• The efficacy of anti-predator behaviour in the wood fog tadpole (Rana sylvatica) /

      Kerling, Candice L.; Department of Biological Sciences (Brock University, 2007-06-04)
      Activity has been suggested as an important behaviour that is tightly linked with predator avoidance in tadpoles. In this thesis I examine predator-prey relationships using wood frog tadpoles {Rana sylvaticd) as prey and dragonfly larvae {AnaxJunius) and backswimmers {Notonecta undulatd) as predators. I explore the role of prey activity in predator attack rates, prey response to single and multiple predator introductions, and prey survivorship. The data suggest that Anax is the more successful predator, able to capture both active and inactive tadpoles. In contrast, Notonecta strike at inactive prey less frequently and are seldom successftil when they do. A mesocosm study revealed that the presence of any predator resulted in reduced activity level of tadpoles. Each predator species alone had similar effects on tadpole activity, as did the combined predator treatment. Tadpole survivorship, however, differed significantly among both predator treatments and prey populations. Tadpwles in the combined predator treatment had enhanced risk; survivorship was lower than that expected if the two predators had additive effects. Differences in survivorship among wood frog populations showed that tadpoles from a lake habitat had the lowest survivorship, those from a shallow pond habitat had an intermediate survivorship, and tadpoles from a marsh habitat had the highest survivorship. The frequency of interactions with predators in the native habitat may be driving the population differences observed. In conclusion, results from this study show that complex interactions exist between predators, prey, and the environment, with activity playing a key role in the survival of tadpoles.
    • Elucidation of odour-potent compounds and sensory profiles of Vidal blanc and Riesling icewines from the Niagara Peninsula : effect of harvest date and crop level

      Bowen, Amy J.; Department of Biological Sciences (Brock University, 2011-10-14)
      I t was hypothesized that the freeze/thaw cycles endured by icewine grapes would change their chemical composition, resulting in unique chemical fingerprint and sensory properties, and would be affected by harvest date (HD) and crop level (CL). The objectives were: 1) to identify odour-active compounds using gas chromatographic and sensory analysis; 2) to determine the effect of CL and HD on these compounds; 3) to determine the icewine sensory profiles; 4) to correlate analytical and sensory results for an overall icewine profile. CharmAnalysis™ determined the Top 15 odour-potent compounds in Vidal and Riesling icewine and table wines; 24 and 23 compounds, respectively. The majority of the compounds had the highest concentrations in the icewines compared to table wines. These compounds were used as the foundation for assessing differences in icewine chemical profiles from different HD and CL. Vidal and Riesling icewine were made from grapes picked at different HD; HI : 19 December; H2: 29 December; H3: 18 January; H4: 11 February (Vidal only). HI wines differed from H3 and H4 wines in both Vidal and Riesling for aroma compounds and sensory profiles. - Three·CL [control (fully cropped), cluster thin at fruit set to one basal cluster/shoot (TFS), and cluster thin at veraison to one basal cluster/shoot (TV)] were evaluated for Riesling and Vidal cultivars over two seasons. Vidal icewines had the highest concentration of aroma compounds in the control and TV icewines in 2003 and in TFS icewines in 2004. In Riesling, most aroma compounds had the highest concentration in the TV icewines and the lowest concentration in the TFS wine for both years. The thinned treatments were associated with almost all of the sensory attributes in both cultivars, both years. HD and CL affected the chemical variables, aroma compounds and sensory properties of Vidal and Riesling icewines and freeze/thaw events changed their sensory profile. The most odour-potent compounds were p-damascenone, cis-rose oxide, 1- octen-3-ol, 4-vinylguaiacol, ethyl octanoate, and ethyl hexanoate. The role of Pdamascenone as a marker compound for icewine requires further investigation. This research provides a strong foundation for the understanding the odour-active volatiles and sensory profiles important to icewine.

      Simone, Jonathan; Department of Biological Sciences
      The present thesis investigated the contributions of adolescent endocannabinoid signalling to brain and behaviour development in male and female rats. In chapter 2, daily administration of the CB1 antagonist AM251, alone or in tandem with a psychological stressor, increased social interactions, reduced dorsal hippocampal CB1 expression, and increased mPFC GAD67 expression in female rats 24-48 h after treatment, with no effects in males. In chapter 3, adolescent CB1 antagonism reduced anxiety in adult males, with no effects in females. Conversely, adolescent AM251 increased contextual fear in adult females, with no effects in males. In chapter 4, AM251 females spent more time initiating social interactions after a 5-day drug washout period than vehicle females, with no effects in males. To identify brain regions underlying the effects of AM251 on social behaviours, I repeated social interaction testing in vehicle and AM251 females and collected brains for immunohistochemical labelling of EGR-1 as a marker of neural activation in the CA1, CA2, and CA3 subfields of the dorsal hippocampus and the shell and core divisions of the nucleus accumbens (NAc). Consistent with my previous findings, AM251 females spent more time initiating social interactions and had greater EGR-1 cell counts in the NAc shell than vehicle females, with no group differences in the NAc core or in any of the hippocampal subfields investigated. EGR-1 cell counts in the dCA2 were negatively correlated with social interactions in vehicle and AM251 females. A positive correlation between NAc shell EGR-1 cell counts and social interactions was observed only in AM251 females. Regression analysis using drug treatment and EGR-1 cell counts in dCA2 and NAc shell resulted in a model with an adjusted R2 of 0.90. Both drug treatment and EGR-1 cell counts in the dorsal CA2 emerged as unique predictors of individual differences in social interaction, and drug and NAc shell EGR-1 cell counts interacted to significantly predict social interactions in AM251 females only. Together, these studies provide support for sex-specific contributions of endocannabinoid signalling to the development of brain and behaviour in adolescence in male and female rats.
    • Erwinia amylovora bacteriophage resistance

