10,233 research outputs found

    Social plasticity and limited resilience of coral-dwelling gobies (genus Gobiodon) to climate change: outlook for coral-fish mutualisms in a changing world

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    Climate change is rapidly altering ecosystems on a global scale, and coral reefs are particularly vulnerable to climate-induced disturbances. Coral reefs depend on mutualisms with their foundation species, i.e. corals, and yet most of the literature has focused on their mutualisms with only one type of symbiont (algae). Little is known about how coral-fish mutualisms respond to climatic disturbances, and yet cyclones and heatwaves are increasingly devastating coral reefs. We urgently need to assess how coral-fish mutualisms respond to disturbances as changes in mutualisms have the potential for causing ecosystem-level changes. Yet fish in coral-fish mutualisms have often been overlooked in studies regarding environmental disturbances. There are multiple aspects of the life history, behaviour, and movement of fish that may impact their mutualisms with corals. Here, I investigated (1) whether both symbionts in coral-fish mutualisms respond similarly to climatic disturbances, and (2) what mechanisms from the fish perspective are likely responsible for how coral-fish mutualisms respond to climatic disturbances. I used a model coral-fish mutualism between coral hosts from the genus Acropora and coral-dwelling gobies from the genus Gobiodon in which both organisms provide important benefits for the resilience of each partner. I implemented a comparative approach by investigating multiple goby and coral species encountered in study locations to provide genus-wide understandings of how their coral-goby mutualisms are impacted by climatic disturbances. Particularly important is that gobies can live in social groups and living in groups can improve coral maintenance. Accordingly, first I provided a comprehensive review on how climate change is impacting the sociality of coral reef fish as the sociality of these taxa have only recently been investigated. Studies have shown that climate change affected the habitat and physiology of fishes, and each of these effects impacted their sociality. The review highlighted key changes to the sociality of these fish depending on how corals respond to disturbances, like reduction in coral size, shifts in coral communities, and health of corals. Secondly, I set the scene by monitoring coral-goby mutualisms throughout four extreme disturbances in the northern Great Barrier Reef (GBR): two cyclones and two heatwaves that caused mass bleaching events. In the aftermath and after a few years of recovery, there were more coral species, but corals were almost three times smaller. For gobies though, there were two times fewer coral species, there were fewer gobies, and most corals became absent of gobies when previously most were occupied. Alarmingly, this study highlighted that gobies declined far more than corals and were far slower to recover than their hosts. Finally, I used a combination of observational and manipulative studies to investigate the potential for coral gobies to exhibit plasticity in their host use, sociality, and movement in relation to disturbances. Following the same four extreme disturbances, I found that gobies shifted hosts to the newly abundant coral species. Although exhibiting host plasticity may be an advantage in the short-term, using alternative coral hosts may reduce the fitness of gobies, i.e. their growth rates. I then investigated whether gobies shifted their social tendencies to live in groups or in pairs following these four extreme disturbances in the northern GBR and following a single extreme disturbance in the southern GBR. Gobies no longer lived in groups, rarely in pairs, and primarily lived as solitary individuals after the four disturbances, whereas there was relatively little change in their social tendencies after the single disturbance. This study suggests that if consecutive disturbances become the norm, gobies may continue to decline if they primarily stay solitary as they need to live in pairs to breed. I then completed another study to investigate how predation risk, coral size and health, and number of group members affected the movement of gobies. I translocated gobies in situ into corals with varying sizes, number of individuals, and health. I replicated the study in a relatively undisturbed environment in Papua New Guinea, and in the highly disturbed environment following the four extreme disturbances in northern GBR. Regardless of the disturbance state, gobies preferred to face high costs of predation and did alter their movement based on coral size, health, or number of group members, even when predation risk was higher in disturbed environments. This suggests that gobies do not alter their movement plasticity based on environmental disturbances even though predation risk is heightened. This means that gobies exhibited host and social plasticity, but they did not exhibit movement plasticity to disturbances. I found that each mechanism of plasticity was likely responsible for a reduced recovery potential of gobies compared to their coral hosts. By combining the findings from each chapter of the thesis, I suggest that coral-fish mutualisms are highly vulnerable to climate change as fish experience barriers to recovery via host, social, and movement plasticity. Future conservation strategies should address declines in fish in order to maintain coral-fish mutualisms important for coral health

