School of BioSciences - Research Publications
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ItemNo Preview AvailableHBO1 (KAT7) Does Not Have an Essential Role in Cell Proliferation, DNA Replication, or Histone 4 Acetylation in Human Cells(American Society for Microbiology, 2020-02-01)HBO1 (MYST2/KAT7) is essential for histone 3 lysine 14 acetylation (H3K14ac) but is dispensable for H4 acetylation and DNA replication in mouse tissues. In contrast, previous studies using small interfering RNA (siRNA) knockdown in human cell lines have suggested that HBO1 is essential for DNA replication. To determine if HBO1 has distinctly different roles in immortalized human cell lines and normal mouse cells, we performed siRNA knockdown of HBO1. In addition, we used CRISPR/Cas9 to generate 293T, MCF7, and HeLa cell lines lacking HBO1. Using both techniques, we show that HBO1 is essential for all H3K14ac in human cells and is unlikely to have a direct effect on H4 acetylation and only has minor effects on cell proliferation. Surprisingly, the loss of HBO1 and H3K14ac in HeLa cells led to the secondary loss of almost all H4 acetylation after 4 weeks. Thus, HBO1 is dispensable for DNA replication and cell proliferation in immortalized human cells. However, while cell proliferation proceeded without HBO1 and H3K14ac, HBO1 gene deletion led to profound changes in cell adhesion, particularly in 293T cells. Consistent with this phenotype, the loss of HBO1 in both 293T and HeLa principally affected genes mediating cell adhesion, with comparatively minor effects on other cellular processes.
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ItemMales evolve to be more harmful under increased sexual conflict intensity in a seed beetle(OXFORD UNIV PRESS INC, 2020-01-28)One conspicuous manifestation of sexual conflict is traumatic mating, in which male genitalia damage the female during copulation. The penis of the seed beetle, Callosobruchus maculatus, is covered in spines that damage the female reproductive tract. Females kick males ostensibly to shorten these harmful copulations. How these iconic conflict behaviors coevolve in response to sexual conflict intensity can provide insight into the economics of these traits. We examined whether male harm and female resistance coevolved in response to elevated sexual conflict. We quantified copulation behavior and female reproductive tract damage of individuals from replicated populations evolving for 32 generations under low or high sexual conflict (female- and male-biased treatments, respectively). First, we permitted females ad libitum matings with males from either sex-ratio treatment, recording her tract damage and longevity. Second, we performed a full-factorial cross of matings by males and females from each of the replicate populations, recording mating and kicking duration and reproductive output. We found manipulation of sexual conflict intensity led to the evolution of male harmfulness, but not female resistance to harm. We also demonstrate that female kicking does not respond to sexual conflict intensity, suggesting it does not function to mitigate male harm in this species. Our findings demonstrate the complexities of behavioral and morphological coevolutionary responses to sexual conflict intensity in an important model species.
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ItemSocially cued anticipatory adjustment of female signalling effort in a moth(The Royal Society Publishing, 2020-12-23)Juvenile population density has profound effects on subsequent adult development, morphology and reproductive investment. Yet, little is known about how the juvenile social environment affects adult investment into chemical sexual signalling. Male gumleaf skeletonizer moths, Uraba lugens, facultatively increase investment into antennae (pheromone receiving structures) when reared at low juvenile population densities, but whether there is comparable adjustment by females into pheromone investment is not known. We investigate how juvenile population density influences the ‘calling' (pheromone-releasing) behaviour of females and the attractiveness of their pheromones. Female U. lugens adjust their calling behaviour in response to socio-sexual cues: adult females reared in high juvenile population densities called earlier and for longer than those from low juvenile densities. Juvenile density also affected female pheromonal attractiveness: Y-maze olfactometer assays revealed that males prefer pheromones produced by females reared at high juvenile densities. This strategic investment in calling behaviour by females, based on juvenile cues that anticipate the future socio-sexual environment, likely reflects a response to avoid mating failure through competition with neighbouring signallers.
