Students in biology

SUMMER RESEARCH PROGRAM

2015 Student Research Abstracts 

SRP 2015

 

Jordan Brown, Marquette University

Program Mentor:  Dr. Allison Abbott

Investigation of the Function of Individual microRNA in Caenorhabditis elegans

 

Karina Correa, University of Puerto Rico Humacao Campus

Program Mentor: Dr. Dale Noel

Lowering the pH Rescues Quinol Oxidase Dependent Rhizobium etli from Death on Peptide-rich Medium TY

 

Tyler J. Halicek, Marquette University

Program Mentor: Dr. Edward Blumenthal

A Role for Tyrosine and AMPK in Mediating Progression through Oogenesis in Drosophila

 

Xiaoyi Hou, Marquette University

Program Mentor: Dr. Michael Schlappi

Identification of Promoter-EARLI1::LUCIFERASE Containing Arabidopsis Lines that Reconstitute Endogenous EARLI1 Gene Expression

 

Catherine Jensen, Marquette University

Program Mentor: Dr. Edward Blumenthal

Examining the Biochemical Role of drop-dead in D. melanogaster

 

Emily Legan, Marquette University

Program Mentor: Dr. Anita Manogaran

Pharmacologically Inhibiting Actin Provides Insight into Prion Formation

 

Alexis Monical, Marquette University

Program Mentor:  Dr. Michelle Mynlieff                

Characterization of Potassium Currents in Neonatal Rat Hippocampal Neurons

 

Trygve Nelson, Marquette University

Program Mentors: Dr. James Maki

Toxicity of Bacillus sp. JK7 and Cobetia Marina to Nematode Worms

 

Garrett Panno, Marquette University

Program Mentor:  Dr. Robert H. Fitts

Action Potential Duration and the KATP Channel: Effect of Wheel Running

 

Jordan Rede, Saint Martin's University

Program Mentor: Dr. Anita Manogaran

Investigating how Gene Deletions Shown to Influence Q/N and PolyQ Aggregation Affect α-synuclein in Yeast

 

Paulina Regan, Framingham State University

Program Mentor: Dr. James Buchanan

The Contribution of GABAA Receptors to Fictive Locomotion in Ichthyomyzon unicuspis

 

Scott Rossing, Marquette University

Program Mentor: Dr. James Buchanan

Interaction Between the Hindbrain and Spinal Cord Locomotor Networks in Ichthyomyzon unicuspis

 

Jorge Sandoval, CSUN

Program Mentor: Dr. Edward Blumenthal

Physiological Effects of drd in Gut Formation and Digestion in Drosophila

 

Katharine Shelledy, Juniata College

Program Mentor: Dr. Krassimira Hristova

The Invader Invaded: Antibiotic Resistance Genes in Lake Michigan Mussel Microbiomes

 

Katelyn Stine, Marquette University

Program Mentor: Dr. Martin St. Maurice

The Effect of Acetyl-CoA on BCCP Movement in Pyruvate Carboxylase

 

Katie Zarbock, St. Catherine University

Program Mentor: Dr. Michael Schlappi

Electrolyte Leakage from Leaves of Oryza sativa During Recovery from Chilling Stress Correlates with Whole Plant Survivability

 

  

 

Jordan Brown, Marquette University

Program Mentor:  Dr. Allison Abbott

 

