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Puberty is an important period of life with physiological changes to enable animals to reproduce. Xiphophorus fish exhibit polymorphism in body size, puberty timing, and reproductive tactics. These phenotypical polymorphisms are controlled by the Puberty (P) locus. In X. nigrensis and X. multilineatus, the P locus encodes the melanocortin 4 receptor (Mc4r) with high genetic polymorphisms.
Mc4r is a member of the melanocortin receptors, belonging to class A G-protein coupled receptors. The Mc4r signaling system consists of Mc4r, the agonist Pomc (precursor of various MSH and of ACTH), the antagonist Agrp and accessory protein Mrap2. In humans, MC4R has a role in energy homeostasis. MC4R and MRAP2 mutations are linked to human obesity but not to puberty.
Mc4rs in X. nigrensis and X. multilineatus are present in three allele classes, A, B1 and B2, of which the X-linked A alleles express functional receptors and the male-specific Y-linked B alleles encode defective receptors. Male body sizes are correlated with B allele type and B allele copy numbers. Late-maturing large males carry B alleles in high copy number while early-maturing small males carry B alleles in low copy number or only A alleles. Cell culture co-expression experiments indicated that B alleles may act as dominant negative receptor mutants on A alleles.
In this study, the main aim was to biochemically characterize the mechanism of puberty regulation by Mc4r in X. nigrensis and X. multilineatus, whether it is by Mc4r dimerization and/or Mrap2 interaction with Mc4r or other mechanisms. Furthermore, Mc4r in X. hellerii (another swordtail species) and medaka (a model organism phylogenetically close to Xiphophorus) were investigated to understand if the investigated mechanisms are conserved in other species.
In medaka, the Mc4r signaling system genes (mc4r, mrap2, pomc, agrp1) are expressed before hatching, with agrp1 being highly upregulated during hatching and first feeding. These genes are mainly expressed in adult brain, and the transcripts of mrap2 co-localize with mc4r indicating a function in modulating Mc4r signaling. Functional comparison between wild-type and mc4r knockout medaka showed that Mc4r knockout does not affect puberty timing but significantly delays hatching due to the retarded embryonic development of knockout medaka. Hence, the Mc4r system in medaka is involved in regulation of growth rather than puberty.
In Xiphophorus, expression co-localization of mc4r and mrap2 in X. nigrensis and X. hellerii fish adult brains was characterized by in situ hybridization. In both species, large males exhibit strikingly high expression of mc4r while mrap2 shows similar expression level in the large and small male and female. Differently, X. hellerii has only A-type alleles indicating that the puberty regulation mechanisms evolved independently in Xiphophorus genus. Functional analysis of Mrap2 and Mc4r A/B1/B2 alleles of X. multilineatus showed that increased Mrap2 amounts induce higher cAMP response but EC50 values do not change much upon Mrap2 co-expression with Mc4r (expressing only A allele or A and B1 alleles). A and B1 alleles were expressed higher in large male brains, while B2 alleles were only barely expressed. Mc4r A-B1 cells have lower cAMP production than Mc4r A cells. Together, this indicates a role of Mc4r alleles, but not Mrap2, in puberty onset regulation signaling. Interaction studies by FRET approach evidenced that Mc4r A and B alleles can form heterodimers and homodimers in vitro, but only for a certain fraction of the expressed receptors. Single-molecule colocalization study using super-resolution microscope dSTORM confirmed that only few Mc4r A and B1 receptors co-localized on the membrane. Altogether, the species-specific puberty onset regulation in X. nigrensis and X. multilineatus is linked to the presence of Mc4r B alleles and to some extent to its interaction with A allele gene products. This is reasoned to result in certain levels of cAMP signaling which reaches the dynamic or static threshold to permit late puberty in large males.
In summary, puberty onset regulation by dominant negative effect of Mc4r mutant alleles is a special mechanism that is found so far only in X. nigrensis and X. multilineatus. Other Xiphophorus species obviously evolved the same function of the pathway by diverse mechanisms. Mc4r in other fish (medaka) has a role in regulation of growth, reminiscent of its role in energy homeostasis in humans. The results of this study will contribute to better understand the biochemical and physiological functions of the Mc4r system in vertebrates including human.
Humans and animals alike use the sun, the moon, and the stars to guide their ways.
However, the position of celestial cues changes depending on daytime, season, and
place on earth. To use these celestial cues for reliable navigation, the rotation of the
sky has to be compensated. While humans invented complicated mechanisms like the
Antikythera mechanism to keep track of celestial movements, animals can only rely on
their brains. The desert ant Cataglyphis is a prime example of an animal using celestial
cues for navigation. Using the sun and the related skylight polarization pattern as a
compass, and a step integrator for distance measurements, it can determine a vector
always pointing homewards. This mechanism is called path integration. Since the sun’s
position and, therefore, also the polarization pattern changes throughout the day,
Cataglyphis have to correct this movement. If they did not compensate for time, the
ants’ compass would direct them in different directions in the morning and the evening.
Thus, the ants have to learn the solar ephemeris before their far-reaching foraging
trips.
To do so, Cataglyphis ants perform a well-structured learning-walk behavior during the
transition phase from indoor worker to outdoor forager. While walking in small loops
around the nest entrance, the ants repeatedly stop their forward movements to perform
turns. These can be small walked circles (voltes) or tight turns about the ants’ body
axes (pirouettes). During pirouettes, the ants gaze back to their nest entrance during
stopping phases. These look backs provide a behavioral read-out for the state of the
path integrator. The ants “tell” the observer where they think their nest is, by looking
back to it. Pirouettes are only performed by Cataglyphis ants inhabiting an environment
with a prominent visual panorama. This indicates, that pirouettes are performed to
learn the visual panorama. Voltes, on the other hand, might be used for calibrating the
celestial compass of the ants.
In my doctoral thesis, I employed a wide range of state-of-the-art techniques from
different disciplines in biology to gain a deeper understanding of how navigational
information is acquired, memorized, used, and calibrated during the transition phase
from interior worker to outdoor forager. I could show, that celestial orientation cues that
provide the main compass during foraging, do not guide the ants during the look-backbehavior
of initial learning walks. Instead Cataglyphis nodus relies on the earth’s
magnetic field as a compass during this early learning phase. While not guiding the
ants during their first walks outside of the nest, excluding the ants from perceiving the
natural polarization pattern of the skylight has significant consequences on learning-related
plasticity in the ants’ brain. Only if the ants are able to perform their learning-walk
behavior under a skylight polarization pattern that changes throughout the day,
plastic neuronal changes in high-order integration centers are induced. Especially the
mushroom bogy collar, a center for learning and memory, and the central complex, a
center for orientation and motor control, showed an increase in volume after learning
walks. This underlines the importance of learning walks for calibrating the celestial
compass. The magnetic compass might provide the necessary stable reference
system for the ants to calibrate their celestial compass and learn the position of
landmark information. In the ant brain, visual information from the polarization-sensitive
ocelli converge in tight apposition with neuronal afferents of the mechanosensitive
Johnston’s organ in the ant’s antennae. This makes the ants’ antennae an interesting
candidate for studying the sensory bases of compass calibration in Cataglyphis ants.