      Roach, Dwayne R.; Department of Biological Sciences (Brock University, 2012-04-04)
      It has been proposed that phages can be used commercially as a biopesticide for the control of fire blight caused by the phytopathogen Erwinia amylovora. The aim of these studies was to investigate two common bacterial resistance mechanisms, lysogeny and exopolysaccharide production and their influence on phage pathogenesis. A multiplex real-time PCR protocol was designed to monitor and quantify Podoviridae and Myoviridae phages. This protocol is compatible with known E. amylovora and Pantoea agglomerans rtPCR primers/probes which allowed simultaneous study of both phage and bacterial targets. Using in vitro positive phage selection, bacteriophage insensitive derivatives were isolated within sensitive populations of E. amylovora. Prophage screening with real-time PCR and mitomycin C induction determined that the insensitive derivatives harboured the temperate Podoviridae phage ΦEaTlOO. Lysogenic conversion resulted in resistance to secondary homologous phage infections. Prophage screening of environmental samples of E. amylovora and P. agglomerans collected from various locations in Canada, United States and Europe did not demonstrate lysogeny. Therefore, lysogeny is rare or absent while these bacterial species reside on the plant. Recombineering was used to construct exopolysaccharide deficient E. amylovora mutants. The EPS amylovoran mutants became resistant to Podoviridae and certain Siphoviridae phages. Increasing amylovoran production increased phage population growth, presumably by increasing the total number of bacterial cell surface receptors which promoted increased phage infections. In contrast, amylovoran did not playa role in Myoviridae infections, nor did production of the EPS levan for any phage pathogenesis.
    • Etiology and Management of Grape Sour Rot

      Huber, Cristina; Department of Biological Sciences
      Sour rot is characterized by increased volatile acidity (VA) in ripe grapes. VA is associated with spoilage organisms and wineries may reject grape crops based on their concentration of acetic acid. Our research associated Hanseniaspora uvarum, Gluconobacter oxydans, and to a lesser extent, Gluconobacter cerinus and Acetobacter malorum with sour rotted grapes in the Niagara Peninsula, designated viticultural area, Ontario, Canada, and the pathogenicity of these organisms was confirmed by laboratory assays. Only G. oxydans was shown to penetrate around the site of pedicel attachment to the grape. The yeasts required further wounding. Candida zemplinina was also associated with the sour rot microbial community. This species showed variable pathogenicity by strain and most strains were not highly pathogenic. C. zemplinina gained dominance in the microbial population of grapes only after sour rot symptoms were observed, indicating a succession which was studied in laboratory assays. There was a correlation between temperature, moisture, and berry ripeness and the development of sour rot when conditions were monitored in a Vitis vinifera cv. Riesling vineyard over four years, and this was confirmed in laboratory assays. Disease management options are limited since sour rot is caused by a complex of yeasts and bacteria, with symptoms developing just as grapes approach maturity. Post-veraison treatments for sour rot were investigated. Wineries routinely add potassium metabisulphite (KMS) to the surface of fruit in bins and to grape juice to kill spoilage organisms. Replicated field trials were conducted in V. vinifera cv. Riesling in 2010 and 2011 to determine the efficacy of KMS at different concentrations and pre-harvest timings as a fruiting-zone spray. Potassium bicarbonate (Milstop) was also evaluated for its efficacy against sour rot. Plots were rated for incidence and severity of sour rot and VA (g acetic acid/L juice). KMS treatments at concentrations above 5 kg/1000L and Milstop sprayed at the label concentration of 5.6 kg/1000L were able to reduce the severity of sour rot compared to untreated control plots which had a severity above 50% (2011). KMS was able to reduce VA to below the winery rejection threshold of 0.24 g acetic acid/L when sour rot severity reached 12% in untreated plots (2010). When tested in the laboratory in disk diffusion assays conducted on yeast peptone dextrose agar, KMS at a concentration of 10 g/L had the greatest efficacy against G. oxydans and H. uvarum. Grape incubation assays showed the potential of KMS acidified with tartaric acid to reduce sour rot symptoms. Acidification did not show as much potential in field trials, calling for further research.
    • Evolutionary Origin and Maintenance of Sociality in the Small Carpenter Bees

      Rehan, Sandra; Department of Biological Sciences (Brock University, 2012-07-31)
      Many arthropods exhibit behaviours precursory to social life, including adult longevity, parental care, nest loyalty and mutual tolerance, yet there are few examples of social behaviour in this phylum. The small carpenter bees, genus Ceratina, provide important insights into the early stages of sociality. I described the biology and social behaviour of five facultatively social species which exhibit all of the preadaptations for successful group living, yet present ecological and behavioural characteristics that seemingly disfavour frequent colony formation. These species are socially polymorphic with both / solitary and social nests collected in sympatry. Social colonies consist of two adult females, one contributing both foraging and reproductive effort and the second which remains at the nest as a passive guard. Cooperative nesting provides no overt reproductive benefits over solitary nesting, although brood survival tends to be greater in social colonies. Three main theories explain cooperation among conspecifics: mutual benefit, kin selection and manipulation. Lifetime reproductive success calculations revealed that mutual benefit does not explain social behaviour in this group as social colonies have lower per capita life time reproductive success than solitary nests. Genetic pedigrees constructed from allozyme data indicate that kin selection might contribute to the maintenance of social nesting -, as social colonies consist of full sisters and thus some indirect fitness benefits are inherently bestowed on subordinate females as a result of remaining to help their dominant sister. These data suggest that the origin of sociality in ceratinines has principal costs and the great ecological success of highly eusociallineages occurred well after social origins. Ecological constraints such as resource limitation, unfavourable weather conditions and parasite pressure have long been considered some of the most important selective pressures for the evolution of sociality. I assessed the fitness consequences of these three ecological factors for reproductive success of solitary and social colonies and found that nest sites were not limiting, and the frequency of social nesting was consistent across brood rearing seasons. Local weather varied between seasons but was not correlated with reproductive success. Severe parasitism resulted in low reproductive success and total nest failure in solitary nests. Social colonies had higher reproductive success and were never extirpated by parasites. I suggest that social nesting represents a form of bet-hedging. The high frequency of solitary nests suggests that this is the optimal strategy when parasite pressure is low. However, social colonies have a selective advantage over solitary nesting females during periods of extreme parasite pressure. Finally, the small carpenter bees are recorded from all continents except Antarctica. I constructed the first molecular phylogeny of ceratinine bees based on four gene regions of selected species covering representatives from all continents and ecological regions. Maximum parsimony and Bayesian Inference tree topology and fossil dating support an African origin followed by an Old World invasion and New World radiation. All known Old World ceratinines form social colonies while New World species are largely solitary; thus geography and phylogenetic inertia are likely predictors of social evolution in this genus. This integrative approach not only describes the behaviour of several previously unknown or little-known Ceratina species, bu~ highlights the fact that this is an important, though previously unrecognized, model for studying evolutionary transitions from solitary to social behaviour.
    • The Fast Regulation of Photosynthesis in Diatoms: an inquiry into the physiological and physical origins of non-photochemical chlorophyll fluorescence quenching.