Investigation of the Function of Individual microRNA in Caenorhabditis elegans

MicroRNAs are short regulatory sequences that control gene expression post-transcriptionally. MicroRNAs are essential in C. elegans for proper development, as worms without the microRNA biogenesis pathway are sterile. MicroRNAs act by marking mRNA for degradation, and the inhibitory activity of individuals is conserved across many species, including humans. However, microRNAs often function redundantly and can be regulated at varying times throughout development. This makes the investigation of the significance of individual microRNA problematic. This study sought to elucidate functions of individual microRNA using ovulation in C. elegans as a model. To find singular microRNA that could be involved in ovulation events, worms with a genetically-sensitized background deficient in a single microRNA were screened for sterility phenotypes. The fecundity of any strain was used as an indicator of ovulation defects due to the absence of the microRNA. Worms with a mutation in mir-1, mir-59, mir-71 or mir-85 caused worms on a genetically-sensitized background to give fewer than 20 progeny in 40% or more samples. Therefore, CRISPR/Cas9 constructs were built for these strains to create new endogenous alleles for these genes and to replace microRNA expression with GFP expression. Production of these new strains will allow for more precise genetic assays to be performed on these individual microRNA to further investigate their functional significance.

 

Karina Correa, University of Puerto Rico Humacao Campus

Program Mentor: Dr. Dale Noel

 

Lowering the pH Rescues Quinol Oxidase Dependent Rhizobium etli from Death on Peptide-rich Medium TY

Rhizobium etli is an aerobic bacterium. Like other aerobic bacteria it has branched respiratory chains, in this case several that terminate in cytochrome c oxidases and one quinol oxidase (Cyo). In exponential phase the Cyo oxidase is required for growth at pH 5. cyo gene expression steeply increases as environmental pH decreases from 7.0 to 4.8. In stationary phase in TY medium the expression of this oxidase is down regulated. Fbc- mutants (dependent on Cyo for respiration) die quickly relative to wild type. The aim of this study was to test whether buffering to lower pH would allow survival after onset to stationary phase. Survival, as colony-forming units (cfu), and pH were measured after 1, 3, 5, 8, 12, and 19 days. The Fbc- (Cyo+) mutant and wild type had greatly increased survival in stationary phase when the medium was buffered to lower pH. Without buffering, Fbc- (Cyo+) lost viability completely at day 8. The pH rose during growth and stationary phase, from 6.5 to 8.6 in unbuffered cultures, and from 5.0 to 6.5 in buffered cultures. Adding buffering to Fbc- bacteria after 3 days rescued a dying culture. Therefore, environmental pH is a major factor in the regulation of bacterial terminal oxidases, not only in exponential growth, but, as shown in this study, also during stationary phase.

 

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Tyler J. Halicek, Marquette University

Program Mentor: Dr. Edward Blumenthal

 

 

A Role for Tyrosine and AMPK in Mediating Progression through Oogenesis in Drosophila

Oogenesis in Drosophila is influenced by diet; however, the precise pathway linking starvation with decreased oogenesis is not known. Female flies with a mutation in the gene that encodes Tdc-1, a tyrosine decarboxylase, have severely reduced oogenesis, suggesting a role for the amino acid tyrosine in regulating responses to starvation. Research on C.elegans by Ferguson et al. supports this hypothesis by demonstrating a pathway between elevated tyrosine levels and starvation-like phenotypes through AMPK (PLoS Genetics, 2013). Ultimately, we seek to determine a similar model that explains the Tdc-1 mutant phenotype and the relationship between starvation and oogenesis. Our recent research has primarily focused on tyrosine and AMPK. First, feeding flies phenylalanine, a tyrosine precursor, significantly decreases oogenesis. This lends support to tyrosine acting as a signal involved with starvation responses. However, flies with reduced phenylalanine hydroxylase activity do not show the expected result of recovered oogenesis when fed phenylalanine. Second, immunostaining of stage 7 egg chambers for active-AMPK yielded no consistent difference between normal and phenylalanine enriched food. In addition, there was also no difference between starved and non-starved flies for active-AMPK. Based on the model, we predicted that AMPK activity would be increased for both phenylalanine-fed and starved flies. Third, knocking down AMPK activity in follicle cells with RNAi appears to give a partial resistance to decreased oogenesis when flies are fed phenylalanine. Despite the immunostaining results, this supports the predicted model by suggesting that tyrosine is activating AMPK, which then decreases oogenesis.