The brain of the desert navigators is well adapted to successfully accomplish their
navigational needs. Females (gynes and workers) have voluminous mushroom bodies,
and the synaptic complexity to store large amount of view-based navigational
information, which they acquire during initial learning walks. The male Cataglyphis
brain is better suited for innate behaviors that support finding a mate.
The results of my thesis show that the well adapted brain of C. nodus ants undergoes
massive structural changes during leaning walks, dependent on a changing celestial
polarization pattern. This underlies the essential role of learning walks in the calibration
of orientation systems in desert ants.
Over the past centuries, anthropogenic utilization has fundamentally changed the appearance of European forest ecosystems. Constantly growing and changing demands have led to an enormous decline in ecological key elements and a structural homogenization of most forests. These changes have been accompanied by widespread declines of many forest-dwelling and especially saproxylic, i.e. species depending on deadwood. In order to counteract this development, various conservation strategies have been developed, but they primarily focus on a quantitative deadwood enrichment. However, the diversity of saproxylic species is furthermore driven by a variety of abiotic and biotic determinants as well as interactions between organisms. A detailed understanding of these processes has so far been largely lacking. The aim of the present thesis was therefore to improve the existing ecological knowledge of determinants influencing saproxylic species and species communities in order to provide the basis for evidence-based and adapted conservation measures.
In chapter II of this thesis, I first investigated the impact of sun exposure, tree species, and their combination on saproxylic beetles, wood-inhabiting fungi, and spiders. Therefore, logs and branches of six tree species were set up under different sun exposures in an experimental approach. The impact of sun exposure and tree species strongly differed among single saproxylic taxa as well as diameters of deadwood. All investigated taxa were affected by sun exposure, whereby sun exposure resulted in a higher alpha-diversity of taxa recorded in logs and a lower alpha-diversity of saproxylic beetles reared from branches compared to shading by canopy. Saproxylic beetles and wood-inhabiting fungi as obligate saproxylic species were additionally affected by tree species. In logs, the respective impact of both determinants also resulted in divergent community compositions. Finally, a rarefaction/extrapolation method was used to evaluate the effectiveness of different combinations of tree species and sun exposure for the conservation of saproxylic species diversity. Based on this procedure, a combination of broadleaved and coniferous as well as hard- and softwood tree species was identified to support preferably high levels of saproxylic species diversity.
The aim of chapter III was to evaluate the individual conservational importance of tree species for the protection of saproxylic beetles. For this, the list of tree species sampled for saproxylic beetles was increased to 42 different tree species. The considered tree species represented large parts of taxonomic and phylogenetic diversity native to Central Europe as well as the most important non-native tree species of silvicultural interest. Freshly cut branches were set up for one year and saproxylic beetles were reared afterwards for two subsequent years.
The study revealed that some tree species, in particular Quercus sp., host a particular high diversity of saproxylic beetles, but tree species with a comparatively medium or low overall diversity were likewise important for red-listed saproxylic beetle species. Compared to native tree species, non-native tree species hosted a similar overall species diversity of saproxylic beetles but differed in community composition.
In chapter IV, I finally analysed the interactions of host beetle diversity and the diversity of associated parasitoids by using experimentally manipulated communities of saproxylic beetles and parasitoid Hymenoptera as a model system. Classical approaches of species identification for saproxylic beetles were combined with DNA-barcoding for parasitoid Hymenoptera. The diversity of the host communities was inferred from their phylogenetic composition as well as differences in seven functional traits. Abundance, species richness, and Shannon-diversity of parasitoid Hymenoptera increased with increasing host abundance. However, the phylogenetic and functional dissimilarity of host communities showed no influence on the species communities of parasitoid Hymenoptera. The results clearly indicate an abundance-driven system in which the general availability, not necessarily the diversity of potential hosts, is decisive.
In summary, the present thesis corroborates the general importance of deadwood heterogeneity for the diversity of saproxylic species by combining different experimental approaches. In order to increase their efficiency, conservation strategies for saproxylic species should generally promote deadwood from different tree species under different conditions of sun exposure on landscape-level in addition to the present enrichment of a certain deadwood amount. The most effective combinations of tree species should consider broadleaved and coniferous as well as hard- and softwood tree species. Furthermore, in addition to dominant tree species, special attention should be given to native, subdominant, silviculturally unimportant, and rare tree species.
Neuropeptides have gained broad attraction in insect neuroscience and physiology, as new genetic tools are increasingly uncovering their wide-ranging pleiotropic functions with high cellular resolution. Allatostatin A (AstA) peptides constitute one of the best studied insect neuropeptide families. In insects and other panarthropods, AstA peptides qualify as brain-gut peptides and have regained attention with the discovery of their role in regulating feeding, growth, activity/sleep and learning. AstA receptor homologs are found throughout the protostomia and group with vertebrate somatostatin/galanin/kisspeptin receptors. In this review, we summarise the current knowledge on the evolution and the pleiotropic and cell-specific non-allatostatic functions of AstA. We speculate about the core functions of AstA signalling, and derive open questions and challengesfor future research on AstA and invertebrate neuropeptides in general.
Climate and land-use changes cause increasing stress to pollinators but the molecular pathways underlying stress responses are poorly understood. Here, we analyzed the transcriptomic response of Bombus lucorum workers to temperature and livestock grazing. Bumblebees sampled along an elevational gradient, and from differently managed grassland sites (livestock grazing vs unmanaged) in the German Alps did not differ in the expression of genes known for thermal stress responses. Instead, metabolic energy production pathways were upregulated in bumblebees sampled in mid- or high elevations or during cool temperatures. Extensive grazing pressure led to an upregulation of genetic pathways involved in immunoregulation and DNA-repair. We conclude that widespread bumblebees are tolerant toward temperature fluctuations in temperate mountain environments. Moderate temperature increases may even release bumblebees from metabolic stress. However, transcriptome responses to even moderate management regimes highlight the completely underestimated complexity of human influence on natural pollinators.