      Derks, Allen Kimbell; Department of Biological Sciences (Brock University, 2015-01-06)
      Diatoms are renowned for their robust ability to perform NPQ (Non-Photochemical Quenching of chlorophyll fluorescence) as a dissipative response to heightened light stress on photosystem II, plausibly explaining their dominance over other algal groups in turbulent light environs. Their NPQ mechanism has been principally attributed to a xanthophyll cycle involving the lumenal pH regulated reversible de-epoxidation of diadinoxanthin. The principal goal of this dissertation is to reveal the physiological and physical origins and consequences of the NPQ response in diatoms during short-term transitions to excessive irradiation. The investigation involves diatom species from different originating light environs to highlight the diversity of diatom NPQ and to facilitate the detection of core mechanisms common among the diatoms as a group. A chiefly spectroscopic approach was used to investigate NPQ in diatom cells. Prime methodologies include: the real time monitoring of PSII excitation and de-excitation pathways via PAM fluorometry and pigment interconversion via transient absorbance measurements, the collection of cryogenic absorbance spectra to measure pigment energy levels, and the collection of cryogenic fluorescence spectra and room temperature picosecond time resolved fluorescence decay spectra to study excitation energy transfer and dissipation. Chemical inhibitors that target the trans-thylakoid pH gradient, the enzyme responsible for diadinoxanthin de-epoxidation, and photosynthetic electron flow were additionally used to experimentally manipulate the NPQ response. Multifaceted analyses of the NPQ responses from two previously un-photosynthetically characterised species, Nitzschia curvilineata and Navicula sp., were used to identify an excitation pressure relief ‘strategy’ for each species. Three key areas of NPQ were examined: (i) the NPQ activation/deactivation processes, (ii) how NPQ affects the collection, dissipation, and usage of absorbed light energy, and (iii) the interdependence of NPQ and photosynthetic electron flow. It was found that Nitzschia cells regulate excitation pressure via performing a high amplitude, reversible antenna based quenching which is dependent on the de-epoxidation of diadinoxanthin. In Navicula cells excitation pressure could be effectively regulated solely within the PSII reaction centre, whilst antenna based, diadinoxanthin de-epoxidation dependent quenching was implicated to be used as a supplemental, long-lasting source of excitation energy dissipation. These strategies for excitation balance were discussed in the context of resource partitioning under these species’ originating light climates. A more detailed investigation of the NPQ response in Nitzschia was used to develop a comprehensive model describing the mechanism for antenna centred non-photochemical quenching in this species. The experimental evidence was strongly supportive of a mechanism whereby: an acidic lumen triggers the diadinoxanthin de-epoxidation and protonation mediated aggregation of light harvesting complexes leading to the formation of quencher chlorophyll a-chlorophyll a dimers with short-lived excited states; quenching relaxes when a rise in lumen pH triggers the dispersal of light harvesting complex aggregates via deprotonation events and the input of diadinoxanthin. This model may also be applicable for describing antenna based NPQ in other diatom species.
    • Functional antagonism of the mesolimbic dopaminergic system on mesolimbic cholinergic system in the vocal expression of an emotional state

      Silkstone, Michael; Department of Biological Sciences
      The overarching goal of this thesis was to determine if the initiation of a positive emotional state could antagonize the expression of a negative emotional state in rats. The hypothesis of the thesis argued that the initiation of a positive emotional state would ameliorate the vocal expression of a negative emotional state. The subjective emotional state of the rat was indexed by the quantity and type of pharmacologically induced ultrasonic vocalizations (USVs). Adolescent and adult rats can emit vocalizations above the upper threshold of human hearing (>20 kHz) termed ultrasonic vocalizations (USVs). These USVs are broadly divided into 50-kHz, reflective of a positive emotional state, and 22-kHz USVs, reflective of a negative emotional state. Pharmacologically, injection of dopamine agonists into the nucleus accumbens shell is sufficient for the initiation of 50-kHz USVs, while injection of cholinergic agonists into the anterior hypothalamic-medial preoptic area (AH-MPO) or the lateral septum (LS) can initiate 22-kHz USVs. In chapter two of the thesis, I demonstrated that microinjection of the dopamine agonist, apomorphine, into the medial shell of the nucleus accumbens attenuated the extent of carbachol-induced 22-kHz USVs from the AH-MPO. I also demonstrated that this effect was dependent upon the microinjection of apomorphine into the central region of the nucleus accumbens shell. In chapter three, I demonstrated that apomorphine could also decrease the extent of carbachol-induced 22-kHz USVs from the LS providing evidence that the effect reported in chapter two was not isolated to the AH-MPO, but rather extending along the medial cholinoceptive vocalization strip. In the third chapter. I also demonstrated that the magnitude of the reduction in the number of 22-kHz USVs was correlated to the number of emitted frequency-modulated (FM) 50-kHz USVs induced by apomorphine. In the fourth chapter, I investigated whether blocking dopamine receptors, either systemically using the typical D2-antipsychotic agent, haloperidol, or microinjection of the D2 antagonist, raclopride, into the nucleus accumbens shell could increase the emission of carbachol-induced 22-kHz USVs from the LS. The results showed that antagonism of dopamine receptors, either systemically or intracerebrally, did not increase the number of 22-kHz USVs. Interestingly, it was also observed that after the prolonged recording of carbachol-induced 22-kHz USVs, some 50-kHz USVs spontaneously appeared after roughly 300 s into the recording. I argued that these 50-kHz USVs, which I defined as “rebound 50-kHz USVs” are not initiated by carbachol since they occurred when the carbachol-response weaned. It was also demonstrated these rebound 50-kHz USVs were dependent upon dopamine release within the nucleus accumbens since both systemic, and intracerebral application of dopamine antagonists into the central division of the nucleus accumbens shell blocked the occurrence of rebound 50-kHz USVs. Altogether, the data supports the thesis that activation of a positive emotional state decreases the expression of the negative emotional state in rats when measured using ultrasonic vocalizations.
    • Functional genomics of O-glucosyltransferases from Concord grape (Vitis labrusca)

