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Generation of an efficient agent-based framework for the simulation of 3D multicellular systems
(2024)
In developmental biology, the focus has shifted from mainly considering genetic and molecular aspects to considering mechanical aspects, as it has become evident in recent years that mechanical forces, tensions, and physical interactions play a significant role alongside molecular mechanisms in developmental biology. Computational models provide a useful tool for the investigation of the complex cell choreography in tissue and organ development. In particular, they allow the identification of principles governing complex behaviours and greatly contribute to understanding self-organising systems. Agent-based models act as a ”virtual laboratory”, facilitating the formulation and testing of biological hypotheses.
In this work, a mathematical model is formulated to describe the dynamics and interactions of multicellular systems. This model formulation results in a large system of coupled stochastic differential equations. Furthermore, a simulation framework is introduced to solve the system of coupled stochastic differential equations numerically. In particular, mechanical processes such as cell-cell interactions, cell growth and division, cell polarity, and active migration are considered. Firstly, a CPU-based version of the simulation framework, implemented in Python and MATLAB, is presented. This version also provides scientists with limited programming experience the abil- ity to simulate systems involving several thousand cells. Additionally, a GPU-based framework version, implemented in CUDA and C++, is introduced. This version primarily targets modellers with advanced programming knowledge. It significantly reduces simulation runtime, allows for the simulation of very large systems, and incorporates additional extensions.
The implemented CPU-based simulation framework was applied to two different biological systems. The first application concerned inner cell mass organoids (ICM organoids), which serve as an experimental model system to study early embryogenesis. In particular, ICM organoids reflect the second cell fate decision, i.e., the differentiation into embryonic tissue and yolk sac, as well as subsequent cell sorting. Using the presented simulation framework, it was demonstrated that the experimentally observed local clustering of cell types can be attributed to mechanical processes, specifically cell growth, cell division, and cell fate inheritance. These results provide evidence that molecular cell fate determination occurs within a short period during the early development of ICM organoids, and that mechanical processes and interactions predominantly characterise subsequent processes. Furthermore, it was shown that differential adhesion and undirected cell movement in a three-dimensional system are sufficient to drive the segregation of different cell types.
The second biological application focused on pancreas-derived organoids, which simulate organ development, in this case, pancreas development. These organoids exhibit high variability in their qualitative behaviour, including volume oscillations, rotation and migration, fusions, and the formation of internal structures. The presented simulation framework was applied to the volume oscillations of the organoids. It was demonstrated that these oscillations depend significantly on the cell division dynamics and size of the organoids, as well as the elasticity and adhesion strength of the cells.
Both biological applications of the framework illustrate its modular structure and, thus, its adaptability to various biological systems. They also emphasise that mechanical processes play a fundamental role in the self-organisation of complex systems. The presented framework en- ables the efficient modelling of multicellular systems and serves as an effective tool for explaining complex behaviour by coupling simple underlying mechanisms.
The study of animal behavior is essential for gaining a better understanding of the behavior, patterns, and needs of animals. A better understanding not only serves scientific progress, but also plays an important role in improving husbandry conditions in zoos, which can help to improve animal welfare (Berger, 2010; Brando and Buchanan-Smith, 2018; Walsh et al., 2019; Rose and Riley, 2021).
The behavior of large herbivores differs significantly between day and night, and most ungulates are diurnal or crepuscular (Bennie et al., 2014; Gravett et al., 2017; Davimes et al., 2018; Wu et al., 2018). In contrast, many studies examine animal behavior during the day, and unfortunately there is little information on nocturnal behavior, including sleep behavior (Berger, 2010; Rose and Robert, 2013). However, sleep behavior, especially the proportion of REM sleep, is of great importance for the well-being of an individual (Hänninen et al., 2008; Fukasawa et al., 2018; Northeast et al., 2020).
To gain more insight into the behavior of ungulates in general, studies based on large samples of different species with a long recording period are useful. This is difficult to achieve with manual data analysis, as data collection and analysis in behavioral biology is time consuming and costly. Therefore, modern methods such as automated analysis are helpful in the field of behavioral biology (Norouzzadeh et al., 2018; Beery et al., 2020; Lürig et al., 2021).