G-protein-coupled receptors (GPCRs) are hypothesized to possess molecular mobility over a wide temporal range. Until now the temporal range has not been fully accessible due to the crucially limited temporal range of available methods. This in turn, may lead relevant dynamic constants to remain masked. Here, we expand this dynamic range by combining fluorescent techniques using a spot confocal setup. We decipher mobility constants of β\(_{2}\)-adrenergic receptor over a wide time range (nanosecond to second). Particularly, a translational mobility (10 µm\(^{2}\)/s), one order of magnitude faster than membrane associated lateral mobility that explains membrane protein turnover and suggests a wider picture of the GPCR availability on the plasma membrane. And a so far elusive rotational mobility (1-200 µs) which depicts a previously overlooked dynamic component that, despite all complexity, behaves largely as predicted by the Saffman-Delbrück model.
∆Np63 is a master regulator of squamous cell identity and regulates several signaling pathways that crucially
contribute to the development of squamous cell carcinoma (SCC) tumors. Its contribution to coordinating the
expression of genes involved in oncogenesis, epithelial identity, DNA repair, and genome stability has been
extensively studied and characterized. For SCC, the expression of ∆Np63 is an essential requirement to
maintain the malignant phenotype. Additionally, ∆Np63 functionally contributes to the development of cancer
resistance toward therapies inducing DNA damage.
SCC patients are currently treated with the same conventional Cisplatin therapy as they would have been
treated 30 years ago. In contrast to patients with other tumor entities, the survival of SCC patients is limited,
and the efficacy of the current therapies is rather low. Considering the rising incidences of these tumor entities,
the development of novel SCC therapies is urgently required. Targeting ∆Np63, the transcription factor, is a
potential alternative to improve the therapeutic response and clinical outcomes of SCC patients.
However, ∆Np63 is considered “undruggable.” As is commonly observed in transcription factors, ∆Np63 does
not provide any suitable domains for the binding of small molecule inhibitors. ∆Np63 regulates a plethora of
different pathways and cellular processes, making it difficult to counteract its function by targeting
downstream effectors. As ∆Np63 is strongly regulated by the ubiquitin–proteasome system (UPS), the
development of deubiquitinating enzyme inhibitors has emerged as a promising therapeutic strategy to target
∆Np63 in SCC treatment.
This work involved identifying the first deubiquitinating enzyme that regulates ∆Np63 protein stability. Stateof-the-art SCC models were used to prove that USP28 deubiquitinates ∆Np63, regulates its protein stability,
and affects squamous transcriptional profiles in vivo and ex vivo. Accordingly, SCC depends on USP28 to
maintain essential levels of ∆Np63 protein abundance in tumor formation and maintenance. For the first time,
∆Np63, the transcription factor, was targeted in vivo using a small molecule inhibitor targeting the activity of
USP28. The pharmacological inhibition of USP28 was sufficient to hinder the growth of SCC tumors in
preclinical mouse models.
Finally, this work demonstrated that the combination of Cisplatin with USP28 inhibitors as a novel therapeutic
alternative could expand the limited available portfolio of SCC therapeutics. Collectively, the data presented
within this dissertation demonstrates that the inhibition of USP28 in SCC decreases ∆Np63 protein abundance,
thus downregulating the Fanconi anemia (FA) pathway and recombinational DNA repair. Accordingly, USP28
inhibition reduces the DNA damage response, thereby sensitizing SCC tumors to DNA damage therapies, such
as Cisplatin.
European honeybee populations are considered to consist only of managed colonies, but recent censuses have revealed that wild/feral colonies still occur in various countries. To gauge the ecological and evolutionary relevance of wild-living honeybees, information is needed on their population demography. We monitored feral honeybee colonies in German forests for up to 4 years through regular inspections of woodpecker cavity trees and microsatellite genotyping. Each summer, about 10% of the trees were occupied, corresponding to average densities of 0.23 feral colonies km\(^{−2}\) (an estimated 5% of the regional honeybee populations). Populations decreased moderately until autumn but dropped massively during winter, so that their densities were only about 0.02 colonies km\(^{−2}\) in early spring. During the reproductive (swarming) season, in May and June, populations recovered, with new swarms preferring nest sites that had been occupied in the previous year. The annual survival rate and the estimated lifespan of feral colonies (n = 112) were 10.6% and 0.6 years, respectively. We conclude that managed forests in Germany do not harbour self-sustaining feral honeybee populations, but they are recolonized every year by swarms escaping from apiaries.
Macroautophagy (hereafter referred to as autophagy) is a homeostatic process that preserves cellular integrity. In mice, autophagy regulates pancreatic ductal adenocarcinoma (PDAC) development in a manner dependent on the status of the tumor suppressor gene Trp53. Studies published so far have investigated the impact of autophagy blockage in tumors arising from Trp53-hemizygous or -homozygous tissue. In contrast, in human PDACs the tumor suppressor gene TP53 is mutated rather than allelically lost, and TP53 mutants retain pathobiological functions that differ from complete allelic loss. In order to better represent the patient situation, we have investigated PDAC development in a well-characterized genetically engineered mouse model (GEMM) of PDAC with mutant Trp53 (Trp53\(^{R172H}\)) and deletion of the essential autophagy gene Atg7. Autophagy blockage reduced PDAC incidence but had no impact on survival time in the subset of animals that formed a tumor. In the absence of Atg7, non-tumor-bearing mice reached a similar age as animals with malignant disease. However, the architecture of autophagy-deficient, tumor-free pancreata was effaced, normal acinar tissue was largely replaced with low-grade pancreatic intraepithelial neoplasias (PanINs) and insulin expressing islet β-cells were reduced. Our data add further complexity to the interplay between Atg7 inhibition and Trp53 status in tumorigenesis.
Cellular stress can induce DNA lesions that threaten the stability of genes. The DNA damage response (DDR) recognises and repairs broken DNA to maintain genome stability. Intriguingly, components of nuclear paraspeckles like the non-POU domain containing octamer-binding protein (NONO) participate in the repair of DNA double-strand breaks (DSBs). NONO is a multifunctional RNA-binding protein (RBP) that facilitates the retention and editing of messenger (m)RNA as well as pre-mRNA processing. However, the role of NONO in the DDR is poorly understood. Here, we establish a novel human U2OS cell line that expresses NONO fused to the engineered ascorbate peroxidase 2 (U2OS:NONO-APEX2-HA). We show that NONO-APEX2-HA accumulates in the nucleolus in response to DNA damage. Combining viability assays, subcellular localisation studies, coimmunoprecipitation experiments and in vivo proximity labeling, we demonstrate that NONO-APEX2-HA is a stably expressed fusion protein that mimics endogenous NONO in terms of expression, localisation and bona fide interactors. We propose that in vivo proximity labeling in U2OS:NONO-APEX2-HA cells is capable for the assessment of NONO interactomes by downstream assays. U2OS:NONO-APEX2-HA cells will likely be a valuable resource for the investigation of NONO interactome dynamics in response to DNA damage and other stimuli.