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Xiaoyi Hou, Marquette University

Program Mentor: Dr. Michael Schlappi

 

Identification of Promoter-EARLI1::LUCIFERASE Containing Arabidopsis Lines that Reconstitute Endogenous EARLI1 Gene Expression

EARLI1 is an abiotic stress responsive Arabidopsis gene that promotes germination and early seedling development under various stress conditions. Promoter-EARLI1::LUCIFERASE (LUC) Arabidopsis transgenic lines were generated to use LUC as a reporter gene to observe real-time gene expression. To identify transgenic lines that can reconstitute expression of the endogenous EARLI1 gene is the foundation for future studies to genetically dissect the regulatory pathways of EARLI1. This project focused on the effects of high salinity and sucrose on gene expressions in three transgenic lines ELM[2-1], ELM[2-3], ELM[2-4]. EARLI1 promoter activity was measured at the protein level by detecting LUC bioluminescence using a cooled CCD camera. LUC and endogenous EARLI1 transcript levels were measured using RT-PCR. High salinity and high sucrose increased the LUC bioluminescence by approximately 2 folds and 1.5 folds, respectively, which was generally consistent with endogenous EARLI1 expression. However, some of the induction effects of high salinity and sucrose on EARLI1 and LUC expression varied and did not always correlate with bioluminescence results. There might be a difference in the post-transcriptional regulation of the transgene and endogenous EARLI1, which currently remains unclear. More experiments and quantitative real-time PCR analyses are needed to confidentially identify the transgenic line that best reconstitutes endogenous EARLI1 expression, which was tentatively assigned to ELM[2-1].

 

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Catherine Jensen, Marquette University

Program Mentor: Dr. Edward Blumenthal

 

Examining the Biochemical Role of drop-dead in D. melanogaster

The drop-dead (drd) gene in Drosophila melanogaster is thought to be important for the formation of epithelial barriers. drd mutant flies display a phenotype of neurodegeneration, gut dysfunction, female sterility, and adult lethality. Although these physiological effects have been studied extensively, the biochemical role of DRD is largely unknown. Based on its sequence, DRD has been classified as an acyl-transferase enzyme; however, this function has not been verified. This research project is aimed at examining this proposed enzymatic function using two approaches. The first is through site-directed mutagenesis targeting amino acid residues that are critical to the structure and function of prokaryotic acyl-transferase enzymes; the second is by examining a mammalian homologue of drd. A proline 477 to alanine point mutation was introduced in the drd gene through Wild West mutagenesis. SPRINP mutagenesis is being applied to create arginine 471 and tryptophan 558 mutants. Gateway cloning is being used to create inducible expression vectors of these mutant drd genes. At this point, the P477A and wild type constructs have been created. The enzymatic function of drd is also being examined by determining the biochemical equivalence of Oacyl, a mammalian homologue, to drop-dead. Similarly to the site-directed mutagenesis, the gateway cloning strategy will be used to create an expression vector containing Oacyl. At this point, amplification of pieces as well as the entire Oacyl gene has been unsuccessful. Ultimately, in vivo experimentation on the Oacyl and mutant drd constructs will give insight on the acyl-transferase function of DROP-DEAD.

 

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Emily Legan, Marquette University

Program Mentor: Dr. Anita Manogaran

 

Pharmacologically Inhibiting Actin Provides Insight into Prion Formation


Prion disease is an infectious disease associated with Mad Cow disease in cows and Creutzfeldt-Jakob disease in humans. The disease is caused by a misfolded protein that causes normal versions of itself to misfold into an alternative state, leading to aggregation. Since the infective nature of mammalian prions has safety concerns, we turn to prions in yeast which behave similarly to mammalian prions but are not transmissible to humans. One prion in yeast is called [PSI+]. The formation of [PSI+] involves an initial misfolding and aggregation of the protein Sup35p, a translation termination protein, followed by transmission to the daughter cell. It has been recently found that actin is involved in prion formation. Actin is a dynamic cytoskeletal network that is responsible for the movement of organelles and other cell components. These networks function by polymerizing into long cables and then depolymerizing into monomers. We propose that these networks are essential for moving newly formed prion particles to daughter cells. Using drugs that inhibit the activity of actin will help us understand actin’s role in prion formation. We have shown that low levels of Latrunculin A, which blocks actin polymerization, increases prion induction. Conversely, the actin stabilizing drug Cytochalasin B has no effect. Our results suggest that actin polymerization is necessary for prion transmission.