      Hall, Dawn.; Department of Biological Sciences (Brock University, 2007-05-28)
      Grape (Vitis spp.) is a culturally and economically important crop plant that has been cultivated for thousands of years, primarily for the production of wine. Grape berries accumulate a myriad of phenylpropanoid secondary metabolites, many of which are glucosylated in plantae More than 90 O-glucosyltransferases have been cloned and biochemically characterized from plants, only two of which have been isolated from Vitis spp. The world-wide economic importance of grapes as a crop plant, the human health benefits associated with increased consumption of grape-derived metabolites, the biological relevance of glucosylation, and the lack of information about Vitis glucosyltransferases has inspired the identification, cloning and biochemical characterization of five novel "family 1" O-glucosyltransferases from Concord grape (Vitis labrusca cv. Concord). Protein purification and associated protein sequencIng led to the molecular cloning of UDP-glucose: resveratrollhydroxycinnamic acid O-glucosyltransferase (VLRSGT) from Vitis labrusca berry mesocarp tissue. In addition to being the first glucosyltransferase which accepts trans-resveratrol as a substrate to be characterized in vitro, the recombinant VLRSGT preferentially produces the glucose esters of hydroxycinnamic acids at pH 6.0, and the glucosides of trans-resveratrol and flavonols at 'pH 9.0; the first demonstration of pH-dependent bifunctional glucosylation for this class of enzymes. Gene expression and metabolite profiling support a role for this enzyme in the bifuncitonal glucosylation ofstilbenes and hydroxycinnamic acids in plantae A homology-based approach to cloning was used to identify three enzymes from the Vitis vinifera TIGR grape gene index which had high levels of protein sequence iii identity to previously characterized UDP-glucose: anthocyanin 5-0-glucosyltransferases. Molecular cloning and biochemical characterization demonstrated that these enzymes (rVLOGTl, rVLOGT2, rVLOGT3) glucosylate the 7-0-position of flavonols and the xenobiotic 2,4,5-trichlorophenol (TCP), but not anthocyanins. Variable gene expression throughout grape berry development and enzyme assays with native grape berry protein are consistent with a role for these enzymes in the glucosylation of flavonols; while the broad substrate specificity, the ability of these enzymes to glucosylate TCP and expression of these genes in tissues which are subject to pathogen attack (berry, flower, bud) is consistent with a role for these genes in the plant defense response. Additionally, the Vitis labrusca UDP-glucose: flavonoid 3-0-glucosyltransferase (VL3GT) was identified, cloned and characterized. VL3GT has 96 % protein sequence identity to the previously characterized Vitis vinifera flavonoid 3-0-glucosyltransferase (VV3GT); and glucosylates the 3-0-position of anthocyanidins and flavonols in vitro. Despite high levels of protein sequence identity, VL3GT has distinct biochemical characteristics (as compared to VV3GT), including a preference for B-ring methylated flavonoids and the inability to use UDP-galactose as a donor substrate. RT-PCR analysis of VL3GT gene expression and enzyme assays with native grape protein is consistent with an in planta role for this enzyme in the glucosylation of anthocyanidins,but not flavonols. These studies reveal the power of combining several biochemistry- and molecular biology-based tools to identify, clone, biochemically characterize and elucidate the in planta function of several biologically relevant O-glucosyltransferases from Vitis spp.

      Ahmed, Musaddeque; Department of Biological Sciences (Brock University, 2014-02-19)
      Genome sequence varies in numerous ways among individuals although the gross architecture is fixed for all humans. Retrotransposons create one of the most abundant structural variants in the human genome and are divided in many families, with certain members in some families, e.g., L1, Alu, SVA, and HERV-K, remaining active for transposition. Along with other types of genomic variants, retrotransponson-derived variants contribute to the whole spectrum of genome variants in humans. With the advancement of sequencing techniques, many human genomes are being sequenced at the individual level, fueling the comparative research on these variants among individuals. In this thesis, the evolution and functional impact of structural variations is examined primarily focusing on retrotransposons in the context of human evolution. The thesis comprises of three different studies on the topics that are presented in three data chapters. First, the recent evolution of all human specific AluYb members, representing the second most active subfamily of Alus, was tracked to identify their source/master copy using a novel approach. All human-specific AluYb elements from the reference genome were extracted, aligned with one another to construct clusters of similar copies and each cluster was analyzed to generate the evolutionary relationship between the members of the cluster. The approach resulted in identification of one major driver copy of all human specific Yb8 and the source copy of the Yb9 lineage. Three new subfamilies within the AluYb family – Yb8a1, Yb10 and Yb11 were also identified, with Yb11 being the youngest and most polymorphic. Second, an attempt to construct a relation between transposable elements (TEs) and tandem repeats (TRs) was made at a genome-wide scale for the first time. Upon sequence comparison, positional cross-checking and other relevant analyses, it was observed that over 20% of all TRs are derived from TEs. This result established the first connection between these two types of repetitive elements, and extends our appreciation for the impact of TEs on genomes. Furthermore, only 6% of these TE-derived TRs follow the already postulated initiation and expansion mechanisms, suggesting that the others are likely to follow a yet-unidentified mechanism. Third, by taking a combination of multiple computational approaches involving all types of genetic variations published so far including transposable elements, the first whole genome sequence of the most recent common ancestor of all modern human populations that diverged into different populations around 125,000-100,000 years ago was constructed. The study shows that the current reference genome sequence is 8.89 million base pairs larger than our common ancestor’s genome, contributed by a whole spectrum of genetic mechanisms. The use of this ancestral reference genome to facilitate the analysis of personal genomes was demonstrated using an example genome and more insightful recent evolutionary analyses involving the Neanderthal genome. The three data chapters presented in this thesis conclude that the tandem repeats and transposable elements are not two entirely distinctly isolated elements as over 20% TRs are actually derived from TEs. Certain subfamilies of TEs themselves are still evolving with the generation of newer subfamilies. The evolutionary analyses of all TEs along with other genomic variants helped to construct the genome sequence of the most recent common ancestor to all modern human populations which provides a better alternative to human reference genome and can be a useful resource for the study of personal genomics, population genetics, human and primate evolution.
    • Identification and characterization of a Catharanthus roseus mutant altered in monoterpenoid indole alkaloid biosynthesis