Background
Bacterial meningitis is a life-threatening disease that occurs when pathogens such as Neisseria meningitidis cross the meningeal blood cerebrospinal fluid barrier (mBCSFB) and infect the meninges. Due to the human-specific nature of N. meningitidis, previous research investigating this complex host–pathogen interaction has mostly been done in vitro using immortalized brain endothelial cells (BECs) alone, which often do not retain relevant barrier properties in culture. Here, we developed physiologically relevant mBCSFB models using BECs in co-culture with leptomeningeal cells (LMCs) to examine N. meningitidis interaction.
Methods
We used BEC-like cells derived from induced pluripotent stem cells (iBECs) or hCMEC/D3 cells in co-culture with LMCs derived from tumor biopsies. We employed TEM and structured illumination microscopy to characterize the models as well as bacterial interaction. We measured TEER and sodium fluorescein (NaF) permeability to determine barrier tightness and integrity. We then analyzed bacterial adherence and penetration of the cell barrier and examined changes in host gene expression of tight junctions as well as chemokines and cytokines in response to infection.
Results
Both cell types remained distinct in co-culture and iBECs showed characteristic expression of BEC markers including tight junction proteins and endothelial markers. iBEC barrier function as determined by TEER and NaF permeability was improved by LMC co-culture and remained stable for seven days. BEC response to N. meningitidis infection was not affected by LMC co-culture. We detected considerable amounts of BEC-adherent meningococci and a relatively small number of intracellular bacteria. Interestingly, we discovered bacteria traversing the BEC-LMC barrier within the first 24 h post-infection, when barrier integrity was still high, suggesting a transcellular route for N. meningitidis into the CNS. Finally, we observed deterioration of barrier properties including loss of TEER and reduced expression of cell-junction components at late time points of infection.
Conclusions
Here, we report, for the first time, on co-culture of human iPSC derived BECs or hCMEC/D3 with meningioma derived LMCs and find that LMC co-culture improves barrier properties of iBECs. These novel models allow for a better understanding of N. meningitidis interaction at the mBCSFB in a physiologically relevant setting.
Ovarian cancer is the second most common gynecological malignancy in women. More than 70% of the cases are diagnosed at the advanced stage, presenting as primary peritoneal metastasis, which results in a poor 5-year survival rate of around 40%. Mechanisms of peritoneal metastasis, including adhesion, migration, and invasion, are still not completely understood and therapeutic options are extremely limited. Therefore, there is a strong requirement for a 3D model mimicking the in vivo situation. In this study, we describe the establishment of a 3D tissue model of the human peritoneum based on decellularized porcine small intestinal submucosa (SIS) scaffold. The SIS scaffold was populated with human dermal fibroblasts, with LP-9 cells on the apical side representing the peritoneal mesothelium, while HUVEC cells on the basal side of the scaffold served to mimic the endothelial cell layer. Functional analyses of the transepithelial electrical resistance (TEER) and the FITC-dextran assay indicated the high barrier integrity of our model. The histological, immunohistochemical, and ultrastructural analyses showed the main characteristics of the site of adhesion. Initial experiments using the SKOV-3 cell line as representative for ovarian carcinoma demonstrated the usefulness of our models for studying tumor cell adhesion, as well as the effect of tumor cells on endothelial cell-to-cell contacts. Taken together, our data show that the novel peritoneal 3D tissue model is a promising tool for studying the peritoneal dissemination of ovarian cancer.
The idea that populations are spatially structured has become a very powerful concept in ecology, raising interest in many research areas. However, despite dispersal being a core component of the concept, it typically does not consider the movement behavior underlying any dispersal. Using individual‐based simulations in continuous space, we explored the emergence of a spatially structured population in landscapes with spatially heterogeneous resource distribution and with organisms following simple area‐concentrated search (ACS); individuals do not, however, perceive or respond to any habitat attributes per se but only to their foraging success. We investigated the effects of different resource clustering pattern in landscapes (single large cluster vs. many small clusters) and different resource density on the spatial structure of populations and movement between resource clusters of individuals. As results, we found that foraging success increased with increasing resource density and decreasing number of resource clusters. In a wide parameter space, the system exhibited attributes of a spatially structured populations with individuals concentrated in areas of high resource density, searching within areas of resources, and “dispersing” in straight line between resource patches. “Emigration” was more likely from patches that were small or of low quality (low resource density), but we observed an interaction effect between these two parameters. With the ACS implemented, individuals tended to move deeper into a resource cluster in scenarios with moderate resource density than in scenarios with high resource density. “Looping” from patches was more likely if patches were large and of high quality. Our simulations demonstrate that spatial structure in populations may emerge if critical resources are heterogeneously distributed and if individuals follow simple movement rules (such as ACS). Neither the perception of habitat nor an explicit decision to emigrate from a patch on the side of acting individuals is necessary for the emergence of such spatial structure.
Dung beetles are important actors in the self-regulation of ecosystems by driving nutrient cycling, bioturbation, and pest suppression. Urbanization and the sprawl of agricultural areas, however, destroy natural habitats and may threaten dung beetle diversity. In addition, climate change may cause shifts in geographical distribution and community composition. We used a space-for-time approach to test the effects of land use and climate on α-diversity, local community specialization (H\(_2\)′) on dung resources, and γ-diversity of dung-visiting beetles. For this, we used pitfall traps baited with four different dung types at 115 study sites, distributed over a spatial extent of 300 km × 300 km and 1000 m in elevation. Study sites were established in four local land-use types: forests, grasslands, arable sites, and settlements, embedded in near-natural, agricultural, or urban landscapes. Our results show that abundance and species density of dung-visiting beetles were negatively affected by agricultural land use at both spatial scales, whereas γ-diversity at the local scale was negatively affected by settlements and on a landscape scale equally by agricultural and urban land use. Increasing precipitation diminished dung-visiting beetle abundance, and higher temperatures reduced community specialization on dung types and γ-diversity. These results indicate that intensive land use and high temperatures may cause a loss in dung-visiting beetle diversity and alter community networks. A decrease in dung-visiting beetle diversity may disturb decomposition processes at both local and landscape scales and alter ecosystem functioning, which may lead to drastic ecological and economic damage.