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Alexis Monical, Marquette University

Program Mentor:  Dr. Michelle Mynlieff                

 

Characterization of Potassium Currents in Neonatal Rat Hippocampal Neurons

Excitable cells such as neurons have the ability to fire action potentials, which can send a signal from one region to another. An action potential starts as a large depolarization due to rapid sodium influx. Repolarization of the membrane is due to a slower efflux of potassium (K+). There are many different types of K+ channels, some of which, are calcium dependent. Influx of calcium through L-type calcium channels has been shown to occur in close timing and proximity to these calcium activated K+ channels, implying they have a part in K+ channel modulation. In the present study we investigated the effects of calcium conducted through L-type channels on K+ currents and described the properties of these channels. The goal is to have a better understanding of how these calcium dependent K+ channels affect action potential duration and the afterhyperpolarization thereby altering excitability of the cell. K+ currents were measured with the whole cell patch clamp technique in voltage clamp mode. Neonatal rat hippocampal neurons exhibited both a transient current, IA, and a sustained current, IK. The current-voltage relationship of K+ currents demonstrated rectification of the transient current. Further experiments to classify these currents showed that exposure to nimodipine, an L-type calcium channel blocker, decreased K+ sustained current, in some neuron types, by an average of 64% and decreased transient current by an average of 30%. Indicating a greater effect of calcium on sustained current type. Neurons lacking a transient component had a 35% average inhibition of the sustained component.

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Trygve Nelson, Marquette University

Program Mentors: Dr. James Maki

Toxicity of Bacillus sp. JK7 and Cobetia Marina to Nematode Worms

Biofouling is defined as the accumulation of both micro- and macro-organisms on a submerged, artificial surface that results in a decrease in performance. Biofilms of the bacterium Bacillus sp. JK7 have been shown to inhibit the reattachment of young adult zebra mussels and biofilms of the bacterium Cobetia marina inhibit attachment of cyprid barnacle larvae, therefore serving as potential antifouling control methods. However, in each case the mechanism for inhibition is unknown. This project investigates the hypothesis that biofilms of these bacterium inhibit invertebrate attachment through the production of toxins. The hypothesis was tested by determining whether the bacteria showed toxicity against the nematode worm Caenorhabditis elegans. Worms were placed on lawns of each bacterium grown on either PGS, death indicates fast killing from toxins, or NG, death indicates slow killing from infection. Lawns of E. coli were used as a control. Worm mortality was scored over time. Worms placed on lawns of JK7 on PGS all died within 1 to 2 days, indicating toxin production, and on NG within 4 days, indicating infection. Worms placed on lawns of C. marina on PGS all died within 2 days, also indicating toxin production, but did not die on lawns grown on NG. Enzyme assays using extracellular material from cultures of the bacteria showed production of a protease and an amylase from JK7 grown on NG (but not on PGS) media. C. marina did not produce extracellular enzymes. The results of this project showed that both bacteria produced toxins to nematode worms. However, the nature of the toxins are currently unknown. Whether these toxins are responsible for the inhibition of invertebrate attachment is also unknown, but the results of the experiments provide a possible mechanism of interaction. Future research will involve answering these questions.

