome occupancy is highest over the subset ofpaused genes as compared to total Hydra genes, which is another indication of paused RNA Pol II at thesegenes. Thus, this study provides evidence for the molecular basis of RNA Pol II pause early during theevolution of multicellular organisms.
ABSTRACT
Resumen La cuenca del Lago de Tota ha sido modificada por diversas actividades humanas, como deforestación, piscicultura y el monocultivo de cebolla larga (Allium fistulosum) con un elevado uso de agroquímicos y gallinaza cruda, causando deterioro de las características ecológicas del sistema léntico de alta montaña más grande de Colombia. En este trabajo se implementaron pruebas de toxicidad para determinar posibles efectos deletéreos sobre H. attenuata y D. magna. Se aclimataron los organismos y validaron los ensayos de toxicidad en condiciones de laboratorio, posteriormente se realizó la evaluación de agua y sedimentos (elutriados) provenientes de afluentes de la cuenca del lago: Hato Laguna, El Tobal, Los Pozos y Agua Blanca, durante dos periodos hidroclimáticos contrastantes. Se evidenció una mayor sensibilidad con los ensayos en H. attenuata, ya que señalan que aguas y elutriados de Hato Laguna, El Tobal y Los Pozos generaron respuestas de subletalidad (Kruskal-Wallis; P < 0.05) y letalidad. Se registra presencia positiva de al menos cinco plaguicidas no cuantificados antes en la cuenca (clorotalonilo, aldrin, dieldrin, DDT y congéneres). Estos resultados indicarían una potencial influencia negativa de las actividades antropogénicas sobre organismos acuáticos nativos, con posibles consecuencias sobre la composición, estructura y función de las comunidades hidrobiológicas.(AU)
Abstract Lago de Tota basin is currently being impacted by human activities like agriculture, deforestation, large-scale fish farming and monoculture of onion long (Allium fistulosum) with high use of agrochemicals and chicken manure that contaminate runoff to aquatic systems in the largest high mountain lake in Colombia. We implemented toxicity tests to evaluate possible deleterious effects of contaminants on H. attenuata and D. magna, model organisms commonly used in aquatic contamination assessment. Firstly, the organisms were acclimated and toxicity tests were validated in laboratory conditions. Later, water and sediments (elutriates) were evaluated from tributaries of Lago de Tota basin: Hato Laguna, El Tobal, Los Pozos, and Agua Blanca stream, during two contrasting hydroclimatic periods. In addition, pesticides in sediments were evaluated with chromatography, spectrometry and ultraviolet detection techniques. Acute toxicity tests showed that H. attenuata was more sensitive than D. magna, as it showed sublethal (Kruskal-Wallis; P < 0.05) and lethal responses to exposure to waters and elutriates from Hato Laguna, El Tobal, and Los Pozos. At least five pesticides not quantified before in the basin were detected in chemical analyses (chlorothalonil, aldrin, dieldrin, DDT y congeners). These results indicate that anthropogenic activities have a potentially negative influence in aquatic communities composition, structure, and function, it´s demand attention in future research.(AU)
Subject(s)
Pesticides/adverse effects , Water Pollution/analysis , Daphnia , Hydra , ColombiaABSTRACT
Objective To investigate the effect of construct the Notch1 (NICD) eukaryotic expression vector on the proliferation and differentiation of rat bone marrow mesenchymal stem cells (BMSCs) in vitro. Methods Rat BMSCs were experimented as the object. NICD eukaryotic expression vector was constructed. pEGFP-N1-NICD expressing plasmids were used to transfect BMSCs. The study included control group (CON group), empty vector group (VEC group) and the trans-fection group (TRA group). After 48-hour transfection, BMSCs were observed for general morphology. The protein expres-sions of NSE, GFAP and Notch1 were detected by real-time PCR and Western blotting assay respectively. The apoptosis, cy-cle distribution and cell proliferation were evaluated by flow cytometry and MTT assay. Results The DNA sequencing con-firmed that the pEGFP-N1-NICD recombinant plasmid was successfully constructed, and both VEC group and TRA group expressed green fluorescence after 48-hour transfection. The relative expression levels of Notch1 and GFAP mRNA and pro-tein were significantly higher in TRA group than those in VEC group and CON group (P<0.05), and there was no significant difference between VEC group and CON group. After 48-hour transfection, the ratio of living cells was significantly lower in TRA group than that of CON group and VEC group, and the early apoptotic rate and late apoptotic rate were significantly higher in TRA group than those of CON group and VEC group (P<0.05). The late apoptotic rate was significantly higher in VEC group than that of CON group. The proportion of G1/G0 cells was significantly higher in TRA group than that of CON group and VEC group, but S and G2/M cells were significantly lower (P<0.05). The value of growth curve was gradually de-creased in TRA group than that of CON group and VEC group (P<0.05). Conclusion The high expression of NICD gene might induce apoptosis of BMSCs, inhibit the proliferation in part, and induce into glial-like cell differentiation.