Breast cancer etiology is associated with both proliferation and DNA damage induced by estrogens. Breast cancer risk factors (BCRF) such as body mass index (BMI), smoking, and intake of estrogen-active drugs were recently shown to influence intratissue estrogen levels. Thus, the aim of the present study was to investigate the influence of BCRF on estrogen-induced proliferation and DNA damage in 41 well-characterized breast glandular tissues derived from women without breast cancer. Influence of intramammary estrogen levels and BCRF on estrogen receptor (ESR) activation, ESR-related proliferation (indicated by levels of marker transcripts), oxidative stress (indicated by levels of GCLC transcript and oxidative derivatives of cholesterol), and levels of transcripts encoding enzymes involved in estrogen biotransformation was identified by multiple linear regression models. Metabolic fluxes to adducts of estrogens with DNA (E-DNA) were assessed by a metabolic network model (MNM) which was validated by comparison of calculated fluxes with data on methoxylated and glucuronidated estrogens determined by GC- and UHPLC-MS/MS. Intratissue estrogen levels significantly influenced ESR activation and fluxes to E-DNA within the MNM. Likewise, all BCRF directly and/or indirectly influenced ESR activation, proliferation, and key flux constraints influencing E-DNA (i.e., levels of estrogens, CYP1B1, SULT1A1, SULT1A2, and GSTP1). However, no unambiguous total effect of BCRF on proliferation became apparent. Furthermore, BMI was the only BCRF to indeed influence fluxes to E-DNA (via congruent adverse influence on levels of estrogens, CYP1B1 and SULT1A2).
Candida auris is a globally emerging fungal pathogen responsible for causing nosocomial outbreaks in healthcare associated settings. It is known to cause infection in all age groups and exhibits multi-drug resistance with high potential for horizontal transmission. Because of this reason combined with limited therapeutic choices available, C. auris infection has been acknowledged as a potential risk for causing a future pandemic, and thus seeking a promising strategy for its treatment is imperative. Here, we combined evolutionary information with reverse vaccinology approach to identify novel epitopes for vaccine design that could elicit CD4+ T-cell responses against C. auris. To this end, we extensively scanned the family of proteins encoded by C. auris genome. In addition, a pathogen may acquire substitutions in epitopes over a period of time which could cause its escape from the immune response thus rendering the vaccine ineffective. To lower this possibility in our design, we eliminated all rapidly evolving genes of C. auris with positive selection. We further employed highly conserved regions of multiple C. auris strains and identified two immunogenic and antigenic T-cell epitopes that could generate the most effective immune response against C. auris. The antigenicity scores of our predicted vaccine candidates were calculated as 0.85 and 1.88 where 0.5 is the threshold for prediction of fungal antigenic sequences. Based on our results, we conclude that our vaccine candidates have the potential to be successfully employed for the treatment of C. auris infection. However, in vivo experiments are imperative to further demonstrate the efficacy of our design.
Interactive effects of climate and land use on pollinator diversity differ among taxa and scales
(2022)
Changes in climate and land use are major threats to pollinating insects, an essential functional group. Here, we unravel the largely unknown interactive effects of both threats on seven pollinator taxa using a multiscale space-for-time approach across large climate and land-use gradients in a temperate region. Pollinator community composition, regional gamma diversity, and community dissimilarity (beta diversity) of pollinator taxa were shaped by climate-land-use interactions, while local alpha diversity was solely explained by their additive effects. Pollinator diversity increased with reduced land-use intensity (forest < grassland < arable land < urban) and high flowering-plant diversity at different spatial scales, and higher temperatures homogenized pollinator communities across regions. Our study reveals declines in pollinator diversity with land-use intensity at multiple spatial scales and regional community homogenization in warmer and drier climates. Management options at several scales are highlighted to mitigate impacts of climate change on pollinators and their ecosystem services.
For SARS-CoV-2, R0 calculations in the range of 2–3 dominate the literature, but much higher estimates have also been published. Because capacity for RT-PCR testing increased greatly in the early phase of the Covid-19 pandemic, R0 determinations based on these incidence values are subject to strong bias. We propose to use Covid-19-induced excess mortality to determine R0 regardless of RT-PCR testing capacity. We used data from the Robert Koch Institute (RKI) on the incidence of Covid cases, Covid-related deaths, number of RT-PCR tests performed, and excess mortality calculated from data from the Federal Statistical Office in Germany. We determined R0 using exponential growth estimates with a serial interval of 4.7 days. We used only datasets that were not yet under the influence of policy measures (e.g., lockdowns or school closures). The uncorrected R0 value for the spread of SARS-CoV-2 based on RT-PCR incidence data was 2.56 (95% CI 2.52–2.60) for Covid-19 cases and 2.03 (95% CI 1.96–2.10) for Covid-19-related deaths. However, because the number of RT-PCR tests increased by a growth factor of 1.381 during the same period, these R0 values must be corrected accordingly (R0corrected = R0uncorrected/1.381), yielding 1.86 for Covid-19 cases and 1.47 for Covid-19 deaths. The R0 value based on excess deaths was calculated to be 1.34 (95% CI 1.32–1.37). A sine-function-based adjustment for seasonal effects of 40% corresponds to a maximum value of R0January = 1.68 and a minimum value of R0July = 1.01. Our calculations show an R0 that is much lower than previously thought. This relatively low range of R0 fits very well with the observed seasonal pattern of infection across Europe in 2020 and 2021, including the emergence of more contagious escape variants such as delta or omicron. In general, our study shows that excess mortality can be used as a reliable surrogate to determine the R0 in pandemic situations.