    TEMPERATURE REGULATION OF PIPECOLIC ACID-MEDIATED PLANT SYSTEMIC IMMUNITY IN ARABIDOPSIS THALIANA

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    Significant crop losses are caused by pathogenic infections annually, which are exacerbated by increasing global temperatures due to climate change. One way by which plants respond to pathogenic attacks is through the activation of pattern-triggered immunity (PTI), effector-triggered immunity (ETI), and systemic acquired resistance (SAR), which lead to production of the central defence phytohormone salicylic acid (SA). Accompanying SA release is the putative mobilization of pipecolic acid (Pip), which acts as an immune regulatory plant metabolite that works with and independently from SA. As demonstrated in the model plant Arabidopsis thaliana following infection with the model bacterial pathogen Pseudomonas syringae pv. tomato (Pst) DC3000, Pip and its hydroxylated derivative N-hydroxypipecolic acid (NHP) accumulate in local and distal tissues to amplify the plant immune response and prime the plant for future infections. Previous studies have only shown that increased temperature negatively impact PTI, ETI and SA production in the local/primary sites of infection. However, how temperature affects plant systemic immunity has not been fully explored. In this thesis, I showed that systemic immunity in Arabidopsis to Pst DC3000 was significantly reduced at elevated temperatures. Elevated temperature decreased expression of the SAR-associated Pip-NHP biosynthetic genes AGD2-LIKE DEFENSE RESPONSE PROTEIN 1 (ALD1) and FLAVIN-DEPENDENT MONOOXYGENASE 1 (FMO1) in systemically primed leaf tissues. Remarkably, exogenous Pip application via local leaf infiltration or root-drench restored immunity to Pst DC3000 at elevated temperature; however, local leaf infiltration did not restore immunity in systemic leaves. I have also shown how Pip-induced gene expression locally and systemically were affected by temperature. Finally, because of the interlinked regulation between SA and Pip/NHP by the master transcription factor CAM-BINDING PROTEIN 60-LIKE G (CBP60g), I have shown that Arabidopsis plants constitutively expressing CBP60g (35S:CBP60g) exhibited SAR at both normal and elevated temperatures. My results suggest that CBP60g controls the temperature-sensitivity of plant systemic immunity by modulating NHP biosynthesis. Overall, this thesis contributes to understanding the signaling pathways regulating local and systemic plant immune responses in our warming climate

    Synthetic Strategies Toward Heterocyclic Seven Membered Ring Systems: Building Libraries of Privileged Scaffolds for Medicinal Chemistry and Forensic Analysis

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    Natural products are often the inspiration for many pharmaceutical compounds as they are found to have drug-like properties. Many times, these compounds exhibit structural commonalities and are therefore referred to as “privileged structures.” Synthetic organic chemists have devoted significant time and effort into developing efficient methods to access these privileged scaffolds for the construction of diverse libraries. This thesis explores novel synthetic strategies to access the privileged scaffolds: cyclohepta[b]indole and the 1,4-benzodiazepine, flubromazepam. The protocols designed to access these heterocyclic seven-membered ring systems include: 1) a formal [5+2] cycloaddition between alkenes and indole fused alkylidenes, 2) a Friedel-Crafts transformation and 3) a nucleophilic arylation. Additionally, through the development of these modular protocols new discoveries were made providing new insights in medicinal chemistry and forensic analysis.Ph.D

    Fish biomass in Taranaki streams in relation to sources and availability of energy

