Biology subjects

de Bekker, C.

Publications and source records attributed to de Bekker, C..

12 recordsLinked to original sources

bioRxiv2025

The First of Us: Ophiocordyceps use a novel scramblase-binding peptide to manipulate zombie ants

Parasite-adaptive manipulation of behavior is a widespread natural phenomenon. While Ophiocordyceps zombie fungi are well-known for hijacking ant behavior to increase their fitness, functionally characterizing the biomolecules involved in behavior manipulation remains difficult in these non-model organisms. To circumvent this problem, we have adopted the powerful genetics toolbox of Caenorhabditis elegans to identify molecular targets and neurophysiological effects of candidate Ophiocordyceps effectors. With this approach, we discovered a novel cysteine-rich, small secreted fungal peptide that binds to well-conserved calcium-dependent scramblase channels in neurons, particularly those associated with sensory tissues. This binding suppressed nematode motor coordination and dampened ant olfactory systems vital for communication. Our findings are the first to directly connect an Ophiocordyceps effector with its extended phenotype, while demonstrating the neuroethological role of Scramblase-1.

molecular biology↗

bioRxiv2025

From omics to enhanced fungal virulence: Overexpression of a putative secreted protein improves Beauveria bassiana biocontrol potential against the insect pests Piezodorus guildinii and Tenebrio molitor

The entomopathogenic fungus Beauveria bassiana is widely used as a biocontrol agent, but its efficacy varies depending on the target insect species. Piezodorus guildinii, a major soybean pest, exhibits low susceptibility to B. bassiana. Thus, biocontrol of this pest requires improving virulence of B. bassiana. Here, we used genomic and transcriptomic analyses to identify novel genes associated with the enhanced virulence of B. bassiana strain ILB308 when exposed to the insect epicuticular hydrocarbon n-pentadecane. Comparative analysis with the lower-virulence strain ILB205 revealed differentially expressed genes (DEGs) linked to genetic information process pathways and immune evasion. Among these DEGs, we identified BbCBM9_1, a secreted carbohydrate-binding protein, as a candidate virulence factor. Overexpression of BbCBM9_1 in ILB205 led to enhanced virulence against P. guildinii and Tenebrio molitor, as well as improved conidial germination, tolerance to oxidative and cell wall stress, and increased growth in nutrient-rich and glycerol-supplemented media. This demonstrates that the enhanced virulence observed in ILB308 grown on n-pentadecane can be replicated by overexpressing an associated gene in a low-virulence strain. Our study, highlights the potential of integrating transcriptomics and targeted genetic modifications to optimize fungal biocontrol agents for improved pest management.

microbiology↗

bioRxiv2024

Pathogenic fungus expresses effector proteins in combination with a symbiotic virus to behaviourally manipulate housefly hosts

Host manipulation by pathogens and parasites is a widespread phenomenon, but the molecular mechanisms are poorly understood. We investigated the summiting disease caused by the fungus Entomophthora muscae in houseflies, where infected flies climb to elevated positions and die, releasing infectious conidia. We performed dual-RNA sequencing of fly heads at different time points and identified candidate genes from both the host and the pathogen that may be involved in this summiting phenotype. Surprisingly, we also detected a high abundance of a novel positive sense single-stranded (+ss-RNA iflavirus in infected fly heads. We show that the virus load increases over time and shows signs of accumulation in fly heads and thoraces. We also reveal predicted interactions between fungal secreted proteins and insect host proteins related to neurological and immune functions, suggesting a possible role of these proteins in host manipulation. Furthermore, we find that E. muscae encodes a homologue of ecdysteroid UDP-glucosyltransferase (egt), a gene that has been implicated in host manipulation by other pathogens. Our study reveals a complex interplay between a fungus, a virus and a fly, and suggests that convergent evolution of egt for host manipulation mechanisms may occur in different pathogens.

evolutionary biology↗

bioRxiv2024

What does your gut tell you? Influences of a zombie-making and generalist fungal entomopathogen on carpenter ant micro- and mycobiota