Hence, the development of a software tool for the automated assessment of nocturnal behavior of ungulates in zoos is part of this dissertation. The resulting software tool is called BOVIDS (Behavioral Observations by Videos and Images using Deep-Learning Software) and allows the automatic evaluation of video material in three steps. In the first step, object detection, the individuals on the images are recognized and cut out in order to classify the behavior in the following step, action classification. In the final step, post-processing, errors of the automated analysis are corrected and the data is prepared for further use (Hahn-Klimroth et al., 2021; Gübert et al., 2022). To create such a system, it must first be trained. Typically, two nights per individual were manually annotated, resulting in a total of 594 manually annotated nights. In addition, 224,922 images were used to evaluate whether the system was already correctly recognizing the animals' behavior. Bounding boxes were either manually drawn or evaluated on a total of 201,827 images to train the object detection network.
The software package BOVIDS was used to analyze data from a total of 196 individuals from 19 different ungulate species over a period of 101,629 hours of video material from 9,239 nights. A night is defined as the period from 7 pm to 6 am. The species studied belong to the two orders of odd-toed ungulates (Perissodactyla) and even-toed ungulates (Artiodactyla). The focus is on the behavioral categories of standing, moving, lying – head up, and lying – head down, the latter corresponding to the typical REM sleep position of ungulates. Based on the analyzed data, several biological questions were discussed in this thesis. In addition to the activity budgets and rhythms underlying the night, factors influencing behavior are also investigated. In addition, the enclosure use by the animals is evaluated.
Zebras as representatives of the Perissodactyla spend about 25% of the night lying, while the average for the Artiodactyla studied is 77%. All species studied spend an average of 8.8% of the night in REM sleep (Gübert et al., 2023a), with a typical REM sleep phase lasting between 2.2 and 7.6 minutes (Gübert et al., 2023b). Only 0.7% of time during the night is spent with movement by the animals (Gübert and Dierkes). While the number of lying phases within the Artiodactyla is very constant with an average of five phases, the number of phases in the REM sleep position varies. Age, average species size and taxonomy were found to be influencing factors (Gübert et al., 2023a). With regard to rhythmicity, it is striking that most of the species studied show an increase in lying during the night and that a strong rhythmicity of behavior can be observed. The time between two lying events is very constant and is about two hours for most animals (Gübert et al., 2023b). With regard to enclosure use, it is striking that only a small part of the enclosure is used regularly. All individuals prefer to lie down on the bedding and most individuals prefer one or two different resting places (Gübert and Dierkes).
The data created as part of this thesis can contribute to a better overall understanding of ungulate behavior. The newly developed software package BOVIDS makes it relatively easy to analyze further data on this topic. Long-term studies can now be carried out more cost-effectively, making it easier to answer many questions in the future, such as investigating other influencing factors or responses to changes in husbandry conditions.
Biodiversity post-2020: Closing the gap between global targets and national-level implementation
(2021)
National and local governments need to step up efforts to effectively implement the post-2020 global biodiversity framework of the Convention on Biological Diversity to halt and reverse worsening biodiversity trends. Drawing on recent advances in interdisciplinary biodiversity science, we propose a framework for improved implementation by national and subnational governments. First, the identification of actions and the promotion of ownership across stakeholders need to recognize the multiple values of biodiversity and account for remote responsibility. Second, cross-sectorial implementation and mainstreaming should adopt scalable and multifunctional ecosystem restoration approaches and target positive futures for nature and people. Third, assessment of progress and adaptive management can be informed by novel biodiversity monitoring and modeling approaches handling the multidimensionality of biodiversity change.
Plants and insects often use the same compounds for chemical communication, but not much is known about the genetics of convergent evolution of chemical signals. The terpene (E)-β-ocimene is a common component of floral scent and is also used by the butterfly Heliconius melpomene as an anti-aphrodisiac pheromone. While the biosynthesis of terpenes has been described in plants and microorganisms, few terpene synthases (TPSs) have been identified in insects. Here, we study the recent divergence of 2 species, H. melpomene and Heliconius cydno, which differ in the presence of (E)-β-ocimene; combining linkage mapping, gene expression, and functional analyses, we identify 2 novel TPSs. Furthermore, we demonstrate that one, HmelOS, is able to synthesise (E)-β-ocimene in vitro. We find no evidence for TPS activity in HcydOS (HmelOS ortholog of H. cydno), suggesting that the loss of (E)-β-ocimene in this species is the result of coding, not regulatory, differences. The TPS enzymes we discovered are unrelated to previously described plant and insect TPSs, demonstrating that chemical convergence has independent evolutionary origins.
