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Poster Full Abstracts - Immunity and Pathogenesis
Poster board number is above title. The first author is the presenter
290
S-Nitrosylation in Immunity and Fertility: A Mechanism Conserved in Plants and Animals.
Krieng Kanchanawatee
1
, Gary Loake
1
, David Finnegan
2
. 1)
Institute of Molecular Plant Sciences , Univeristy of Edinburgh, Edinburgh, United Kingdom; 2) Institute of Cell Biology, Univeristy of Edinburgh,
Edinburgh, United Kingdom.
Post-translational modification is an intracellular process that modifies the properties of proteins to extend the range of protein function without spending
energy in de novo peptide synthesis. S-Nitrosylation is a post-translational modification which adds nitric oxide (NO) to sulfhydryl group at cysteine residue
to form S-nitrosothiol (SNO), and is required for plant immunity and fertility. Cellular NO changes between a pool of free NO and bound SNO. During
pathogen infection, nitrosative stress in plants is mainly controlled by S-nitrosothiolglutathione reductase (GSNOR) via the decomposition of GSNO.
GSNOR is an alcohol dehydrogenase type 3 (ADH3) which has both GSNOR and formaldehyde dehydrogenase (FDH) activities. The roles of S-
nitrosylation in mammals overlap with those in plants. This conservation led us to explore the relationship between S-nitrosylation, immune response, and
fertility in Drosophila melanogaster as it might prove to be a good genetic model for further analysis of the role of S-nitrosylation in animals. I have
identified Fdh as the likely GSNOR in D. melanogaster and have knocked this out using an overlapping deficiency technique in order to observe the effect
on immunity and fertility. There are two main pathways in the Drosophila innate immune response, the Toll pathway for protecting against gram-positive
bacteria and fungi, and the IMD pathway against gram-negative bacteria. I have investigated the effect of removing GSNOR on sensitivity to gram-negative
bacteria (Escherichia coli and Erwinia carotovora) by septic and natural infection, and to fungi (Beauveria brassiana) by natural infection. Susceptibility to
infection by the gram negative bacteria was similar to wild-type but susceptibility to B. brassiana was increased. This suggests that GSNOR is required for
the normal activity of the Toll pathway. We also observed that GSNOR knockout impairs fertility and development of embryos.
592A
Characterization of a candidate immune receptor in Drosophila.
Erin S. Keebaugh, Todd A. Schlenke. Dept Biol, Emory Univ, Altanta, GA.
To gain a better understanding of non-self recognition between eukaryotes we study the interaction between fruitflies and one of their natural metazoan
pathogens, parasitic wasps. Parasitic wasps lay eggs in Drosophila larvae that hatch, consume larval tissues, and eclose from the fly pupal case, killing the
fly in the process. Drosophila larvae can mount a robust cellular immune response against the wasp eggs termed melanotic encapsulation, where fly
hemocytes form a capsule around and kill the entrapped wasp egg. As a first step in the encapsulation response, the host must be able to recognize the
parasite as foreign. We are interested in identifying the immune receptors Drosophila use to identify parasitic wasps as non-self, and uncovering the
evolutionary history of such genes as a first step towards understanding the selective forces parasites impose on their hosts in nature. Microarray analysis of
Drosophila larvae post-wasp attack identified several promising candidate immune receptors including a C-type lectin,
lectin-24A
. Expression analysis of
this candidate immune receptor shows enriched expression in immune tissue and a wasp-specific regulatory response. We are currently investigating the
effects of mutant levels of
lectin-24A
on hemocyte viability, structure, and ability to form melanotic capsules, and have designed experiments to test Lectin-
24A's binding specificity.
593B
Altered metabolism influences survival from infection.
Karla L. Lightfield, David Schneider. Microgiology and Immunology, Stanford University,
Stanford, CA.
The ability of a host to survive infection is dependent upon two main classes of responses. First, the host uses resistance mechanisms to isolate and kill the
pathogen to limit pathogen burden. Secondly, the host must employ a wide variety of mechanisms in order to survive the infection long enough for the
resistance mechanisms to work. The host must both prevent and heal from damage caused by the infection itself and the resultant immune response. The host
must also regulate its energy balance and metabolism such that it can properly mount an efficient immune response while at the same time maintaining other
key physiological processes. Here we use the well-established model of infecting Drosophila melanogaster with Listeria monocytogenes to probe the
crosstalk between metabolism and the immune response. Drosophila mutants lacking adipokinetic hormone receptor are less able to mobilize energy stores
after being stressed. We show that although these mutants can initially restrict the growth of Listeria they eventually succumb to infection. This death occurs
much faster than that of their wild-type counterparts that are capable of efficiently accessing their energy stores. In conclusion, despite the fact that these
mutants can mount an effective immune response initially, their inability to properly regulate energy metabolism renders them less able to survive the
infection.
594C
Recovery from Infection.
Alexander Louie, David Schneider. Microbiology and Immunology, Stanford University, Stanford, CA.
During an effective immune response, pathogens are eliminated and host physiologies return to baseline. When we discuss infection we do a good job of
describing immune effectors but seldom look at recovery. Our goal is to identify the mechanisms that drive recovery from infection. To this end, we
developed a system with two criteria. 1) The flies get sick and then recover from infection. 2) We can monitor the effects of microbe levels on pathology.
The median survival of flies infected with 100 colony-forming units of Listeria monocytogenes is 13 days, and without support the infection is inevitably
fatal. Ampicillin treatment of infected flies eliminates L. monocytogenes, and the cured flies live as long as control flies. As the number of bacteria decrease,
the expression of antimicrobial peptides decreases and returns to baseline levels. We are currently analyzing gene expression changes across the full course
of infection in ampicillin treated and untreated infected flies. This dataset will let us track transcription through high dimensional phase space along the full
course of infection. Gene expression patterns that differ between flies that die and flies that recover will help to identify recovery mechanisms.
595A
Fat metabolic effects to immune responses in Drosophila melanogaster.
Kyung Han SONG, David Schneider. Microbiology and Immunology, Stanford
University, Stanford, CA.
Our goal is to understand whether metabolic disruptions that occur during infections aid survival or contribute to pathology. We use an infection model in
which we challenge fruit flies with Listeria monocytogenes. Preliminary work from others in the lab suggested that fatty acid biosynthesis decreases during
infection. We followed up on this work by testing mutants in this biosynthetic pathway for immune phenotypes. Triglyceride is synthesized by the addition
of fatty acids to a glycerol backbone by fatty acyl transferases. We tested three of these enzymes and found a difference in their immune behavior. Normally