      Thamm, Antje MK; Department of Biological Sciences (Brock University, 2014-09-09)
      The Madagascar periwinkle [Catharanthus roseus (L.) G. Don] is a commercially important horticultural flower species and is the only source for several pharmaceutically valuable monoterpenoid indole alkaloids (MIAs), including the powerful antihypertensive ajmalicine and the antineoplastic agents vincristine and vinblastine. While biosynthesis of MIA precursors has been elucidated, conversion of the common MIA precursor strictosidine to MIAs of different families, for example ajmalicine, catharanthine or vindoline, remains uncharacterized. Deglycosylation of strictosidine by the key enzyme Strictosidine beta-glucosidase (SGD) leads to a pool of uncharacterized reaction products that are diverted into the different MIA families, but the downstream reactions are uncharacterized. Screening of 3600 EMS (ethyl methane sulfonate) mutagenized C. roseus plants to identify mutants with altered MIA profiles yielded one plant with high ajmalicine, and low catharanthine and vindoline content. RNA sequencing and comparative bioinformatics of mutant and wildtype plants showed up-regulation of SGD and the transcriptional repressor Zinc finger Catharanthus transcription factor (ZCT1) in the mutant line. The increased SGD activity in mutants seems to yield a larger pool of uncharacterized SGD reaction products that are channeled away from catharanthine and vindoline towards biosynthesis of ajmalicine when compared to the wildtype. Further bioinformatic analyses, and crossings between mutant and wildtype suggest a transcription factor upstream of SGD and ZCT1 to be mutated, leading to up-regulation of Sgd and Zct1. The crossing experiments further show that biosynthesis of the different MIA families is differentially regulated and highly complex. Three new transcription factors were identified by bioinformatics that seem to be involved in the regulation of Zct1 and Sgd expression, leading to the high ajmalicine phenotype. Increased cathenamine reductase activity in the mutant converts the pool of SGD reaction products into ajmalicine and its stereoisomer tetrahydroalstonine. The stereochemistry of ajmalicine and tetrahydroalstonine biosynthesis in vivo and in vitro was further characterized. In addition, a new clade of perakine reductase-like enzymes was identified that reduces the SGD reaction product vallesiachotamine in a stereo-specific manner, characterizing one of the many reactions immediately downstream of SGD that determine the different MIA families. This study establishes that RNA sequencing and comparative bioinformatics, in combination with molecular and biochemical characterization, are valuable tools to determine the genetic basis for mutations that trigger phenotypes, and this approach can also be used for identification of new enzymes and transcription factors.
    • Identification and characterization of retinoic acid-induced morphological and electrophysiological changes in an invertebrate nervous system

      Vesprini, Nicholas; Department of Biological Sciences (Brock University, 2012-07-31)
      The vitamin A metabolite, retinoic acid (RA) is known to play an important role in the development, patterning and regeneration of nervous tissue, both in the embryo and in the adult. Classically, RA is known to mediate the transcription of target genes through the binding and activation ofits nuclear receptors: the retinoic acid receptors (RARs) and retinoid X receptors (RXRs). Recently, mounting evidence from many animal models has implicated a number of RA-mediated effects operating independently of gene transcription, and thus highlights nove~ nongenornic actions of RA. For example, recent work utilizing cultured neurons from the pond snaa Lymnaea stagnalis, has shown that RA can elicit a regenerative response, growth cone turning, independently of "classical" transcriptional activation While this work illustrates a novel regeneration-inducing effect in culture, it is currently -unknown whether RA also induces regeneration in situ. This study has sought to determine RA's regenerative effucts at the morphological and molecular levels by utilizing an in situ approach focusing on a single identified dopaminergic neuron which possesses a known "mapped" morphology within the CNS. These studies show, for the first time in an invertebrate, that RA can increase neurite outgrowth of dopaminergic cells that have undergone a nerve-crush injury. Utilizing Western blot analysis, it was shown that this effect appears to be independent of any changes in whole CNS expression levels of either the RAR or RXR. Additionally, utilizing immunohistochemistry, to examine protein localization, there does not appear to be any obvious changes in the RXR expression level at the crush site. Changes in cell morphology such as neurity extension are known to be modulated by changes in neuronal firing activity. It has been previously shown that exposure to RA over many days can lead to changes in the electrophysiological properties of cultured Lymnaea neurons; however, no studies have investigated whether short-term exposure to RA can elicit electrophysiological changes and/or changes in firing pattern of neurons in Lymnaea or any other species. The studies performed here show, for the first time in any species, that short-tenn treatment with RA can elicit significant changes in the firing properties of both identified dopaminergic neurons and peptidergic neurons. This effect appears to be independent of protein synthesis, activation of protein kinase A or phospholipase C, and calcium influx but is both dose-dependent and isomer-dependent. These studies provide evidence that the RXR, but not RAR, may be involved, and that intracellular calcium concentrations decrease upon RAexposure with a time course, dose-dependency and isomer-dependency that coincide with the RA-induced electrophysiological changes. Taken together, these studies provide important evidence highlighting RA as a multifunctional molecule, inducing morphological, molecular and electrophysiological changes within the CNS, and highlight the many pathways through which RA may operate to elicit its effects.
    • Identification of novel retinoid receptors and their roles in vertebrate and invertebrate nervous systems

      Charter, Christopher J; Department of Biological Sciences (Brock University, 2012-07-30)
      In vertebrates, signaling by retinoic acid (RA) is known to play an important role in embryonic development, as well as organ homeostasis in the adult. In organisms such as adult axolotls and newts, RA is also important for regeneration of the CNS, limb, tail, and many other organ systems. RA mediates many of its effects in development and regeneration through nuclear receptors, known as retinoic acid receptors (RARs) and retinoid X receptors (RXRs). This study provides evidence for an important role of the RA receptor, RAR~2, in ,( '. regeneration ofthe spinal cord and tail of the adult newt. It has previously been proposed that the ability of the nervous system to regenerate might depend on the presence or absence of this RAR~2 isoform. Here, I show for the very first time, that the regenerating spinal cord of the adult newt expresses this ~2 receptor isoform, and inhibition of retinoid signaling through this specific receptor with a selective antagonist inhibits tail and spinal cord regeneration. This provides the first evidence for a role of this receptor in this process. Another species capable of CNS ~~generation in the adult is the invertebrate, " Lymnaea stagnalis. Although RA has been detected in a small number of invertebrates (including Lymnaea), the existence and functional roles of the retinoid receptors in most invertebrate non-chordates, have not been previously studied. It has been widely believed, however, that invertebrate non-chordates only possess the RXR class of retinoid receptors, but not the RARs. In this study, a full-length RXR cDNA has been cloned, which was the first retinoid receptor to be discovered in Lymnaea. I then went on to clone the very first full-length RAR eDNA from any non-chordate, invertebrate species. The functional role of these receptors was examined, and it was shown that normal molluscan development was altered, to varying degrees, by the presence of various RXR and RAR agonists or antagonists. The resulting disruptions in embryogenesis ranged from eye and shell defects, to complete lysis of the early embryo. These studies strongly suggest an important role for both the RXR and RAR in non-chordate development. The molluscan RXR and RAR were also shown to be expressed in the adult, nonregenerating eNS, as well as in individual motor neurons regenerating in culture. More specifically, their expression displayed a non-nuclear distfibution, suggesting a possible non-genomic role for these 'nuclear' receptors. It was shown that immunoreactivity for the RXR was present in almost all regenerating growth cones, and (together with N. Farrar) it was shown that this RXR played a novel, non-genomic role in mediating growth cone turning toward retinoic acid. Immunoreactivity for the novel invertebrate RAR was also found in the regenerating growth cones, but future work will be required to determine its functional role in nerve cell regeneration. Taken together, these data provide evidence for the importance of these novel '. retinoid receptors in development and regeneration, particularly in the adult nervous system, and the conservation of their effects in mediating RA signaling from invertebrates to vertebrates.
    • Impact of different irrigation strategies on grapes and wine quality of four grapevine cultivars (Vitis sp.) in cool climate conditions. An investigation into the relationships among ABA, water status, grape cultivar and wine quality