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Garrett Panno, Marquette University

Program Mentor:  Dr. Robert H. Fitts

Action Potential Duration and the KATP Channel: Effect of Wheel Running

Coronary Heart Disease is the leading cause of death worldwide with a primary contributing factor being ischemia-induced arrhythmias and cell death. Exercise-training is known to protect against heart disease but the cellular/molecular nature of the protection is not well understood. The purpose of this study was to investigate the role of the KATP channel in protecting the heart during stress conditions such as regional ischemia (RI) and high heart rates (400bpm), and assess how regular exercise aiters the channel. Following the administration of the anesthetic Na+ pentobarbital (50mg/kg body wt i.p.), rat hearts were removed from control and wheel trained Sprague-Dawley rats, and back perfused through the aorta with oxygenated saline. Monophasic action potentials (MAPs) and left ventricular developed pressure (LVDP) were measured at resting and high HR (400 bpm) and before, during and following regional ischemia produced by tying off the left anterior descending coronary artery with and without the drug glibenclamide (a KATP channel blocker). In males, high heart rate lowered the monophasic action potential durations (APDs) in control and trained rats, and the KATP channel blocker increased APDs. these findings were observed in both the base and apex region of the heart. Regional ischemia shortened the APDs in hearts from both control and trained male rats, while glibenclamide prevented the Ischemia-induced shortening. Due to insufficient observations, we are unable to draw conclusion about the affects of glibenclamide on hearts from female rats. In conclusion, the protective effect of reduced APDs with ischemia appears to be at least in part due to activation of the KATP channel causing a more rapid repolarization of the MAP. Our data doesn’t support the hypothesis that protection due to regular exercise is caused by increased KATP channel function.

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Jordan Rede, Saint Martin's University

Program Mentor: Dr. Anita Manogaran

Investigating how Gene Deletions Shown to Influence Q/N and PolyQ Aggregation Affect α-synuclein in Yeast


Alpha-synuclein (α-syn) is a neuronal protein implicated in the pathogenesis of Parkinson’s disease (PD), a multisystem neurodegenerative disorder affecting 10 million people worldwide. In PD, α-syn misfolds and in turn recruits normally folded proteins to the misfolded form. These misfolded proteins aggregate, leading to the fibrous amyloid structures termed Lewy bodies. Modern medicine has only progressed so far as to treat PD symptomatically, and no treatment exists that can arrest or reverse the neurological degradation. Better understanding the nature of α-syn and the cellular processes involved in aggregation and cell toxicity may help lead to the development of targeted treatments to cure PD. Our model employs Saccharomyces cerevisiae (Baker’s yeast), an organism easily manipulated to express α-syn and study aggregation and toxicity. Previous research using yeast has shown that deleting the genes sac6 and vps5 suppress aggregation of the glutamine rich (PolyQ) Huntingtin protein (Htt) and glutamine/asparagine (Q/N) rich [PSI+] prion. We investigate the effects of α-syn, a non-Q/N rich protein, in sac6Δ and vps5Δ strains. Our results show that vps5Δ cells display a distinct increase in aggregation as well as a more punctate peripheral localization of α-syn, whereas sac6Δ cells show a mixture of localization resembling a cross between wildtype and vps5Δ cells. Interestingly, both sac6Δ and vps5Δ show an increase in toxicity. These findings suggest SAC6 and VPS5 may play specific roles in aggregation and toxicity that is unique to α-syn, warranting further investigation into characterizing their behavior when interacting with α-syn.

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Paulina Regan, Framingham State University

Program Mentor: Dr. James Buchanan

 

The Contribution of GABAA Receptors to Fictive Locomotion in Ichthyomyzon unicuspis

Central pattern generators (CPGs) are neuronal networks that generate rhythmic patterns for breathing and locomotion without the need of sensory input. In lamprey, a lower vertebrate, it has been found that locomotor CPGs reside both in the spinal cord and in the hind brain. The inhibitory neurotransmitters, GABA and glycine, are present in both the brain and spinal cord, but glycine is the predominant inhibitory neurotransmitter in the spinal cord. Previous research in lamprey found that glycine is necessary for alternating left-right bursting during locomotor activity in the spinal cord. However, the contribution of GABAA receptors to locomotor activity in the hind brain and spinal cord of Ichthyomyzon unicuspis is not known. In our experiments using isolated spinal cord or hind brain preparations, D-glutamic acid was used to induce swimming activity, which was recorded from motor nerves with extracellular electrodes. Application of 10 µM GABAzine to block GABAA receptors resulted in a significant decrease in the swim cycle period in the spinal cord but had no significant effect on the hind brain cycle period. Alternating left-right bursting was maintained in both spinal cord and hind brain. Activation of GABAA receptors by 1.5 µM muscimol did not alter cycle period but weakened the swim rhythm and silenced motor neuron firing in both spinal cord and hind brain. Overall, our research suggests that GABAA receptors do not play a large role in the generation of locomotor activity or in the patterning of left-right alternating bursting.