ABSTRACT
The Hydra is the most common representative of freshwater cnidarians. In general, it is found in freshwaters on every continent, with the exception of Antarctica. The aim of the present study is to gather biological and ecological data on aspects of two species of Hydra native to Brazil: Hydra viridissima and Hydra salmacidis. Predation and food selectivity experiments were performed to assess the possible predators and the prey preferences, respectively, of the two species. The results indicate that the two species of Hydra were not consumed by any of the predators that were tested, which are typical predators of invertebrates in freshwater: nymphs of Odonata Anisoptera and the phantom midge larvae of Chaoborus sp. (Insecta), adults of Copepoda Cyclopoida (Crustacea) and the small fish Poecilia reticulata. It was observed that the smaller Hydra, H. viridissima, positively selected the nauplii and copepodites of calanoid copepods and small cladocerans and rejected large prey, such as the adults of calanoid copepods and ostracods. The larger H. salmacidis, besides the nauplii and copepodites of the calanoid copepods and small cladocerans, also positively selected the large adults of the calanoid copepods. It can be concluded that both H. viridissima and H. salmacidis are most likely preyed on little or not preyed on at all in many freshwater bodies, as they are top predators in the food chain. At the same time, they are efficient predators, and a positive relationship was observed between the prey size and the Hydra species size. Food selectivity was related to prey size as well as other prey characteristics, such as carapace thickness and swimming efficiency.
As hidras são os representantes mais comuns dos cnidários de água doce. Em geral, estes organismos são encontrados em todos os continentes, exceto na Antártica. O presente estudo teve como objetivo obter informações mais aprofundadas sobre aspectos biológicos e ecológicos de duas espécies de Hydra nativas no Brasil, Hydra viridissima e Hydra salmacidis. Foram realizados experimentos de predação e seletividade alimentar para se determinar, respectivamente, os potenciais predadores e as presas preferenciais destas duas espécies. Os resultados indicaram que as duas espécies de Hydra não foram consumidas por nenhum dos predadores testados, os quais são usuais predadores de invertebrados em águas doces: ninfas de Odonata e larvas de Chaoborus sp. (Insecta), adultos de Copepoda Cyclopoida (Crustacea) e peixes da espécie Poecilia reticulata. Observou-se que H. viridissima ao se alimentar selecionou positivamente as fases jovens de copépodos calanóides e os pequenos cladóceros, e selecionou negativamente as presas grandes, como os adultos de copépodos calanóides e os ostrácodos. Já a espécie H. salmacidis, a qual apresenta um tamanho maior, além de ter preferência pelos náuplios e copepoditos de copépodos calanóides e pequenos cladóceros, também selecionou positivamente os indivíduos adultos dos copépodos calanóides. Os resultados obtidos evidenciaram que as espécies H. viridissima e H. salmacidis provavelmente são pouco ou não são predadas em muitos ambientes naturais, sendo elas próprias os predadores de topo da cadeia alimentar nestes ambientes. Por outro lado, estes organismos são predadores eficientes e observou-se uma relação positiva entre o tamanho da espécie de Hydra e o tamanho da presa. A seletividade alimentar destas espécies esteve relacionada com o tamanho das presas, assim como com outras características, tais como a espessura da carapaça e a eficiência de natação.