Highlights
• Histone modifications alter chromatin structure and gene accessibility, allowing timely stress response, and enhancing tomato's ability to cope with environmental challenges.
• miRNAs and lncRNAs fine-tune gene expression, playing essential roles in stress tolerance, particularly in heat and drought stress responses.
• Leveraging epigenetic modifications can develop tomato varieties that maintain high productivity and quality under adverse environmental conditions.
• Detailed mapping of the tomato epigenome under various stress conditions can identify key regulatory regions and guide targeted breeding programs
Abstract
Climate change poses a major challenge to agriculture, affecting crop production through shifting weather patterns and an increase in extreme conditions such as heat waves, droughts, and floods, all of which are further compounded by biotic stress factors. Tomatoes, a vital dietary staple and significant agricultural product worldwide, are particularly susceptible to these changes. The need for developing climate-resilient tomato varieties is more urgent than ever to ensure food security. Epigenetic modifications, such as DNA methylation and histone modifications, play essential roles in gene expression regulation. These modifications can affect plant traits and responses to environmental stresses, enabling tomatoes to maintain productivity despite variable climates or disease pressures. Tomato, as a model plant, offers valuable insights into the epigenetic mechanisms underlying fruit development and responses to stress. This review provides an overview of key discoveries regarding to tomato response and resilience mechanisms related to epigenetics, highlighting their potential in breeding strategies to enhance tomato resilience against both abiotic and biotic challenges, thereby promoting sustainable agricultural practices in the context of global climate change.
Background: Bacteria of the genus Photorhabdus and Xenorhabdus are motile, Gram-negative bacteria that live in symbiosis with entomopathogenic nematodes. Due to their complex life cycle, they produce a large number of specialized metabolites (natural products) encoded in biosynthetic gene clusters (BGC). Genetic tools for Photorhabdus and Xenorhabdus have been rare and applicable to only a few strains. In the past, several tools have been developed for the activation of BGCs and the deletion of individual genes. However, these often have limited efficiency or are time consuming. Among the limitations, it is essential to have versatile expression systems and genome editing tools that could facilitate the practical work.
Results: In the present study, we developed several expression vectors and a CRISPR-Cpf1 genome editing vector for genetic manipulations in Photorhabdus and Xenorhabdus using SEVA plasmids. The SEVA collection is based on modular vectors that allow exchangeability of different elements (e.g. origin of replication and antibiotic selection markers with the ability to insert desired sequences for different end applications). Initially, we tested different SEVA vectors containing the broad host range origins and three different resistance genes for kanamycin, gentamycin and chloramphenicol, respectively. We demonstrated that these vectors are replicative not only in well-known representatives, e.g. Photorhabdus laumondii TTO1, but also in other rarely described strains like Xenorhabdus sp. TS4. For our CRISPR/Cpf1-based system, we used the pSEVA231 backbone to delete not only small genes but also large parts of BGCs. Furthermore, we were able to activate and refactor BGCs to obtain high production titers of high value compounds such as safracin B, a semisynthetic precursor for the anti-cancer drug ET-743.
Conclusions: The results of this study provide new inducible expression vectors and a CRISPR/CPf1 encoding vector all based on the SEVA (Standard European Vector Architecture) collection, which can improve genetic manipulation and genome editing processes in Photorhabdus and Xenorhabdus.
Highlights
• Different NADPH supply strategies are compared in Saccharomyces cerevisiae.
• Example products are d-xylitol and l-galactonate.
• ZWF1 overexpression is the most robust strategy in the diauxic batch fermentation.
• Carbon source dependencies and interferences of different strategies are explored.