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    Light and temperature are the principal drivers of ecosystem function influencing nutrient cycling, energy flows, and food web dynamics. Solar irradiance controls stream thermodynamics, and in-stream temperature governs the metabolic rate of stream biota. The loss of riparian vegetation can lead to unpredictable changes in fish biomass due to variations in metabolic requirements and energy availability. In New Zealand, unshaded pasture streams have been shown to support greater fish biomass, leading to questions about supply and demand synchronies and energy sources that support fish biomass under differing light and temperature regimes. This thesis focuses on the ecological processes in relation to the interactions among stream biota and their physical and chemical environment linking freshwater fish biomass, food web dynamics and energy availability. Using a variety of field assessments, I investigate food web dynamics and characterise energy flow with respect to land use and longitudinal riparian fragmentation in mountainous Taranaki streams, New Zealand. I further analyse the influence of alternative energy sources derived from terrestrial and marine environments and their subsidiary role in supporting fish biomass. Fish densities and biomasses were five-fold greater in pasture than in forest streams and significant correlations were found with light intensity and water temperature (p < 0.05). Body mass to abundance (M-N) allometry was similar between land uses, but the effects of increased light and temperature in pasture streams likely resulted in increased abundance for the equivalent body sizes across the entire community. Stable isotope analyses (SIA) revealed evidence for energetic and functional food web alterations, in response to land use. Changes in food sources were reflected by the transition in physical variables at the forest to pasture boundary. Here, non-predatory invertebrates showed a distinct food dominance transition between land uses, predominantly assimilating leaf litter (77%) in forest and shifting to periphyton (73%) in pasture. Periphyton biomass was significantly greater in pasture streams and was the most important food source for crayfish (Paranephrops planifrons), contributing 76% to crayfish diet in forest and 97% to crayfish diet in pasture. This highlights the importance of periphyton for energy transfer to higher trophic levels in streams. Fish showed a distinct dietary reliance on both crayfish and terrestrial invertebrates in both land uses. Unexpectedly, terrestrial invertebrate inputs were five-fold greater at pasture sites when compared to forest sites (p < 0.05). Since terrestrial invertebrates are an important food source consumed by New Zealand fish species, these terrestrially derived food sources may play a significant role in the observed fish biomass. This research highlighted the role of terrestrially derived invertebrates in providing a significant subsidiary energy source, irrespective of land use. Temperature plays a fundamental role in metabolic rates and energetic requirements of fish, emphasising the importance of temperature-driven changes in supply-demand synchronies. Importantly, summer water temperatures at pasture sites were closer to the thermal preferences of New Zealand fish species. This suggests that higher temperatures increase metabolic scope and food requirements. However, there must be sufficient food supply to compensate for rising metabolic demands of fish. On a longitudinal scale, Taranaki streams showed localised variations in energy utilisation in response to riparian fragmentation. Non-predatory invertebrates showed a food dominance transition back to allochthonous sources at lower sites, corresponding with greater riparian vegetation cover downstream. Transitions in source dominance were also observed in longfin eel (Anguilla dieffenbachii) and shortfin eel (Anguilla australis) diets, where the proportional dominance shifted from aquatic invertebrates to terrestrial invertebrates at vegetated downstream sites. These data were more reflective of recent conceptualised models derived from the Riverine Ecosystem Synthesis (RES), rather than the River Continuum Concept (RCC), with localised processes influencing pathways of energy transfer. There is limited research on the contribution of marine-derived nitrogen (MDN) by diadromous New Zealand fish, which may provide an important subsidiary source of nutrients for stream production. MDN was detected in migratory inanga larvae (Galaxias maculatus) and shrimp (Paratya curvirostris), with these species showing comparable δ15N that reflected a period of marine residence. The incorporation of MDN was not expressed in the food web, however, most likely due to low densities of inanga and shrimp in the study reaches. High δ15N in inanga shows the potential for MDN to be incorporated into stream food webs where significant seasonal whitebait migrations occur. This research provides critical insight into the drivers behind fish biomass, highlighting temperature-driven supply and demand synchronies and the importance of resource availability in sustaining New Zealand fish populations

    Molecular Research in Rice: Agronomically Important Traits 2.0

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    This volume presents recent research achievements concerning the molecular genetic basis of agronomic traits in rice. Rice (Oryza sativa L.) is the most important food crop in the world, being a staple food for more than half of the world’s population. Recent improvements in living standards have increased the worldwide demand for high-yielding and high-quality rice cultivars. To develop novel cultivars with superior agronomic performance, we need to understand the molecular basis of agronomically important traits related to grain yield, grain quality, disease resistance, and abiotic stress tolerance. Decoding the whole rice genome sequence revealed that ,while there are more than 37,000 genes in the ~400 Mbp rice genome, there are only about 3000 genes whose molecular functions are characterized in detail. We collected in this volume the continued research efforts of scholars that elucidate genetic networks and the molecular mechanisms controlling agronomically important traits in rice

    Drivers of Spatiotemporal Patterns of Surface Water Inputs in a Catchment at the Rain-Snow Transition Zone of the Water-Limited Western United States

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    Spatial and temporal dynamics of rainfall and snowmelt (i.e., surface water inputs, SWI) control soil moisture, groundwater recharge, and streamflow at annual, seasonal, and event scales. In the rain-snow transition zone, comprising a large portion of the mountainous western United States, there is limited understanding of the sensitivity of spatiotemporal SWI dynamics across hydrologically variable water years (WYs). We modeled rainfall and snowpack dynamics in a small headwater catchment (1.8 km2) spanning the rain-snow transition in southwestern Idaho, USA, for two hydrologically distinct WYs (2011 and 2014). In wet WY 2011 and dry WY 2014, total precipitation drove spatial variability in annual SWI. Snow drifts generated more SWI (901–2080 mm) than high-elevation scour zones (442–640 mm), which generated less SWI than mid-elevation, non-drift locations (452–784 mm). Seasonally, energy fluxes differed most during the snowmelt period, where higher net radiation at lower elevations and south-facing slopes drove SWI production. At the rain-on-snow (ROS) event scale, higher elevations and north-facing slopes generated 15–20 % of annual SWI, due mainly to higher turbulent fluxes. The most productive ROS events occurred after peak snow water equivalent (SWE), when rainfall fell onto ripe snowpacks. Snow drift locations were less susceptible to melt during ROS events, offset by the larger cold content and snowpack mass. Thus, catchment water resources depend on SWI magnitude, location, and timing, which are moderated by drift persistence at all temporal scales. As the climate warms, shifts in spatiotemporal SWI distribution are expected with declines in snowfall and snowfall redistribution in this area