ABSTRACT
Noggin, along with other secreted bone morphogenetic protein (BMP) inhibitors, plays a crucial role in neural induction and neural tube patterning as well as in somitogenesis, cardiac morphogenesis and formation of the skeleton in vertebrates. The BMP signalling pathway is one of the seven fundamental pathways that drive embryonic development and pattern formation in animals. Understanding its evolutionary origin and role in pattern formation is, therefore, important to evolutionary developmental biology (evo-devo).We have studied the evolutionary origin of BMP–Noggin antagonism in hydra, which is a powerful diploblastic model to study evolution of pattern-forming mechanisms because of the unusual cellular dynamics during its pattern formation and its remarkable ability to regenerate. We cloned and characterized the noggin gene from hydra and found it to exhibit considerable similarity with its orthologues at the amino acid level. Microinjection of hydra Noggin mRNA led to duplication of the dorsoventral axis in Xenopus embryos, demonstrating its functional conservation across the taxa. Our data, along with those of others, indicate that the evolutionarily conserved antagonism between BMP and its inhibitors predates bilateral divergence. This article reviews the various roles of Noggin in different organisms and some of our recent work on hydra Noggin in the context of evolution of developmental signalling pathways.
ABSTRACT
Receptor tyrosine kinases (RTKs) are key components of cell–cell signalling required for growth and development of multicellular organisms. It is therefore likely that the divergence of RTKs and associated components played a significant role in the evolution of multicellular organisms. We have carried out the present study in hydra, a diploblast, to investigate the divergence of RTKs after parazoa and before emergence of triploblast phyla. The domain-based screening using Hidden Markov Models (HMMs) for RTKs in Genomescan predicted gene models of the Hydra magnipapillata genome resulted in identification of 15 RTKs. These RTKs have been classified into eight families based on domain architecture and homology. Only 5 of these RTKs have been previously reported and a few of these have been partially characterized. A phylogeny-based analysis of these predicted RTKs revealed that seven subtype duplications occurred between ‘parazoan–eumetazoan split’ and ‘diploblast–triploblast split’ in animal phyla. These results suggest that most of the RTKs evolved before the radiata–bilateria divergence during animal evolution.
ABSTRACT
Hydras, the most representative freshwater Cnidaria, are of common occurrence in bodies of water in every continent except Antarctica. This study was planned with the aim of maintaining a population of Hydra viridissima in laboratory culture to enable the determination of the individual and population growth-rates of this species, as well as its population doubling time and generation time, with a view to employing these common animals as test-organisms in ecotoxicological assays. The organisms were maintained in reconstituted water at 20 ± 2 °C, illuminated at 800 lux with a photoperiod of 12 hours light: 12 hours dark, and were fed on neonates of the cladoceran Ceriodaphnia silvestrii (3 or 4 neonates per hydra, 3 times a week). The individual growth-rate (k) of the species was 0.43, the maximum length of the column 2.53 mm and the generation time 6.6 ± 1.5 days on average. The hydra population showed an intrinsic growth-rate (r) of 0.0468, according to the fitted curve, and a doubling time of 14.8 ± 2.63 days. Hydra viridissima is easy to grow in the laboratory and performs well in the conditions used in this study. It is thus a promising candidate test-organism for ecotoxicological studies.
As hidras, os mais representativos Cnidaria de água doce, são organismos comuns em corpos de água doce de todos os continentes, exceto na Antártida. O objetivo do presente estudo foi manter o cultivo em laboratório da espécie Hydra viridissima, determinando-se o crescimento individual e populacional desta espécie, assim como seu tempo de duplicação da população e de geração, visando sua utilização como organismo-teste em ensaios ecotoxicológicos. Os organismos foram mantidos em água reconstituída, a uma temperatura de 20 ± 2 °C, com luminosidade de 800 lux e fotoperíodo de 12 horas luz/ 12 horas escuro, e foram alimentados com neonatas do Cladocera Ceriodaphnia silvestrii (3 a 4 neonatas por indivíduo). A taxa de crescimento individual (k) obtida foi de 0,43, o comprimento máximo da coluna das hidras foi de 2,53 mm e o tempo de geração foi, em média, de 6,6 ± 1,5 dias. A espécie apresentou uma taxa intrínseca de crescimento populacional (r) igual a 0,0468 para a curva ajustada e um tempo de duplicação da população de 14,8 ± 2,63 dias. A espécie Hydra viridissima é de fácil cultivo em laboratório e apresentou um bom desempenho nas condições testadas, sendo, portanto, um potencial organismo-teste para estudos ecotoxicológicos.