Abstract
Enhancing the supply of the redox cofactor NADPH in metabolically engineered cells is a critical target for optimizing the synthesis of many product classes, such as fatty acids or terpenoids. In S. cerevisiae, several successful approaches have been developed in different experimental contexts. However, their systematic comparison has not been reported. Here, we established the reduction of xylose to xylitol by an NADPH-dependent xylose reductase as a model reaction to compare the efficacy of different NADPH supply strategies in the course of a batch fermentation, in which glucose and ethanol are sequentially used as carbon sources and redox donors. We show that strains overexpressing the glucose-6-phosphate dehydrogenase Zwf1 perform best, producing up to 16.9 g L−1 xylitol from 20 g L−1 xylose in stirred tank bioreactors. The beneficial effect of increased Zwf1 activity is especially pronounced during the ethanol consumption phase. The same notion applies to the deletion of the aldehyde dehydrogenase ALD6 gene, albeit at a quantitatively lower level. Reduced expression of the phosphoglucose isomerase Pgi1 and heterologous expression of the NADP+-dependent glyceraldehyde-3-phosphate dehydrogenase Gdp1 from Kluyveromyces lactis acted synergistically with ZWF1 overexpression in the presence of glucose, but had a detrimental effect after the diauxic shift. Expression of the mitochondrial NADH kinase Pos5 in the cytosol likewise improved the production of xylitol only on glucose, but not in combination with enhanced Zwf1 activity. To demonstrate the generalizability of our observations, we show that the most promising strategies – ZWF1 overexpression and deletion of ALD6 - also improve the production of l-galactonate from d-galacturonic acid. Therefore, we expect that these findings will provide valuable guidelines for engineering not only the production of xylitol but also of diverse other pathways that require NADPH.
Highlights
• Determination of styrene-butadiene rubber as tire constituent using TED-GC/MS.
• Determination of zinc content as tire constituent using ICP-OES.
• Representative sampling strategy with large-volume mixed samples.
• Tire wear content is decreasing with increasing sampling depth and distance to road.
• Deposited tire wear particles are mainly present in soil fraction <100 μm.
Abstract
Tire wear (TW) constitutes a significant source of microplastic in terrestrial ecosystems. It is known that particles emitted by roads can have an effect up to 100 m into adjacent areas. Here, we apply for the first-time thermal extraction desorption gas chromatography-mass spectrometry (TED-GC/MS) to determine TW in soil samples by detection of thermal decomposition products of styrene-butadiene rubber (SBR), without additional enrichment. Additionally, zinc contents were determined as an elemental marker for TW. Mixed soil samples were taken along three transects along a German motorway in 0.3, 2.0, and 5.0 m distance from the road. Sampling depths were 0–2, 2–5, 5–10, and 10–20 cm. Four fine fractions, 1 000–500, 500–100, 100–50, and <50 μm, were analyzed.
TW contents based on SBR ranged from 155 to 15 898 mg kg−1. TW contents based on zinc were between 413 and 44 812 mg kg−1. Comparison of individual values of SBR and zinc reveals SBR as a more specific marker. Results confirm that most TW ends up in the topsoil within a 2 m distance.
The sampling strategy resulted in representative data for a larger area. Standard deviations of quadruple TED-GC/MS determination of SBR were <10% for all grain size fractions. TED-GC/MS is a suitable analytical tool for determining TW in soil samples without the use of toxic chemicals, enrichment, or special sample preparation.
The main goal of this work is to contribute to the existing knowledge of soil micro-fungi in Panama and Germany. Studies about soil degradation and its influents in the soil fungi diversity have not been investigated as extensively in these countries. This is an extensive and challenging topic to examine since there is an immense phenotypic and genetic diversity in the soil fungal community and relating this community together with factors of soil degradation is an extensive task. For this reason, the present thesis studies the species identified in the study areas, in other words, the soil fungal diversity in relation to environmental factors in the Taunus Mountain range in Frankfurt, Germany, and in the Majagua valley in Chiriquí, Panama. Two complementary objectives were achieved, the first was the development of a theoretical irrigation model for degraded soils. The second was the development of a mobile application to facilitate laboratory work in the cultivation of soil micro-fungi.