      Balint, Gabriel; Department of Biological Sciences (Brock University, 2012-04-04)
      Niagara Peninsula of Ontario is the largest viticultural area in Canada. Although it is considered to be a cool and wet region, in the last decade many water stress events occurred during the growing seasons with negative effects on grape and wine quality. This study was initiated to understand and develop the best strategies for water management in vineyards and those that might contribute to grape maturity advancement. The irrigation trials investigated the impact of time of initiation (fruit set, lag phase and veraison), water replacement level based on theoretical loss through crop evapotranspiration (ETc; 100,50 and 25%) and different irrigation strategies [partial root zone drying (PRD) versus regulated deficit irrigation (RD!)] on grape composition and wine sensory profiles. The irrigation experiments were conducted in a commercial vineyard (Lambert Vineyards Inc.) located in Niagara-on-the-Lake, Ontario, from 2005 through 2009. The two experiments that tested the combination of different water regimes and irrigation time initiation were set up in a randomized block design as follows: Baco noir - three replicates x 10 treatments [(25%, 50% and 100% of ETc) x (initiation at fruit set, lag phase and veraison) + control]; Chardonnay - three replicates x seven treatments [(25%, 50% and 100% of ETc) x (initiation at fruit set and veraison) + control]. The experiments that tested different irrigation strategies were set up on two cultivars as follows: Sauvignon blanc - four replicates x four treatments [control, fully irrigated (100% ETc), PRD (100% ETc) and RDI (25% ETc)]; Cabemet Sauvignon - four replicates x five treatments [control, fully irrigated (100% ETc), PRD (100% ETc), RDI (50% ETc) and RDI (25% ETc)]. The controls in each experiment were nonirrigated. The irrigation treatments were compared for many variables related to soil water status, vine physiology, berry composition, wine sensory profile, and hormone composition [(abscisic acid (ABA) and its catabolites]. Soil moisture profile was mostly affected by irrigation treatments between 20 and 60 em depth depending on the grapevine cultivar and the regime of water applied. Overall soil moisture was consistently higher throughout the season in 100 and 50% ETc compare to the control. Transpiration rates and leaf temperature as well as shoot growth rate were the most sensitive variables to soil water status. Drip irrigation associated with RDI treatments (50% ETc and 25% ETc) had the most beneficial effects on vine physiology, fruit composition and wine varietal typicity, mainly by maintaining a balance between vegetative and reproductive parts of the vine. Neither the control nor the 100 ETc had overall a positive effect on grape composition and wine sensory typicity. The time of irrigation initiation affected the vine physiology and grape quality, the most positive effect was found in treatments initiated at lag phase and veraison. RDI treatments were overall more consistent in their positive effect on grape composition and wine varietal typicity comparing to PRD treatment. The greatest difference between non-irrigated and irrigated vines in most of the variables studied was found in 2007, the driest and hottest season of the experimental period. Soil water status had a greater and more consistent effect on red grapevine cultivars rather than on white winegrape cultivars. To understand the relationships among soil and plant water status, plant physiology and the hormonal profiles associated with it, abscisic acid (ABA) and its catabolites [phaseic acid (PA), dihydrophaseic acid (DPA), 7-hydroxy-ABA (TOH-ABA), 8' -hydroxy-ABA, neophaseic acid and abscisic acid glucose ester (ABA-GE)] were analyzed in leaves and berries from the Baco noir and Chardonnay irrigation trials over two growing seasons. ABA and some of its catabolites accurately described the water status in the vines. Endogenous ABA and some of its catabolites were strongly affected in Baco noir and Chardonnay by both the water regime (i.e. ET level) and timing of irrigation initiation. Chardonnay grapevines produced less ABA in both leaves and berries compared to Baco noir, which indicated that ABA synthesis is also cultivar dependant. ABA-GE was the main catabolite in treatments with high water deficits, while PA and DPA were higher in treatments with high water status, suggesting that the vine produced more ABA-GE under water deficits to maintain rapid control of the stomata. These differences between irrigation treatments with respect to ABA and catabolites were particularly noticeable in the dry 2007 season. Two trials using exogenous ABA investigated the effect of different concentrations of ABA and organs targeted for spraying, on grape maturation and berry composition of Cabemet Sauvignon grapevines, in two cool and wet seasons (2008-2009). The fIrst experiment consisted of three replicates x three treatments [(150 and 300 mg/L, both applications only on clusters) + untreated control] while the second experiment consisted in three replicates x four treatments [(full canopy, only clusters, and only leaves sprayed with 300 ppm ABA) + untreated control]. Exogenous ABA was effective in hastening veraison, and improving the composition of Cabemet Sauvignon. Ability of ABA to control the timing of grape berry maturation was dependant on both solution concentration and the target organ. ABA affected not only fruit composition but also yield components. Berries treated with ABA had lower weight and higher skin dry mass, which constitutes qualitative aspects desired in the wine grapes. Temporal advancement of ripening through hormonal control can lead to earlier fruit maturation, which is a distinct advantage in cooler areas or areas with a high risk of early frost occurrence. Exogenous ABA could provide considerable benefits to wine industry in terms of grape composition, wine style and schedule activities in the winery, particularly in wet and cool years. These trials provide the ftrst comprehensive data in eastern North America on the response of important hybrid and Vitis vinifera winegrape cultivars to irrigation management. Results from this study additionally might be a forward step in understanding the ABA metabolism, and its relationship with water status. Future research should be focused on ftnding the ABA threshold required to trigger the ripening process, and how this process could be controlled in cool climates.
    • Influence of adolescent social instability stress on the intake of ethanol and sucrose in a rodent model

