PhD Transfer Exam
Tuesday, May 22, 2018 at 1:10 pm – Earth Science Building, Room 3087
Kevin Xue (D. Christendat lab)
“Elucidating the Protocatechuate Biosynthetic Pathway in Listeria monocytogenes and its Role in Microbial Interactions”
Listeria monocytogenes is a ubiquitous bacterial saprophyte capable of causing fatal listeriosis in mammalian hosts. L. monocytogenes boasts a high tolerance to sanitation measures and persists in food processing environments. Although much investigation of its pathogen lifestyle has been conducted, its role as a saprophyte remains poorly understood. Our lab has identified and partially characterized two operons containing genes for the biosynthesis of protocatechuate, a compound derived from plant material degradation and industrial waste (Prezioso et al. 2018 and Bonfa et al. 2013). Though other microorganisms will produce and utilize protocatechuate to generate energy or produce protocatechuate type siderophores, L. monocytogenes lacks these pathways. L. monocytogenes produces protocatechuate when the LysR type transcriptional regulator (LTTR), QuiR, induces qui1 and qui2 with its coinducer and ligand, shikimate. Shikimate supplementation leads to accelerated growth of Listeria innocua followed by rapid cell density loss. I hypothesize that L. monocytogenes generates protocatechuate, which it will exchange mutualistically with other microorganisms. Alternatively, L. monocytogenes is utilizing protocatechuate to generate a novel metabolite. The former hypothesis is supported by the loss of cell density when protocatechuate accumulates in shikimate supplied monoculture. I plan to characterize the qui1 and qui2 operons by gene deletion to study their roles in protocatechuate biosynthesis. I will also study the effect of protocatechuate on Listeria growth. Furthermore, I plan to investigate the role of protocatechuate in microbial interactions by performing co-cultured growth analysis between Listeria and other bacterial species.
PhD Transfer Exam
Tuesday, April 17, 2018 at 1:30 pm – Earth Science Building, Room 3087
Stuart Macgregor (D. Goring lab)
“Investigating the role of secretion in the Arabidopsis thaliana compatible pollen response pathway”
The acceptance of compatible pollen in the Brassicaceae is tightly regulated through interactions between the pollen and the pistil. Secretion in the stigmatic papillae is proposed to be key to this interaction to provide resources to the pollen for hydration and germination. The objective of this proposed research is to investigate components of the Arabidopsis thaliana secretory pathway machinery for their requirement in compatible pollen acceptance. Fluorescently-tagged markers that identify different compartments in the endomembrane system will be examined to gain a fuller understanding of the secretory activity that occurs following compatible pollinations. This includes tracking of secretory markers from the initiation of secretion at the endoplasmic reticulum to the final site of vesicle release at the papillar plasma membrane under the pollen contact site. The requirement of SNARE complex subunits, which are implicated in vesicle fusion and cargo release, will also be investigated through loss-of-function mutants. This will be accomplished by using a combination of SNARE T-DNA insertion mutants and generating CRISPR/Cas9 gene editing mutants when needed. This proposed research will provide a better understanding of the stigmatic papilla’s secretory system, and how this system is employed in the acceptance of compatible pollen.
PhD Transfer Exam
Thursday, January 25th, 2018 at 1:10pm –University of Toronto at Mississauga – CCT2134
Nawar Alwash (Levine lab)
“The role of foraging gene (for) in Drosophila melanogaster social interaction networks (SINs)”
Drosophila melanogaster display social behaviours such as courtship, mating, aggression and foraging in groups. Recent studies have shown that different strains of D. melanogaster form social interaction networks (SINs) with different properties, suggesting that genes influence network phenotypes. The foraging gene (for) regulates food-related behaviours in several species including D. melanogaster. There are two naturally occurring alleles of the for gene: rover and sitter, where the rover flies are characterized with higher mobility in the presence of food. However, the role of the two variants in the formation of social networks remains unknown and that will be the focus of my research. I hypothesize that the for gene influences the formation of SINs and thus manipulating the for gene would lead to formation of networks with different SIN properties. I have shown that SINs formed by rover females have different properties than those formed by sitter females. I have also shown an effect of for copy number that is reflected in SIN phenotypes. To investigate this further, I aim to characterize the role of the for gene on social structure by investigating the effect of for on the formation of SINs during different developmental stages. I will also examine the allelic dominance pattern of the rover/sitter variant of for in the formation of SINs. Furthermore, I will explore the effect of external factors, such as stress and social experience, on SIN formation of the rover/sitter variants. This research will be the first to identify a specific gene influencing social network structure in D. melanogaster. In addition, understanding the role of for in the formation of SINs could potentially provide an insight into understanding the role of this gene in SIN formation of other organisms.