The design of the methodology was based on identifying the species and relating the diversity found to soil factors. Soil samples were taken in both countries: the Taunus Mountain range was sampled eight times from January to November 2012 and the Majagua valley was sampled on three occasions between February and July 2012. In both studies, the areas included three different vegetation types (forest, grassland, and bare soil). Samples were separated for two purposes: the assessment of fungal diversity by molecular and morphological methods and soil characterization.
Soil samples used in the methodology of pyrosequencing were related to global climatic factors. Morphological identification was achieved with identification keys. Micro-fungi were cultivated in different media until obtaining pure cultures. Molecular identification was performed by getting the DNA sequences using the ITS1 and ITS4 primers and comparing the sequences with other reference sequences from GenBank. This was done considering the BLAST algorithm, which considered sequences that matched 98 % or more of maximum identity as reliable identifications.
Soil characterization was carried out to measure the soil's Physico-chemical properties; those abiotic factors were compaction, temperature, pH, moisture, and soil composition.
Species richness was calculated in each study area with the estimators Chao, Jackknife, and Bootstrap. Furthermore, the species accumulation curves were performed to observe the species discovery rate and estimate sample completeness. Estimate linear regression models correlated the influence between the soil factors (temperature, moisture, pH, soil compaction, and soil composition) and the species richness. In the same way, an analysis of ecological distance was undertaken based on the similarity in the species composition, compared across samples, and correlated with soil factors, using non-metric multidimensional scaling (NMDs).
Study of abundance showed differences between the bare soil abundances and the forest abundances in Germany and Panama; the grasslands in both countries work as transitional areas in the fungi abundance. The key stone species in Germany were Penicillium daleae, and Pochonia bulbillosa, whereas in Panama were Purpureocillium lilacinum and Trichoderma harzianum. Based on Pareto analysis, a theoretical irrigation model was developed to counteract the degradation effects on the abundance of micro-fungi in the soil.
Applications for mobile devices dealing with the cultivation of soil micro fungi were sought. Due to the small number of existing applications, a new App called Soil-Fungi-Cultures (SFC) was developed to facilitate data collection of cultivated soil micro fungi. App Inventor was the program used to design, program, test, and publish the application developed. The developed application was compared with other applications used in identifying bacteria cultures. The results showed that the new application needed more time to capture the records because it saves more information, the navigation flow was acceptable, the number of clicks was high, but it is due to the usefulness in data capture, and finally, the users rated it as a good application with an eight out of ten rating.
Pyrosequencing resulted in 204 Operational Taxonomic Units (OTUs) considering the two study areas (the Taunus Mountain range and the Majagua valley). The Pyrosequencing database was used to contribute to the most important study of fungal diversity globally based on OTUs, which surpasses any study of molecular and taxonomic diversity previously conducted. The principal result in this study was that the climatic factor is the best predictor of fungal richness and community composition on a global scale. However, the part of the research that focused on the local scale, that is to say, on the correlation patterns between the distribution of fungal species and abiotic factors, showed that the soil properties and degradation levels were not associated with fungal richness, diversity or soil composition in the study areas in Germany or Panama. The above confirms that there are exceptions to the way relationships between soil factors with fungal diversity are established at the local level.
In the case of soil samples used for morphological identification, 71 fungal species were obtained, 47 from Germany, and 32 from Panama.
Reactive oxygen species (ROS) are constant by-products of aerobic life. In excess, ROS lead to cytotoxic protein aggregates, which are a hallmark of ageing in animals and linked to age-related pathologies in humans. Acylamino acid-releasing enzymes (AARE) are bifunctional serine proteases, acting on oxidized proteins. AARE are found in all domains of life, albeit under different names, such as acylpeptide hydrolase (APEH/ACPH), acylaminoacyl peptidase (AAP), or oxidized protein hydrolase (OPH). In humans, AARE malfunction is associated with age-related pathologies, while their function in plants is less clear. Here, we provide a detailed analysis of AARE genes in the plant lineage and an in-depth analysis of AARE localization and function in the moss Physcomitrella and the angiosperm Arabidopsis. AARE loss-of-function mutants have not been described for any organism so far. We generated and analysed such mutants and describe a connection between AARE function, aggregation of oxidized proteins and plant ageing, including accelerated developmental progression and reduced life span. Our findings complement similar findings in animals and humans, and suggest a unified concept of ageing may exist in different life forms.