Microbial rhodopsins are abundant membrane proteins often capable of ion transport and are found in all three domains of life. Thus, many fungi, especially phyto-associated or phyto-pathogenic ones, contain these green-light-sensing photoreceptors. Proteins that perceive other wavelengths are often well characterized in terms of their impact on fungal biology whereas little is known about the function of fungal rhodopsins. In this work, five fungal rhodopsins, UmOps1 and UmOps2 from the corn smut Ustilago maydis as well as ApOps1, ApOps2 and ApOps3 from the black yeast Aureobasidium pullulans, were characterized electrophysiologically using mammalian expression systems and the patch-clamp technique to explore their ion transport properties. The latter three were modified using a membrane trafficking cassette, termed “2.0” that consists of the lucy rho motif, two Kir2.1 Golgi apparatus trafficking signals and a Kir2.1 endoplasmic reticulum export signal, what resulted in better plasma membrane localization. Rhodopsin mutants were created to identify amino acid residues that are key players in the ion transport process. Current enhancement in the presence of weak organic acids, that was already described before for the fungal rhodopsin CarO from Fusarium fujikuroi (García-Martínez et al., 2015; Adam et al., 2018), was investigated for the U. maydis rhodopsins as well as for ApOps2 by supplementing acetate in the patch-clamp electrolyte solutions. All five rhodopsins were found to be proton pumps unidirectionally transporting protons out of the cytosol upon green-light exposure with every rhodopsin exhibiting special features or unique characteristics in terms of the photocurrents. To name just a few, UmOps1, for example, showed a striking pH-dependency with massive enhancement of pump currents in the presence of extracellular acidic pH. Moreover, especially ApOps2 and ApOps3 showed very high current densities, however, the ones of ApOps3 were impaired when exchanging intracellular sodium to cesium. Concerning the mutations, it was found, that the electron releasing group in UmOps1 seems to be involved in the striking pH effect and that the mutation of the proton donor site resulted in almost unfunctional proteins. Moreover, a conserved arginine inside ApOps2 was mutated to turn the proton pump into a channel. Regarding the effect of weak organic acids, acetate was able to induce enhanced pump currents in UmOps1 and ApOps2, but not in UmOps2. Due to the capability of current production upon light illumination, microbial rhodopsins are used in the research field of optogenetics that aims to control neuronal activity by light. ApOps2 was used to test its functionality in differentiated NG108-15 cells addressing the question whether it is a promising candidate that can be used as an optogenetic tool. Indeed, this rhodopsin could be functionally expressed in this experimental system. Furthermore, microscopic studies were done to elucidate the localization of selected rhodopsins in fungal cells. Therefore, conventional (confocal laser scanning or structured illumination microscopy) as well as novel super-resolution techniques (expansion or correlated light and electron microscopy) were used. This was done on U. maydis sporidia, the yeast-like form of this fungus, via eGFP-tagged UmOps1 or UmOps2 expressing strains. Moreover, CarO-eYFP expressing F. fujikuroi was imaged microscopically to confirm the plasma membrane and tonoplast localization (García-Martínez et al., 2015) with the help of counterstaining experiments. UmOps1 was found to reside in the plasma membrane, UmOps2 localized to the tonoplast and CarO was indeed found in both of these localizations. This work gains further insight into rhodopsin functions and paves the way for further research in terms of the biological role of rhodopsins in fungal life cycles.
Anthropogenic activities are causing air pollution. Amongst air pollutants, tropospheric ozone is a major threat to human health and ecosystem functioning. In this dissertation, I present three studies that aimed at increasing our knowledge on how plant exposure to ozone affects its reproduction and its interactions with insect herbivores and pollinators.
For this purpose, a new fumigation system was built and placed in a greenhouse. The annual plant Sinapis arvensis (wild mustard) was used as the model plant.
Plants were exposed to either 0 ppb (control) or 120 ppb of ozone, for variable amounts of time and at different points of their life cycle. After fumigation, plants were exposed to herbivores or pollinators in the greenhouse, or to both groups of insects in the field.
My research shows that ozone affected reproductive performance differently, depending on the timing of exposure: plants exposed at earlier ages had their reproductive fitness increased, while plants exposed later in their life cycle showed a tendency for reduced reproductive fitness. Plant phenology was a key factor influencing reproductive fitness: ozone accelerated flowering and increased the number of flowers produced by plants exposed at early ages, while plants exposed to ozone at later ages tended to have fewer flowers. On the other hand, the ozone-mediated changes in plant-insect interactions had little impact on plant reproductive success.
The strongest effect of ozone on plant-pollinator interactions was the change in the number of flower visits received per plant, which was strongly linked to the number of open flowers. This means that, as a rule, exposure of plants to ozone early in the life cycle resulted in a higher number of pollinator visits, while exposure later in the life cycle resulted in fewer flower visits by potential pollinators. An exception was observed: the higher number of visits performed by large syrphid flies to young ozone-exposed plants than to the respective control plants went beyond the increase in the number of open flowers in those plants. Also, honeybees spent more time per flower in plants exposed to ozone than on control plants, while other pollinators spent similar amounts of time in control and ozone-exposed plants. This guild-dependent preference for ozone-exposed plants may be due to species-specific preferences related to changes in the quality and quantity of floral rewards.
In the field, ozone-exposed plants showed only a tendency for increased colonization by sucking herbivores and slightly more damage by chewing herbivores than control plants. On the other hand, in the greenhouse experiment, Pieris brassicae butterflies preferred control plants over ozone-exposed plants as oviposition sites. Eggs laid on ozone-exposed plants took longer to hatch, but the chances of survival were higher. Caterpillars performed better in control plants than in ozone-exposed plants, particularly when the temperature was high.
Most of the described effects were dependent on the duration and timing of the ozone exposure and the observed temperature, with the strongest effects being observed for longer exposures and higher temperatures. Furthermore, the timing of exposure altered the direction of the effects.
The expected climate change provides ideal conditions for further increases in tropospheric ozone concentrations, therefore for stronger effects on plants and plant-insect interactions. Acceleration of flowering caused by plant exposure to ozone may put plant-pollinator interactions at risk by promoting desynchronization between plant and pollinator activities. Reduced performance of caterpillars feeding on ozone-exposed plants may weaken herbivore populations. On the other hand, the increased plant reproduction that results from exposing young plants to ozone may be a source of good news in the field of horticulture, when similar results would be achieved in high-value crops. However, plant response to ozone is highly species-specific. In fact, Sinapis arvensis is considered a weed and the advantage conferred by ozone exposure may increase its competitiveness, with negative consequences for crops or plant communities in general. Overall, plant exposure to ozone might constitute a threat for the balance of natural and agro-ecosystems.