Microbiome composition impacts many host aspects including health, nutrition, reproduction, and behavior. This warrants the recent uptick in insect microbiota research across species and ecosystems. Commensurate with this, the bacterial microbiome of the ant Camponotus floridanus has been well characterized across body regions and maturation levels. However, potential effects of entomopathogens on the gut microbiome, and the fungal communities therein, are yet to be assessed. Investigation of the microbiome during infection could provide insight into entomopathogenic infection and manipulation strategies and inform effective biopesticide strategies. Additionally, the mycobiome remains often overlooked despite playing a vital role in gut ecology with potential implications for health and infection outcomes. To improve our limited understanding of fungal infections in insects, and ants in particular, we characterized the effects of two entomopathogens with different infection strategies on the gut micro- and mycobiota of C. floridanus over time; Ophiocordyceps camponoti-floridani and Beauveria bassiana. Specialist, zombie-making O. camponoti-floridani fungi hijack the behavior of C. floridanus ants over three weeks, causing them to find an elevated position, and fix themselves in place with their mandibles. This summiting behavior is adaptive to Ophiocordyceps as the ant transports the fungus to conditions that favor fruiting body development, spore production, dispersal, and transmission. In contrast, the generalist entomopathogen B. bassiana infects and kills the ant within a few days, without the induction of obvious fungus-adaptive behaviors. By comparing healthy ants with Beauveria- and Ophiocordyceps-infected ants we aimed to 1) describe the dynamics of the micro- and mycobiome of C. floridanus during infection, and 2) determine if the effects on gut microbiota are distinctive between fungi that have different infection strategies. While Beauveria did not measurably affect the ant host micro-and mycobiome, Ophiocordyceps did, especially for the mycobiome. Moreover, ants that were sampled during Ophiocordyceps-adaptive summiting behavior had a significantly different micro- and mycobiome composition compared to healthy controls and those sampled before and after manipulation took place. This suggests that the host microbiome might have a role to play in the manipulation strategy of Ophiocordyceps. HighlightsO_LIOphiocordyceps and Beauveria infections impact the gut microbiota of carpenter ants differently C_LIO_LIThe fungal ASVs present in the ant gut are more diverse and dynamic across infection conditions compared to the bacterial ASVs C_LIO_LIThere is significant dysbiosis in the bacterial and fungal microbiota of ants that display Ophiocordyceps-manipulated summiting behavior C_LIO_LIDysbiosis in Ophiocordyceps-infected ants might be contributing to observed host behavioral changes while a comparable dysbiosis is not observed in Beauveria infections C_LI

microbiology↗

bioRxiv2023

Metabolomic characterization of behaviorally manipulated ants with multiomic data integration

Camponotus floridanus ants show altered behaviors followed by a fatal summiting phenotype when infected with manipulating Ophiocordyceps camponoti-floridani fungi. Host summiting as a strategy to increase transmission is also observed with parasite taxa beyond fungi, including aquatic and terrestrial helminths and baculoviruses. The drastic phenotypic changes can sometimes reflect significant physiological changes within host cells that span molecular levels from metabolites to nucleic acids. Nevertheless, the underlying mechanisms still need to be fully characterized. To investigate the small molecules producing summiting behavior, we infected C. floridanus ants with O. camponoti-floridani and sampled their heads for LC-MS/MS when we observed the characteristic summiting phenotype. We link this metabolomic data with our previous genomic and transcriptomic data to propose mechanisms that underlie manipulated summiting behavior in "zombie ants." This "multiomic" evidence points toward the dysregulation of neurotransmitter levels and neuronal signaling. We propose that these processes are altered during infection and manipulation based on 1) differential expression of neurotransmitter synthesis and receptor genes, 2) altered abundance of metabolites and neurotransmitters (or their precursors) with known behavioral effects in ants and other insects, and 3) possible suppression of a connected immunity pathway. We additionally report signals for metabolic activity during manipulation related to primary metabolism, detoxification, and anti-stress protectants.

bioinformatics↗

bioRxiv2023

Both behavior-manipulating and non-manipulating entomopathogenic fungi affect rhythmic gene expression in carpenter ant foragers upon infection

