Research

The innate immune response against parasitic wasps
Innate immunity is often divided into two main components, the humoral response
and the cellular response.  The Drosophila humoral response has been intensely
studied for its role in combating bacterial and fungal infections, but the genes
underlying the cellular innate immune response of Drosophila (or of any other
organism) are poorly characterized.  Parasitic wasps are natural parasites of
Drosophila that induce a cellular immune response.  A main focus of our lab is to
functionally characterize candidate D.  melanogaster anti-wasp immune response
genes identified in previous microarray and other studies (e.g., Schlenke et al. 2007).

Venom components used by parasitic wasps to overcome
host immune systems
Like many other arthropods, Drosophila are frequently infected by parasitic wasps.
Fieldwork and laboratory studies undertaken by our lab have resulted in the
collection and lab rearing of several wasp species that attack D.  melanogaster in
nature, and in robust protocols for extracting and manipulating wasp venom.  Our
goal is to identify and functionally characterize venom components from parasitoid
wasp species that utilize diverse infection strategies to overcome the Drosophila
immune response.  Click here for one of our wasp attack videos.

Evolution of host immunity proteins and pathogen virulence
proteins
We are also interested in long-term patterns of immune system and virulence
protein evolution.  For example, in previous work in D. simulans, we showed that it is
immune signaling proteins, not recognition or attack proteins, that rapidly evolve
(Schlenke and Begun 2003).  These data identified “weak links” in the Drosophila
immune system pathogens tend to exploit, and suggested that the most common
microbial infection strategies involve active suppression of host immunity rather
than passive evasion.

Evolutionary ecology of host-pathogen interactions
The fruitfly-wasp interaction can be exploited to answer general questions about the
ecology of host-pathogen interactions.  In particular, we are using this system to
determine (1) whether generalist parasites tend to be more immune suppressive
and less immune evasive than specialist parasites (Schlenke et al. 2007), (2) the
potential for horizontal transfer of microbial pathogens between eukaryotic hosts
and pathogens, and (3) the role that plant secondary compounds play in host
defense against parasites.

Insecticide resistance evolution
Finally, insecticide resistance evolution has become a major problem in dealing
with agricultural pests and insect vectors of human diseases.  Drosophila are not
agricultural pests but they are regularly exposed to insecticides, and rapidly evolve
resistance.  We previously identified a transposon insertion in D. simulans that
inserted regulatory information upstream of a detoxification gene, causing the gene
to be constitutively upregulated and increasing resistance to DDT and other
insecticides (Schlenke and Begun 2004).  A parallel discovery was made in the
sister species D. melanogaster.  We have genetically mapped new insecticide
resistance loci in D. melanogaster and are functionally characterizing the candidate
genes.

Publications

Schlenke, T.A., Lazzaro, B.P. (2008) Fruit flies like a (rotten) banana. Fly 2: 159-164.

Drosophila 12 Genomes Consortium (2007) Evolution of genes and genomes on the Drosophila phylogeny.
Nature 450: 203-218.

Sackton, T.B., B.P. Lazzaro, T.A. Schlenke, J.D. Evans, D. Hultmark, and A.G. Clark (2007) Dynamic evolution of the innate
immune system in Drosophila. Nature Genetics 39: 1461-1468.

Schlenke, T.A., J. Morales, S. Govind, and A.G. Clark (2007) Contrasting infection strategies in generalist and specialist
wasp parasitoids of Drosophila melanogaster. PLoS Pathogens 3: 1486-1501.

Schlenke, T.A. and D.J. Begun (2005) Linkage disequilibrium and recent selection in three potential pattern recognition
receptor loci in Drosophila simulans. Genetics 169: 2013-2022.

Schlenke, T.A. and K.A. McKean (2005) A role for ADH in the Drosophila immune response?
Insect Molecular Biology 14: 175-178.

Schlenke, T.A. and D.J. Begun (2004) Strong selective sweep associated with a transposon insertion in Drosophila
simulans. PNAS 101: 1626-1631.

Schlenke, T.A. and D.J. Begun (2003) Natural selection drives the evolution of the Drosophila immune system.
Genetics 164: 1471-1490.