    TGF-b Signaling Mechanisms in \u3ci\u3eCaenorhabditis elegans\u3c/i\u3e Response to Bacterial Pathogens

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    When exposed to infection, the nematode C. elegans mounts an innate immune response through secretion of antimicrobial peptides (AMPs). Different signaling pathways in the worm regulate release of these AMPs. One highly conserved pathway is the C. elegans BMP like pathway – regulated by the ligand DBL-1. The DBL-1 pathway is noted for its significant role in development but has also been shown to regulate many post-developmental processes within the worm, including the immune response. We are interested in determining how DBL-1 signaling can mediate a response specific to immunity, separate from its other functions in the worm. Through survival analysis we have shown that when exposed to pathogenic bacteria, expression of the DBL-1 effector SMA-3 in either the hypodermis or pharynx improves survival rate compared to sma-3 mutants. These results suggest crosstalk between the pharynx and the intestinal site of infection. Using qRT-PCR we have found two immune-related genes with expression patterns that indicate regulation by DBL-1 signaling through SMA-3. We have demonstrated that sma-3 expression in either the hypodermis or pharynx is sufficient to induce expression of these two AMPs in infection conditions. These results suggest that non cell- autonomous signaling of the DBL-1 pathway to regulate gene expression plays a role in the response to infection. We have also looked at the role that all five TGF- β ligands – DBL-1, TIG- 2, T IG-3, UNC-129, DAF-7 – play in the C. elegans immune response and show that mutations in any of these ligands have an effect on survival against bacterial infection. Through the use of double mutant analyses, we have shown that multiple TGF- β ligands demonstrate cooperative interaction in the immune response. Finally, we have shown that multiple canonical signaling components of the DBL-1 pathway are involved in the response to bacterial infection, whereas the DAF-7 R-Smad DAF-14 has no effect on survival. Taken together, our work shows that when faced with bacterial infection C. elegans mounts an immune response that uses complex signaling from the five TGF- β ligands and that through DBL-1, regulation of AMP expression is mediated by non cell-autonomous signaling

    Characterisation of extracellular vesicles (EVs) from dysfunctional endothelial cells following exposure to alcohol

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    Endothelial cell (EC) dysfunction is classically associated with subclinical atherosclerosis and the development of atheroprone lesions. Extracellular vesicles (EVs) are biological nanoparticles secreted by most cell types that contain a complex mix of cell-type specific signalling proteins and nucleic acids. At high concentrations, alcohol is a known risk factor for atherosclerosis but may be protective at lower concentrations. In this study, we first investigated whether alcohol (EtOH) at varying concentrations can alter the number and/or phenotype of EVs released from endothelial cells before the proteomic profile of endothelial cell-derived EVs was assessed. Human aortic endothelial (HAEC) and smooth aortic vascular muscle cells (HuSMCs) were first characterised for lineage specific markers before endothelial cell dysfunction was induced following treatment of HAECs with low and high doses of EtOH. EVs released from HAEC were isolated from conditioned cell media, enumerated and characterised using dynamic light scattering (DLS), immunoblot and AmnisTM Cell Stream FACS analysis for EV biomarkers before the proteomic profile of the EVs was evaluated using Liquid chromatography massspectrometry (LC-MS) analysis. The data generated suggest that the number of endothelial derived-EVs released following endothelial dysfunction increases following exposure of cells to different concentrations of EtOH. Moreover, the protein cargo within these EVs varies, even though the EVs originated from the same cell source. Proteomic and bioinformatic analysis revealed that protein metabolism and cell growth and/or maintenance are the key pathways and biological processes associated with these EVs and provides further insight into elucidating their putative role following endothelial dysfunction. Lastly, EVs from dysfunctional HAECs had little effect on the growth and migration of HuSMCs but did promote HuSMC de-differentiation following treatment with 25-EXO. These data highlight the potential important role for EVs released following endothelial dysfunction on the underlying smooth muscle cell population that may contribute to arteriosclerotic lesion formatio
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