      de Lima Marcolin, Marina; Department of Biological Sciences
      Adolescence is a sensitive period in which the effects of stress and alcohol can have long-lasting impacts. Social instability stress in adolescent rats (SS; postnatal day 30-45, daily 1 hour isolation + new cage partner) alters behavioural responses to psychostimulants and increases anxiety-like behaviour, but differences in voluntary consumption of natural and drug rewards are unknown. The main goal of my thesis was to investigate the effects of adolescent social instability stress (SS) on immediate and long-lasting changes on reward-related behaviours in male rats using voluntary alcohol intake paradigms. Another goal was to investigate the influence of social context on the propensity to drink alcohol, as well as the influence of these factors on sucrose intake. In chapter 2, I found that adolescent SS increased alcohol intake irrespective of social context, and adolescents drank more alcohol than adults. The intake of sucrose was not altered by stress, except during context of competition. In chapter 3, I found that history of alcohol drinking reduced synaptic plasticity markers in the dorsal hippocampus and prefrontal cortex, and this reduction was sometimes further reduced by SS. The propensity to drink alcohol was found not to differ between SS and CTL rats in the first experiment, and reduced among SS rats in the second experiment. After nine days of alcohol absence, the propensity to drink alcohol was not increased by previous alcohol access, and SS increased intake only in alcohol-naïve rats. History of alcohol drinking reduced anxiety-like behaviours and blunted SS-induced reduction in social interactions. Both SS and alcohol decreased corticosterone levels at baseline and after fear recall without changing freezing behaviour. My findings indicate that using a model of mild social stressor can have great impact on adolescent rats, but moderate effects in adult rats. The behavioural changes caused by stress can be enhanced later in life by history of alcohol drinking, but that does not necessarily cause an increase in the propensity to drink during adulthood, as other studies have shown. Adolescent stressed rats drink more alcohol than other groups, but they don’t seem to continue drinking more when they reach adulthood. These results indicate that the effects of social instability stress are transient in regards to propensity to drink, and can be the basis for alterations caused by both alcohol and stress.
    • Intracellular antioxidant and DNA repair enzymes as correlates of stress resistance and longevity in vertebrates

      Page, Melissa Maire; Department of Biological Sciences (Brock University, 2011-10-14)
      In animals, both stress resistance and longevity appear to be influenced by the insulin/insulin-like growth factor-l signaling (lIS) pathway, the basic organization of which is highly conserved from invertebrates to vertebrates. Reduced lIS or genetic disruption of the lIS pathway leads to the activation of forkhead box transcription factors, which is thought to upregulate the expression of genes involved in enhancing stress resistance, including perhaps key antioxidant enzymes as well as DNA repair enzymes. Enhanced antioxidant and DNA repair capacities may underlie the enhanced cellular stress resistance observed in long-lived animals, however little data is available that directly supports this idea. I used three. experimental approaches to test the association of intracellular antioxidant and DNA base excision repair (BER) capacities with stress resistance and longevity: (1) a comparison of multiple vertebrate endotherm species of varying body masses and longevities; (2) a comparison of long-lived Snell dwarf mice and their normallittermates; and (3) a comparison of hypometabolic animals undergoing hibernation or estivation with their active counterparts. The activities of the five major intracellular antioxidant enzymes as well as the two rate-limiting enzymes in the BER pathway, apurininc/apyrimidinic (AP) endonuclease and polymerase ~, were measured. These measurements were performed in one or more of the following: (1) cultured dermal fibroblasts; (2) brain tissue; (3) heart tissue; (4) liver tissue. My results indicate that antioxidant enzymes are not universally upregulated in association with enhanced stress resistance and longevity. I also did not find that BER enzyme activity was positively correlated with longevity, in an inter-species context, though there was evidence for enhanced BER in long-lived Snell dwarf mice. Thus, while there were instances in which enhanced antioxidant and BER enzyme activities were associated with increased stress resistance and/or longevity, this was not universally the case, indicating that other mechanisms must be involved. These results suggest the need to re-examine existing 'oxidative stress' hypotheses of longevity and probe further into the molecular physiology of longevity to discover its mechanistic basis.
    • Investigating the Effect of Cell Culture Compositions on Mitochondrial Metabolism, Dynamics, and Transcriptome and Proteome of cells

      Moradi, Fereshteh; Department of Biological Sciences
      The phytoestrogen Resveratrol (RES) is a natural polyphenol that has been detected in more than 70 plant species. RES has structural similarity to mammalian estrogens and can bind to estrogen receptors, eliciting genomic and non-genomic effects. Both RES and physiological estrogens like 17-β-estradiol (E2) have wide-ranging effects on mitochondria. In this thesis, I began by investigating RES’s effects on mitochondrial network dynamics (Chapter 2) and discovered a pro-fusion activity apparently mediated by the mitofusin enzyme Mfn2. RES stimulated mitochondrial network hyper-fusion morphology in all three cell lines investigated (C2C12 (mouse myoblast), PC3 (prostate cancer), and MEFs (mouse embryonic fibroblast)), but the effect was absent in Mfn2-null MEFs. As this work was being completed; several research groups introduced ‘physiologic cell culture media’ that are modeled on the human plasma metabolome. I co-authored a study (not in this thesis) demonstrating that RES’s effects on mitochondrial dynamics are dependent on cell culture conditions. To follow up on this, I investigated whether E2’s mitochondrial effects might also be dependent on the cell culture environment, and showed conclusively that this is indeed the case, using C2C12 cells as a model system (Chapter 3). These results and those published by others in 2017-2019 suggested that medium composition can profoundly affect cellular functions. In Chapter 4, I followed this up by studying how culture conditions affect mitochondrial bioenergetics and network morphology using four cancer cell lines and showed that this is a significant issue. Finally, to gain a more complete understanding of this phenomenon, I completed a full transcriptomic and proteomic analysis of media effects using MCF7 breast cancer cells as a model (Chapter 5). I showed that hundreds of transcripts and proteins are affected according to culture conditions. Taken together, the results presented in this thesis emphasize the significant extent to which the cell culture environment affects experimental outcomes, particularly with respect to mitochondrial bioenergetics and dynamics. This information contributes to the development of cell culture experiments providing results that can be translated in vivo.
    • Investigating the role of apoptosis regulator EndoG on exogenous DNA uptake, stability, replication and recombination