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Scott Rossing, Marquette University

Program Mentor: Dr. James Buchanan

 

Interaction Between the Hindbrain and Spinal Cord Locomotor Networks in Ichthyomyzon unicuspis

 

Ichthyomyzon unicuspis (silver lamprey) is a primitive vertebrate fish that is used as a model for the study of the vertebrate nervous system. When isolated, the hindbrain and spinal cord produce neural activity that is comparable to swimming. This rhythmic “fictive swimming” is produced by local circuits in the central nervous system without the need for sensory input. This project looked at how these circuits in the hindbrain and spinal cord interact with each other to produce the overall oscillatory pattern in the lamprey. The isolated central nervous system was placed into physiological solution and a Vaseline barrier was built between the hindbrain and spinal cord so each half could be independently perfused. D-glutamate (an excitatory neurotransmitter) was used to initiate fictive swimming while high divalent cation solution was used to suppress it. After swimming began, one side was suppressed while the other was kept active. This process was repeated with the opposite side after washout. At the same concentrations of D-glutamate, the hindbrain locomotor network had a slower intrinsic swim rate compared to the spinal cord. Also, the regularity of the swim pattern in the spinal cord was better than the hindbrain’s. Finally, peak-to-trough swim oscillation amplitude of the hindbrain motor neurons decreased when the spinal cord was suppressed or when the hindbrain was suppressed. While the data suggest that about 75% of the swim oscillation amplitude in hindbrain motor neurons originates in local circuits, both portions of the central nervous system play key roles.

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Jorge Sandoval, CSUN

Program Mentor: Dr. Edward Blumenthal

 

Physiological Effects of drd in Gut Formation and Digestion in Drosophila


Epithelial barriers perform various secretory, transporting and regulatory functions; and expression of the drd gene appears to be necessary for proper formation of these barriers. The peritrophic matrix (PM) is a barrier within the gut that is believed to aid in digestion. The objective was to study how the mild drdG3 allele affects barrier formation in digestive tract and survival in Drosophila. Dissection of drdlwf, drdG3 and WT indicated that only drdlwf is missing the peritrophic matrix. 24 hour defecation assays found that drdlwf defecates significantly less compared to drdG3 and WT. To visualize apoptosis, guts were immunolabeled with caspase anti-body to stain for apoptosis. Surprisingly, the results showed that drdG3 undergoes apoptosis in the midgut at higher levels than drdlwf and WT. Further staining was done with anti-dityrosine to probe for barriers other than the PM that may be absent in the drdG3 mutants and contributing to apoptosis, but no such barrier was observed. drd expression in cardia and midgut was measured by qPCR and drdG3 expressed significantly less in both tissues by a factor of 30 in the midgut and by a factor of 10 in the cardia. Clearly, drd expression levels do influence viability and understanding barrier formation is important to life.