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ItemCharacterization of the apicoplast-localized enzyme TgUroD in Toxoplasma gondii reveals a key role of the apicoplast in heme biosynthesis(ELSEVIER, 2020-02-07)Apicomplexan parasites such as Toxoplasma gondii possess an unusual heme biosynthesis pathway whose enzymes localize to the mitochondrion, cytosol, or apicoplast, a nonphotosynthetic plastid present in most apicomplexans. To characterize the involvement of the apicoplast in the T. gondii heme biosynthesis pathway, we investigated the role of the apicoplast-localized enzyme uroporphyrinogen III decarboxylase (TgUroD). We found that TgUroD knockdown impaired parasite proliferation, decreased free heme levels in the parasite, and decreased the abundance of heme-containing c-type cytochrome proteins in the parasite mitochondrion. We validated the effects of heme loss on mitochondrial cytochromes by knocking down cytochrome c/c1 heme lyase 1 (TgCCHL1), a mitochondrial enzyme that catalyzes the covalent attachment of heme to c-type cytochromes. TgCCHL1 depletion reduced parasite proliferation and decreased the abundance of c-type cytochromes. We further sought to characterize the overall importance of TgUroD and TgCCHL1 for both mitochondrial and general parasite metabolism. TgUroD depletion decreased cellular ATP levels, mitochondrial oxygen consumption, and extracellular acidification rates. By contrast, depletion of TgCCHL1 neither diminished ATP levels in the parasite nor impaired extracellular acidification rate, but resulted in specific defects in mitochondrial oxygen consumption. Together, our results indicate that the apicoplast has a key role in heme biology in T. gondii and is important for both mitochondrial and general parasite metabolism. Our study highlights the importance of heme and its synthesis in these parasites.
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ItemIntegrating the underlying structure of stochasticity into community ecology(WILEY, 2020-02)Stochasticity is a core component of ecology, as it underlies key processes that structure and create variability in nature. Despite its fundamental importance in ecological systems, the concept is often treated as synonymous with unpredictability in community ecology, and studies tend to focus on single forms of stochasticity rather than taking a more holistic view. This has led to multiple narratives for how stochasticity mediates community dynamics. Here, we present a framework that describes how different forms of stochasticity (notably demographic and environmental stochasticity) combine to provide underlying and predictable structure in diverse communities. This framework builds on the deep ecological understanding of stochastic processes acting at individual and population levels and in modules of a few interacting species. We support our framework with a mathematical model that we use to synthesize key literature, demonstrating that stochasticity is more than simple uncertainty. Rather, stochasticity has profound and predictable effects on community dynamics that are critical for understanding how diversity is maintained. We propose next steps that ecologists might use to explore the role of stochasticity for structuring communities in theoretical and empirical systems, and thereby enhance our understanding of community dynamics.
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ItemAdvantages of the Combination of Conscious Sedation Epidural Anesthesia Under Fluoroscopy Guidance in Lumbar Spine Surgery(DOVE MEDICAL PRESS LTD, 2020)BACKGROUND: With the increase in life expectancy seen throughout the world, the prevalence of degenerative spinal pathology and surgery to treat it has increased. Spinal surgery under general anesthesia leads to various problems and complications, especially in patients with numerous medical comorbidities or elderly patients. For this reason, there is a need for safer anesthetic methods applicable to unhealthy, elderly patients undergoing spinal surgery. PURPOSE: To report our experience with utilizing fluoroscopy-guided epidural anesthesia in conjunction with conscious sedation in spinal surgery. PATIENTS AND METHODS: We performed a retrospective review of 111 patients at our institution that received fluoroscopy-guided epidural anesthesia for lumbar surgery from February to September 2018. Patients' records were evaluated to evaluate patient demographics, American Society of Anesthesiology Physical Classification System (ASA) class, and pain numerical rating scores (NRS) preoperatively and throughout their recovery postoperatively. Intraoperative data including volume of epidural anesthetic used, extent of epidural spread, and inadvertent subdural injection was collected. Postoperative recovery time was also collected. RESULTS: The mean age of our patients was 60 years old with a range between 31 and 83 years old. All patients experienced decreases in postoperative pain with no significant differences based on age or ASA class. There was no association between ASA class and time to recovery postoperatively. Older patients (age 70 years or greater) had a significantly longer recovery time when compared to younger patients. Recovery also was longer for patients who received higher volumes of epidural anesthesia. For every 1 mL increase of epidural anesthetic given, there was an increase in the extent of spread of 1.8 spinal levels. CONCLUSION: We demonstrate the safety and feasibility of utilizing conscious sedation in conjunction with fluoroscopy-guided epidural anesthesia in the lumbar spinal surgery.
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ItemFrom micro- to macroevolution: brood parasitism as a driver of phenotypic diversity in birds.(Oxford University Press (OUP), 2020-10)A fundamental question in biology is how diversity evolves and why some clades are more diverse than others. Phenotypic diversity has often been shown to result from morphological adaptation to different habitats. The role of behavioral interactions as a driver of broadscale phenotypic diversity has received comparatively less attention. Behavioral interactions, however, are a key agent of natural selection. Antagonistic behavioral interactions with predators or with parasites can have significant fitness consequences, and hence act as strong evolutionary forces on the phenotype of species, ultimately generating diversity between species of both victims and exploiters. Avian obligate brood parasites lay their eggs in the nests of other species, their hosts, and this behavioral interaction between hosts and parasites is often considered one of the best examples of coevolution in the natural world. In this review, we use the coevolution between brood parasites and their hosts to illustrate the potential of behavioral interactions to drive evolution of phenotypic diversity at different taxonomic scales. We provide a bridge between behavioral ecology and macroevolution by describing how this interaction has increased avian phenotypic diversity not only in the brood parasitic clades but also in their hosts.