      Misic, Vanja; Department of Biological Sciences (Brock University, 2013-11-05)
      Endonuclease G (EndoG) is a well conserved mitochondrial nuclease with dual lethal and vital roles in the cell. It non-specifically cleaves endogenous DNA following apoptosis induction, but is also active in non-apoptotic cells for mitochondrial DNA (mtDNA) replication and may also be important for replication, repair and recombination of genomic DNA. The aim of our study was to examine whether EndoG exerts similar activities on exogenous DNA substrates such as plasmid DNA (pDNA) and viral DNA vectors, considering their importance in gene therapy applications. The effects of EndoG knockdown on pDNA stability and levels of encoded reporter gene expression were evaluated in the cervical carcinoma HeLa cells. Transfection of pDNA vectors encoding short-hairpin RNAs (shRNAs) reduced levels of EndoG mRNA and nuclease activity in HeLa cells. In physiological circumstances, EndoG knockdown did not have an effect on the stability of pDNA or the levels of encoded transgene expression as measured over a four day time-course. However, when endogenous expression of EndoG was induced by an extrinsic stimulus (a cationic liposome transfection reagent), targeting of EndoG by shRNA improved the perceived stability and transgene expression of pDNA vectors. Therefore, EndoG is not a mediator of exogenous DNA clearance, but in non-physiological circumstances it may non-specifically cleave intracellular DNA regardless of its origin. To investigate possible effects of EndoG on viral DNA vectors, we constructed and evaluated AdsiEndoG, a first generation adenovirus (Ad5 ΔE1) vector encoding a shRNA directed against EndoG mRNA, along with appropriate Ad5 ΔE1 controls. Infection of HeLa cells with AdsiEndoG at a multiplicity of infection (MOI) of 10 p.f.u./cell resulted in an early cell proliferation defect, absent from cells infected at equivalent MOI with control Ad5 ΔE1 vectors. Replication of Ad5 ΔE1 DNA was detected for all vectors, but AdsiEndoG DNA accumulated to levels that were 50 fold higher than initially, four days after infection, compared to 14 fold for the next highest control Ad5 ΔE1 vector. Deregulation of the cell cycle by EndoG depletion, which is characterized by an accumulation of cells in the G2/M transition, is the most likely reason for the observed cell proliferation defect. The enhanced replication of AdsiEndoG is consistent with this conclusion, as Ad5 ΔE1 DNA replication is intimately related to cell cycling and prolongation or delay in G2/M greatly enhances this process. Furthermore, infection of HeLa with AdsiEndoG at MOI of 50 p.f.u./cell resulted in an almost complete disappearance of viable, adherent tumour cells from culture, whereas almost a third of the cells were still adherent after infection with control Ad5 ΔE1 vectors, relative to the non-infected control. Therefore, targeting of EndoG by RNAi is a viable strategy for improving the oncolytic properties of first generation adenovirus vectors. In addition, AdsiEndoG-mediated knockdown of EndoG reduced homologous recombination between pDNA substrates in HeLa cells. The effect was modest but, nevertheless demonstrated that the proposed role of EndoG in homologous recombination of cellular DNA also extends to exogenous DNA substrates.
    • Investigating the Role of MicroRNAs in Regeneration and Axonal Pathfinding

      Walker, Sarah; Department of Biological Sciences
      During both development and regeneration, axons must navigate through a complex and changing environment to reach their proper synaptic target. To do so, axons utilize a specialized structure, the growth cone, which senses and interprets guidance cues in its surrounding environment to change the direction of axonal outgrowth. MicroRNAs, which regulate mRNA translation, have recently been shown to regulate both neurite outgrowth and growth cone guidance in response to classical guidance cues during vertebrate development. However, little is known of their regulation of neuronal regeneration in an invertebrate. Thus, the main aim of this thesis was to study the role of microRNAs during CNS regeneration of the pond snail, Lymnaea stagnalis. Specifically, I determined the expression patterns and relative abundance of microRNAs in the regenerating CNS in response to retinoic acid (RA). Using miRNA-Sequencing, I identified one neuronally enriched microRNA, miR-124, that was up-regulated in RA-induced regenerating CNS. Using PCR and in situ hybridization, I characterized its distribution in the snail CNS, and discovered it shared similar expression patterns to that of vertebrates. In cell culture, I found miR-124 was abundant within regenerating motorneurons and was localized to their growth cones. I next determined that miR-124 contributed to RA-induced growth cone turning behaviour. During attractive growth cone turning to RA, the abundance and distribution of miR-124 was altered, in both a cue and context-dependent manner. Finally, I demonstrated that miR-124 targeted the Rho kinase, ROCK, during turning responses to RA, likely to promote the formation of a neurite shaft, or to maintain growth cone polarity. Together, these findings provide the first evidence for a role of microRNAs in mediating growth cone behaviours to RA in regenerating motorneurons.
    • Metarhizium robertsii interactions with Phaseolus vulgaris (Haricot Bean)

      Hu, Shasha; Department of Biological Sciences
      Metarhizium is an insect pathogenic fungus, as well as a plant root symbiont. During symbiotic interactions, it can benefit the plant by improving plant growth, antagonizing plant pathogens and herbivores, and enhancing plant tolerance to abiotic stresses. In this thesis, the interactions between Metarhizium robertsii and Phaseolus vulgaris (haricot bean) were studied from two aspects. First, a phenotypically degenerated (low conidia production) strain of Metarhizium was serially passaged through bean plant. Second, the immune responses of haricot bean during endophytic colonization were assessed. Commercial application of Metarhizium for insect biocontrol requires optimal production of conidia as infective propagules. It was demonstrated that conidial production and virulence of phenotypically degenerated Metarhizium were restored by serial passages through bean roots, as well as switchgrass roots, and wax moth larvae. A decrease in the expression of fungal DNA methyltransferase was observed in the phenotypically degenerated Metarhizium strain through bean passages. Whole genome bisulfite sequencing analysis showed differences in the distribution of differentially methylated regions in the degenerated and subsequently recovered strains. Metarhizium can antagonize the plant pathogen, Fusarium solani f. sp. phaseoli during bean root colonization. Using comprehensive plant hormone analysis, transcriptional expression, and stomatal size analysis, bean immune responses to colonization by Metarhizium and/or Fusarium were assessed. In comparison to un-inoculated bean, root colonization by Metarhizium resulted in reduction of abscisic acid (ABA), increased stomatal size, and decreased expression of plant immunity genes in bean leaves, which is different from those in bean colonized by Fusarium. Furthermore, exogenous application of ABA resulted in reduction of bean root colonization by Metarhizium but increased colonization by Fusarium, compared to corresponding plants without ABA application. Therefore, ABA was implicated in differential responses of bean plants to root colonization by Metarhizium and Fusarium. In conclusion, this thesis provided new insights into the study of the interactions between Metarhizium and haricot bean. Some novel findings were that fungal DNA methyltransferase was implicated in the recovery of phenotypically degenerated Metarhizium and a plant hormone, abscisic acid was implicated in differential interactions of endophytic colonization by Metarhizium when compared to a pathogenic interaction by Fusarium.