BackgroundBehavioral plasticity in the nocturnal ant Camponotus floridanus is associated with changes in daily rhythms of core clock and clock-controlled genes in the brain. Plasticity in clock-controlled output, although adaptive, has been hypothesized to be a target for parasites that change host behavior in a timely manner to complete their life cycle. This study aims to explore this hypothesis by characterizing how the transcriptomic rhythms of the ant host change upon infection by a behavior manipulating parasite. We compared and contrasted the daily gene expression profile of uninfected C. floridanus ant heads to ants infected by a manipulating fungal parasite Ophiocordyceps camponoti-floridani and a non-manipulating fungus Beauveria bassiana, to test if changes to host clock and clock-controlled gene expression are specific to behavioral modifying diseases, or if such changes are a general hallmark of infectious diseases. ResultsThe repertoire of genes oscillating every 24h in the ant heads showed almost three-fold reduction during O. camponoti-floridani infections, as compared to uninfected controls. Control-like nocturnal activity of 24h-rhythmic genes was maintained during O. camponoti-floridani infections, but not in B. bassiana infected ant heads. Half of all genes that showed 24h rhythms in the heads and brains of uninfected ants displayed highly synchronized changes in their rhythmic expression during both diseases, but in a species-specific manner. Network analyses revealed that both fungal parasites affected the same links between behavioral plasticity and clock output, albeit in a different manner. ConclusionChanges to clock-controlled transcriptomic rhythms of hosts might be a general hallmark of infectious diseases. However, the infection-associated changes to clock-controlled rhythms of the host are species-specific, and likely depends on the life history strategies used by the parasite.

animal behavior and cognition↗

bioRxiv2023

Using RNASeq to investigate the involvement of the Ophiocordyceps clock in ant host infection and behavioral manipulation

IntroductionParasites can modify host behavior to ensure their own growth and transmission. Multiple species of the fungi Ophiocordyceps infect ants, but in a species-specific manner; one fungal species co-evolved to successfully modify the behavior of one ant species. However, several characteristics of the behavioral modification seem to be similar across different Ophiocordyceps-ant systems, including a preference for the time of the day for manipulating host behavior. In this study, we explored the various mechanisms via which the circadian clock of Ophiocordyceps might be playing a role in modifying host behavior. We studied O. camponoti-floridani that modifies the behavior of its ant host Camponotus floridanus. To separate the role of the clock in behavior manipulation, from its role in growth and survival, we compared the daily gene expression profile of O. camponoti-floridani to a generalist, non-manipulating fungal parasite, Beauveria bassiana, which also successfully infects the same ant host. ResultsMajority of the 24h rhythmic O. camponoti-floridani genes show peak expression before or at the transitions between light and dark. Rhythmic genes in O. camponoti-floridani, for which B. bassiana lacks an ortholog, were overrepresented for enterotoxin genes. Around half of all genes that show 24h rhythms in either O. camponoti-floridani or B. bassiana showed a consistent difference in their temporal pattern of daily expression. At the halfway mark in O. camponoti-floridani infections, when diseased ants show a loss of 24h rhythms in daily foraging, several fungal clock genes, including Frequency, showed differential expression. Network analyses revealed a single gene cluster, containing White Collar 1 and 2, that showed overrepresentation for genes oscillating every 24h in liquid culture as well as genes differentially expressed while growing inside the ant head. ConclusionThis study identifies several sets of putatively clock-controlled genes and biological processes in O. camponoti-floridani that likely plays a role in modifying the behavior of its ant host. Differential expression of O. camponoti-floridani clock genes or 24h-rhythmic genes during infection is suggestive of either a loss of daily rhythm or a change in the amplitude of rhythmic gene expression. Both possibilities would suggest that a disease-associated change occurs to the functioning of the O. camponoti-floridani clock, and its output, while the fungi grows inside the ant head.

molecular biology↗

bioRxiv2022

Natural history and ecological effects on the establishment and fate of Florida carpenter ant cadavers infected by the parasitic manipulator Ophiocordyceps camponoti-floridani.