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ItemMitochondria in the Nuclei of Rat Myocardial Cells.(MDPI AG, 2020-03-14)Electron microscopic study of cardiomyocytes taken from healthy Wistar and OXYS rats and naked mole rats (Heterocephalus glaber) revealed mitochondria in nuclei that lacked part of the nuclear envelope. The direct interaction of mitochondria with nucleoplasm is shown. The statistical analysis of the occurrence of mitochondria in cardiomyocyte nuclei showed that the percentage of nuclei with mitochondria was roughly around 1%, and did not show age and species dependency. Confocal microscopy of normal rat cardiac myocytes revealed a branched mitochondrial network in the vicinity of nuclei with an organization different than that of interfibrillar mitochondria. This mitochondrial network was energetically functional because it carried the membrane potential that responded by oscillatory mode after photodynamic challenge. We suggest that the presence of functional mitochondria in the nucleus is not only a consequence of certain pathologies but rather represents a normal biological phenomenon involved in mitochondrial/nuclear interactions.
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ItemClimate stress resistance in male Queensland fruit fly varies among populations of diverse geographic origins and changes during domestication.(Springer Science and Business Media LLC, 2020-12-18)BACKGROUND: The highly polyphagous Queensland fruit fly (Bactrocera tryoni Froggatt) expanded its range substantially during the twentieth century and is now the most economically important insect pest of Australian horticulture, prompting intensive efforts to develop a Sterile Insect Technique (SIT) control program. Using a "common garden" approach, we have screened for natural genetic variation in key environmental fitness traits among populations from across the geographic range of this species and monitored changes in those traits induced during domestication. RESULTS: Significant variation was detected between the populations for heat, desiccation and starvation resistance and wing length (as a measure of body size). Desiccation resistance was correlated with both starvation resistance and wing length. Bioassay data for three resampled populations indicate that much of the variation in desiccation resistance reflects persistent, inherited differences among the populations. No latitudinal cline was detected for any of the traits and only weak correlations were found with climatic variables for heat resistance and wing length. All three stress resistance phenotypes and wing length changed significantly in certain populations with ongoing domestication but there was also a strong population by domestication interaction effect for each trait. CONCLUSIONS: Ecotypic variation in heat, starvation and desiccation resistance was detected in Australian Qfly populations, and these stress resistances diminished rapidly during domestication. Our results indicate a need to select source populations for SIT strains which have relatively high climatic stress resistance and to minimise loss of that resistance during domestication.
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ItemSeparating two tightly linked species-defining phenotypes in Bactrocera with hybrid recombinant analysis.(Springer Science and Business Media LLC, 2020-12-18)BACKGROUND: Bactrocera tryoni and Bactrocera neohumeralis mate asynchronously; the former mates exclusively around dusk while the latter mates during the day. The two species also differ in the colour of the post-pronotal lobe (callus), which is predominantly yellow in B. tryoni and brown in B. neohumeralis. We have examined the genetic relationship between the two characters in hybrids, backcrosses and multigeneration hybrid progeny. RESULTS: Our analysis of the mating time of the parental species revealed that while B. tryoni mate exclusively at dusk, B. neohumeralis females pair with B. neohumeralis males during the day and with B. tryoni males at dusk. We found considerable variance in mating time and callus colour among hybrid backcross individuals of both sexes but there was a strong although not invariant trend for callus colour to co-segregate with mating time in both sexes. To genetically separate these two phenotypes we allowed the interspecific F1 hybrids to propagate for 25 generations (F25) without selection for mating time or callus colour, finding that the advanced hybrid population had moved towards B. tryoni phenotypes for both traits. Selection for day mating in replicate lines at F25 resulted in significant phenotypic shifts in both traits towards B. neohumeralis phenotypes in F26. However, we were unable to completely recover the mating time profile of B. neohumeralis and relaxation of selection for day mating led to a shift back towards dusk mating, but not yellow callus colour, by F35. CONCLUSION: We conclude that the inheritance of the two major species-defining traits is separable but tightly linked and involves more than one gene in each case. It also appears that laboratory conditions select for the B. tryoni phenotypes for mating time. We discuss our findings in relation to speciation theory and the likely effects of domestication during the generation of mass release strains for sterile insect control programmes.