Ribosomal biogenesis and protein synthesis are deregulated in most cancers, suggesting that interfering with translation machinery may hold significant therapeutic potential. Here, we show that loss of the tumor suppressor adenomatous polyposis coli (APC), which constitutes the initiating event in the adenoma carcinoma sequence for colorectal cancer (CRC), induces the expression of RNA polymerase I (RNAPOL1) transcription machinery, and subsequently upregulates ribosomal DNA (rDNA) transcription. Targeting RNAPOL1 with a specific inhibitor, CX5461, disrupts nucleolar integrity, and induces a disbalance of ribosomal proteins. Surprisingly, CX5461-induced growth arrest is irreversible and exhibits features of senescence and terminal differentiation. Mechanistically, CX5461 promotes differentiation in an MYC-interacting zinc-finger protein 1 (MIZ1)- and retinoblastoma protein (Rb)-dependent manner. In addition, the inhibition of RNAPOL1 renders CRC cells vulnerable towards senolytic agents. We validated this therapeutic effect of CX5461 in murine- and patient-derived organoids, and in a xenograft mouse model. These results show that targeting ribosomal biogenesis together with targeting the consecutive, senescent phenotype using approved drugs is a new therapeutic approach, which can rapidly be transferred from bench to bedside.
Neisseria gonorrhoeae is a human-specific pathogen that causes gonorrhea, the second most common sexually transmitted infection worldwide. Disease progression, drug discovery, and basic host-pathogen interactions are studied using different approaches, which rely on models ranging from 2D cell culture to complex 3D tissues and animals. In this review, we discuss the models used in N. gonorrhoeae research. We address both in vivo (animal) and in vitro cell culture models, discussing the pros and cons of each and outlining the recent advancements in the field of three-dimensional tissue models. From simple 2D monoculture to complex advanced 3D tissue models, we provide an overview of the relevant methodology and its application. Finally, we discuss future directions in the exciting field of 3D tissue models and how they can be applied for studying the interaction of N. gonorrhoeae with host cells under conditions closely resembling those found at the native sites of infection.
Introduction
Surgical site infections (SSIs) are one of the most common postoperative complications after appendectomy leading to recurrent surgery, prolonged hospital stay, and the use of antibiotics. Numerous studies and meta-analyses have been published on the effect of open versus conventional laparoscopic appendectomy (CLA) reporting faster postoperative recovery and less postoperative pain for CLA. A development from CLA has been the single-port appendectomy (SPA), associated with a better cosmesis but seemingly having a higher risk of wound infections. The aim of this systematic literature review and meta-analysis is to investigate whether reduced port or SPA alters the ratio of SSIs.
Methods
Pubmed, Embase, and Cochrane databases were screened for suitable articles. All articles published between January 1, 2002, and March 23, 2022, were included. Articles regarding children below the age of 18 were excluded as well as manuscripts that investigated solemnly open appendectomies. Articles were screened for inclusion criteria by two independent authors. Incidence of SSI was the primary outcome. Duration of operation and length of hospital stay were defined as secondary outcomes.
Results
A total of 25 studies were found through a database search describing 5484 patients. A total of 2749 patients received SPA and 2735 received CLA. There was no statistical difference in the rate of SSI (P = 0.98). A total of 22 studies including 4699 patients reported the duration of operation (2223 SPA and 2476 CLA). There was a significantly shorter operation time seen in CLA. The length of hospital stay was reported in 23 studies (4735 patients: 2235 SPA and 2500 CLA). A shorter hospital stay was seen in the SPA group (P < 0.00001). Separately performed analysis of randomized controlled trials could not confirm this effect (P = 0.29).
Discussion
SPA is an equally safe procedure considering SSI compared to CLA and does not lead to an increased risk of SSI. A longer operation time for SPA and a minor difference in the length of stay does lead to the use of SPA in selected patients only.
Patterns of resource use by animals can clarify how ecological communities have assembled in the past, how they currently function and how they are likely to respond to future perturbations. Bumble bees (Hymentoptera: Bombus spp.) and their floral hosts provide a diverse yet tractable system in which to explore resource selection in the context of plant–pollinator networks. Under conditions of resource limitation, the ability of bumble bees species to coexist should depend on dietary niche overlap. In this study, we report patterns and dynamics of floral morphotype preferences in a mountain bumble bee community based on ~13 000 observations of bumble bee floral visits recorded along a 1400 m elevation gradient. We found that bumble bees are highly selective generalists, rarely visiting floral morphotypes at the rates predicted by their relative abundances. Preferences also differed markedly across bumble bee species, and these differences were well-explained by variation in bumble bee tongue length, generating patterns of preference similarity that should be expected to predict competition under conditions of resource limitation. Within species, though, morphotype preferences varied by elevation and season, possibly representing adaptive flexibility in response to the high elevational and seasonal turnover of mountain floral communities. Patterns of resource partitioning among bumble bee communities may determine which species can coexist under the altered distributions of bumble bees and their floral hosts caused by climate and land use change.
Fish are amongst vertebrates the group with the highest diversity of known sex-determining genes. Particularly, the genus Oryzias is a suitable taxon to understand how different sex determination genetic networks evolved in closely related species. Two closely related species, O. latipes and O. curvinotus, do not only share the same XX/XY sex chromosome system, but also the same male sex-determining gene, dmrt1bY. We performed whole mRNA transcriptomes and morphology analyses of the gonads of hybrids resulting from reciprocal crosses between O. latipes and O. curvinotus. XY male hybrids, presenting meiotic arrest and no production of sperm were sterile, and about 30% of the XY hybrids underwent male-to-female sex reversal. Both XX and XY hybrid females exhibited reduced fertility and developed ovotestis while aging. Transcriptome data showed that male-related genes are upregulated in the XX and XY female hybrids. The transcriptomes of both types of female and of the male gonads are characterized by upregulation of meiosis and germ cell differentiation genes. Differences in the parental species in the downstream pathways of sexual development could explain sex reversal, sterility, and the development of intersex gonads in the hybrids. We hypothesize that male-to-female sex reversal may be connected to a different development time between species at which dmrt1bY expression starts. Our results provide molecular clues for the proximate mechanisms of hybrid incompatibility and Haldane’s rule.
For a large fraction of the proteins expressed in the human brain only the primary
structure is known from the genome project. Proteins conserved in evolution can
be studied in genetic models such as Drosophila. In this doctoral thesis monoclonal
antibodies (mAbs) from the Wuerzburg Hybridoma library are produced and
characterized with the aim to identify the target antigen. The mAb ab52 was found
to be an IgM which recognized a cytosolic protein of Mr ~110 kDa on Western
blots. The antigen was resolved by two-dimensional gel electrophoresis (2DE) as a
single distinct spot. Mass spectrometric analysis of this spot revealed EPS-15
(epidermal growth factor receptor pathway substrate clone 15) to be a strong
candidate. Another mAb from the library, aa2, was already found to recognize
EPS-15, and comparison of the signal of both mAbs on Western blots of 1D and
2D electrophoretic separations revealed similar patterns, hence indicating that both
antigens could represent the same protein. Finally absence of the wild-type signal
in homozygous Eps15 mutants in a Western blot with ab52 confirmed the ab52
antigen to be EPS-15. Thus both the mAbs aa2 and ab52 recognize the Drosophila
homologue of EPS-15. The mAb aa2, being an IgG, is more suitable for
applications like immunoprecipitation (IP). It has already been submitted to the
Developmental Studies Hybridoma Bank (DSHB) to be easily available for the
entire research community.