O_LIOphiocordyceps fungi manipulate the behavior of their ant hosts to produce a summit disease phenotype, thereby establishing infected ant cadavers onto vegetation at elevated positions suitable for fungal growth and transmission. Multiple environmental and ecological factors have been proposed to shape the timing, positioning, and outcome of these manipulations. C_LIO_LIWe conducted a long-term field study of Ophiocordyceps camponoti-floridani infections of Camponotus floridanus ants - the Florida zombie ants. We propose and refine hypotheses on the factors that shape infection outcomes by tracking the occurrence of and fungal growth from hundreds of ant cadavers. We modeled and report these data in relation to weather, light, vegetation, and attack by hyperparasites. C_LIO_LIWe investigated environmental factors that could affect the occurrence and location of newly manipulated ant cadavers. New cadaver occurrence was preferentially biased toward epiphytic Tillandsia bromeliads, canopy openness, and summer weather conditions (an interactive effect of temperature, humidity, and precipitation). Furthermore, we suggest that incident light at the individual cadaver level reflects microhabitat choice by manipulated ants or selective pressure on cadaver maintenance for conditions that improve fungal survival. C_LIO_LIWe also asked which environmental conditions affect fungal fitness. Continued fungal development of reproductive structures and putative transmission increased with moist weather conditions (interaction of humidity and precipitation) and canopy openness, while being reduced by hyperparasitic mycoparasite infections. Moreover, under the most open canopy conditions, we found an atypical Ophiocordyceps growth morphology that could represent a plastic response to conditions influenced by high light levels. C_LIO_LITaken together, we explore general trends and the effects of various ecological conditions on host and parasite disease outcomes in the Florida zombie ant system. These insights from the field can be used to inform experimental laboratory setups that directly test the effects of biotic and abiotic factors on fungus-ant interactions or aim to uncover underlying molecular mechanisms. C_LI

ecology↗

bioRxiv2022

28 Minutes Later: A behavioral and transcriptomic investigation into the potential role of aflatrem-like compounds in establishing Ophiocordyceps extended phenotypes in zombie ants

Coevolutionary relationships between parasites and their hosts can lead to the emergence of diverse phenotypes over time, as seen in Ophiocordyceps fungi that manipulate insect and arachnid behaviour to aid fungal spore transmission. The most conspicuous examples are found in ants of the Camponotini tribe, colloquially known as "zombie ants". While the behaviours induced during infection are well described, their molecular underpinnings remain unknown. Recent genomics and transcriptomics analyses of Ophiocordyceps camponoti-floridani have identified several highly upregulated biomolecules produced by the fungus during infection of Camponotus floridanus. Among them is an ergot alkaloid related to the mycotoxin aflatrem, known to cause "staggers syndrome" in cows. Staggering, defined as unsteady movements side to side, is also observed in C. floridanus ants during late-stage infection. To test if aflatrem-like compounds could be responsible, we injected healthy ants with aflatrem and recorded their behaviour for 30 minutes. Using both the automated object-tracking software MARGO and manual behavioural quantification, we found that aflatrem reduced ant activity and speed, and increased staggering behaviours. To examine underlying transcriptomic changes, we performed RNA-Seq on the heads of aflatrem-injected ants, keeping in step with previous transcriptomic work on Ophiocordyceps-manipulated ants. We identified 261 genes that were significantly dysregulated in the aflatrem-injected ants compared to sham-injected controls. When compared with RNA-Seq data from Ophiocordyceps-manipulated ants, we found that both groups shared 113 differentially regulated genes. These included sensory neuron membrane protein genes, several odorant-binding protein genes, and musculoskeletal genes such as titin and obscurin. Together, these results indicate that aflatrem-like compounds significantly affect neuromuscular and sensory function in C. floridanus. The conservation of staggers phenotype between C. floridanus and Bos taurus suggests that behaviour manipulating strategies exhibited across the Tree of Life may be more similar in approach, if not widely different in application, than we realize.

animal behavior and cognition↗

bioRxiv2022

Using machine learning to predict protein-protein interactions between a zombie ant fungus and its carpenter ant host