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Katharine Shelledy, Juniata College

Program Mentor: Dr. Krassimira Hristova

 

The Invader Invaded: Antibiotic Resistance Genes in Lake Michigan Mussel Microbiomes

 

Bacteria isolated from invasive mussels in Lake Michigan exhibit high abundance of multi-drug resistance, which may be connected to antibiotic resistance genes being exchanged between bacteria. This study compared antibiotic resistance, plasmid profiles, and culturable bacterial diversity of mussels collected at Milwaukee’s inner harbor, outer harbor, and further out in Lake Michigan. Mussel gut tissue was extracted and plated on a variety of media, and resulting bacterial isolates were selected for resistance to streptomycin. Antibiotic resistance assays, with 9 different antibiotics from a total of 6 classes, and plasmids extracted from isolated cultures indicate highest multi-drug resistance and plasmid diversity in strains from the outer harbor, with 89% of outer harbor strains exhibiting multi-drug resistance, compared with 76% of inner harbor strains and 68% of the lake strains. Outer harbor mussels impacted by the proximate wastewater treatment plant thus carry multi-drug resistant bacteria that show higher potential to transfer these resistances to the surrounding environment. Across all sites, bacteria were resistant to streptomycin, gentamycin, erythromycin, and ampicillin while most of the isolates exhibited sensitivity to neomycin, fosfomycin, chloramphenicol, and tetracycline. The prevalence of antibiotic resistant bacteria in this study raises concerns over the continued pollution of Lake Michigan, especially concerning society’s reliance on antibiotics for medical purposes.

 

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Katelyn Stine, Marquette University

Program Mentor: Dr. Martin St. Maurice

 

The Effect of Acetyl-CoA on BCCP Movement in Pyruvate Carboxylase

 

Pyruvate carboxylase (PC) is a biotin-dependent enzyme that replenishes the citric acid cycle by catalyzing the carboxylation of pyruvate to oxaloacetate (OAA). This is the first committed step of gluconeogenesis and is important in the regulation of metabolism. To achieve catalytic activity, the biotin carboxyl carrier protein (BCCP) domain must swing between the active sites of the biotin carboxylase (BC) domain and the carboxyltransferase (CT) domain. Our study investigates whether the allosteric activator acetyl-CoA increases activity due to an effect on BCCP movement in Rhizobium etli PC. This was explored in the context of CT dimers and the complete PC tetramer. The movement of BCCP was kinetically assayed through a series of dilution ratios (1:0, 1:1, 1:1.5, 1:2, 1:2.5, 1:3) of wild-type PC to inactivated PC. In the context of the CT dimers, BCCP showed a ~80% preference for cis activity, meaning that it moved to a CT domain contained within the same polypeptide chain. The addition of acetyl-CoA did not have a significant impact on BCCP movement in the context of CT dimers. Conversely, in the context of the tetramer, the addition of acetyl-CoA showed an increased preference for trans movement, meaning that BCCP moved to a CT domain contained on a separate polypeptide chain. Thus, it was concluded that the addition of acetyl-CoA affects BCCP’s movement within the tetramer, which could contribute to its increased activity.

 

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Katie Zarbock, St. Catherine University

Program Mentor: Dr. Michael Schlappi

 

Electrolyte Leakage from Leaves of Oryza sativa During Recovery from Chilling Stress Correlates with Whole Plant Survivability

 

Domesticated rice, or Oryza sativa, substantiates the diets of 2.7 billion people but its cold sensitivity limits the regions of its growth. Some cultivars of rice can tolerate cold stress, which may be accomplished through the maintenance of plasma membrane integrity. Twelve-day-old seedlings of cold sensitive and tolerant cultivars were submitted to cold stress (10 °C) for one week and the degree of plasma membrane damage was quantified using the electrolyte leakage (EL) assay following cold stress. Low-temperature survivability in seedlings (LTSS) was assessed after seven days of recovery. A weak negative correlation between EL and survivability was observed in experiments performing the EL assays immediately after cold stress. Stronger correlations were observed when the EL assays were conducted at various times after cold stress during the recovery period. Electrolyte leakage was most strongly correlated to survivability at one and six hours of recovery. Further experimentation to correlate recovery EL and LTSS with a larger sample of cultivars may show that maintaining plasma membrane integrity is a mechanism of superior chilling tolerance, which could lead to generation of strains with improved tolerance.

 

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Biology Summer Research group

 


 

 


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