The mAb na21 was also found to be an IgM. It recognizes a membrane associated
antigen of Mr ~10 kDa on Western blots. Due to the membrane associated nature
of the protein, it was not possible to resolve it by 2DE and due to the IgM nature of
the mAb it was not possible to enrich the antigen by IP. Preliminary attempts to
biochemically purify the endogenously expressed protein from the tissue, gave
99
promising results but could not be completed due to lack of time. Thus
biochemical purification of the protein seems possible in order to facilitate its
identification by mass spectrometry. Several other mAbs were studied for their
staining pattern on cryosections and whole mounts of Drosophila brains. However,
many of these mAbs stained very few structures in the brain, which indicated that
only a very limited amount of protein would be available as starting material.
Because these antibodies did not produce signals on Western blots, which made it
impossible to enrich the antigens by electrophoretic methods, we did not attempt
their purification. However, the specific localization of these proteins makes them
highly interesting and calls for their further characterization, as they may play a
highly specialized role in the development and/or function of the neural circuits
they are present in. The purification and identification of such low expression
proteins would need novel methods of enrichment of the stained structures.
Biodiversity loss, as often found in intensively managed agricultural landscapes, correlates with reduced ecosystem functioning, for example, pollination by insects, and with altered plant composition, diversity, and abundance. But how does this change in floral resource diversity and composition relate to occurrence and resource use patterns of trap-nesting solitary bees? To better understand the impact of land-use intensification on communities of trap-nesting solitary bees in managed grasslands, we investigated their pollen foraging, reproductive fitness, and the nutritional quality of larval food along a land-use intensity gradient in Germany. We found bee species diversity to decrease with increasing land-use intensity irrespective of region-specific community compositions and interaction networks. Land use also strongly affected the diversity and composition of pollen collected by bees. Lack of suitable pollen sources likely explains the absence of several bee species at sites of high land-use intensity. The only species present throughout, Osmia bicornis (red mason bee), foraged on largely different pollen sources across sites. In doing so, it maintained a relatively stable, albeit variable nutritional quality of larval diets (i.e., protein to lipid (P:L) ratio). The observed changes in bee–plant pollen interaction patterns indicate that only the flexible generalists, such as O. bicornis, may be able to compensate the strong alterations in floral resource landscapes and to obtain food of sufficient quality through readily shifting to alternative plant sources. In contrast, other, less flexible, bee species disappear.
The monitoring of species and functional diversity is of increasing relevance for the development of strategies for the conservation and management of biodiversity. Therefore, reliable estimates of the performance of monitoring techniques across taxa become important. Using a unique dataset, this study investigates the potential of airborne LiDAR-derived variables characterizing vegetation structure as predictors for animal species richness at the southern slopes of Mount Kilimanjaro. To disentangle the structural LiDAR information from co-factors related to elevational vegetation zones, LiDAR-based models were compared to the predictive power of elevation models. 17 taxa and 4 feeding guilds were modeled and the standardized study design allowed for a comparison across the assemblages. Results show that most taxa (14) and feeding guilds (3) can be predicted best by elevation with normalized RMSE values but only for three of those taxa and two of those feeding guilds the difference to other models is significant. Generally, modeling performances between different models vary only slightly for each assemblage. For the remaining, structural information at most showed little additional contribution to the performance. In summary, LiDAR observations can be used for animal species prediction. However, the effort and cost of aerial surveys are not always in proportion with the prediction quality, especially when the species distribution follows zonal patterns, and elevation information yields similar results.
Chlamydia trachomatis (Ctr) can persist over extended times within their host cell and thereby establish chronic infections. One of the major inducers of chlamydial persistence is interferon-gamma (IFN-γ) released by immune cells as a mechanism of immune defence. IFN-γ activates the catabolic depletion of L-tryptophan (Trp) via indoleamine-2,3-dioxygenase (IDO), resulting in persistent Ctr. Here, we show that IFN-γ induces the downregulation of c-Myc, the key regulator of host cell metabolism, in a STAT1-dependent manner. Expression of c-Myc rescued Ctr from IFN-γ-induced persistence in cell lines and human fallopian tube organoids. Trp concentrations control c-Myc levels most likely via the PI3K-GSK3β axis. Unbiased metabolic analysis revealed that Ctr infection reprograms the host cell tricarboxylic acid (TCA) cycle to support pyrimidine biosynthesis. Addition of TCA cycle intermediates or pyrimidine/purine nucleosides to infected cells rescued Ctr from IFN-γ-induced persistence. Thus, our results challenge the longstanding hypothesis of Trp depletion through IDO as the major mechanism of IFN-γ-induced metabolic immune defence and significantly extends the understanding of the role of IFN-γ as a broad modulator of host cell metabolism.
Coral reefs are one of the most diverse marine ecosystems, providing numerous ecosystem services. This present study investigated the relationship between coral reef condition and the diversity and abundance of fishes, on a heavily fished East African coral reef at Gazi Bay, Kenya. Underwater visual censuses were conducted on thirty 50 × 5 m belt transects to assess the abundance and diversity of fishes. In parallel, a 25-m length of each of the same transects was recorded with photo-quadrats to assess coral community structure and benthic characteristics. For statistical analyses, multi-model inference based on the Akaike Information Criterion was used to evaluate the support for potential predictor variables of coral reef and fish diversity. We found that coral genus richness was negatively correlated with the abundance of macroalgae, whereas coral cover was positively correlated with both the abundance of herbivorous invertebrates (sea urchins) and with fish family richness. Similarly, fish family richness appeared mainly correlated with coral cover and invertebrate abundance, although no correlates of fish abundance could be identified. Coral and fish diversity were very low, but it appears that, contrary to some locations on the same coast, sea urchin abundance was not high enough to be having a negative influence on coral and fish assemblages. Due to increasing threats to coral reefs, it is important to understand the relationship among the components of the coral reef ecosystem on overfished reefs such as that at Gazi Bay.