Parasitic fungi produce proteins that modulate virulence, alter host physiology, and trigger host responses. These proteins, classified as a type of "effector," often act via protein-protein interactions (PPIs). The fungal parasite Ophiocordyceps camponoti-floridani (zombie ant fungus) manipulates Camponotus floridanus (carpenter ant) behavior to promote transmission. The most striking aspect of this behavioral change is a summit disease phenotype where infected hosts ascend and attach to an elevated position. Plausibly, interspecific PPIs drive aspects of Ophiocordyceps infection and host manipulation. Machine learning PPI predictions offer high-throughput methods to produce mechanistic hypotheses on how this behavioral manipulation occurs. Using D-SCRIPT to predict host-parasite PPIs, we found ca. 6,000 interactions involving 2,083 host proteins and 129 parasite proteins, which are encoded by genes upregulated during manipulated behavior. We identified multiple overrepresentations of functional annotations among these proteins. The strongest signals in the host highlighted neuromodulatory G-protein coupled receptors and oxidation-reduction processes. We also detected Camponotus structural and gene-regulatory proteins. In the parasite, we found enrichment of Ophiocordyceps proteases and frequent involvement of novel small secreted proteins with unknown functions. From these results, we provide new hypotheses on potential parasite effectors and host targets underlying zombie ant behavioral manipulation.

molecular biology↗

bioRxiv2021

Time-course RNASeq of Camponotus floridanus forager and nurse ant brains indicate links between plasticity in the biological clock and behavioral division of labor

BackgroundCircadian clocks allow organisms to anticipate daily fluctuations in their environment by driving rhythms in physiology and behavior. Inter-organismal differences in daily rhythms, called chronotypes, exist and can shift with age. In ants, age, caste-related behavior and chronotype appear to be linked. "Around-the-clock" active nurse ants are usually younger and, with age, transition into rhythmically active foragers. Moreover, ants can shift between these behavioral castes depending on social context. We investigated how changes in daily gene expression could be contributing to such behavioral plasticity in Camponotus floridanus carpenter ants by combining time-course behavioral assays and RNA-Sequencing of forager and nurse brains. ResultsWe found that nurse brains have three times fewer 24h oscillating genes than foragers. However, several hundred genes that oscillated every 24h in forager brains showed robust 8h oscillations in nurses, including the core clock genes Period and Shaggy. These differentially rhythmic genes consisted of several components of the circadian entrainment pathway, and showed enrichments for functions related to metabolism, cellular communication and protein modification. We additionally found that Vitellogenin, known to regulate division of labor in social insects, showed robust 24h oscillations in nurse brains but not in foragers. Furthermore, the protein products of several genes that were differentially expressed between the two ant castes were previously found in the trophallactic fluid of C. floridanus. This suggests a putative role for trophallaxis in regulating behavioral division of labor through caste-specific gene expression. ConclusionWe provide a first look at the chronobiological differences in gene expression between forager and nurse ant brains. This endeavor allowed us to identify putative molecular mechanisms underlying plastic timekeeping. Several components of the ant circadian clock and its output can seemingly oscillate at different harmonics of the circadian rhythm. We propose that such chronobiological plasticity has evolved to allow for distinct regulatory networks that underlie behavioral castes, while supporting swift caste transitions in response to colony demands. Behavioral division of labor is common among social insects. The links between chronobiological and behavioral plasticity that we found in C. floridanus, thus, likely represent a more general phenomenon that warrants further investigation.

animal behavior and cognition↗

bioRxiv2020

Genetic underpinnings of host manipulation by Ophiocordyceps as revealed by comparative transcriptomics

AO_SCPLOWBSTRACTC_SCPLOWThe ant-infecting Ophiocordyceps fungi are globally distributed, host manipulating, specialist parasites that drive aberrant behaviors in infected ants, at a lethal cost to the host. An apparent increase in activity and wandering behaviors precedes a final summiting and biting behavior on to vegetation, positioning the manipulated ant in a site beneficial for fungal growth and transmission. Notably, across Ophiocordyceps species and other known host manipulators, the molecular mechanisms underlying behavioral changes remain largely unclear. We explored possible genetic underpinnings of host manipulation by: (i) producing a hybrid assembly of the Ophiocordyceps camponoti-floridani genome, (ii) conducting laboratory infections coupled with RNAseq of both O. camponoti-floridani and its host, Campontous floridanus, and (iii) using these data for a comparative analysis to similar work performed in Ophiocordyceps kimflemingiae and Camponotus castaneus. We propose differentially expressed genes tied to ant neurobiology, odor response, circadian rhythms, and foraging behavior may be the result of putative fungal effectors such as enterotoxins, aflatrem, and mechanisms disrupting nutrition-sensing or caste-identity pathways.

genomics↗